Zoom lens and imaging device

Abstract

To provide a compact zoom lens with high optical performance. [Solution] A zoom lens comprising 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 positive refractive power, and a fifth lens group (B5) with positive or negative refractive power, arranged in order from the object side to the image side, wherein when zooming from the wide-angle end to the telephoto end, at least the first, third, and fifth lens groups remain stationary, the second lens group moves toward the image side, the fourth lens group moves, the spacing between adjacent lens groups changes, and the fifth lens group has the negative lens element closest to the object side and the positive lens element closest to the image side.

Description

Technical Field

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

Background Art

[0002] Conventionally, a zoom lens including a first lens group with a positive refractive power, a second lens group with a negative refractive power, a third lens group with a positive refractive power, a fourth lens group with a positive refractive power, and a fifth lens group with a positive or negative refractive power, which are arranged in order from the object side to the image side, is known.

Summary of the Invention

Problems to be Solved by the Invention

[0003] A zoom lens that is smaller and has higher optical performance than conventional ones is desired.

Means for Solving the Problems

[0004] A zoom lens according to one aspect of the present invention is a zoom lens including a first lens group with a positive refractive power, a second lens group with a negative refractive power, a third lens group with a positive refractive power, a fourth lens group with a positive refractive power, and a fifth lens group with a positive or negative refractive power, which are arranged in order from the object side to the image side. When zooming from the wide-angle end to the telephoto end, at least the first lens group, the third lens group, and the fifth lens group are stationary, the second lens group moves toward the image side, the fourth lens group moves, the interval between adjacent lens groups changes, and the fifth lens group has a negative lens element on the most object side and a positive lens element on the most image side.

Brief Description of the Drawings

[0005] [[ID=3?]] [Figure 1] [Figure 2] It is a cross-sectional view and a movement locus diagram of the zoom lens at the wide-angle end in Example 1. [Figure 3] ​This shows a cross-sectional view and a movement trajectory diagram of the zoom lens at the wide-angle end in Example 2. [Figure 4] These are aberration diagrams of the zoom lens at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end in Example 2. [Figure 5] This shows a cross-sectional view and a movement trajectory diagram of the zoom lens at the wide-angle end in Example 3. [Figure 6] These are aberration diagrams of the zoom lens at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end in Example 3.

[0006] [Figure 7] This shows a cross-sectional view and a movement trajectory diagram of the zoom lens at the wide-angle end in Example 4. [Figure 8] These are aberration diagrams of the zoom lens at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end in Example 4. [Figure 9] This shows a cross-sectional view and a movement trajectory diagram of the zoom lens at the wide-angle end in Example 5. [Figure 10] These are aberration diagrams of the zoom lens at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end in Example 5. [Figure 11] This is a schematic diagram of an imaging device equipped with a zoom lens in each embodiment. [Modes for carrying out the invention]

[0007] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0008] The zoom lens in each embodiment consists of 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 positive refractive power, and a fifth lens group B5 with either positive or negative refractive power, arranged in order from the object side to the image side. In embodiments 1, 2, 3, and 5, the fifth lens group B5 has negative refractive power. In embodiment 4, the fifth lens group B5 has positive refractive power. This configuration makes it possible to achieve miniaturization of the zoom lens (entire system) and a high zoom ratio.

[0009] Furthermore, when zooming from the wide-angle end to the telephoto end, at least the first lens group B1, the third lens group B3, and the fifth lens group B5 remain stationary (fixed), the second lens group B2 moves toward the image, the fourth lens group B4 moves, and the spacing between adjacent lens groups changes.

[0010] Throughout the entire zoom range, the third lens group B3 requires a relatively large number of lenses to effectively correct various aberrations, particularly axial chromatic aberration, spherical aberration, and coma aberration. Therefore, by keeping the third lens group B3 stationary during zooming, high positional accuracy is ensured, while also enabling the miniaturization and simplification of the zoom lens.

[0011] By moving the negative second lens group B2, which is sandwiched between the positive first lens group B1 and the positive third lens group B3, toward the image side, efficient zooming can be achieved.

[0012] By moving the fourth lens group B4, the fluctuations in the image formation position on the optical axis that occur due to the movement of the second lens group B2 can be suitably corrected.

[0013] 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 and imaging device that maintain high optical performance. In addition, it becomes easier to ensure the mechanical strength when attaching accessories such as converter lenses.

[0014] The fifth lens group B5 has the negative lens element closest to the object and the positive lens element closest to the image. Here, a lens element refers to a single component of a lens, whether a single lens or a cemented lens. Due to this configuration, the fifth lens group B5 has a relatively weak refractive power as a whole, but it contributes to the miniaturization of zoom lenses by providing an image height expansion effect.

[0015] Furthermore, by positioning the positive lens element closest to the image plane in the fifth lens group B5, it is possible to achieve both an appropriate setting of the zoom lens's back focus and an appropriate setting of the angle of light incidence on the image plane.

[0016] In Examples 1, 2, 3, and 4, a negative single lens (lens G51) is positioned as a negative lens element at the object-side end of the fifth lens group B5. In Example 5, a bonded lens (negative lens element) formed by joining a negative lens (lens G51) and a positive lens (lens G52) is positioned at the object-side end of the fifth lens group B5.

[0017] In each embodiment, a positive single lens (lens G52) or a positive single lens (lens G53) is disposed on the most image side in the fifth lens group B5. However, each embodiment is not limited thereto, and a cemented lens formed by cementing a positive lens and a negative lens may be disposed on the most image side in the fifth lens group B5.

[0018] By changing the lens element on the most object side or the most image side in the fifth lens group B5 from a single lens to a cemented lens, it is possible to suppress longitudinal chromatic aberration or chromatic flare.

[0019] Next, each condition that the zoom lens of each embodiment preferably satisfies will be described. In each embodiment, it is preferable to satisfy at least one of the following conditional expressions.

[0020] In each embodiment, when the focal length of the first lens group B1 is f1 and the focal length of the fourth lens group B4 is f4, it is preferable to satisfy the following conditional expression (1).

[0021] 0.80 < |f1 / f4| < 2.00 …(1) Conditional expression (1) is an expression that defines the ratio of the focal length of the first lens group B1 to the focal length of the fourth lens group B4. If the upper limit value of conditional expression (1) is exceeded, the refractive power of the fourth lens group B4 becomes strong, and aberration variations such as field curvature due to the movement of the fourth lens group B4 during zooming are insufficiently corrected, which is not preferable. On the other hand, if it is below the lower limit value of conditional expression (1), the refractive power of the fourth lens group B4 becomes weak, and the amount of movement of the fourth lens group B4 required during zooming increases, leading to an increase in the overall optical length, which is not preferable.

[0022] More preferably, the upper limit value of conditional expression (1) is set to 1.90, 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, or 1.20. Also preferably, the lower limit value of conditional expression (1) is set to 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, or 0.87.

[0023] In each embodiment, when the focal length of the third lens group B3 is f3, it is preferable that the following condition (2) is satisfied.

[0024] 0.00 < |f3 / f4| < 0.45 …(2) Conditional equation (2) specifies the ratio of the focal length of the third lens group B3 to the focal length of the fourth lens group B4. If the upper limit of conditional equation (2) is exceeded, the refractive power of the fourth lens group B4 becomes too strong, and aberrations such as field curvature caused by the movement of the fourth lens group B4 during zooming will not be adequately corrected, which is undesirable. Note that since conditional equation (2) is defined by an absolute value, the lower limit is a positive number.

[0025] Preferably, the upper limit of conditional equation (2) is set to 0.43, 0.41, 0.39, 0.37, 0.35, or 0.34. Also preferably, the lower limit of conditional equation (2) is set to 0.03, 0.06, 0.10, 0.12, 0.15, 0.18, 0.20, or 0.23. Note that if the lower limit of conditional equation (2) is too small, the refractive power of the third lens group B3 becomes too strong, which may result in insufficient correction of aberrations such as spherical aberration and field curvature across the entire zoom range.

[0026] The first lens group B1 plays a role in extending the focal length of the zoom lens (entire system) while suitably correcting spherical aberration and field curvature, especially at the telephoto end of the zoom range. For this reason, it is preferable that the first lens group B1 has at least two positive lenses and one negative lens.

[0027] As mentioned above, the second lens group B2 has negative refractive power and, when zooming from the wide-angle end to the telephoto end, is sandwiched between the positive first lens group and the positive third lens group, moving from the object side to the image side, thereby achieving efficient zooming.

[0028] In order to suppress fluctuations in various aberrations such as spherical aberration, field curvature, or axial chromatic aberration that occur when zooming from the wide-angle end to the telephoto end as the second lens group B2 moves, it is preferable that the second lens group B2 has at least two negative lenses and one positive lens.

[0029] The third lens group B3 plays a role in correcting various aberrations throughout the entire zoom range, particularly chromatic aberration, spherical aberration, or coma aberration. For this reason, it is preferable that the third lens group B3 has at least two positive lenses and one negative lens.

[0030] When focusing from an object at infinity to a nearby object, it is preferable that the fourth lens group B4 moves from the image side to the object side. By making the fourth lens group B4 the focusing lens group, the amount of movement of the focusing group for focusing from an object at infinity to a nearby 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.

[0031] Furthermore, since the fourth lens group B4 plays both the role of correcting the image position that occurs during magnification and focusing, the number of moving groups in the zoom lens can be reduced, simplifying the overall device.

[0032] In each embodiment, when the focal length of the negative lens element closest to the object in the fifth lens group B5 is f5f, it is preferable that the following condition (3) is satisfied.

[0033] 3.00 < |f4 / f5f| < 10.00 …(3) Conditional equation (3) specifies the ratio of the focal length of the fourth lens group B4 to the focal length of the negative lens element closest to the object in the fifth lens group B5. If the upper limit of conditional equation (3) is exceeded, the refractive power of the negative lens element closest to the object in the fifth lens group B5 becomes strong, resulting in insufficient correction of field curvature and coma aberration throughout the entire zoom range, which is undesirable. On the other hand, if the lower limit of conditional equation (3) is exceeded, the refractive power of the fourth lens group B4 becomes strong, resulting in insufficient correction of aberrations such as field curvature caused by the movement of the fourth lens group B4 during magnification, which is also undesirable.

[0034] Preferably, the upper limit of condition expression (3) is set to 9.90, 9.80, 9.70, 9.60, 9.50, 9.40, 9.30, 9.20, 9.10, or 9.00. Also preferably, the lower limit of condition expression (3) is set to 3.20, 3.40, 3.60, 3.80, 4.00, 4.20, 4.40, 4.60, 4.80, or 5.00.

[0035] In each embodiment, when the focal length of the fifth lens group B5 is f5, it is preferable that the following condition (4) is satisfied.

[0036] 0.00 < |f4 / f5| < 1.00 …(4) Conditional equation (4) specifies the ratio of the focal length of the fourth lens group B4 to the focal length of the fifth lens group B5. If this ratio exceeds the upper limit of conditional equation (4), the refractive power of the fourth lens group B4 weakens, increasing the amount of movement of the fourth lens group required for magnification, which leads to an increase in the overall optical length and is therefore undesirable. Note that since conditional equation (4) is defined by absolute values, the lower limit is a positive number.

[0037] Preferably, the upper limit of condition expression (4) is set to 0.95, 0.90, 0.85, 0.80, 0.75, or 0.70. Also preferably, the lower limit of condition expression (4) is set to 0.02, 0.04, 0.06, 0.08, 0.10, or 0.11.

[0038] In each embodiment, it is preferable that the following condition (5) is satisfied.

[0039] 0.00 < |f3 / f5| < 0.50 …(5) Conditional equation (5) specifies the ratio of the focal length of the third lens group B3 to the focal length of the fifth lens group B5. If this ratio exceeds the upper limit of conditional equation (5), the refractive power of the fifth lens group B5 becomes too strong, resulting in insufficient correction of field curvature and coma aberration across the entire zoom range, which is undesirable. Note that since conditional equation (5) is defined by absolute values, the lower limit is a positive number.

[0040] Preferably, the upper limit of condition expression (5) is set to 0.45, 0.40, 0.35, 0.30, 0.25, or 0.20. Also preferably, the lower limit of condition expression (5) is set to 0.010, 0.015, 0.020, 0.025, or 0.030.

[0041] In each embodiment, when the focal length of the positive lens element closest to the image in the fifth lens group B5 is f5r, it is preferable that the following condition (6) is satisfied.

[0042] 0.30 < |f5f / f5r| < 0.90 …(6) Conditional equation (6) defines the ratio of the focal length of the negative lens element closest to the object in the fifth lens group B5 to the focal length of the positive lens element closest to the image in the fifth lens group B5. Exceeding the upper limit of conditional equation (6) is undesirable because it weakens the refractive power of the negative lens element closest to the object in the fifth lens group B5, resulting in insufficient image height expansion and leading to an increase in the overall optical length. On the other hand, exceeding the lower limit of conditional equation (6) is undesirable because it strengthens the refractive power of the negative lens element closest to the object in the fifth lens group B5, resulting in insufficient correction of field curvature and coma aberration throughout the entire zoom range.

[0043] Preferably, the upper limit of condition expression (6) is set to 0.86, 0.82, 0.78, 0.74, 0.70, or 0.66. Also preferably, the lower limit of condition expression (6) is set to 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, or 0.44.

[0044] In each embodiment, it is preferable that the following condition (7) is satisfied.

[0045] 0.00 < |f5f / f5| < 0.20 …(7) Conditional equation (7) specifies the ratio of the focal length of the negative lens element closest to the object in the fifth lens group B5 to the focal length of the fifth lens group B5. Exceeding the upper limit of conditional equation (7) is undesirable because it weakens the refractive power of the negative lens element closest to the object in the fifth lens group B5, preventing sufficient image height expansion and leading to an increase in the overall optical length. Since conditional equation (7) is defined by absolute values, the lower limit is a positive number.

[0046] Preferably, the upper limit of condition expression (7) is set to 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, or 0.11. Also preferably, the lower limit of condition expression (7) is set to 0.005, 0.010, 0.015, or 0.020.

[0047] In each embodiment, it is preferable that the following condition (8) is satisfied.

[0048] 0.00 < |f5r / f5| < 0.40 …(8) Conditional equation (8) specifies the ratio of the focal length of the positive lens element closest to the image in the fifth lens group B5 to the focal length of the fifth lens group B5. If the upper limit of conditional equation (8) is exceeded, the refractive power of the positive lens element closest to the image in the fifth lens group B5 weakens, the back focus of the zoom lens increases, leading to an increase in the overall optical length and insufficient control of the angle of incidence of light rays on the image plane, which is undesirable. Note that since conditional equation (8) is defined by absolute values, the lower limit is a positive number.

[0049] Preferably, the upper limit of condition expression (8) is set to 0.36, 0.32, 0.28, 0.24, 0.20, or 0.18. Also preferably, the lower limit of condition expression (8) is set to 0.005, 0.010, 0.015, 0.020, 0.025, or 0.030.

[0050] Let L3 be the distance along the optical axis from the lens surface closest to the object in the third lens group B3 to the lens surface closest to the image in the fifth lens group B5, and let L5 be the distance along the optical axis from the lens surface closest to the object in the fifth lens group B5. In this case, it is preferable that the following condition (9) is satisfied in each embodiment.

[0051] 0.30 <L5 / L3<2.00 …(9) Conditional equation (9) defines the ratio of the distance along the optical axis from the object-side lens surface to the image-side lens surface in the third lens group B3 to the distance along the optical axis from the object-side lens surface to the image-side lens surface in the fifth lens group B5. If the ratio exceeds the upper limit of conditional equation (9), the distance along the optical axis from the object-side lens surface to the image-side lens surface in the fifth lens group B5 becomes longer, leading to an increase in the overall optical length, which is undesirable. On the other hand, if the ratio falls below the lower limit of conditional equation (9), the distance along the optical axis from the object-side lens surface to the image-side lens surface in the fifth lens group B5 becomes shorter, leading to insufficient image height expansion effect and difficulty in controlling the back focus and the angle of light incidence on the image plane, which is also undesirable.

[0052] Preferably, the upper limit of condition expression (9) is set to 1.90, 1.80, 1.70, 1.60, 1.50, 1.40, 1.30, 1.20, or 1.25. Also preferably, the lower limit of condition expression (9) is set to 0.35, 0.40, 0.45, 0.50, or 0.55.

[0053] In each embodiment, it is preferable that the following condition (10) is satisfied.

[0054] 0.50 < |f5f / L5| < 2.00 …(10) Conditional equation (10) defines the ratio between the focal length of the object-side negative lens element in the fifth lens group B5 and the distance on the optical axis from the object-side lens surface to the image-side lens surface in the fifth lens group B5. If the value exceeds the upper limit of conditional equation (10), the refractive power of the object-side negative lens element in the fifth lens group B5 becomes weak, and the image height expansion effect is not sufficiently obtained, which leads to an increase in the overall optical length and is therefore undesirable. On the other hand, if the value falls below the lower limit of conditional equation (10), the refractive power of the object-side negative lens element in the fifth lens group B5 becomes strong, and image field curvature and coma aberration are not adequately corrected throughout the zoom range, which is also undesirable.

[0055] Preferably, the upper limit of condition expression (10) is set to 1.95, 1.90, 1.85, 1.80, 1.75, 1.70, 1.65, 1.60, 1.55, 1.50, or 1.45. Also preferably, the lower limit of condition expression (10) is set to 0.54, 0.58, 0.62, 0.66, 0.70, 0.74, or 0.78.

[0056] In each embodiment, when the focal length of the zoom lens at the telephoto end is ft, it is preferable that the following condition (11) is satisfied.

[0057] 0.75 <f4 / ft<1.50 …(11) Conditional equation (11) specifies the ratio of the focal length of the fourth lens group B4 to the focal length of the zoom lens at the telephoto end. Exceeding the upper limit of conditional equation (11) is undesirable because it increases the amount of extension required for focusing, weakening the ability to focus very close. It also requires space to accommodate the extension, leading to an increase in the overall optical length, which is undesirable. On the other hand, falling below the lower limit of conditional equation (11) is undesirable because it makes it difficult to stop the fourth lens group B4 at the precise focus position due to the excessively short extension amount. It is also undesirable because it becomes difficult to suppress variations in various aberrations such as spherical aberration and field curvature during focusing.

[0058] Preferably, the upper limit of condition expression (11) is set to 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, or 1.45. Also preferably, the lower limit of condition expression (11) is set to 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, or 0.84.

[0059] Next, the zoom lenses of Examples 1 to 5 will be described with reference to Figures 1 to 10. Figures 1, 3, 5, 7, and 9 are cross-sectional views of each of the zoom lenses of Examples 1 to 5 at infinity focus. Figures 2, 4, 6, 8, and 10 are aberration diagrams of each of the zoom lenses of Examples 1 to 5 at infinity focus.

[0060] The zoom lenses in each embodiment are zoom lenses used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and in-vehicle cameras. In each cross-sectional view, the left side is the object side and the right side is the image side. The zoom lenses in each embodiment may also be used as projection lenses for projectors, etc. In this case, the left side is the screen side and the right side is the projected image side. The solid arrows pointing downwards in each cross-sectional view represent the movement trajectory of each lens group when zooming from the wide-angle end to the telephoto end.

[0061] In each cross-sectional view, B1 is the first lens group, B2 is the second lens group, B3 is the third lens group, B4 is the fourth lens group, B5 is the fifth lens group, SP is the aperture (diaphragm), G is the optical block, and IP is the image plane. When the zoom lenses of each embodiment are used in digital still cameras or digital video cameras, the image plane IP is where the image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed. When the zoom lenses of each embodiment are used as the photographic optical system of a silver halide film camera, the image plane IP is where the photosensitive surface corresponding to the film plane is placed.

[0062] The optical block includes the cover glass for the image sensor surface (image plane IP), a low-pass filter, an IR cut filter, and dummy glass for correcting the optical path length. Furthermore, to compensate for changes in the optical path length caused by inserting or removing the IR cut filter, a structure may be adopted in which the IR cut filter and dummy glass can be switched within the optical path.

[0063] In Examples 1, 2, 4, and 5, the first lens group B1 consists of lenses G11, G12, G13, and G14. In Example 3, the first lens group B1 consists of lenses G11, G12, and G13.

[0064] In Examples 1, 2, 4, and 5, the second lens group B2 consists of lenses G21, G22, and G23. In Example 3, the second lens group B2 consists of lenses G21, G22, G23, and G24.

[0065] In each embodiment, the third lens group B3 consists of lenses G31, G32, G33, G34, and G35.

[0066] In each embodiment, the fourth lens group B4 consists of lenses G41 and G42.

[0067] In Examples 1, 2, and 3, the fifth lens group B5 consists of lenses G51 and G52. In Examples 4 and 5, the fifth lens group B5 consists of lenses G51, G52, and G53.

[0068] Each lens group may consist of one lens or multiple lenses. Furthermore, a lens group may include an aperture (SP).

[0069] In the zoom lens of each embodiment, when zooming from the wide-angle end to the telephoto end, each lens group moves as shown by the arrows in each cross-sectional view. In each embodiment, the fourth lens group B4 is the focusing lens group that moves for focusing, and the solid and dotted arrows in each cross-sectional view show the movement trajectories when focusing on an object at infinity and an object at close range, respectively. Arrow F indicates the direction of movement of the focusing lens group when focusing from an object at infinity to an object at close range.

[0070] In each aberration diagram, (A) shows the aberration diagram at the telephoto end, (B) shows the aberration diagram at the intermediate zoom position, and (C) shows the aberration diagram at the telephoto end. In the spherical aberration diagram, Fno is the F number, the solid line shows the amount of spherical aberration with respect to the d line (wavelength 587.6 nm), and the dashed line shows the amount of spherical aberration with respect to the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line shows the amount of aberration at the sagittal image plane, and the dashed line shows the amount of aberration at the meridional image plane. In the distortion diagram, the amount of distortion with respect to the d line is shown. In the chromatic aberration diagram, the amount of lateral chromatic aberration with respect to the g line is shown. ω is the half-angle of view (°).

[0071] The following shows numerical examples 1 to 5 corresponding to Examples 1 to 5. In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance on the optical axis) between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the light incident side. Also, 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 with respect to the d line. In this specification, the Abbe number νd of a certain material with respect to the d line is given by Nd, NF, and NC when the refractive indices of the Fraunhofer lines d line (587.6 nm), F line (486.1 nm), C line (656.3 nm), and g line (wavelength 435.8 nm) are Nd, NF, and NC, respectively. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0072] In each numerical example, d, focal length (mm), F-number, and half-angle of view (degrees) are all values ​​when the zoom lens of each example is in focus at infinity. The back focus BF is the air-equivalent value (length excluding the optical block G) of the distance along the optical axis from the final lens surface (the lens surface closest to the image among the optically powerful lens surfaces) to the image surface (paraxial image surface). The total lens length is the value obtained by adding the back focus BF to the distance along the optical axis from the first lens surface (the lens surface closest to the object) to the final lens surface. In each numerical example, the two surfaces closest to the image are planes corresponding to the optical block G. Regarding the angle of view, it is the numerical value of the half-angle of view ω (degrees) related to the photographable angle of view considering distortion aberration.

[0073] (Numerical Example 1) Unit: mm Surface data Face number rd nd νd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.20 3 42.480 4.74 1.49700 81.5 4 183.274 6.79 5 59.189 3.58 1.49700 81.5 6 -442.551 1.40 1.83481 42.7 7 48.432 (variable) 8 -136.725 1.20 1.59522 67.7 9 35.412 2.52 10 -39.387 1.00 1.49700 81.5 11 43.662 1.71 1.85478 24.8 12 154.213 (variable) 13 (aperture) ∞ 0.69 14 146.687 3.11 1.49700 81.5 15 -46.247 0.20 16 59.224 4.23 1.49700 81.5 17 -40.377 1.20 1.83400 37.2 18 -2045.361 0.20 19 23.015 4.96 1.49700 81.5 20 -161.085 1.06 21 -131.830 1.20 1.51823 58.9 22 105.104 (variable) 23 81.285 3.33 1.80100 35.0 24 -21.515 1.00 2.00100 29.1 25 -115.511 (variable) 26 -17.148 1.00 1.51823 58.9 27 32.595 10.10 28 30.368 3.86 1.88300 40.8 29 -631.919 6.50 30 ∞ 1.20 1.51633 64.1 31 ∞ 5.30 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.50 87.00 116.49 F-number 3.30 3.30 3.30 Half-angle 10.4 6.97 5.17 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 12.60 12.60 12.60 d 7 3.16 16.40 25.24 d12 24.91 11.67 2.83 d22 19.32 16.47 19.32 d25 4.33 7.18 4.33 Zoom lens group data Group starting plane focal length 1 1 107.16 2 8 -31.43 3 13 32.66 4 23 108.31 5 26 -948.77 (Numerical Example 2) Unit: mm Surface data Face number rd nd νd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.20 3 43.318 5.36 1.49700 81.5 4 578.704 6.53 5 162.844 2.64 1.49700 81.5 6 -160.995 1.40 1.83481 42.7 7 66.671 (variable) 8 -312.100 1.20 1.59522 67.7 9 35.310 2.75 10 -36.007 1.00 1.49700 81.5 11 54.836 1.65 1.85478 24.8 12 315.054 (variable) 13 (aperture) ∞ 0.69 14 82.118 3.50 1.49700 81.5 15 -49.216 0.20 16 47.926 4.72 1.49700 81.5 17 -38.673 1.20 1.88300 40.8 18 186.938 0.19 19 23.798 4.13 1.49700 81.5 20 422.257 13.72 21 -52.942 1.20 1.51823 58.9 22 -49.516 (variable) 23 78.918 1.74 1.88300 40.8 24 -74.172 0.45 25 -39.361 1.00 1.85478 24.8 26 -98.589 (variable) 27 -17.908 1.00 1.60311 60.6 28 32.078 11.50 29 28.041 4.33 1.88300 40.8 30 ∞ 5.50 31 ∞ 1.20 1.51633 64.1 32 ∞ 5.33 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.49 86.96 116.48 F-number 3.30 3.30 3.30 Half-angle 10.4 6.96 5.17 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 11.63 11.63 11.63 d 7 2.68 17.07 26.66 d12 26.65 12.26 2.66 d22 6.26 4.02 6.26 d26 4.09 6.33 4.09 Zoom lens group data Group starting plane focal length 1 1 113.87 2 8 -34.14 3 13 32.65 4 23 98.18 5 27 -634.10 (Numerical Example 3) 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 Wide-angle, Medium, Telephoto 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 4) Unit: mm Surface data Face number rd nd νd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.20 3 44.670 5.23 1.49700 81.5 4 677.750 6.43 5 184.423 2.56 1.49700 81.5 6 -162.586 1.40 1.83481 42.7 7 69.912 (variable) 8 -323.089 1.20 1.59522 67.7 9 36.379 2.75 10 -37.134 1.00 1.49700 81.5 11 54.750 1.66 1.85478 24.8 12 282.813 (variable) 13 (aperture) ∞ 0.70 14 63.673 3.35 1.49700 81.5 15 -70.938 0.20 16 44.308 4.92 1.49700 81.5 17 -39.740 1.20 1.88300 40.8 18 469.488 0.20 19 24.460 4.43 1.49700 81.5 20 -474.004 5.46 21 17.518 1.20 1.80810 22.8 22 15.966 (Variable) 23 68.212 3.14 1.71700 47.9 24 -22.507 1.00 1.88300 40.8 25 -191.650 (variable) 26 -18.534 1.00 1.80610 40.9 27 31.672 10.50 28 -127.214 1.41 2.00100 29.1 29 -56.434 0.52 30 27.115 4.84 1.88300 40.8 31 424.886 7.10 32 ∞ 1.20 1.51633 64.1 33 ∞ 5.31 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.50 87.29 116.50 F-number 3.30 3.30 3.30 Half-angle 10.4 6.93 5.17 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 13.20 13.20 13.20 d 7 2.66 17.45 27.32 d12 27.36 12.56 2.69 d22 9.91 7.10 9.39 d25 3.97 6.79 4.49 Zoom lens group data Group starting plane focal length 1 1 116.03 2 8 -34.97 3 13 29.90 4 23 128.39 5 26 202.36 (Numerical Example 5) Unit: mm Surface data Face number rd nd νd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.20 3 40.599 5.91 1.49700 81.5 4 7336.958 5.66 5 168.891 2.86 1.49700 81.5 6 -121.963 1.40 1.83481 42.7 7 65.187 (variable) 8 -213.137 1.20 1.59522 67.7 9 32.410 2.86 10 -33.737 1.00 1.49700 81.5 11 48.928 1.73 1.85478 24.8 12 262.230 (variable) 13 (aperture) ∞ 0.68 14 87.859 3.23 1.49700 81.5 15 -55.077 0.19 16 61.609 4.53 1.49700 81.5 17 -35.311 1.20 1.88300 40.8 18 382.223 0.19 19 28.064 3.90 1.49700 81.5 20 -786.337 0.20 21 72.093 1.46 1.49700 81.5 22 283.257 (variable) 23 63.735 3.34 1.72342 38.0 24 -24.984 1.00 2.00100 29.1 25 -102.597 (variable) 26 -19.694 1.00 1.48749 70.2 27 11.802 2.12 1.59522 67.7 28 17.813 11.37 29 25.206 4.30 1.80400 46.5 30 246.106 6.40 31 ∞ 1.20 1.51633 64.1 32 ∞ 5.30 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.50 87.09 116.49 F-number 3.30 3.30 3.30 Half-angle 10.4 6.95 5.17 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 12.49 12.49 12.49 d 7 2.75 15.70 24.34 d12 24.28 11.33 2.69 d22 18.47 16.24 18.50 d25 4.09 6.32 4.06 Zoom lens group data Group starting plane focal length 1 1 104.38 2 8 -30.74 3 13 31.93 4 23 99.76 5 26 -243.53 Table 1 shows the relationship between the aforementioned conditional formulas and each numerical example in Examples 1 to 5.

[0074] [Table 1]

[0075] Next, with reference to Figure 11, an imaging device (surveillance camera) 100 using the zoom lens of each embodiment as the imaging optical system will be described. Figure 11 is a configuration diagram of the imaging device 100. 11 is the surveillance camera body. 15 is the imaging optical system composed of any of the zoom lenses of Embodiments 1 to 5. 12 is an image sensor (photoelectric conversion element) built into the surveillance camera body 11 that receives light from the subject image formed by the imaging optical system 15 (photoelectric conversion of the subject image formed by the optical system). The image sensor 12 is, for example, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor. 13 is a memory (recording unit) that records information corresponding to the subject image photoelectrically converted by the image sensor 12. 14 is a network cable (transfer unit) for transferring the subject image photoelectrically converted by the image sensor 12. The imaging device may be configured with a protective cover attached to the object side of the zoom lens of each embodiment, or with a hemispherical dome attached. Furthermore, the imaging device is not limited to surveillance cameras; it can also be used as other imaging devices such as video cameras or digital cameras.

[0076] Furthermore, a system (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 each lens group so that each lens group moves as described above when zooming. 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.

[0077] Furthermore, the following configurations may be adopted in each embodiment. (1) Changing the shape or number of glass pieces shown in each example. (2) Move some of the lenses and lens groups 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 imaging device that are smaller and have higher optical performance than conventional devices.

[0078] Each embodiment disclosed includes the following configuration: (Composition 1) A zoom lens comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power, and a fifth lens group with positive or negative refractive power, arranged in order from the object side to the image side, When zooming from the wide-angle end to the telephoto end, at least the first, third, and fifth lens groups remain stationary, the second lens group moves toward the image, the fourth lens group moves, and the spacing between adjacent lens groups changes. The fifth lens group has the negative lens element closest to the object and the positive lens element closest to the image. When the focal length of the first lens group is f1, the focal length of the third lens group is f3, and the focal length of the fourth lens group is f4, 0.80 < |f1 / f4| < 2.00 0.00 < |f3 / f4| < 0.45 A zoom lens characterized by satisfying the following conditional equation. (Configuration 2) When the focal length of the negative lens element is f5f, 3.00<|f4 / f5f|<10.00 A zoom lens according to configuration 1, characterized in that it satisfies the following condition. (Composition 3) When the focal length of the fifth lens group is f5, 0.00 < |f4 / f5| < 1.00 A zoom lens according to configuration 1 or 2, characterized by satisfying the following conditional expression. (Composition 4) When the focal length of the fifth lens group is f5, 0.00 < |f3 / f5| < 0.50 A zoom lens according to any one of configurations 1 to 3, characterized by satisfying the following conditional expression. (Composition 5) When the focal length of the negative lens element is f5f and the focal length of the positive lens element is f5r, 0.30<|f5f / f5r|<0.90 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 negative lens element is f5f and the focal length of the fifth lens group is f5, 0.00 < |f5f / f5| < 0.20 A zoom lens according to any one of configurations 1 to 5, characterized in that it satisfies the following conditional expression. (Composition 7) When the focal length of the positive lens element is f5r and the focal length of the fifth lens group is f5, 0.00 < |f5r / f5| < 0.40 A zoom lens according to any one of configurations 1 to 6, characterized by satisfying the following conditional expression. (Composition 8) When L3 is the distance along the optical axis from the lens surface closest to the object in the third lens group to the lens surface closest to the image in the fifth lens group to the distance along the optical axis from the lens surface closest to the object in the fifth lens group to the lens surface closest to the image, 0.30 <L5 / L3<2.00 A zoom lens according to any one of configurations 1 to 7, characterized by satisfying the following conditional expression. (Composition 9) When the focal length of the negative lens element is f5f, and the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image in the fifth lens group is L5, 0.50<|f5f / L5|<2.00 A zoom lens according to any one of configurations 1 to 8, characterized by satisfying the following conditional expression. (Composition 10) When the focal length of the fourth lens group is f4 and the focal length of the zoom lens at the telephoto end is ft, 0.75 <f4 / ft<1.50 A zoom lens according to any one of configurations 1 to 9, characterized by satisfying the following conditional expression. (Composition 11) The zoom lens according to any one of configurations 1 to 10, characterized in that the negative lens element is a negative single lens. (Composition 12) The zoom lens according to any one of configurations 1 to 10, characterized in that the negative lens element is a bonded lens formed by joining a negative lens and a positive lens. (Composition 13) A zoom lens comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power, and a fifth lens group with positive or negative refractive power, arranged in order from the object side to the image side, When zooming from the wide-angle end to the telephoto end, at least the first, third, and fifth lens groups remain stationary, the second lens group moves toward the image, the fourth lens group moves, and the spacing between adjacent lens groups changes. The fifth lens group is a zoom lens characterized by having a negative lens element on the object side and a positive lens element on the image side. (Composition 14) An imaging device characterized by having a zoom lens as described in any of configurations 1 to 13 and an image sensor.

[0079] 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]

[0080] 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 comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power, and a fifth lens group with positive or negative refractive power, arranged in order from the object side to the image side, When zooming from the wide-angle end to the telephoto end, at least the first lens group, the third lens group and the fifth lens group remain stationary, the second lens group moves toward the image, the fourth lens group moves, and the spacing between adjacent lens groups changes. The fifth lens group has a negative lens element closest to the object and a positive lens element closest to the image. When the focal length of the first lens group is f1, the focal length of the third lens group is f3, and the focal length of the fourth lens group is f4, 0.80<|f1 / f4|<2.00 0.00<|f3 / f4|<0.45 A zoom lens characterized by satisfying the following conditional equation.

2. When the focal length of the negative lens element is f5f, 3.00<|f4 / f5f|<10.00 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

3. When the focal length of the fifth lens group is f5, 0.00<|f4 / f5|<1.00 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

4. When the focal length of the fifth lens group is f5, 0.00<|f3 / f5|<0.50 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

5. When the focal length of the negative lens element is f5f and the focal length of the positive lens element is f5r, 0.30<|f5f / f5r|<0.90 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

6. When the focal length of the negative lens element is f5f and the focal length of the fifth lens group is f5, 0.00<|f5f / f5|<0.20 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

7. When the focal length of the positive lens element is f5r and the focal length of the fifth lens group is f5, 0.00<|f5r / f5|<0.40 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

8. When L3 is the distance along the optical axis from the lens surface closest to the object in the third lens group to the lens surface closest to the image in the fifth lens group to the distance along the optical axis from the lens surface closest to the object in the fifth lens group to the lens surface closest to the image, 0.30<L5 / L3<2.00 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

9. When the focal length of the negative lens element is f5f, and the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image in the fifth lens group is L5, 0.50<|f5f / L5|<2.00 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

10. When the focal length of the fourth lens group is f4 and the focal length of the zoom lens at the telephoto end is ft, 0.75<f4 / ft<1.50 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

11. The zoom lens according to claim 1, characterized in that the negative lens element is a negative single lens.

12. The zoom lens according to claim 1, characterized in that the negative lens element is a bonded lens formed by joining a negative lens and a positive lens.

13. A zoom lens comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power, and a fifth lens group with positive or negative refractive power, arranged in order from the object side to the image side, When zooming from the wide-angle end to the telephoto end, at least the first lens group, the third lens group and the fifth lens group remain stationary, the second lens group moves toward the image, the fourth lens group moves, and the spacing between adjacent lens groups changes. The fifth lens group is a zoom lens characterized by having a negative lens element closest to the object and a positive lens element closest to the image.

14. An imaging device characterized by having a zoom lens according to any one of claims 1 to 13 and an image sensor.

Images