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 from a wide-angle end to a telephoto end, at least the third lens group is fixed, the second lens group moves to the image side, the fourth lens group moves, and an interval between the adjacent lens groups changes. A focal length f3 of the third lens group, a focal length f4 of the fourth lens group, a distance B3L on an optical axis from a surface on a most object side to a surface on a most image side in the third lens group, and a total optical length TLt at a telephoto end of the zoom lens, 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 Publication No. 2020-086073 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-118736 Summary of the Invention [Problem to be solved by the invention]

[0004] Zoom lenses are required to have high optical performance throughout the entire zoom range while being short and compact. However, the zoom lens disclosed in Patent Document 1 ensures a sufficient zoom ratio and focal length, but it is difficult to shorten the overall length of the optical system. The zoom lens disclosed in Patent Document 2 is compact, but it is difficult to improve optical performance such as field curvature and coma aberration.

[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 consisting of, 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, wherein, during zooming from the wide-angle end to the telephoto end, at least the third lens group is fixed, the second lens group moves toward the image side, and the fourth lens group moves, so that the spacing between adjacent lens groups changes; wherein the focal length of the third lens group is f3, the focal length of the fourth lens group is f4, the distance on the optical axis from the surface of the third lens group closest to the object side to the surface closest to the image side is B3L, and the total optical length of the zoom lens at the telephoto end is TLt: 0.5 <f3 / |f4|<0.9 0.19 <B3L / TLt<0.50 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] FIG. 13 is a cross-sectional view of a zoom lens at the wide-angle end in Example 7. [Figure 14] 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 7. [Figure 15] 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 third lens group B3 remains fixed, the second lens group B2 moves toward the image side, and the fourth lens group B4 moves, changing the spacing between adjacent lens groups.

[0012] Throughout the entire zoom range, the third lens group B3 has a relatively large number of lenses and a long overall length to effectively correct various aberrations, particularly axial chromatic aberration, spherical aberration, and coma. Therefore, by keeping the third lens group B3 stationary during zooming, high positional accuracy is ensured and the overall device is made compact and simple. 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 also has positive refractive power, moves toward the image side, thereby achieving efficient zooming. The movement of the fourth lens group B4 effectively corrects fluctuations in the image position on the optical axis that occur as the second lens group B2 moves.

[0013] 1, 3, 5, 7, 9, and 11, in the zoom lenses of Examples 1 to 6, the first lens unit B1 does not move during zooming from the wide-angle end to the telephoto end. On the other hand, as shown in Fig. 13, in the zoom lens of Example 7, the first lens unit B1 moves toward the object side during zooming from the wide-angle end to the telephoto end.

[0014] As in Examples 1 to 6, by making the first lens unit B1 stationary, it is possible to maintain high positional accuracy of the first lens unit B1 and to keep the total optical length constant throughout the entire zoom range. Here, the total optical length is the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image among the lens surfaces having optical power, plus the "back focus" described below. However, if an optical element such as a glass block is disposed in the back focus, the amount of extension caused by the optical element is also added to the back focus. In other words, the total optical length is the distance from the object-side surface of the first lens unit B1 to the image plane.

[0015] By keeping the total optical length constant throughout the entire zoom range, it is possible to simplify the mechanical components, making it easier to construct a zoom lens that maintains high optical performance, and an imaging device that uses the same. It also makes it easier to ensure the mechanical strength when attaching accessories such as a converter lens.

[0016] On the other hand, as in Example 7, by moving the first lens unit B1 toward the object side, the change in the distance between the first lens unit B1 and the second lens unit B2, which moves toward the image side, is increased, thereby ensuring a favorable zoom ratio.

[0017] The zoom lens of each embodiment satisfies the following conditional expressions (1) and (2).

[0018] 0.5 <f3 / |f4|<0.9 …(1) 0.19 <B3L / TLt<0.50 …(2) Here, f3 is the focal length of the third lens group B3, f4 is the focal length of the fourth lens group B4, B3L is the distance on the optical axis from the surface of the third lens group B3 closest to the object to the surface closest to the image, and TLt is the total optical length of the zoom lens at the telephoto end.

[0019] Conditional expression (1) defines the ratio between the focal length of the third lens group B3 and the focal length of the fourth lens group B4. If the upper limit of conditional expression (1) is exceeded, the refractive power of the third lens group B3 becomes weak, and the distance from the third lens group B3 to the image plane becomes long, which undesirably leads to an increase in the overall optical length. On the other hand, if the lower limit of conditional expression (1) is exceeded, the refractive power of the third lens group B3 becomes strong, which undesirably leads to insufficient correction of various aberrations, such as spherical aberration and coma, throughout the entire zoom range.

[0020] Conditional expression (2) defines the ratio between the overall length of the third lens group B3 and the overall optical length at the telephoto end. Exceeding the upper limit of conditional expression (2) undesirably increases the overall length of the third lens group B3 relative to the overall optical length, resulting in an insufficient range of movement for the second lens group B2 and the fourth lens group B4, which move during zooming. On the other hand, exceeding the lower limit of conditional expression (2) undesirably makes it difficult to achieve an appropriate lens arrangement within the third lens group B3 to correct various aberrations, such as spherical aberration and coma, throughout the entire zoom range.

[0021] In each embodiment, the numerical ranges of conditional expressions (1) and (2) are preferably set as shown in the following conditional expressions (1a) and (2a), respectively.

[0022] 0.60 <f3 / |f4|<0.88 …(1a) 0.19 <B3L / TLt<0.40 …(2a) In each embodiment, it is more preferable that the numerical ranges of conditional expressions (1a) and (2a) are set as shown in the following conditional expressions (1b) and (2b), respectively.

[0023] 0.63 <f3 / |f4|<0.87 …(1b) 0.19 <B3L / TLt<0.28 …(2b) The object of the present invention is achieved by the above configuration (first configuration).

[0024] The zoom lenses of Examples 1 to 6 can also achieve the object of the present invention by using the following configuration (second configuration). That is, the zoom lenses of Examples 1 to 6 are zoom lenses 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. In the zoom lenses of Examples 1 to 6, 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, the second lens group B2 moves toward the image side, and the fourth lens group B4 moves, changing the spacing between adjacent lens groups. The effect of keeping the first lens group B1 stationary, as in Examples 1 to 6, is as described above.

[0025] In this case, the zoom lenses of Examples 1 to 6 satisfy the following conditional expressions (1') and (2').

[0026] 0.2 <f3 / |f4|<0.9 …(1’) 0.18 <B3L / TLt<0.50 …(2’) Conditional formula (1') defines the ratio between the focal length of the third lens group B3 and the focal length of the fourth lens group B4. Exceeding the upper limit of conditional formula (1') undesirably weakens the refractive power of the third lens group B3, increasing the distance from the third lens group B3 to the imaging plane and thereby increasing the overall optical length. On the other hand, exceeding the lower limit of conditional formula (1') undesirably weakens the refractive power of the fourth lens group B4, increasing the amount of movement of the fourth lens group B4 required to correct fluctuations in the imaging position on the optical axis that occur during zooming, thereby increasing the overall optical length.

[0027] Conditional formula (2') defines the ratio between the overall length of the third lens group B3 and the overall optical length at the telephoto end. Exceeding the upper limit of conditional formula (2') undesirably makes the overall length of the third lens group B3 in relation to the overall optical length excessively long, resulting in an insufficient range of movement for the second lens group B2 and the fourth lens group B4, which move during zooming. Exceeding the lower limit of conditional formula (2') undesirably makes it difficult to achieve an appropriate lens arrangement within the third lens group B3 to correct various aberrations, such as spherical aberration and coma, throughout the entire zoom range with the third lens group B3.

[0028] In the first to sixth embodiments, the numerical ranges of the conditional expressions (1') and (2') are preferably set as shown in the following conditional expressions (1'a) and (2'a), respectively.

[0029] 0.50 <f3 / |f4|<0.88 …(1’a) 0.19 <B3L / TLt<0.30 …(2’a) It is more desirable that the numerical ranges of the conditional expressions (1'a) and (2'a) be set to the following ranges.

[0030] 0.63 <f3 / |f4|<0.87 …(1’b) 0.20 <B3L / TLt<0.28 …(2’b) With the above configuration (second configuration), the object of the present invention is achieved.

[0031] Next, conditions that are preferably satisfied for the zoom lens of each embodiment (each of the first and second configurations) will be described.

[0032] As mentioned above, the third lens group B3 plays a role in effectively correcting various aberrations, particularly chromatic aberration, spherical aberration, coma, etc., throughout the entire zoom range, and therefore it is preferable that the third lens group B3 include at least six lenses.

[0033] In the area on the object side of the third lens unit B3, spherical aberration and axial chromatic aberration in particular are corrected, and in the area on the image side of the third lens unit B3, coma aberration and lateral chromatic aberration are corrected.

[0034] It is preferable that the third lens group B3 has at least two positive lenses closest to the object side to correct spherical aberration with multiple optical surfaces, and it is also preferable that the third lens group B3 has a negative lens closest to the image side with a concave surface closest to the object side to correct coma and chromatic aberration of magnification.

[0035] When focusing from an object at infinity to a close object, it is preferable to move the fourth lens unit B4 from the object side to the image side. By using the fourth lens unit B4 as the focusing unit, the amount of movement of the focusing unit when focusing from an object at infinity to a close object becomes small over the entire magnification range from the wide-angle end to the telephoto end, making it easier to shorten the overall length of the zoom lens (entire system).

[0036] Furthermore, by having the fourth lens unit B4 move in a manner that contributes to both correcting the image position that occurs during zooming and focusing, the number of moving units in the entire system can be reduced, making it easier to simplify the entire device.

[0037] In each embodiment, it is preferable to satisfy at least one of the following conditional expressions (3) to (9).

[0038] 2.0 <f1 / f3<5.0 …(3) 1.5 <f1 / |f4|<4.0 …(4) 0.8<|f2| / f3<1.5 …(5) 1.5<|f4| / L35<5.0 …(6) 1.0 <B3L / L35<4.0 …(7) 50 <V2ave<100 …(8) 50 <VPave<100 …(9) Here, f1 is the focal length of the first lens group B1, and f2 is the focal length of the second lens group B2. L35 is the distance on the optical axis from the lens surface in the third lens group B3 closest to the image to the lens surface in the fifth lens group B5 closest to the object at the wide-angle end of the zoom lens. V2ave is the average Abbe number, based on the d-line, of the two positive lenses located closest to the object in the aforementioned third lens group B3. VPave is the average Abbe number, based on the d-line, of all positive lenses constituting the third lens group B3.

[0039] Conditional expression (3) defines the ratio of the focal length of the first lens group B1 to the focal length of the third lens group B3. If the upper limit of conditional expression (3) is exceeded, the refractive power of the third lens group B3 becomes too strong, which is undesirable because various aberrations, such as spherical aberration and coma, are undercorrected throughout the entire zoom range. On the other hand, if the lower limit of conditional expression (3) is exceeded, the refractive power of the first lens group B1 becomes too strong, which is undesirable because it becomes difficult to correct spherical aberration and curvature of field at the telephoto side.

[0040] Conditional expression (4) defines the ratio between the focal length of the first lens group B1 and the focal length of the fourth lens group B4. Exceeding the upper limit of conditional expression (4) is undesirable because the refractive power of the first lens group B1 becomes weak, leading to an increase in the overall optical length. On the other hand, exceeding the lower limit of conditional expression (4) is undesirable because the refractive power of the fourth lens group B4 becomes weak, increasing the amount of movement of the fourth lens group B4 required to correct fluctuations in the image position on the optical axis that occur during zooming.

[0041] Conditional expression (5) defines the ratio between the focal length of the second lens unit B2 and the focal length of the third lens unit B3. Exceeding the upper limit of conditional expression (5) is undesirable because the refractive power of the third lens unit B3 becomes too strong, resulting in insufficient correction of aberrations such as spherical aberration and coma throughout the entire zoom range. On the other hand, exceeding the lower limit of conditional expression (5) is undesirable because the refractive power of the second lens unit B2 becomes too strong, making it difficult to adequately correct fluctuations in spherical aberration and field curvature that occur during zooming.

[0042] Conditional expression (6) defines the ratio of the focal length of the fourth lens group B4 to the distance on the optical axis from the lens surface of the third lens group B3 closest to the image to the lens surface of the fifth lens group B5 closest to the object at the wide-angle end. Exceeding the upper limit of conditional expression (6) weakens the refractive power of the fourth lens group B4, increasing the amount of movement of the fourth lens group B4 required to correct for fluctuations in the image position on the optical axis that occur during zooming, which undesirably increases the overall optical length. On the other hand, exceeding the lower limit of conditional expression (6) strengthens the refractive power of the fourth lens group B4, making it difficult to suppress fluctuations in field curvature and coma that occur when the fourth lens group B4 moves during zooming or focusing, which is also undesirable.

[0043] Conditional expression (7) defines the ratio of the overall length of the third lens group B3 to the distance on the optical axis from the lens surface of the third lens group B3 closest to the image to the lens surface of the fifth lens group B5 closest to the object at the wide-angle end. Exceeding the upper limit of conditional expression (7) is undesirable because the distance between the third lens group B3 and the fifth lens group B5 becomes too narrow, making the range of movement of the fourth lens group B4 for zooming or focusing insufficient. On the other hand, exceeding the lower limit of conditional expression (7) is undesirable because it becomes difficult to appropriately position lenses within the third lens group B3 to correct various aberrations, such as spherical aberration and coma, throughout the entire zoom range.

[0044] Conditional expression (8) defines the average Abbe number, based on the d-line, of the two positive lenses arranged closest to the object in the third lens group B3. Exceeding the upper limit of conditional expression (8) is advantageous for correcting axial chromatic aberration, but is undesirable because it becomes difficult to ensure the desired refractive power of the glass material. On the other hand, exceeding the lower limit of conditional expression (8) is undesirable because it becomes difficult to correct axial chromatic aberration.

[0045] Conditional expression (9) defines the average Abbe number of all positive lenses in the third lens group B3 based on the d-line. Exceeding the upper limit of conditional expression (9) is advantageous for correcting axial chromatic aberration, but is undesirable because it makes it difficult to ensure the desired refractive power of the glass material. On the other hand, exceeding the lower limit of conditional expression (9) is undesirable because it makes it difficult to correct axial chromatic aberration.

[0046] In each embodiment, it is more preferable that the numerical ranges of conditional expressions (3) to (9) are set as shown in the following conditional expressions (3a) to (9a), respectively.

[0047] 2.8 <f1 / f3<4.0 …(3a) 1.8 <f1 / |f4|<3.2 …(4a) 0.9<|f2| / f3<1.2 …(5a) 2.0<|f4| / L35<4.0 …(6a) 1.3 <B3L / L35<2.7 …(7a) 60 <V2ave<90 …(8a) 55 <VPave<90 …(9a) In each embodiment, it is more preferable that the numerical ranges of conditional expressions (3a) to (9a) are set as shown in the following conditional expressions (3b) to (9b), respectively.

[0048] 2.89 <f1 / f3<3.64 …(3b) 1.89 <f1 / |f4|<3.11 …(4b) 0.93<|f2| / f3<1.17 …(5b) 2.3<|f4| / L35<3.4 …(6b) 1.4 <B3L / L35<2.5 …(7b) 62 <V2ave<82 …(8b) 59 <VPave<77 …(9b) Next, zoom lenses in Examples 1 to 7 will be described with reference to FIGS. 1 to 14. FIGS. 1, 3, 5, 7, 9, 11, and 13 are cross-sectional views of the zoom lenses in Examples 1 to 7. 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.

[0049] 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 7, 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.

[0050] 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.

[0051] In the zoom lenses of Examples 1 to 7, 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.

[0052] 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 lenses of Examples 6 and 7, 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 Examples 6 and 7, fluctuations in field curvature and the like that occur due to movement of the fourth lens unit B4 during zooming are easily reduced.

[0053] 2, 4, 6, 8, 10, 12, and 14 are aberration diagrams of the zoom lenses in Examples 1 to 7 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.

[0054] Numerical Examples 1 to 7 corresponding to Examples 1 to 7 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:

[0055] 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 numerical value (unit: degrees) of the half angle of view (ω) relating to the photographable angle of view taking distortion into consideration. The total lens length is expressed as the air-equivalent length (the distance when the optical block G is not included) that is the distance on the optical axis from the lens surface closest to the object among the lens surfaces that have optical power to the paraxial image plane. BF is the back focus, and is expressed as the air-equivalent length that is the distance on the optical axis from the lens surface closest to the image among the lens surfaces that have optical power to the paraxial image plane.

[0056] [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 [Numerical Example 7] Unit: mm Surface Data Surface number rd nd νd 1 64.722 6.81 1.49700 81.5 2 -155.273 0.77 3 92.273 5.83 1.49700 81.5 4 -89.543 1.50 1.77250 49.6 5 131.425 (variable) 6 114.320 1.20 1.49700 81.5 7 22.954 5.68 8 -33.257 1.00 1.49700 81.5 9 78.760 1.06 10 51.907 1.60 1.90366 31.3 11 198.048 (variable) 12 (Aperture) ∞ 0.59 13 60.874 2.37 1.49700 81.5 14 -86.058 0.18 15 18.546 3.33 1.83481 42.7 16 78.161 0.18 17 14.605 3.73 1.49700 81.5 18 120.041 0.80 1.73800 32.3 19 10.344 3.39 20 -33.679 1.20 1.89286 20.4 21 -759.186 4.03 22 370.146 2.31 1.90366 31.3 23 -28.157 3.10 24 -15.751 1.20 1.83400 37.2 25 -24.208 (variable) 26 47.944 2.00 1.95906 17.5 27 -367.908 0.20 28 -138.991 1.20 2.00100 29.1 29 27.969 (variable) 30 23.441 6.74 1.49700 81.5 31 -72.211 (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 35.33 62.97 100.76 F-number 2.88 2.88 2.88 Half angle of view 17.37 9.61 5.97 Image height 10.72 10.72 10.72 Lens total length 128.10 130.70 133.09 BF 11.12 12.64 11.03 d 5 1.49 28.00 46.33 d11 41.07 17.16 1.22 d25 3.16 6.25 2.50 d29 9.25 4.64 10.01 d31 4.97 6.50 4.89 Zoom lens group data Group starting plane focal length 1 1 125.40 2 6 -38.74 3 12 34.50 4 26 -52.56 5 30 36.46 Table 1 shows the relationship between the above-mentioned conditional expressions and the various values ​​in the numerical examples.

[0057] [Table 1]

[0058] Next, with reference to FIG. 15 , an imaging device (surveillance camera) 100 using the zoom lens of each embodiment as an imaging optical system will be described. FIG. 15 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 7. 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.

[0059] 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.

[0060] 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.

[0061] 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; a zoom lens in which, during zooming from a wide-angle end to a telephoto end, at least the third lens group is fixed, the second lens group moves toward the image side, and the fourth lens group moves, and the interval between adjacent lens groups changes; Let f3 be the focal length of the third lens group, f4 be the focal length of the fourth lens group, B3L be the distance on the optical axis from the surface of the third lens group closest to the object to the surface of the third lens group closest to the image, and TLt be the total optical length at the telephoto end of the zoom lens. 0.5 <f3 / |f4|<0.9 0.19 <B3L / TLt<0.50 A zoom lens characterized by satisfying the following conditional expressions: (Configuration 2) 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; a zoom lens in which, during zooming from a wide-angle end to a telephoto end, at least the first lens group and the third lens group are fixed, the second lens group moves toward the image side, and the fourth lens group moves, and the spacing between the groups changes; Let f3 be the focal length of the third lens group, f4 be the focal length of the fourth lens group, B3L be the distance on the optical axis from the surface of the third lens group closest to the object to the surface of the third lens group closest to the image, and TLt be the total optical length at the telephoto end of the zoom lens. 0.2 <f3 / |f4|<0.9 0.18 <B3L / TLt<0.50 A zoom lens characterized by satisfying the following conditional expressions: (Configuration 3) The zoom lens according to configuration 1 or 2, wherein the third lens group has at least six lenses, at least two positive lenses closest to the object side, and a negative lens closest to the image side whose surface closest to the object side is concave. (Configuration 4) 4. A zoom lens according to any one of configurations 1 to 3, 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 5) When the focal length of the first lens group is f1, 2.0 <f1 / f3<5.0 5. The zoom lens according to any one of configurations 1 to 4, characterized in that the following conditional expression is satisfied: (Configuration 6) When the focal length of the first lens group is f1, 1.5 <f1 / |f4|<4.0 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 second lens group is f2, 0.8<|f2| / f3<1.5 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 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, 1.5<|f4| / L35<5.0 8. A zoom lens according to any one of configurations 1 to 7, characterized in that the following conditional expression is satisfied: (Configuration 9) 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, 1.0 <B3L / L35<4.0 9. A zoom lens according to any one of configurations 1 to 8, wherein the following condition is satisfied: (Configuration 10) 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 10. The zoom lens according to any one of configurations 1 to 9, wherein the following condition is satisfied: (Configuration 11) 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 11. The zoom lens according to any one of configurations 1 to 10, wherein the following condition is satisfied: (Configuration 12) 12. An imaging device comprising: the zoom lens according to any one of configurations 1 to 11; and an imaging element that receives an optical image formed by the zoom lens.

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

[0063] 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; a zoom lens in which, during zooming from a wide-angle end to a telephoto end, at least the third lens group is fixed, the second lens group moves toward an image side, and the fourth lens group moves, and the interval between adjacent lens groups changes; Let f3 be the focal length of the third lens group, f4 be the focal length of the fourth lens group, B3L be the distance on the optical axis from the surface of the third lens group closest to the object side to the surface of the third lens group closest to the image side, and TLt be the total optical length of the zoom lens at the telephoto end. 0.5<f3 / |f4|<0.9 0.19<B3L / TLt<0.50 A zoom lens characterized by satisfying the following conditional expressions:

2. 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; a zoom lens in which, during zooming from a wide-angle end to a telephoto end, at least the first lens group and the third lens group are fixed, the second lens group moves toward an image side, and the fourth lens group moves, and the spacing between the groups changes; Let f3 be the focal length of the third lens group, f4 be the focal length of the fourth lens group, B3L be the distance on the optical axis from the surface of the third lens group closest to the object side to the surface of the third lens group closest to the image side, and TLt be the total optical length of the zoom lens at the telephoto end. 0.2<f3 / |f4|<0.9 0.18<B3L / TLt<0.50 A zoom lens characterized by satisfying the following conditional expressions:

3. 2. The zoom lens according to claim 1, wherein the third lens group includes at least six lenses, at least two positive lenses closest to the object side, and a negative lens closest to the image side whose surface closest to the object side is concave.

4. 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.

5. When the focal length of the first lens group is f1, 2.0<f1 / f3<5.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. When the focal length of the first lens group is f1, 1.5<f1 / |f4|<4.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

7. When the focal length of the second lens group is f2, 0.8<|f2| / f3<1.5 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. 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, 1.5<|f4| / L35<5.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

9. 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, 1.0<B3L / L35<4.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

10. 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:

11. 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:

12. 12. 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