Zoom lens, imaging device, and imaging system

Abstract

To provide a zoom lens that is shorter and more compact than conventional lenses, while still possessing high optical performance across the entire zoom range. [Solution] The zoom lens has multiple lens groups, and the distance between adjacent lens groups changes when zooming. The multiple lens groups are arranged in order from the object side to the image side, and include a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power. When zooming from the wide-angle end to the telephoto end, the first and third lens groups are fixed, and the second lens group moves toward the image side. A positive lens is positioned on the object side of the second lens group. The distance along the optical axis from the lens surface on the object side of the second lens group to the lens surface on the image side, the distance along the optical axis from the image-side lens surface of the positive lens to the object-side lens surface of the lens positioned adjacent to the image side of the positive lens, the focal length of the second lens group, and the focal length of the positive lens are each appropriately set.

Description

Technical Field

[0005] , , [Figure 1] , , ,

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

Background Art

[0002] Conventionally, a zoom lens having first to third lens groups with positive, negative, and positive refractive powers, and a positive single lens disposed on the most object side of the second lens group is known.

Summary of the Invention

Problems to be Solved by the Invention

[0003] A zoom lens that is shorter in overall length and smaller than conventional ones, and has high optical performance over the entire zoom range is desired.

Means for Solving the Problems

[0004] A zoom lens as one aspect of the present invention has a plurality of lens groups, and is a zoom lens in which the distance between adjacent lens groups changes during zooming. The plurality of lens groups include a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, which are arranged in order from the object side to the image side. During zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group are fixed, the second lens group moves toward the image side, a positive lens is disposed on the most object side of the second lens group, and when the distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the second lens group is L2, the distance on the optical axis from the image-side lens surface of the positive lens to the object-side lens surface of the lens disposed adjacent to the image side of the positive lens is L21, the focal length of the second lens group is f2, and the focal length of the positive lens is f21, 0.35 < L21 / L2 < 0.80 -10.0 < f21 / f2 < -2.0 It is characterized by satisfying the following conditional expressions.

Brief Description of the Drawings

[0005] <0000This is a cross-sectional view of the zoom lens of Example 1 at its wide-angle end. [Figure 2] These are aberration diagrams of the zoom lens of Example 1 at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end. [Figure 3] This is a cross-sectional view of the zoom lens of Example 2 at its wide-angle end. [Figure 4] These are aberration diagrams of the zoom lens of Example 2 at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end. [Figure 5] This is a cross-sectional view of the zoom lens of Example 3 at its wide-angle end. [Figure 6] These are aberration diagrams of the zoom lens of Example 3 at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end. [Figure 7] This is a schematic diagram of the imaging device. [Modes for carrying out the invention]

[0006] The embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same reference numeral is used for identical components, and redundant explanations are omitted.

[0007] Figures 1, 3, and 5 are cross-sectional views of the zoom lenses of Examples 1 to 3 at their wide-angle ends, respectively. The zoom lenses of each example are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and in-vehicle cameras.

[0008] In each cross-sectional view, the left side is the object side and the right side is the image side. Note that the zoom lens L0 in each embodiment may also be used as a projection lens for a projector or the like. In this case, the left side is the screen side and the right side is the projected image side.

[0009] Each embodiment of the zoom lens is composed of multiple lens groups. In this specification, a lens group is a collection of lenses that move or remain stationary as a whole during zooming (magnification). That is, in each embodiment of the zoom lens, the distance between adjacent lens groups changes during zooming. A lens group may consist of one lens or multiple lenses. A lens group may also include an aperture diaphragm.

[0010] In each cross-sectional view, Bi represents the i-th lens group (where i is a natural number) from the object side. SP is the aperture diaphragm. IP is the image plane, and when the zoom lens of each embodiment is used as the photographic optical system of a digital still camera or digital video camera, the image plane of an image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed there. When the zoom lens of each embodiment is used as the photographic optical system of a silver halide film camera, a photosensitive surface corresponding to the film plane is placed on the image plane IP. G is an optical block, and is, for example, a cover glass for the image plane, a low-pass filter, an IR cut filter, and a dummy glass for optical path length correction. In order to correct the change in optical path length due to the insertion and removal of the IR cut filter, a structure may be adopted in which the IR cut filter and the dummy glass can be switched within the optical path.

[0011] The arrows shown in each cross-sectional diagram indicate the direction of movement of the lens group when zooming from the wide-angle end to the telephoto end. The solid and dotted arrows indicate the direction of movement when focusing on an object at infinity and a nearby object, respectively.

[0012] Figures 2, 4, and 6 are aberration diagrams of the zoom lenses of Examples 1 to 3, respectively. In each aberration diagram, (A) is the aberration diagram at the wide-angle end, (B) is the aberration diagram at the intermediate zoom position, and (C) is the aberration diagram at the telephoto end.

[0013] In the spherical aberration diagram, Fno is the F-number and indicates the amount of spherical aberration for the d-line (wavelength 587.6 nm) and the g-line (wavelength 435.8 nm). In the astigmatism diagram, S indicates the amount of astigmatism at the sagittal image plane, and M indicates the amount of astigmatism at the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration at the g-line is shown. ω is the half-angle of view (°).

[0014] Next, we will describe the characteristic configurations of the zoom lenses in each embodiment.

[0015] The zoom lens in each embodiment has a first lens group B1 with positive refractive power, a second lens group B2 with negative refractive power, and a third lens group B3 with positive refractive power, arranged in order from the object side to the image side.

[0016] When zooming from the wide-angle end to the telephoto end, the first lens group B1 and the third lens group B3 remain fixed, while the second lens group moves toward the image.

[0017] By having the second lens group B2, which has negative refractive power, positioned between the first lens group B1 with positive refractive power and the third lens group B3 with positive refractive power, move toward the image side, the zoom lens can be made smaller by efficiently changing the magnification.

[0018] Furthermore, by keeping the first lens group B1 stationary, it is possible to maintain high positional accuracy of the first lens group B1, and the optical length remains constant throughout the entire zoom range. Here, the optical length is the length along the optical axis from the lens surface closest to the object to the lens surface closest to the image among the optically powerful lens surfaces, plus the "back focus" described later. However, if an optical element such as a glass block is placed in the back focus, the extension due to the optical element is also added to the back focus. By keeping the optical length constant throughout the entire zoom range, the mechanical parts are simplified, making it easier to construct a zoom lens that maintains high optical performance. In addition, it becomes easier to ensure the mechanical strength when attaching accessories such as converter lenses.

[0019] In addition, the third lens group B3 preferably corrects spherical aberration, field curvature, axial chromatic aberration, etc. throughout the zoom range. By keeping it stationary during zooming, high positional accuracy can be ensured, and the entire apparatus can be made smaller and simpler.

[0020] On the most object side of the second lens group B2, a positive lens G21 is disposed. The positive lens G21 is disposed adjacent to the most object side of the second lens group B2 having a negative refractive power and the image side of the first lens group B1 having a positive refractive power. Further, as a part of the second lens group B2, the positive lens G21 moves toward the image side during zooming from the wide-angle end to the telephoto end, whereby the following aberration correction effects can be obtained. Note that the positive lens G21 is a positive single lens in each embodiment, but the present invention is not limited thereto, and it may be a cemented lens having a positive refractive power.

[0021] First, in the wide-angle side region, correction of field curvature and an effect of suppressing fluctuations in field curvature that occur during zooming can be obtained. In the wide-angle side region, the positive lens G21 has an appropriate refractive power, and the distance from the first lens group B1 is closer than the distance from the lens having a negative refractive power within the second lens group B2, thereby improving the above effects.

[0022] Also, in the telephoto side region, correction of spherical aberration and an effect of suppressing fluctuations in spherical aberration that occur during zooming can be obtained. In the telephoto side region, the first lens group B1, the positive lens G21, and the lens group disposed on the image side of the positive lens G21 of the second lens group B2 are arranged at appropriate distances in order from the object side to the image side, thereby improving the above effects.

[0023] The zoom lens of each embodiment satisfies the following conditional expression (1).

[0024] 0.35 < L21 / L2 < 0.80 (1) Here, L2 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the second lens group B2. L21 is the distance along the optical axis from the image-side lens surface of the positive lens G21 to the object-side lens surface of lens G22, which is positioned adjacent to the image side of the positive lens G21.

[0025] Conditional equation (1) defines the ratio of the distance along the optical axis from the image side of the positive lens G21 to the object plane of lens G22 to the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image in the second lens group B2. If the value exceeds the upper limit of conditional equation (1), the distance along the optical axis from the image side of the positive lens G21 to the object plane of lens G22 becomes long, making it difficult for the positive lens G21 to correct field curvature at the wide-angle end, which is undesirable. If the value falls below the lower limit of conditional equation (1), the distance along the optical axis from the image side of the positive lens G21 to the object plane of lens G22 becomes short, resulting in insufficient correction of spherical aberration at the telephoto end by the positive lens G21, which is also undesirable.

[0026] As explained above, each embodiment makes it possible to realize a zoom lens that is shorter in overall length and more compact than conventional lenses, while still having high optical performance throughout the entire zoom range.

[0027] Furthermore, it is more preferable that the lower limit of condition (1) be set to 0.352, 0.354, 0.356, 0.358, 0.360, 0.362, 0.364, 0.366, 0.368, or 0.370. Also, it is more preferable that the upper limit of condition (1) be set to 0.77, 0.74, 0.71, 0.68, 0.65, 0.62, 0.60, 0.58, 0.56, or 0.53.

[0028] Next, we will describe the preferred configurations for each embodiment of the zoom lens.

[0029] The first lens group B1 is preferably composed of positive lenses, where both the object side and the image side are convex, and cemented lenses, where a positive lens with a convex object side and a negative lens with a concave image side are joined together, arranged in order from the object side to the image side. This configuration is preferable because it allows for effective correction of spherical aberration and field curvature in the telephoto range.

[0030] The second lens group B2 preferably comprises two or more negative lenses and one or more positive lenses positioned on the image side of the positive lens G21. This configuration is preferable because it ensures the refractive power necessary for zooming from the wide-angle end to the telephoto end, and also allows for effective correction of fluctuations such as spherical aberration and field curvature that occur during zooming.

[0031] Furthermore, it is preferable to arrange the lenses within the second lens group B2 such that the distance along the optical axis from the image-side lens surface of the positive lens G21 to the object-side lens surface of lens G22 is the longest air gap within the second lens group B2. This configuration is preferable because it allows for efficient acquisition of the aforementioned aberration correction effect due to the arrangement of the positive lens G21, and by minimizing the overall length of the second lens group B2, the overall length of the zoom lens can be shortened.

[0032] Next, we will describe the conditions that the zoom lens of each embodiment preferably satisfies. The zoom lens of each embodiment preferably satisfies one or more of the following conditional equations (2) to (8).

[0033] -10.0 <f21 / f2<-2.0 (2) 0.5 <f21 / f1<2.5 (3) 0.5 <L1 / L2<1.0 (4) 15<νd21<50 (5) 1.7 <Nd21<2.0 (6) 2.0 < |f1 / f2| < 5.0 (7) 0.5 < |f2 / f3| < 1.5 (8) Here, f2 is the focal length of the second lens group B2. f21 is the focal length of the positive lens G21, which is positioned closest to the object in the second lens group B2. f1 is the focal length of the first lens group B1. L1 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image in the first lens group B1. νd21 is the Abbe number of the positive lens G21 on the d line. Nd21 is the refractive index of the positive lens G21 on the d line. f3 is the focal length of the third lens group.

[0034] Conditional equation (2) specifies the ratio of the focal length of the positive lens G21, which is positioned closest to the object in the second lens group B2, to the focal length of the second lens group B2. If the ratio exceeds the upper limit of conditional equation (2), the refractive power of the positive lens G21 becomes too strong, making it difficult to properly correct field curvature in the wide-angle range and spherical aberration in the telephoto range, which is undesirable. If the ratio falls below the lower limit of conditional equation (2), the refractive power of the second lens group B2 becomes too strong, making it difficult to suppress fluctuations such as field curvature that occur during zooming, which is also undesirable.

[0035] Conditional equation (3) specifies the ratio of the focal length of the positive lens G21 to the focal length of the first lens group B1. If the ratio exceeds the upper limit of conditional equation (3), the refractive power of the first lens group B1 becomes too strong, making it difficult to properly correct spherical aberration and field curvature in the telephoto range, which is undesirable. If the ratio falls below the lower limit of conditional equation (3), the refractive power of the positive lens G21 becomes too strong, making it difficult to properly correct field curvature in the wide-angle range and spherical aberration in the telephoto range, which is also undesirable.

[0036] Conditional equation (4) defines the ratio of the distance along the optical axis from the object-side lens surface to the image-side lens surface of the first lens group B1 to the distance along the optical axis from the object-side lens surface to the image-side lens surface of the second lens group B2. If the ratio exceeds the upper limit of conditional equation (4), the distance along the optical axis from the object-side lens surface to the image-side lens surface of the first lens group B1 becomes longer, which is undesirable as it leads to an increase in the length of the zoom lens and an increase in the front element diameter. If the ratio falls below the lower limit of conditional equation (4), the distance along the optical axis from the object-side lens surface to the image-side lens surface of the second lens group B2 becomes longer, which is undesirable as it increases the overall length of the group that moves during zooming, leading to an increase in the length of the zoom lens.

[0037] Conditional equation (5) specifies the Abbe number of the positive lens G21 at the d line. Since the second lens group B2 as a whole is a lens group with negative refractive power, the positive lens G21 has the aforementioned aberration correction effect at the design wavelength, while also functioning as a lens for chromatic aberration correction within the second lens group B2. For this reason, it is preferable that the positive lens G21 is a lens with relatively high dispersion. If it exceeds the upper limit of conditional equation (5), the dispersion of the positive lens G21 becomes weak, and the chromatic aberration correction effect within the second lens group B2 becomes insufficient, which is undesirable. If it falls below the lower limit of conditional equation (5), the dispersion of the positive lens G21 becomes strong, and the fluctuation of chromatic aberration during zooming becomes large, which is undesirable.

[0038] Conditional equation (6) specifies the refractive index of the positive lens G21 at the d line. As mentioned above, the positive lens G21 corrects various aberrations throughout the zoom range by having an appropriate balance of refractive power and position between the first lens group B1 and the lens group in the second lens group B2 that is positioned closer to the image than the positive lens G21. Therefore, it is preferable for the positive lens G21 to have a relatively high refractive index. If it exceeds the upper limit of conditional equation (6), the refractive index of the positive lens G21 at the d line becomes high, making it difficult to appropriately set the radius of curvature of the positive lens G21, which is undesirable. If it falls below the lower limit of conditional equation (6), the refractive index of the positive lens G21 at the d line becomes weak, and the radius of curvature of the positive lens G21 becomes strong, making it difficult to correct field curvature at the wide-angle end and spherical aberration at the telephoto end, which is undesirable.

[0039] Conditional equation (7) specifies the ratio of the focal length of the first lens group B1 to the focal length of the second lens group B2. If the ratio exceeds the upper limit of conditional equation (7), the refractive power of the second lens group B2 becomes too strong, making it difficult to suppress fluctuations such as field curvature that occur during zooming, which is undesirable. If the ratio falls below the lower limit of conditional equation (7), the refractive power of the first lens group B1 becomes too strong, making it difficult to correct spherical aberration and field curvature at the telephoto end, which is also undesirable.

[0040] Conditional equation (8) specifies the ratio of the focal length of the second lens group B2 to the focal length of the third lens group B3. If the ratio exceeds the upper limit of conditional equation (8), the refractive power of the third lens group B3 becomes too strong, making it difficult to correct spherical aberration and other distortions throughout the zoom range, which is undesirable. If the ratio falls below the lower limit of conditional equation (8), the refractive power of the second lens group B2 becomes too strong, making it difficult to suppress fluctuations such as field curvature that occur during zooming, which is also undesirable.

[0041] Furthermore, it is more preferable that the lower limit of condition (2) be set to -9.40, -9.20, -8.80, -8.40, -8.00, -7.60, -7.20, -6.80, -6.40, or -6.15. Also, it is more preferable that the upper limit of condition (2) be set to -2.10, -2.20, -2.30, -2.40, -2.50, -2.55, -2.60, -2.62, -2.64, or -2.66.

[0042] Furthermore, it is more preferable that the lower limit of condition (3) be set to 0.56, 0.59, 0.62, 0.65, 0.68, 0.71, 0.74, 0.80, 0.84, or 0.87. Also, it is more preferable that the upper limit of condition (3) be set to 2.43, 2.36, 2.29, 2.22, 2.15, 2.08, 2.00, 1.95, or 1.89.

[0043] Furthermore, it is more preferable that the lower limit of conditional expression (4) be set to 0.52, 0.54, 0.56, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, or 0.64. Also, it is more preferable that the upper limit of conditional expression (4) be set to 0.98, 0.96, 0.94, 0.92, 0.90, 0.88, 0.85, 0.80, 0.79, or 0.78.

[0044] Furthermore, it is more preferable that the lower limit of condition (5) be set to 16.0, 17.0, 18.0, 19.0, 20.0, 20.5, 21.0, 21.5, 22.0, or 22.5. Also, it is more preferable that the upper limit of condition (5) be set to 48.0, 45.0, 43.0, 42.0, 41.0, 40.0, 39.0, 38.0, 37.0, or 36.0.

[0045] Furthermore, it is more preferable that the lower limit of conditional expression (6) be set to 1.705, 1.710, 1.715, 1.720, 1.725, 1.730, 1.745, 1.750, 1.755, or 1.760. Also, it is more preferable that the upper limit of conditional expression (6) be set to 1.980, 1.970, 1.960, 1.950, 1.940, 1.930, 1.925, 1.920, 1.915, or 1.910.

[0046] Furthermore, it is more preferable that the lower limit of conditional expression (7) be set to 2.20, 2.40, 2.60, 2.80, 2.84, 2.88, 2.92, 2.96, 3.00, or 3.02. Also, it is more preferable that the upper limit of conditional expression (7) be set to 4.70, 4.40, 4.10, 3.80, 3.50, 3.45, 3.40, 3.35, 3.30, or 3.25.

[0047] Furthermore, it is more preferable that the lower limit of conditional expression (8) be set to 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, or 0.99. Also, it is more preferable that the upper limit of conditional expression (8) be set to 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1.15, 1.12, 1.10, or 1.08.

[0048] Next, the optical systems of each embodiment will be described in detail.

[0049] The multiple lens groups in Examples 1 and 3 consist of first to fifth lens groups with positive, negative, positive, negative, and positive refractive powers, arranged sequentially from the object side to the image side. The fourth lens group B4 moves in a convex trajectory toward the image side when zooming from the wide-angle end to the telephoto end. Also, the fourth lens group B4 moves from the object side to the image side when focusing from an object at infinity to a nearby object.

[0050] The lens groups in Example 2 consist of first to fifth lens groups with positive, negative, positive, positive, and negative refractive powers, arranged sequentially from the object side to the image side. The fourth lens group B4 moves in a convex trajectory toward the object side when zooming from the wide-angle end to the telephoto end. Also, the fourth lens group B4 moves from the image side to the object side when focusing from an object at infinity to a nearby object.

[0051] In each embodiment, the second lens group B2 is composed of a positive lens G21, a negative lens G22 with a concave image side, and a cemented lens formed by joining a negative lens G23 with both concave object and image sides and a positive lens G24 with a convex object side, arranged in order from the object side to the image side.

[0052] In each embodiment, the fourth lens group B4 moves to compensate for the change in image position that occurs when the second lens group B2 moves during zooming. The fourth lens group B4 has a negative refractive power in embodiments 1 and 3, and a positive refractive power in embodiment 2. For the fourth lens group B4, either a positive or negative refractive power can be selected considering the device configuration and the balance of aberration correction.

[0053] In each embodiment, by making the fourth lens group B4 the focusing group, the amount of movement of the focusing group for focusing from an infinity-edge object to a close object is reduced across the entire zoom range from the wide-angle end to the telephoto end, making it easier to shorten the overall length of the zoom lens.

[0054] The fourth lens group B4 plays a dual role in correcting the image position during zooming and in focusing, reducing the number of moving lens groups in the zoom lens and simplifying the overall device.

[0055] In each embodiment, the inclusion of the fifth lens group B5 facilitates the correction of field curvature and Petzval sum across the entire zoom range. It also facilitates the correction of chromatic aberration and other distortions. In Embodiment 2, the fifth lens group B5 has negative refractive power, but the aforementioned effects can also be obtained if it has positive refractive power.

[0056] The numerical values ​​corresponding to Examples 1 to 3 are shown below.

[0057] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance along the optical axis) between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the light incidence side. Furthermore, nd represents the refractive index of each optical element with respect to the d-line, and νd represents the Abbe number of the optical element. Note that the Abbe number νd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC, respectively. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0058] In each numerical example, d, focal length (mm), F-number, and half-angle of view (°) are all values ​​when the zoom lens of each example is focused on an object at infinity. "Lens length" is the distance along the optical axis from the lens surface closest to the object among the optically powerful lens surfaces to the paraxial image plane, expressed as the air-equivalent length (length excluding optical block G). "BF" is the back focus, expressed as the distance along the optical axis from the lens surface closest to the image among the optically powerful lens surfaces to the paraxial image plane, expressed as the air-equivalent length.

[0059] Furthermore, in each numerical embodiment, the two planes closest to the image are planes corresponding to the optical block G.

[0060] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd 1 106.068 4.08 1.49700 81.5 2 -163.349 0.20 3 45.828 4.80 1.49700 81.5 4 588.931 1.40 1.90525 35.0 5 88.514 (variable) 6 139.815 1.63 1.90525 35.0 7 -415.478 7.79 8 -118.284 1.20 1.72916 54.7 9 33.982 2.96 10 -34.237 1.00 1.59522 67.7 11 53.344 1.69 2.00100 29.1 12 289.922 (variable) 13 (aperture) ∞ 0.69 14 50.973 3.75 1.49700 81.5 15 -66.335 0.20 16 49.710 5.39 1.49700 81.5 17 -30.026 1.20 1.83481 42.7 18 86.376 0.20 19 24.080 5.23 1.49700 81.5 20 -106.099 18.00 21 123.701 1.48 1.95375 32.3 22 -89.798 1.60 23 -19.852 1.00 1.88300 40.8 24 -43.382 (variable) 25 -24.458 1.00 1.49700 81.5 26 -617.337 1.89 2.00069 25.5 27 -28.426 4.39 28 -25.056 1.00 1.80810 22.8 29 38.791 (Variable) 30 28.016 4.33 1.90525 35.0 31 -719.638 4.50 32 ∞ 1.20 1.51633 64.1 33 ∞ 5.33 Image plane ∞ Various data Zoom ratio 1.99 Focal length 58.50 86.69 116.50 F-number 3.30 3.30 3.30 Half-angle (°): 10.4 7.03 5.19 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 10.62 10.62 10.62 d 5 2.05 15.84 25.03 d12 25.67 11.88 2.69 d24 5.50 6.94 3.27 d29 5.69 4.25 7.91 Zoom lens group data Group starting plane focal length 1 1 103.24 2 6 -33.54 3 13 33.33 4 25 -27.58 5 30 29.87 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd 1 86.873 4.46 1.49700 81.5 2 -197.187 0.20 3 48.155 5.33 1.49700 81.5 4 -549.759 1.40 1.67300 38.3 5 72.034 (variable) 6 507.772 1.53 1.80810 22.8 7 -230.578 9.15 8 -93.249 1.20 1.59522 67.7 9 32.426 3.03 10 -32.897 1.00 1.49700 81.5 11 44.977 1.70 1.88300 40.8 12 147.439 (variable) 13 (aperture) ∞ 1.04 14 43.973 4.62 1.49700 81.5 15 -46.380 0.20 16 38.840 6.13 1.49700 81.5 17 -27.728 1.20 1.95375 32.3 18 -1160.069 0.20 19 28.584 1.70 1.49700 81.5 20 45.016 4.27 21 -47.299 1.22 1.95906 17.5 22 -34.944 (variable) 23 69.201 1.38 1.95375 32.3 24 -213.486 0.36 25 -66.180 1.00 1.95906 17.5 26 -204.901 (variable) 27 -19.464 1.00 1.72916 54.7 28 40.185 8.39 29 28.520 4.38 1.85150 40.8 30 -233.264 4.20 31 ∞ 1.20 1.51633 64.1 32 ∞ 5.29 Image plane ∞ Various data Zoom ratio 1.99 Focal length 58.50 86.79 116.49 F-number 3.30 3.30 3.30 Half-angle (°): 10.4 6.98 5.17 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 10.28 10.28 10.28 d 5 2.67 16.11 25.07 d12 25.27 11.83 2.87 d22 18.64 15.71 19.29 d26 4.66 7.59 4.01 Zoom lens group data Group starting plane focal length 1 1 104.01 2 6 -32.07 3 13 32.20 4 23 117.01 5 27 -168.72 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd 1 93.699 4.33 1.49700 81.5 2 -158.880 0.20 3 43.968 5.21 1.49700 81.5 4 3982.811 1.40 1.85150 40.8 5 73.687 (variable) 6 117.067 1.92 1.76634 35.8 7 -194.809 5.33 8 -107.797 1.20 1.72916 54.7 9 34.254 3.23 10 -32.010 1.00 1.49700 81.5 11 52.826 1.62 1.95375 32.3 12 182.339 (variable) 13 (aperture) ∞ 0.69 14 46.010 3.98 1.49700 81.5 15 -71.284 0.20 16 52.181 5.47 1.49700 81.5 17 -30.225 1.20 1.83481 42.7 18 85.191 0.19 19 23.573 5.42 1.49700 81.5 20 -115.712 17.54 21 121.998 1.52 1.95375 32.3 22 -80.561 1.51 23 -19.762 1.00 1.88300 40.8 24 -52.291 (variable) 25 -25.370 1.00 1.49700 81.5 26 143.407 2.10 1.96300 24.1 27 -29.420 4.10 28 -25.288 1.00 1.89286 20.4 29 40.365 (Variable) 30 28.803 4.18 1.90366 31.3 31 -346.120 4.50 32 ∞ 1.20 1.51633 64.1 33 ∞ 5.21 Image plane ∞ Various data Zoom ratio 1.99 Focal length 58.50 86.72 116.49 F-number 3.30 3.30 3.30 Half-angle (°): 10.4 7.03 5.19 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 10.50 10.50 10.50 d 5 2.10 17.00 26.93 d12 27.64 12.75 2.82 d24 5.09 6.64 3.33 d29 5.75 4.20 7.50 Zoom lens group data Group starting plane focal length 1 1 109.01 2 6 -36.06 3 13 33.70 4 25 -26.43 5 30 29.58 The various values ​​in each numerical example are summarized in Table 1 below.

[0061] [Table 1]

[0062] [Imaging device] Figure 7 is a schematic diagram of a surveillance camera, which is an example of an imaging device using the zoom lens of each embodiment as the imaging optical system. In Figure 7, 11 is the surveillance camera body, and 12 is the imaging optical system composed of any of the zoom lenses of Embodiments 1 to 3. 13 is an image sensor, such as a CCD sensor or CMOS sensor, built into the surveillance camera body 11, which receives the optical image formed by the imaging optical system 12 and converts it into photoelectric energy. 14 is a memory unit that records information corresponding to the subject image converted into photoelectric energy by the image sensor 13. 15 is a network cable for transferring the subject image converted into photoelectric energy by the image sensor 13.

[0063] Furthermore, when the imaging device is used as a surveillance camera, for example, it may be configured with a protective cover attached to the object side of the zoom lens in each embodiment, or as an alternative configuration, with a hemispherical dome attached.

[0064] Furthermore, the imaging device is not limited to surveillance cameras; it can also be used with video cameras, digital cameras, and other similar devices.

[0065] Furthermore, by using an electronic image sensor such as a CCD, the output image quality can be further improved by electronically correcting aberrations.

[0066] Furthermore, each embodiment may adopt the following configuration of means. The shape and number of glass pieces shown in the examples are not limited to those shown and may be modified as appropriate. - To correct image blur caused by vibrations such as camera shake by moving some lenses and lens groups so that they have a component perpendicular to the optical axis. • Correcting distortion, chromatic aberration, etc., using electrical correction means. [Imaging System] Furthermore, an imaging system (surveillance camera system) may be configured that includes the zoom lens of each embodiment and a control unit that controls the zoom lens. In this case, the control unit can control the zoom lens so that each lens group moves as described above during zooming, focusing, and image blur correction. At this time, the control unit does not need to be integrated with the zoom lens; the control unit may be configured separately from the zoom lens. For example, a control unit (control device) located far away from the drive unit that drives each lens of the zoom lens may be configured to include a transmission unit that sends control signals (commands) for controlling the zoom lens. With such a control unit, the zoom lens can be remotely operated.

[0067] Alternatively, the control unit may be equipped with an operating section such as a controller or buttons for remotely operating the zoom lens, thereby enabling the zoom lens to be controlled in response to user input to the operating section. For example, the operating section may include a zoom-in button and a zoom-out button. In this case, the control unit should be configured to send a signal to the zoom lens drive unit so that when the user presses the zoom-in button, the magnification of the zoom lens increases, and when the user presses the zoom-out button, the magnification of the zoom lens decreases.

[0068] Furthermore, the imaging system may have a display unit, such as an LCD panel, that displays information (movement status) related to the zoom of the zoom lens. This information could include, for example, the zoom magnification (zoom status) or the amount of movement of each lens group (movement status). In this case, the user can remotely operate the zoom lens via the control unit while viewing the zoom information displayed on the display unit. The display unit and the control unit may be integrated by, for example, using a touch panel.

[0069] This embodiment includes the following configuration. (Composition 1) A zoom lens having multiple lens groups, wherein the distance between adjacent lens groups changes during zooming, The aforementioned group of lenses comprises a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged in order from the object side to the image side. When zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group remain fixed, and the second lens group moves toward the image side. A positive lens is positioned at the object-side end of the second lens group. When L2 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the second lens group, L21 is the distance along the optical axis from the image-side lens surface of the positive lens to the object-side lens surface of the lens adjacent to the image-side of the positive lens, f2 is the focal length of the second lens group, and f21 is the focal length of the positive lens, 0.35 <L21 / L2<0.80 -10.0 <f21 / f2<-2.0 A zoom lens characterized by satisfying the following conditional equation. (Configuration 2) When the focal length of the first lens group is f1, 0.5 <f21 / f1<2.5 A zoom lens according to configuration 1, characterized in that it satisfies the following condition. (Composition 3) When L1 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the first lens group, 0.5 <L1 / L2<1.0 A zoom lens according to configuration 1 or 2, characterized by satisfying the following conditional expression. (Composition 4) When the Abbe number on the d line of the positive lens is denoted as νd21, 15<νd21<50 A zoom lens according to any one of configurations 1 to 3, characterized by satisfying the following conditional expression. (Composition 5) When the refractive index of the positive lens at the d line is Nd21, 1.7 <Nd21<2.0 A zoom lens according to any one of configurations 1 to 4, characterized by satisfying the following conditional expression. (Composition 6) When the focal length of the first lens group is f1, 2.0 < |f1 / f2| < 5.0 A zoom lens according to any one of configurations 1 to 5, characterized by satisfying the following conditional expression. (Composition 7) When the focal length of the third lens group is f3, 0.5 < |f2 / f3| < 1.5 A zoom lens according to any one of configurations 1 to 6, characterized by satisfying the following conditional expression. (Composition 8) The zoom lens is characterized in that the plurality of lens groups consist of one of the configurations 1 to 7, arranged in order from the object side to the image side, the first lens group, the second lens group, the third lens group, the fourth lens group with negative refractive power, and the fifth lens group with positive refractive power. (Composition 9) The zoom lens according to any one of configurations 1 to 7, characterized in that the plurality of lens groups consist of the first lens group, the second lens group, the third lens group, the fourth lens group with positive refractive power, and the fifth lens group with negative refractive power, arranged in order from the object side to the image side. (Composition 10) The zoom lens is characterized in that the plurality of lens groups consist of the first lens group, the second lens group, the third lens group, the fourth lens group with positive refractive power, and the fifth lens group with positive refractive power, arranged in order from the object side to the image side. (Composition 11) The zoom lens according to any one of configurations 1 to 10, characterized in that the first lens group is composed of positive lenses, where both the lens surface on the object side and the lens surface on the image side are convex, and a bonded lens formed by joining a positive lens with a convex lens surface on the object side and a negative lens with a concave lens surface on the image side. (Composition 12) The zoom lens according to any one of configurations 1 to 11, characterized in that the second lens group comprises two or more negative lenses and one or more positive lenses positioned on the image side of the positive lens. (Composition 13) The zoom lens according to any one of configurations 1 to 12, characterized in that the second lens group is composed of a positive lens, a negative lens with a concave lens surface on the image side, and a bonded lens formed by joining a negative lens with both concave lens surfaces on the object side and an positive lens with a convex lens surface on the object side, arranged in order from the object side to the image side. (Composition 14) A zoom lens having multiple lens groups, wherein the distance between adjacent lens groups changes during zooming, The aforementioned group of lenses comprises a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged in order from the object side to the image side. When zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group remain fixed, and the second lens group moves toward the image side. A positive lens is positioned at the object-side end of the second lens group. When L2 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the second lens group, and L21 is the distance along the optical axis from the image-side lens surface of the positive lens to the object-side lens surface of the lens adjacent to the image side of the positive lens, 0.35 <L21 / L2<0.80 A zoom lens characterized by satisfying the following conditional equation. (Composition 15) An imaging device characterized by comprising a zoom lens described in any one of configurations 1 to 14, and an image sensor that receives light to receive the image formed by the zoom lens. (Composition 16) An imaging system characterized by comprising a zoom lens described in any one of configurations 1 to 15, and a control unit that controls the zoom lens during zooming. (Composition 17) The imaging system according to configuration 16, characterized in that the control unit is configured separately from the zoom lens and has a transmitting unit that transmits control signals for controlling the zoom lens. (Composition 18) The imaging system according to configuration 16 or 17, characterized in that the control unit is configured separately from the zoom lens and has an operating section for operating the zoom lens. (Composition 19) An imaging system according to any one of configurations 16 to 18, characterized in that it has a display unit that displays information regarding the zoom of the zoom lens.

[0070] Although 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 its essence. [Explanation of symbols]

[0071] B1 First lens group B2 Second lens group B3 Third lens group

Claims

1. A zoom lens having multiple lens groups, wherein the distance between adjacent lens groups changes during zooming, The aforementioned group of lenses comprises a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged in order from the object side to the image side. When zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group remain fixed, and the second lens group moves toward the image side. A positive lens is positioned at the object-side end of the second lens group. When L2 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the second lens group, L21 is the distance along the optical axis from the image-side lens surface of the positive lens to the object-side lens surface of the lens adjacent to the image-side of the positive lens, f2 is the focal length of the second lens group, and f21 is the focal length of the positive lens, 0.35<L21 / L2<0.80 -10.0<f21 / f2<-2.0 A zoom lens characterized by satisfying the following conditional equation.

2. When the focal length of the first lens group is f1, 0.5<f21 / f1<2.5 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

3. When L1 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the first lens group, 0.5<L1 / L2<1.0 A zoom lens according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. When the Abbe number in the d-line of the positive lens is denoted as νd21, 15 < νd21 < 50 A zoom lens according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

5. When the refractive index of the positive lens at the d line is Nd21, 1.7<Nd21<2.0 A zoom lens according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

6. When the focal length of the first lens group is f1, 2.0<|f1 / f2|<5.0 A zoom lens according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

7. When the focal length of the third lens group is f3, 0.5<|f2 / f3|<1.5 A zoom lens according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

8. The zoom lens according to 1 or 2, characterized in that the plurality of lens groups consist of the first lens group, the second lens group, the third lens group, the fourth lens group with negative refractive power, and the fifth lens group with positive refractive power, arranged in order from the object side to the image side.

9. The zoom lens according to claim 1 or 2, characterized in that the plurality of lens groups consist of the first lens group, the second lens group, the third lens group, the fourth lens group with positive refractive power, and the fifth lens group with negative refractive power, arranged in order from the object side to the image side.

10. The zoom lens according to 1 or 2, characterized in that the plurality of lens groups consist of the first lens group, the second lens group, the third lens group, the fourth lens group with positive refractive power, and the fifth lens group with positive refractive power, arranged in order from the object side to the image side.

11. The zoom lens according to claim 1 or 2, characterized in that the first lens group is composed of positive lenses, in which both the lens surface on the object side and the lens surface on the image side are convex, and a bonded lens formed by joining a positive lens with a convex lens surface on the object side and a negative lens with a concave lens surface on the image side, arranged in order from the object side to the image side.

12. The zoom lens according to claim 1 or 2, characterized in that the second lens group comprises two or more negative lenses and one or more positive lenses arranged on the image side of the positive lens.

13. The zoom lens according to claim 1 or 2, characterized in that the second lens group is composed of a positive lens, a negative lens with a concave lens surface on the image side, and a bonded lens formed by joining a negative lens with both a concave lens surface on the object side and a positive lens with a convex lens surface on the object side, arranged in order from the object side to the image side.

14. A zoom lens having multiple lens groups, wherein the distance between adjacent lens groups changes during zooming, The aforementioned group of lenses comprises a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, arranged in order from the object side to the image side. When zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group remain fixed, and the second lens group moves toward the image side. A positive lens is positioned at the object-side end of the second lens group. When L2 is the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the second lens group, and L21 is the distance along the optical axis from the image-side lens surface of the positive lens to the object-side lens surface of the lens adjacent to the image side of the positive lens, 0.35<L21 / L2<0.80 A zoom lens characterized by satisfying the following conditional equation.

15. An imaging device characterized by comprising a zoom lens according to claim 1 or 2, and an image sensor that receives light from an image formed by the zoom lens.

16. An imaging system characterized by comprising a zoom lens according to claim 1 or 2, and a control unit that controls the zoom lens during zooming.

17. The imaging system according to claim 16, characterized in that the control unit is configured separately from the zoom lens and has a transmitting unit that transmits control signals for controlling the zoom lens.

18. The imaging system according to claim 16, characterized in that the control unit is configured separately from the zoom lens and has an operating section for operating the zoom lens.

19. The imaging system according to claim 16, characterized in that it has a display unit that displays information regarding the zoom of the zoom lens.

Images