Zoom lens and imaging apparatus

Abstract

To provide a zoom lens that can obtain high optical performance over the entire zoom area despite its short total length and small size.SOLUTION: A zoom lens has a plurality of lens groups. The plurality of lens groups comprise, in order from an object side to an image side, a first lens group (B1) having a positive refractive power, a second lens group (B2) having a negative refractive power, a third lens group (B3) having a positive refractive power, a fourth lens group (B4) having a negative refractive power, and a fifth lens group (B5) having a positive refractive power. In zooming, at least the first lens group and the third lens group are fixed, the second lens group and the fourth lens group move, and the interval between the adjacent lens groups changes. A thickness B1L on an optical axis of the first lens group, a thickness B3L on the optical axis of the third lens group, a focal length f4 of the fourth lens group, a focal length f5 of the fifth lens group, and a back focus BFw at a wide-angle end, satisfy predetermined conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, with the trend toward higher resolution imaging devices and display devices, there has been a demand for zoom lenses with high optical performance, in which various aberrations, such as chromatic aberration and curvature of field, are well corrected. Furthermore, there is a demand for compact zoom lenses to be mounted on surveillance cameras and the like. Furthermore, there is a demand for zoom lenses used for long-distance surveillance to have a long focal length. Patent Documents 1 and 2 disclose zoom lenses each consisting of first to fifth lens groups with positive, negative, positive, negative, and positive refractive powers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-215165 [Patent Document 2] Japanese Patent Application Publication No. 2017-116678 Summary of the Invention [Problem to be solved by the invention]

[0004] In the zoom lens disclosed in Patent Document 1, the first lens group is thick. This makes it difficult to shorten the overall length of the zoom lens, particularly in a telephoto zoom lens. The zoom lens disclosed in Patent Document 2 has a fast F-number, but the overall length of the zoom lens is long relative to the size of the image plane.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a zoom lens that is compact and has a short overall length, yet provides high optical performance over the entire zoom range. [Means for solving the problem]

[0006] 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 comprising, 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, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power; during zooming, at least the first lens group and the third lens group are fixed, the second lens group and the fourth lens group are moved, and a spacing between adjacent lens groups changes; when the thickness of the first lens group on the optical axis is B1L, the thickness of the third lens group on the optical axis is B3L, the focal length of the fourth lens group is f4, the focal length of the fifth lens group is f5, and the back focus at the wide-angle end is BFw, 0.20≦B1L / B3L≦0.80 -3.00≦f4 / f5≦-1.06 2.00≦f5 / BFw≦6.00 The following condition is satisfied.

[0007] Other objects and features of the present invention are illustrated in the following examples. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a zoom lens that is small and has a short overall length, yet provides high optical performance over the entire zoom range. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens at a wide-angle end in a first embodiment. [Figure 2] 4A to 4C are aberration diagrams of the zoom lens at the wide-angle end, at the intermediate zoom position, and at the telephoto end in Example 1. [Figure 3] FIG. 10 is a cross-sectional view of a zoom lens at a wide-angle end in a second embodiment. [Figure 4] 10A to 10C are aberration diagrams of the zoom lens at the wide-angle end, at the intermediate zoom position, and at the telephoto end in Example 2. [Figure 5] FIG. 10 is a cross-sectional view of a zoom lens at the wide-angle end in Example 3. [Figure 6] 10A to 10C are aberration diagrams of the zoom lens at the wide-angle end, at the intermediate zoom position, and at the telephoto end in Example 3. [Figure 7] FIG. 10 is a cross-sectional view of a zoom lens at the wide-angle end in Example 4. [Figure 8] 10A to 10C are aberration diagrams of the zoom lens at the wide-angle end, at the intermediate zoom position, and at the telephoto end in Example 4. [Figure 9] FIG. 10 is a cross-sectional view of a zoom lens at the wide-angle end in Example 4. [Figure 10] 10A to 10C are aberration diagrams of the zoom lens at the wide-angle end, at the intermediate zoom position, and at the telephoto end in Example 4. [Figure 11] FIG. 13 is a cross-sectional view of a zoom lens at the wide-angle end in Example 6. [Figure 12] 13A to 13C are aberration diagrams of the zoom lens at the wide-angle end, at the intermediate zoom position, and at the telephoto end in Example 6. [Figure 13] 1 is a schematic diagram of an imaging device equipped with a zoom lens in each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] The zoom lens of each embodiment is a zoom lens having multiple lens groups. The multiple lens groups are, in order from the object side to the image side, a first lens group B1 with positive refractive power, a second lens group B2 with negative refractive power, a third lens group B3 with positive refractive power, a fourth lens group B4 with negative refractive power, and a fifth lens group B5 with positive refractive power. This configuration achieves a compact overall zoom lens system and a high zoom ratio. Furthermore, in the zoom lens of each embodiment, during zooming (variable magnification) from the wide-angle end to the telephoto end, at least the first lens group B1 and the third lens group B3 are fixed, while the second lens group B2 and the fourth lens group B4 move, changing the spacing between adjacent lens groups.

[0012] Because the first lens group B1 is large and heavy, it is not moved during zooming. It is preferable that the third lens group B3 be configured with multiple lenses to effectively correct various aberrations, particularly axial chromatic aberration, spherical aberration, and coma, throughout the entire zoom range. Because the third lens group B3 is heavy, it is not moved during zooming. The second lens group B2, which has negative refractive power and is located between the first lens group B1, which has positive refractive power, and the third lens group B3, which has positive refractive power, moves toward the image side, achieving efficient zooming (variable magnification). The fourth lens group B4 moves during zooming, effectively correcting fluctuations in the image position on the optical axis OA that occur as the second lens group B2 moves.

[0013] The zoom lens of each embodiment also satisfies the following conditional expressions (1) to (3).

[0014] 0.20≦B1L / B3L≦0.80 …(1) -3.00≦f4 / f5≦-1.06 …(2) 2.00≦f5 / BFw≦6.00 …(3) Here, B1L is the axial thickness of the first lens unit B1, B3L is the axial thickness of the third lens unit B3, f4 is the focal length of the fourth lens unit B4, f5 is the focal length of the fifth lens unit B5, and BFw is the back focus at the wide-angle end. The back focus is the air-equivalent distance on the optical axis from the surface of the fifth lens unit B5 closest to the image plane.

[0015] Conditional formula (1) defines the ratio between the axial thickness of the first lens unit B1 and the axial thickness of the third lens unit B3. If the upper limit of conditional formula (1) is exceeded, the lens configuration of the third lens unit B3 is limited, making it difficult to arrange the lenses to effectively correct spherical aberration and coma, particularly at the wide-angle end. Conversely, if the lower limit of conditional formula (1) is exceeded, the lens configuration of the first lens unit B1 is limited, making it difficult to arrange the lenses to effectively correct spherical aberration, particularly at the telephoto end.

[0016] Conditional formula (2) defines the ratio between the focal length of the fourth lens group B4 and the focal length of the fifth lens group B5. Exceeding the upper limit of conditional formula (2) is undesirable because it reduces the positive refractive power on the image side, making the back focus longer and increasing the overall optical length. Here, the overall optical length refers to the distance from the object-side surface of the first lens group B1 to the image plane. If a glass block or the like is provided in the back focus, the increase in the back focus due to the glass block or the like is also taken into account. Conversely, exceeding the lower limit of conditional formula (2) is undesirable because it weakens the refractive power of the fourth lens group B4, making focusing with the fourth lens group B4 difficult and limiting the freedom of selection of the focusing group.

[0017] Conditional formula (3) defines the ratio between the focal length of the fifth lens unit B5 and the back focal length at the wide-angle end. If the upper limit of conditional formula (3) is exceeded, it becomes difficult to arrange a cover glass, a low-pass filter, an IR cut filter, etc. on the imaging surface of the image sensor. Conversely, if the lower limit of conditional formula (3) is exceeded, the back focal length tends to become long, which leads to an increase in the overall optical length, which is undesirable.

[0018] In each embodiment, it is preferable to satisfy the following conditional expression (4):

[0019] 0.22≦f5 / f1≦0.43 …(4) Here, f1 is the focal length of the first lens group B1. Conditional formula (4) defines the ratio between the focal length of the fifth lens group B5 and the focal length of the first lens group B1. If the upper limit of conditional formula (4) is exceeded, the refractive power of the first lens group B1 becomes too strong, making it difficult to effectively correct spherical aberration, particularly at the telephoto end. Conversely, if the lower limit of conditional formula (4) is exceeded, the telephoto ratio (total lens length / focal length) tends to become large, and the total optical length tends to become long, which is undesirable.

[0020] In each embodiment, it is preferable to satisfy the following conditional expression (5):

[0021] -3.52≦f1 / f2≦-2.63 …(5) Here, f2 is the focal length of the second lens group B2. Conditional formula (5) defines the ratio between the focal length of the first lens group B1 and the focal length of the second lens group B2. Exceeding the upper limit of conditional formula (5) is undesirable because the refractive power of the second lens group B2, which has a large magnification-varying effect, weakens, making it difficult to achieve the desired magnification ratio. Conversely, exceeding the lower limit of conditional formula (5) weakens the telephoto effect of the first lens group B1, making it difficult to achieve a telephoto zoom lens.

[0022] In each embodiment, it is preferable to satisfy the following conditional expression (6):

[0023] 0.69≦f1 / TLt≦1.18 …(6) Here, TLt is the total optical length at the telephoto end. Conditional formula (6) defines the ratio between the focal length of the first lens unit B1 and the total optical length at the telephoto end. If the upper limit of conditional formula (6) is exceeded, the telephoto effect of the first lens unit B1 will be weakened, making it difficult to realize a telephoto zoom lens. Conversely, if the lower limit of conditional formula (6) is exceeded, the total optical length will be too long, which is undesirable.

[0024] In each embodiment, it is preferable to satisfy the following conditional expression (7):

[0025] 0.43≦L13 / B3L≦0.84 …(7) Here, L13 is the distance on the optical axis from the surface of the first lens group B1 closest to the image to the surface of the third lens group B3 closest to the object. Conditional formula (7) defines the ratio of the distance on the optical axis from the surface of the first lens group B1 closest to the image to the surface of the third lens group B3 closest to the object to the thickness of the third lens group B3 on the optical axis. If the upper limit of conditional formula (7) is exceeded, the lens configuration of the third lens group B3 is limited, making it difficult to arrange the lenses to effectively correct spherical aberration and coma, particularly at the wide-angle end. Conversely, if the lower limit of conditional formula (7) is exceeded, the distance that the second lens group B2 can move becomes shorter, making it difficult to achieve the desired zoom ratio, which is undesirable.

[0026] In each embodiment, it is preferable to satisfy the following conditional expression (8).

[0027] -3.69≦L35 / f4≦-2.09 …(8) Here, L35 is the axial distance from the surface of the third lens group B3 closest to the image at the wide-angle end to the surface of the fifth lens group B5 closest to the object at the wide-angle end. Conditional formula (8) defines the ratio of the axial distance from the surface of the third lens group B3 closest to the image at the wide-angle end to the surface of the fifth lens group B5 closest to the object at the wide-angle end to the focal length of the fourth lens group B4. Exceeding the upper limit of conditional formula (8) undesirably weakens the refractive power of the fourth lens group B4, increasing the amount of movement of the fourth lens group B4 during zooming (variable magnification), and increasing the overall optical length. Conversely, exceeding the lower limit of conditional formula (8) undesirably strengthens the refractive power of the fourth lens group B4, making it difficult to correct field curvature during zooming.

[0028] In each embodiment, it is preferable to satisfy the following conditional expression (9):

[0029] 2.60≦f1 / f3≦3.97 …(9) Here, f3 is the focal length of the third lens group B3. Conditional formula (9) defines the ratio between the focal length of the first lens group B1 and the focal length of the third lens group B3. If the upper limit of conditional formula (9) is exceeded, the refractive power of the third lens group B3 becomes too strong, making it difficult to correct spherical aberration, coma, and the like, particularly at the wide-angle end. Conversely, if the lower limit of conditional formula (9) is exceeded, the refractive power of the first lens group B1 becomes too strong, making it difficult to effectively correct spherical aberration, particularly at the telephoto end.

[0030] In each embodiment, it is preferable to satisfy the following conditional expression (10):

[0031] 0.20≦m2 / TLt≦0.35 …(10) Here, m2 is the movement distance of the second lens group B2 from the wide-angle end to the telephoto end, and has a positive sign when the second lens group B2 is located closer to the image at the telephoto end than at the wide-angle end. Conditional formula (10) defines the ratio between the movement distance of the second lens group B2 from the wide-angle end to the telephoto end and the total optical length at the telephoto end. If the upper limit of conditional formula (10) is exceeded, it becomes difficult to increase the thickness of the third lens group B3, making it difficult to arrange the lenses to effectively correct spherical aberration and coma, particularly at the wide-angle end. Conversely, if the lower limit of conditional formula (10) is exceeded, the movement distance of the second lens group B2 becomes shorter, making it difficult to achieve the desired zoom ratio, which is undesirable.

[0032] In each embodiment, the third lens group B3 preferably includes five or more lenses. The third lens group B3 is important for correcting spherical aberration and coma, particularly at the wide-angle end. By including five or more lenses in the third lens group B3, it becomes possible to effectively correct axial chromatic aberration, spherical aberration, and coma throughout the entire zoom range.

[0033] In each embodiment, it is preferable that the fourth lens unit B4 moves from the object side to the image side when focusing from an object at infinity to a close object. By using the fourth lens unit B4 as the focus unit, the amount of movement of the focus unit when focusing from an object at infinity to a close object becomes small, which is advantageous for shortening the overall optical length.

[0034] In each embodiment, it is preferable to satisfy the following conditional expression (11).

[0035] 50 <V2ave<100 …(11) Here, V2ave is the average Abbe number, based on the d-line, of the two positive lenses that are located closest to the object among the multiple positive lenses that make up the third lens group B3. Conditional expression (11) defines the average Abbe number of the two positive lenses that are located closest to the object among the multiple positive lenses that make up the third lens group B3. Exceeding the upper limit of conditional expression (11) limits the number of material options, which is undesirable in terms of aberration correction. Conversely, exceeding the lower limit of conditional expression (11) makes it difficult to correct axial chromatic aberration.

[0036] In each embodiment, it is preferable to satisfy the following conditional expression (12):

[0037] 50 <VPave<100 …(12) Here, VPave is the average Abbe number of all positive lenses constituting the third lens group B3, referenced to the d-line. Conditional formula (12) defines the average Abbe number of all positive lenses constituting the third lens group B3, referenced to the d-line. If the upper limit of conditional formula (12) is exceeded, the number of material options becomes limited, which is undesirable in terms of aberration correction. Conversely, if the lower limit of conditional formula (12) is exceeded, it becomes difficult to correct axial chromatic aberration.

[0038] In each embodiment, it is more preferable that the numerical ranges of the conditional expressions (1) to (12) are set as shown in the following conditional expressions (1a) to (12a), respectively.

[0039] 0.28≦B1L / B3L≦0.62 …(1a) -2.00≦f4 / f5≦-1.20 …(2a) 2.64≦f5 / BFw≦4.19 …(3a) 0.23≦f5 / f1≦0.42 …(4a) -3.45≦f1 / f2≦-2.69 …(5a) 0.71≦f1 / TLt≦1.16 …(6a) 0.44≦L13 / B3L≦0.83 …(7a) -3.62≦L35 / f4≦-2.13…(8a) 2.66≦f1 / f3≦3.90 …(9a) 0.21≦m2 / TLt≦0.34 …(10a) 57.2 <V2ave<88.1 …(11a) 54.5 <VPave<83.0 …(12a) In each embodiment, it is more preferable that the numerical ranges of conditional expressions (1a) to (12a) are set as shown in the following conditional expressions (1b) to (12b), respectively.

[0040] 0.29≦B1L / B3L≦0.61 …(1b) -1.54≦f4 / f5≦-1.24 …(2b) 2.73≦f5 / BFw≦4.07 …(3b) 0.23≦f5 / f1≦0.41 …(4b) -3.36≦f1 / f2≦-2.78 …(5b) 0.73≦f1 / TLt≦1.12 …(6b) 0.45≦L13 / B3L≦0.80 …(7b) -3.52≦L35 / f4≦-2.20…(8b) 2.75≦f1 / f3≦3.79 …(9b) 0.22≦m2 / TLt≦0.33 …(10b) 59.0 <V2ave<85.6 …(11b) 56.3 <VPave<80.7 …(12b) Next, zoom lenses in Examples 1 to 6 will be described with reference to FIGS. 1 to 12. FIGS. 1, 3, 5, 7, 9, and 11 are cross-sectional views of the zoom lenses in Examples 1 to 6. The zoom lenses in each Example have multiple lens groups. The multiple lens groups are composed of, arranged in order from the object side to the image side, a first lens group B1 with positive refractive power, a second lens group B2 with negative refractive power, a third lens group B3 with positive refractive power, a fourth lens group B4 with negative refractive power, and a fifth lens group B5 with positive refractive power.

[0041] In each embodiment, the first lens group B1 consists of three lenses G11, G12, and G13, the second lens group B2 consists of three lenses G21, G22, and G23, and the third lens group B3 consists of seven lenses G31, G32, G33, G34, G35, G36, and G37. In Example 1, the fourth lens group B4 consists of one lens G41. In Examples 2 to 6, the fourth lens group B4 consists of two lenses G41 and G42. In each embodiment, the fifth lens group B5 consists of one lens G51.

[0042] In each embodiment, SP is a diaphragm (aperture stop), G is an optical block, and IP is an image plane. The optical block G may be, for example, a cover glass on the image sensor surface, a low-pass filter, an IR cut filter, or dummy glass for correcting the optical path length, but is not limited to these. Note that the optical path may be configured so that the IR cut filter and dummy glass can be switched within the optical path to correct changes in the optical path length caused by inserting or removing the IR cut filter.

[0043] In the zoom lenses of Examples 1 to 6, when zooming (varying magnification) from the wide-angle end to the telephoto end, each lens group moves as shown by the arrows in each cross-sectional view. The solid and dotted arrows indicate the movement locus of the fourth lens group B4 when focusing on an object at infinity and a close distance, respectively.

[0044] In the zoom lenses of Examples 1 to 5, the fifth lens unit B5 remains stationary (does not move) during zooming from the wide-angle end to the telephoto end. On the other hand, in the zoom lens of Example 6, the fifth lens unit B5 moves during zooming from the wide-angle end to the telephoto end. By keeping the fifth lens unit B5 stationary as in Examples 1 to 5, mechanical components in the area close to the image sensor within the image pickup device are simplified. On the other hand, by moving the fifth lens unit B5 as in Example 6, fluctuations in field curvature and the like that occur due to movement of the fourth lens unit B4 during zooming are easily reduced.

[0045] 2, 4, 6, 8, 10, and 12 are aberration diagrams of the zoom lenses in Examples 1 to 6 at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end, respectively. In each aberration diagram, d and g indicate the d-line and g-line, respectively, and M and S indicate the meridional and sagittal image planes, respectively. Chromatic aberration of magnification is represented by the g-line.

[0046] Numerical Examples 1 to 6 corresponding to Examples 1 to 6 are shown below. In each numerical example, the surface numbers are indicated in order from the object side, r is the radius of curvature, d is the spacing, and nd and vd are the refractive index and Abbe number based on the d-line, respectively. The Abbe number vd is given by: where Nd, NF, and NC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines, respectively. νd=(Nd-1) / (NF-NC) It is expressed as:

[0047] In each numerical example, the two surfaces closest to the image are flat surfaces corresponding to the optical block G. The angle of view is the value (unit: degrees) of the half angle of view (ω) relating to the photographic angle of view taking distortion into consideration. The total lens length is the distance on the optical axis from the lens surface closest to the object among the lens surfaces having optical power to the paraxial image plane, while the thickness of the optical block G is the air-equivalent length. BF is the back focus, which is the distance on the optical axis from the lens surface closest to the image among the lens surfaces having optical power to the paraxial image plane, expressed as the air-equivalent length.

[0048] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1 64.858 5.39 1.49700 81.5 2 -150.026 0.20 3 65.006 4.01 1.49700 81.5 4 -338.193 1.96 5 -161.259 1.20 1.67300 38.3 6 101.482 (variable) 7 338.675 1.00 1.59522 67.7 8 21.499 5.19 9 -29.555 0.80 1.49700 81.5 10 58.558 0.85 11 46.197 1.72 1.90366 31.3 12 809.260 (variable) 13 (Aperture) ∞ 1.50 14 53.043 2.87 1.49700 81.5 15 -52.660 0.20 16 -215.485 3.61 1.49700 81.5 17 -19.470 1.00 1.69930 51.1 18 -100.998 0.20 19 17.232 6.90 1.43875 94.7 20 -90.435 9.84 21 -23.674 1.00 1.60342 38.0 22 24.292 2.75 23 55.388 3.33 1.77250 49.6 24 -25.358 1.90 25 -13.271 1.00 1.51633 64.1 26 -24.966 (variable) 27 3580.546 1.00 1.49700 81.5 28 23.780 (variable) 29 20.399 8.51 1.59522 67.7 30 533.475 3.00 31 ∞ 1.20 1.51633 64.1 32∞5.35 Image plane ∞ Various data Zoom ratio 2.86 Wide-angle Mid-range Telephoto Focal length 34.18 61.86 97.58 F-number 2.88 2.88 2.88 Half angle of view 17.74 9.71 6.15 Image height 10.72 10.72 10.72 Lens length 127.59 127.59 127.59 BF 9.14 9.14 9.14 d 6 1.92 22.12 35.59 d12 35.23 15.03 1.56 d26 2.50 7.71 2.50 d28 10.88 5.67 10.88 Zoom lens group data Group starting plane focal length 1 1 98.10 2 7 -30.67 3 13 32.93 4 27 -48.17 5 29 35.42 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1 65.277 5.36 1.49700 81.5 2 -152.996 0.19 3 83.397 3.70 1.49700 81.5 4 -249.635 1.94 5 -138.028 1.40 1.67300 38.3 6 132.076 (variable) 7 -1156.405 1.20 1.49700 81.5 8 24.000 3.74 9 -34.434 1.20 1.49700 81.5 10 33.570 0.93 11 36.156 2.03 1.89190 37.1 12 189.608 (variable) 13 (Aperture) ∞ 0.70 14 153.707 2.12 1.49700 81.5 15 -61.504 0.20 16 21.985 3.37 1.72916 54.7 17 210.774 0.19 18 16.959 4.30 1.49700 81.5 19 -2255.267 1.20 1.67300 38.3 20 12.576 3.30 21 -32.290 1.20 1.76182 26.5 22 -246.969 6.63 23 154.916 2.83 1.95375 32.3 24 -29.147 2.15 25 -19.936 1.20 1.96300 24.1 26 -36.191 (variable) 27 54.968 4.01 1.89286 20.4 28 -28.672 0.21 29 -28.142 1.20 2.00069 25.5 30 31.060 (variable) 31 23.526 6.44 1.49700 81.5 32 -110.780 5.28 33 ∞ 1.20 1.51633 64.1 34 ∞ 5.35 Image plane ∞ Various data Zoom ratio 2.85 Wide-angle Mid-range Telephoto Focal length 35.43 63.77 101.02 F-number 2.88 2.88 2.88 Half angle of view 17.33 9.44 5.94 Image height 10.72 10.72 10.72 Lens length 128.10 128.10 128.10 BF 11.42 11.42 11.42 d 6 1.86 23.69 38.24 d12 37.61 15.78 1.23 d26 2.50 8.48 2.50 d30 11.78 5.80 11.78 Zoom lens group data Group starting plane focal length 1 1 104.66 2 7 -33.18 3 13 34.89 4 27 -54.81 5 31 39.68 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1 65.816 1.80 1.73800 32.3 2 43.086 3.92 1.49700 81.5 3 146.467 0.18 4 67.061 3.37 1.49700 81.5 5 -7728.282 (variable) 6 224.281 1.20 1.49700 81.5 7 22.217 6.93 8 -34.154 1.00 1.49700 81.5 9 72.095 0.59 10 48.636 1.71 1.90366 31.3 11 194.337 (variable) 12 (Aperture) ∞ 0.58 13 110.242 2.50 1.49700 81.5 14 -60.882 0.16 15 20.878 3.61 1.83481 42.7 16 108.632 0.14 17 16.887 4.13 1.49700 81.5 18 1084.269 0.80 1.73800 32.3 19 12.231 3.57 20 -34.506 1.19 1.85896 22.7 21 -213.511 6.05 22 278.579 2.47 1.83400 37.2 23 -31.914 4.26 24 -17.670 1.20 1.72916 54.7 25 -27.349 (variable) 26 74.694 2.48 1.95906 17.5 27 -62.226 0.53 28 -50.492 1.20 1.96300 24.1 29 33.388 (variable) 30 25.523 5.98 1.49700 81.5 31 -83.338 5.04 32 ∞ 1.20 1.51633 64.1 33∞5.35 Image plane ∞ Various data Zoom ratio 2.85 Wide-angle Mid-range Telephoto Focal length 35.41 63.57 100.79 F-number 2.88 2.88 2.88 Half angle of view 17.34 9.50 5.96 Image height 10.72 10.72 10.72 Lens length 128.11 128.11 128.11 BF 11.18 11.18 11.18 d 5 1.48 24.68 40.15 d11 39.92 16.71 1.24 d25 3.02 9.23 2.49 d29 10.95 4.74 11.47 Zoom lens group data Group starting plane focal length 1 1 103.58 2 6 -35.43 3 12 35.80 4 26 -54.78 5 30 40.05 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd 1 69.834 4.49 1.49700 81.5 2 -188.505 0.20 3 46.920 4.32 1.49700 81.5 4 694.485 5.03 5 -341.526 1.40 1.61340 44.3 6 46.439 (variable) 7 89.961 1.20 1.49700 81.5 8 30.296 6.38 9 -43.141 1.20 1.59522 67.7 10 79.242 0.30 11 60.416 2.00 1.85478 24.8 12 218.322 (variable) 13 (Aperture) ∞ 0.60 14 59.288 2.43 1.49700 81.5 15 -111.486 0.19 16 21.755 3.71 1.59522 67.7 17 411.598 0.20 18 17.210 4.52 1.49700 81.5 19 767.930 1.20 1.70154 41.2 20 13.160 3.34 21 -25.956 1.20 1.89286 20.4 22 -48.607 5.73 23 864.963 2.45 1.73800 32.3 24 -26.691 4.94 25 -17.574 1.20 1.72916 54.7 26 -40.203 (variable) 27 166.878 2.26 1.80810 22.8 28 -41.156 2.92 29 -31.991 1.20 2.00100 29.1 30 51.253 (variable) 31 29.192 4.67 1.77250 49.6 32 -237.803 5.68 33 ∞ 1.20 1.51633 64.1 34 ∞ 5.35 Image plane ∞ Various data Zoom ratio 2.00 Wide-angle Mid-range Telephoto Focal length 58.24 86.98 116.45 F-number 3.30 3.30 3.30 Half angle of view 10.44 6.96 5.18 Image height 10.72 10.72 10.72 Lens length 128.10 128.10 128.10 BF 11.82 11.82 11.82 d 6 2.01 20.65 33.07 d12 32.28 13.65 1.23 d26 4.30 6.70 2.50 d30 8.39 5.99 10.19 Zoom lens group data Group starting plane focal length 1 1 137.62 2 7 -44.41 3 13 38.09 4 27 -44.27 5 31 33.92 [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd 1 116.681 3.49 1.49700 81.5 2 -169.526 0.20 3 46.226 4.46 1.49700 81.5 4 657.704 8.88 5 -611.075 1.40 1.67300 38.3 6 58.909 (variable) 7 78.638 1.20 1.49700 81.5 8 30.763 2.69 9 -43.611 1.20 1.59522 67.7 10 54.447 1.61 11 52.760 1.99 1.85478 24.8 12 149.029 (variable) 13 (Aperture) ∞ 0.60 14 79.885 2.23 1.49700 81.5 15 -89.184 0.19 16 22.051 3.47 1.59522 67.7 17 237.162 0.19 18 19.171 5.36 1.49700 81.5 19 335.806 1.20 1.83400 37.2 20 15.549 3.28 21 -21.236 1.20 1.73800 32.3 22 -39.269 3.41 23 166.401 2.61 1.77250 49.6 24 -28.539 7.59 25 -16.741 1.20 1.49700 81.5 26 -51.719 (variable) 27 138.958 2.50 1.85478 24.8 28 -40.705 1.95 29 -33.408 1.20 2.00100 29.1 30 57.346 (variable) 31 28.674 4.53 1.67300 38.3 32 -271.118 5.73 33 ∞ 1.20 1.51633 64.1 34 ∞ 5.35 Image plane ∞ Various data Zoom ratio 2.00 Wide-angle Mid-range Telephoto Focal length 58.26 86.94 116.44 F-number 3.30 3.30 3.30 Half angle of view 10.45 6.97 5.18 Image height 10.72 10.72 10.72 Lens length 128.10 128.10 128.10 BF 11.87 11.87 11.87 d 6 1.54 19.30 31.13 d12 30.91 13.15 1.32 d26 4.13 7.27 2.50 d30 9.82 6.68 11.45 Zoom lens group data Group starting plane focal length 1 1 134.76 2 7 -42.21 3 13 37.45 4 27 -56.91 5 31 38.77 [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd 1 60.121 7.12 1.49700 81.5 2 -144.417 0.20 3 85.117 5.84 1.49700 81.5 4 -83.467 1.50 1.77250 49.6 5 121.315 (variable) 6 118.296 1.20 1.49700 81.5 7 22.727 5.74 8 -33.333 1.00 1.49700 81.5 9 62.501 1.45 10 49.821 1.65 1.90366 31.3 11 185.728 (variable) 12 (Aperture) ∞ 0.59 13 56.266 2.39 1.49700 81.5 14 -91.729 0.18 15 18.546 3.31 1.83481 42.7 16 79.558 0.18 17 14.618 3.74 1.49700 81.5 18 143.989 0.80 1.73800 32.3 19 10.310 3.23 20 -39.016 1.20 1.89286 20.4 21 1281.449 4.45 22 219.011 2.21 1.90366 31.3 23 -31.567 2.91 24 -15.991 1.20 1.83400 37.2 25 -24.067 (variable) 26 49.544 1.96 1.95906 17.5 27 -356.249 0.20 28 -136.601 1.20 2.00100 29.1 29 28.434 (variable) 30 23.637 6.60 1.49700 81.5 31 -70.948 (variable) 32 ∞ 1.20 1.51633 64.1 33∞5.35 Image plane ∞ Various data Zoom ratio 2.85 Wide-angle Mid-range Telephoto Focal length 34.48 62.07 98.30 F-number 2.88 2.88 2.88 Half angle of view 17.77 9.73 6.11 Image height 10.72 10.72 10.72 Lens length 128.10 128.10 128.10 BF 11.03 12.20 11.04 d 5 1.49 25.59 41.65 d11 41.39 17.29 1.23 d25 2.82 6.40 2.50 d29 9.33 4.58 9.64 d31 4.89 6.06 4.90 Zoom lens group data Group starting plane focal length 1 1 115.91 2 6 -36.68 3 12 34.06 4 26 -52.06 5 30 36.52 Table 1 shows the relationship between the above-mentioned conditional expressions and the various values ​​in the numerical examples.

[0049] [Table 1]

[0050] Next, with reference to FIG. 13, an imaging device (surveillance camera) 100 using the zoom lens of each embodiment as an imaging optical system will be described. FIG. 13 is a configuration diagram of the imaging device 100. 11 denotes the surveillance camera body. 15 denotes an imaging optical system configured with any of the zoom lenses of Embodiments 1 to 6. 12 denotes an imaging element (photoelectric conversion element) built into the surveillance camera body 11 and receiving a subject image (optical image) formed by the imaging optical system 15. The imaging element 12 is, for example, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor. 13 denotes a memory (recording unit) that records information corresponding to the subject image photoelectrically converted by the imaging element 12. 14 denotes a network cable (transfer unit) for transferring the subject image photoelectrically converted by the imaging element 12. The imaging device may be configured such that a protective cover or a hemispherical dome is attached to the object side of the zoom lens of each embodiment. Furthermore, the imaging device is not limited to a surveillance camera, but can also be used as other imaging devices such as a video camera, a digital camera, etc. By using an electronic imaging element such as a CCD as the imaging element 12 and performing electronic aberration correction, the image quality of the output image can be further improved.

[0051] It is also possible to configure a system (image capture system; surveillance camera system) 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 each lens group so that it moves as described above during zooming. 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 control unit (control device) located far from the drive units that drive each lens of the zoom lens may be configured with 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.

[0052] In each embodiment, the following configuration may be adopted. (1) Changing the shape or number of glass sheets shown in each example (2) Some lenses and lens groups are moved so that they have a component perpendicular to the optical axis, thereby correcting image blur caused by vibrations such as camera shake. (3) Correcting distortion, chromatic aberration, etc. using electrical correction means According to each embodiment, it is possible to provide a zoom lens and an imaging device that are small and have a short overall length, yet provide high optical performance over the entire zoom range.

[0053] The disclosure of each embodiment includes the following configuration. (Configuration 1) A zoom lens having a plurality of lens groups, the plurality of lens groups comprise, 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, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power; During zooming, at least the first lens group and the third lens group are fixed, and the second lens group and the fourth lens group are moved, so that the interval between adjacent lens groups changes; When the thickness of the first lens group on the optical axis is B1L, the thickness of the third lens group on the optical axis is B3L, the focal length of the fourth lens group is f4, the focal length of the fifth lens group is f5, and the back focus at the wide-angle end is BFw, 0.20≦B1L / B3L≦0.80 -3.00≦f4 / f5≦-1.06 2.00≦f5 / BFw≦6.00 A zoom lens characterized by satisfying the following conditional expressions: (Configuration 2) When the focal length of the first lens group is f1, 0.22≦f5 / f1≦0.43 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 and the focal length of the second lens group is f2, -3.52≦f1 / f2≦-2.63 3. The zoom lens according to configuration 1 or 2, wherein the following condition is satisfied: (Configuration 4) When the focal length of the first lens group is f1 and the total optical length at the telephoto end is TLt, 0.69≦f1 / TLt≦1.18 4. The zoom lens according to any one of the configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) When the distance on the optical axis from the surface of the first lens group closest to the image side to the surface of the third lens group closest to the object side is L13, 0.43≦L13 / B3L≦0.84 5. A zoom lens according to any one of configurations 1 to 4, characterized in that the following conditional expression is satisfied: (Configuration 6) When the distance on the optical axis from the surface of the third lens group closest to the image side to the surface of the fifth lens group closest to the object side at the wide-angle end is L35, -3.69≦L35 / f4≦-2.09 6. A zoom lens according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 2.60≦f1 / f3≦3.97 7. The zoom lens according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) When the movement amount of the second lens group from the wide-angle end to the telephoto end (the sign is positive when the second lens group is located closer to the image at the telephoto end than at the wide-angle end) is m2, 0.20≦m2 / TLt≦0.35 8. A zoom lens according to any one of configurations 1 to 7, characterized in that the following conditional expression is satisfied: (Configuration 9) 9. A zoom lens according to any one of configurations 1 to 8, wherein the third lens group has five or more lenses. (Configuration 10) 10. A zoom lens according to any one of configurations 1 to 9, wherein the fourth lens group moves from the object side to the image side during focusing from an object at infinity to a close object. (Configuration 11) Let V2ave be the average Abbe number of the two positive lenses located closest to the object in the third lens group, based on the d-line, 50 <V2ave<100 11. A zoom lens according to any one of configurations 1 to 10, wherein the following condition is satisfied: (Configuration 12) When VPave is the average Abbe number of all the positive lenses in the third lens group with reference to the d-line, 50 <VPave<100 12. A zoom lens according to any one of configurations 1 to 11, characterized in that the following conditional expression is satisfied: (Configuration 13) 13. An imaging device comprising: the zoom lens according to any one of configurations 1 to 12; and an imaging element that receives an optical image formed by the zoom lens.

[0054] 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]

[0055] B1 First lens group B2 Second lens group B3 Third lens group B4 4th lens group B5 5th lens group

Claims

1. A zoom lens having a plurality of lens groups, the plurality of lens groups comprise, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power; During zooming, at least the first lens group and the third lens group are fixed, and the second lens group and the fourth lens group are moved, so that the interval between adjacent lens groups changes; When the thickness of the first lens group on the optical axis is B1L, the thickness of the third lens group on the optical axis is B3L, the focal length of the fourth lens group is f4, the focal length of the fifth lens group is f5, and the back focus at the wide-angle end is BFw, 0.20≦B1L / B3L≦0.80 -3.00≦f4 / f5≦-1.06 2.00≦f5 / BFw≦6.00 A zoom lens characterized by satisfying the following conditional expressions:

2. When the focal length of the first lens group is f1, 0.22≦f5 / f1≦0.43 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 and the focal length of the second lens group is f2, −3.52≦f1 / f2≦−2.63 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the first lens group is f1 and the total optical length at the telephoto end is TLt, 0.69≦f1 / TLt≦1.18 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

5. When the distance on the optical axis from the surface of the first lens group closest to the image side to the surface of the third lens group closest to the object side is L13, 0.43≦L13 / B3L≦0.84 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. When the distance on the optical axis from the surface of the third lens group closest to the image side to the surface of the fifth lens group closest to the object side at the wide-angle end is L35, −3.69≦L35 / f4≦−2.09 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

7. When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, 2.60≦f1 / f3≦3.97 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. When the movement amount of the second lens group from the wide-angle end to the telephoto end (a positive sign is given when the second lens group is located closer to the image at the telephoto end than at the wide-angle end) is m2, 0.20≦m2 / TLt≦0.35 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

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

10. 2. The zoom lens according to claim 1, wherein the fourth lens group moves from the object side to the image side during focusing from an object at infinity to a close object.

11. When the average Abbe number of the two positive lenses arranged closest to the object side in the third lens group with respect to the d-line is V2ave, 50<V2ave<100 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

12. When the average Abbe number of all the positive lenses in the third lens group with reference to the d-line is VPave, 50<VPave<100 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

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

Images