Zoom lens and imaging device

Abstract

This invention provides a zoom lens that is compact and has a short overall length while possessing high optical performance by reducing aberration fluctuations in field curvature during focusing. [Solution] The system comprises, in order from the object side to the image side, a first lens group that does not move for zooming and has positive refractive power, a second lens group that moves during zooming and has negative refractive power, a third lens group that does not move for zooming and has positive refractive power, a fourth lens group that moves during zooming and has positive refractive power, and a fifth lens group that does not move for zooming. During zooming, the distance between adjacent lens groups changes, and the focal length of the first lens group, the focal length of the fourth lens group, the distance along the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fourth lens group at the wide-angle end when the object distance is infinity, and the distance along the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fifth lens group are appropriately set.

Description

Technical Field

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

Background Art

[0002] In imaging optical systems used in imaging devices such as surveillance cameras, digital cameras, and video cameras using solid-state imaging devices, lenses having high optical performance capable of coping with the high definition of the imaging device are desired.

[0003] In recent years, with the rapid expansion of the surveillance market, various demands have been raised for lenses for surveillance cameras. For example, there is a strong demand for miniaturization from the viewpoints of installation and inconspicuousness. Furthermore, in order to aim at a surveillance target without a time lag, rapid zooming control and focusing control are required. Also, in long-distance surveillance, an optical system having a long focal length is desired.

[0004] Patent Document 1 discloses a zoom lens composed of five lens groups having positive, negative, positive, positive, and positive refractive powers.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The zoom lens of Patent Document 1 has a problem that although it is small, it is difficult to reduce the aberration variation of field curvature during focusing. In view of this problem, an object of the present invention is to obtain a zoom lens having high optical performance that is small and reduces the aberration variation of field curvature during focusing.

Means for Solving the Problems

[0007] To achieve the above objective, a zoom lens as one aspect of the present invention has, in order from the object side to the image side, a first lens group that does not move for zooming and has positive refractive power, a second lens group that moves during zooming and has negative refractive power, a third lens group that does not move for zooming and has positive refractive power, a fourth lens group that moves during zooming and has positive refractive power, and a fifth lens group that does not move for zooming, wherein the distance between adjacent lens groups changes during zooming, and when the focal length of the first lens group is f1, the focal length of the fourth lens group is f4, the distance on the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fourth lens group at the wide-angle end at an object distance of infinity is L34w, and the distance on the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fifth lens group is L35, 0.07 <f4 / f1<0.65 0.00 <L34w / L35<0.39 It is characterized by satisfying the following conditions.

[0008] Furthermore, as another aspect of the present invention, the zoom lens comprises, in order from the object side to the image side, a first lens group that does not move for zooming and has positive refractive power, a second lens group that moves during zooming and has negative refractive power, a third lens group that does not move for zooming and has positive refractive power, a fourth lens group that moves during zooming and has positive refractive power, and a fifth lens group that does not move for zooming, wherein the distance between adjacent lens groups changes during zooming, and when the focal length of the first lens group is f1 and the focal length of the fourth lens group is f4, 0.07 <f4 / f1<0.65 It is characterized by satisfying the following conditions. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a zoom lens that is compact yet has high optical performance with good correction of aberration fluctuations in field curvature during focusing. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens of Example 1 at the wide-angle end when the object distance is infinite. [Figure 2] These are aberration diagrams of the zoom lens of Example 1 at (A) wide-angle end, (B) intermediate focal length, and (C) telephoto end, with the object distance at infinity. [Figure 3] These are aberration diagrams of the zoom lens of Example 1 at an object distance of 5m, at (A) the wide-angle end, (B) the intermediate focal length, and (C) the telephoto end. [Figure 4] This figure shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens of Example 2 at the wide-angle end when the object distance is infinite. [Figure 5] These are aberration diagrams of the zoom lens of Example 2 at (A) the wide-angle end, (B) the intermediate focal length, and (C) the telephoto end, with the object distance at infinity. [Figure 6] These are aberration diagrams of the zoom lens of Example 2 at an object distance of 5m, at (A) the wide-angle end, (B) the intermediate focal length, and (C) the telephoto end. [Figure 7] This figure shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens of Example 3 at the wide-angle end when the object distance is infinite. [Figure 8] These are aberration diagrams of the zoom lens of Example 3 at (A) the wide-angle end, (B) the intermediate focal length, and (C) the telephoto end, with the object distance at infinity. [Figure 9] These are aberration diagrams of the zoom lens of Example 3 at an object distance of 5m, at (A) the wide-angle end, (B) the intermediate focal length, and (C) the telephoto end. [Figure 10] This figure shows a cross-sectional view and a movement trajectory of the zoom lens of Example 4 at the wide-angle end when the object distance is infinite. [Figure 11] These are aberration diagrams of the zoom lens of Example 4 at (A) the wide-angle end, (B) the intermediate focal length, and (C) the telephoto end, with the object distance at infinity. [Figure 12] It is an aberration diagram at the wide-angle end (A), intermediate focal length (B), and telephoto end (C) of the zoom lens of Example 4 at an object distance of 5 m. [Figure 13] It is a cross-sectional view and a diagram of the movement locus at the wide-angle end of the zoom lens of Example 5 at an infinite object distance. [Figure 14] It is an aberration diagram at the wide-angle end (A), intermediate focal length (B), and telephoto end (C) of the zoom lens of Example 5 at an infinite object distance. [Figure 15] It is an aberration diagram at the wide-angle end (A), intermediate focal length (B), and telephoto end (C) of the zoom lens of Example 5 at an object distance of 5 m. [Figure 16] It is a schematic diagram of an imaging device equipped with the zoom lens in each example.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the zoom lens of the present invention will be described in detail while referring to the drawings. First, referring to FIG. 1, the zoom lens in Example 1 will be described. FIG. 1 is a cross-sectional view at the wide-angle end of the zoom lens in Example 1 at an infinite object distance and a schematic diagram of the movement locus in zooming and focusing.

[0012] The zoom lens is a zoom lens used in an imaging device such as a surveillance camera. In FIG. 1, the left side is the subject side (object side), and the right side is the image side. The wide-angle end and the telephoto end refer to the zoom positions when the zoom lens is located at both ends of the range where it can move in the direction along the optical axis due to the mechanism.

[0013] When zooming from the wide-angle end to the telephoto end, the movement of each lens group follows a locus like the arrow (solid line) shown in FIG. 1. The solid-line and broken-line arrows are the movement loci when focusing on an infinite object and a near-distance object, respectively. Arrow F is the movement direction of the focus group when focusing from infinity to the closest distance. Note that the above description is the same for each cross-sectional view of the zoom lenses in Examples 2 to 5.

[0014] The zoom lens of the present invention comprises, in order from the object side to the image side, a first lens group U1 having positive refractive power, a second lens group U2 having negative refractive power, a third lens group U3 having positive refractive power, a fourth lens group U4 having positive refractive power and moving during zooming, and a fifth lens group U5. SP is an aperture diaphragm, positioned adjacent to the object side of the third lens group U3, and does not move for zooming. G is an optical block corresponding to an optical filter, faceplate, etc. IP is the image plane, and when the zoom lens of the present invention is used as the imaging optical system of an imaging device, it corresponds to the imaging plane of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor.

[0015] During zooming or focusing, the spacing between adjacent lens groups changes. In the zoom lens of the present invention, as shown by the arrows in Figure 1, when zooming from the wide-angle end to the telephoto end, the second lens group U2 moves toward the object, and the fourth lens group U4 moves along a different trajectory than the second lens group U2. The first lens group U1, the third lens group U3, and the fifth lens group U5 do not move for zooming.

[0016] This configuration is ideal for obtaining a zoom lens that is compact yet possesses high optical performance by reducing aberration fluctuations in field curvature during focusing. In order to satisfy the objectives of this invention, the following conditions are specifically added to achieve the desired effect.

[0017] The zoom lens of the present invention, when the focal length of the first lens group U1 is f1 and the focal length of the fourth lens group U4 is f4, 0.07 <f4 / f1<0.65 ···(1) The conditions are met.

[0018] Conditional equation (1) defines the relationship between the focal length of the first lens group U1 and the focal length of the fourth lens group U4. By suitably setting the ratio between the focal length of the first lens group U1 and the focal length of the fourth lens group U4, the afocality of the light beam incident on the fourth lens group U4 can be increased.

[0019] If the upper limit of condition (1) is exceeded, the power of the fourth lens group U4 becomes too weak, making it difficult to miniaturize the zoom lens, which is undesirable. If the lower limit of condition (1) is exceeded, the power of the fourth lens group U4 becomes too strong, making aberration correction difficult, which is also undesirable.

[0020] Furthermore, it is even more desirable that the numerical range for condition (1) be within the following range. 0.20 <f4 / f1<0.63 ···(1a) Furthermore, it is even more desirable that the numerical range of conditional expression (1a) be within the following range. 0.42 <f4 / f1<0.60 ···(1b)

[0021] In the zoom lens of the present invention, when the object distance is infinity and the wide-angle end, the distance along the optical axis from the object-side lens surface of the third lens group U3 to the image-side lens surface of the fourth lens group U4 is L34w, and the distance along the optical axis from the object-side lens surface of the third lens group U3 to the image-side lens surface of the fifth lens group U5 is L35, 0.00 <L34w / L35<0.39 ···(2) The conditions are met.

[0022] Conditional equation (2) specifies the ratio of the distance along the optical axis from the third lens group U3 to the fourth lens group U4 and the distance along the optical axis from the third lens group U3 to the fifth lens group U5 at the wide-angle end when the object distance is infinity. By optimizing this ratio, it becomes possible to bring the fourth lens group U4 closer to the third lens group U3, thereby suppressing aberration fluctuations in field curvature during focusing.

[0023] If the upper limit of condition (2) is exceeded, the lens in the fourth lens group U4 that is positioned closest to the image becomes too far from the third lens group U3, making it difficult to reduce the aberration variation of field curvature during focusing, which is undesirable. Note that since the values ​​of L34w and L35 are both defined as positive numbers, the value of condition (2) will always be a positive number.

[0024] Furthermore, it is even more desirable that the numerical range for condition (2) be within the following range. 0.00 <L34w / L35<0.38 ···(2a) Furthermore, it is even more desirable that the numerical range of conditional expression (2a) be within the following range. 0.00 <L34w / L35<0.37 ···(2b)

[0025] Furthermore, in the zoom lens of the present invention, when the distance on the optical axis from the lens surface closest to the object in the third lens group U3 to the lens surface closest to the image in the fourth lens group U4 at the telephoto end when the object distance is infinity is L34t, 0.00 <L34t / L35<0.39 ···(3) The condition should be satisfied.

[0026] Conditional equation (3) specifies the ratio of the distance along the optical axis from the third lens group U3 to the fourth lens group U4 and the distance along the optical axis from the third lens group U3 to the fifth lens group U5 at the telephoto end when the object distance is infinity. By optimizing this ratio, it becomes possible to bring the fourth lens group U4 closer to the third lens group U3, and it is necessary to suppress aberration fluctuations of field curvature during focusing.

[0027] If the upper limit of condition (3) is exceeded, the lens closest to the image in the fourth lens group U4 becomes too far from the third lens group U3, making it difficult to reduce the aberration variation of field curvature during focusing, which is undesirable. Since both L34t and L35 are defined as positive numbers, the value of condition (3) will always be a positive number.

[0028] Furthermore, it is even more desirable that the numerical range for condition (3) be within the following range. 0.10 <L34t / L35<0.37 ···(3a) Furthermore, it is even more desirable that the numerical range of conditional expression (3a) be within the following range. 0.26 <L34t / L35<0.35 ···(3b)

[0029] Furthermore, in the zoom lens of the present invention, when the combined focal length of the first lens group U1, the second lens group U2, and the third lens group U3 at the wide-angle end is f13w, 0.00 < |f1 / f13w| < 0.55 ···(4) The condition should be satisfied.

[0030] Conditional equation (4) specifies the ratio of the focal length of the first lens group U1 to the combined focal length of the first lens group U1, the second lens group U2, and the third lens group U3 at the wide-angle end. By optimizing this ratio, it is possible to improve the afocality of the light beam incident on the fourth lens group U4.

[0031] If the upper limit of condition (4) is exceeded, the combined power of the first lens group U1, the second lens group U2, and the third lens group U3 becomes too strong (the combined focal length becomes too short), which is undesirable because it reduces the afocality of the light beam incident on the fourth lens group U4. Since condition (4) is defined by its absolute value, the value of condition (4) will always be a positive number.

[0032] Furthermore, it is even more desirable that the numerical range for conditional expression (4) be within the following range. 0.03<|f1 / f13w|<0.50 ···(4a) Furthermore, it is even more desirable that the numerical range of conditional expression (4a) be within the following range. 0.09<|f1 / f13w|<0.46 ···(4b)

[0033] Furthermore, in the zoom lens of the present invention, when the combined focal length of the first lens group U1, the second lens group U2, and the third lens group U3 at the telephoto end is f13t, 0.00 < |f1 / f13t| < 0.25 ···(5) The condition should be satisfied.

[0034] Conditional equation (5) specifies the ratio of the focal length of the first lens group U1 to the combined focal length of the first lens group U1, the second lens group U2, and the third lens group U3 at the telephoto end. By optimizing this ratio, it is possible to enhance the afocality of the light beam incident on the fourth lens group U4.

[0035] If the upper limit of condition (5) is exceeded, the combined power of the first lens group U1, the second lens group U2, and the third lens group U3 becomes too strong (the combined focal length becomes too short), which reduces the afocality of the light beam incident on the fourth lens group U4, and is undesirable. Since condition (5) is defined by its absolute value, the value of condition (5) will always be a positive number.

[0036] Furthermore, it is even more desirable that the numerical range for condition (5) be within the following range. 0.05<|f1 / f13t|<0.20 ···(5a) Furthermore, it is even more desirable that the numerical range of conditional expression (5a) be within the following range. 0.10<|f1 / f13t|<0.16 (5b)

[0037] Furthermore, in the zoom lens of the present invention, when the focal length of the fifth lens group U5 is set to f5, 0.00 < |f4 / f5| < 0.38 ···(6) It would be good if the following conditions were met.

[0038] Condition (6) specifies the ratio of the focal length of the fourth lens group U4 to the focal length of the fifth lens group U5. By satisfying condition (6), it becomes possible to enhance the aberration correction by the fifth lens group U5.

[0039] If the upper limit of condition (6) is exceeded, the power of the fifth lens group U5 becomes too strong, resulting in insufficient correction of field curvature and coma aberration across the entire zoom range, which is undesirable. Since condition (6) is defined by an absolute value, the value of condition (6) is always a positive number.

[0040] Furthermore, it is even more desirable that the numerical range for conditional expression (6) be within the following range. 0.01 < |f4 / f5| < 0.37 ···(6a) Furthermore, it is even more desirable that the numerical range of conditional expression (6a) be within the following range. 0.02 < |f4 / f5| < 0.36 ···(6b)

[0041] Furthermore, the zoom lens of the present invention includes at least one positive lens (lens element) and at least one negative lens (lens element) in the third lens group. This allows for effective correction of various aberrations, particularly chromatic aberration, spherical aberration, and coma aberration, throughout the entire zoom range. The specific configuration of the zoom lens in each embodiment will be described in detail below. [Examples]

[0042] Figure 1 shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens at the wide-angle end when the object distance is infinity in Example 1. The zoom lens of Example 1 has, in order from the object side to the image side, a first lens group U1 having positive refractive power, a second lens group U2 having negative refractive power, a third lens group U3 having positive refractive power, a fourth lens group U4 having positive refractive power, and a fifth lens group U5 having positive refractive power.

[0043] When zooming from the wide-angle end to the telephoto end, the second lens group moves towards the image, the fourth lens group moves, while the first, third, and fifth lens groups do not move for zooming. Also, when focusing from infinity to close distance, the fourth lens group moves towards the object. In the zoom lens of Example 1, the spacing between adjacent lens groups changes during zooming or focusing.

[0044] The first lens group U1 consists of a biconvex positive lens G11, a meniscus positive lens G12 with a convex shape on the object side, and a biconvex positive lens G13 and a biconcave negative lens G14, arranged in order from the object side to the image side. The second lens group U2 consists of a double concave negative lens G21, a double concave negative lens G22, and a meniscus positive lens G23 with a convex shape on the object side, arranged in order from the object side to the image side.

[0045] The third lens group U3 consists of a biconvex positive lens G31, a biconvex positive lens G32, and a biconcave negative lens G33, arranged in order from the object side to the image side. Adjacent to the object side of the third lens group U3 is an aperture diaphragm SP that does not move for zooming. The fourth lens group U4 is composed of a biconvex positive lens G41.

[0046] The fifth lens group U5 consists of a meniscus positive lens G51 with an object-side convex shape, a meniscus negative lens G52 with an object-side convex shape, a biconvex positive lens G53 and a biconcave negative lens G54, a meniscus negative lens G55 with an image-side convex shape, and a meniscus positive lens G56 with an object-side convex shape, arranged in order from the object side to the image side.

[0047] G13 and G14, G22 and G23, G32 and G33, and G53 and G54 each constitute a cemented lens. These cemented lenses effectively correct chromatic aberration by creating an Abbe number difference and refractive index difference between the two constituent lenses.

[0048] Figure 2 shows the aberration diagrams for the zoom lens of Example 1 at an object distance of infinity: at the wide-angle end (A), at an intermediate focal length (B), and at the telephoto end (C). Figure 3 shows the aberration diagrams for the zoom lens of Example 1 at an object distance of 5m: wide-angle end (A), intermediate focal length (B), and telephoto end (C).

[0049] In the aberration diagrams of Figures 2 and 3, d and g represent the d-line and g-line, respectively, and M and S represent the meridional and sagittal image planes. For astigmatism, M and S are shown on the d-line; for distortion, the d-line is shown; and for chromatic aberration, the aberration of the g-line relative to the d-line is shown. ω is the half-angle of view, and Fno is the F-number. In each aberration diagram, spherical aberration is drawn on a scale of 0.08 mm, astigmatism on 0.08 mm, distortion on 10%, and chromatic aberration on 0.01 mm. The same applies to the aberration diagrams of the zoom lenses in Examples 2 to 5. As shown in the aberration diagrams in Figures 2 and 3, each aberration is well corrected at object distances of infinity and 5m.

[0050] Next, we will describe the numerical data for Example 1, which corresponds to Example 1. In the numerical data of all numerical examples, not just Numerical Example 1, i indicates the order of the surfaces (optical surfaces) from the object side, ri indicates the radius of curvature of the i-th surface from the object side, and di indicates the distance on the optical axis between the i-th surface and the (i+1)-th surface from the object side. ndi and νdi indicate the refractive index and Abbe number, respectively, with respect to the d-line of the medium (optical material) between the i-th surface and the (i+1)-th surface.

[0051] Here, the Abbe number νd is given by the Fraunhofer lines d (wavelength 587.6 nm), F (wavelength 486.1 nm), and C (wavelength 656.3 nm), where Nd, NF, and NC are the refractive indices of the d (wavelength 587.6 nm), F (wavelength 486.1 nm), and C (wavelength 656.3 nm), respectively. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0052] Furthermore, in each numerical example, the four surfaces closest to the image are planes corresponding to the optical block G. The angle of view is the numerical value of the half-angle of view (ω) related to the photographic angle of view considering distortion aberration. The total lens length is expressed as the air-equivalent length (length excluding the optical block G), which 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.

[0053] BF stands for back focus, and it represents the distance along the optical axis from the lens surface closest to the image plane (among the optically powerful lens surfaces) to the paraxial image plane, expressed in air equivalent length.

[0054] Table 1 shows the numerical values ​​in Example 1 corresponding to conditional equations (1) to (6). The zoom lens of Example 1 satisfies conditional equations (1) to (6). Thus, the zoom lens of Example 1 achieves high optical performance by reducing aberration fluctuations in field curvature during focusing, despite its compact size. [Examples]

[0055] Figure 4 shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens at the wide-angle end when the object distance is infinite in Example 2. The zoom lens of Example 2 has, in order from the object side to the image side, a first lens group U1 with positive refractive power, a second lens group U2 with negative refractive power, a third lens group U3 with positive refractive power, a fourth lens group U4 with positive refractive power, and a fifth lens group U5 with negative refractive power.

[0056] When zooming from the wide-angle end to the telephoto end, the second lens group moves towards the image, the fourth lens group moves, while the first, third, and fifth lens groups remain stationary. Also, when focusing from infinity to close range, the fourth lens group moves towards the object. In the zoom lens of Example 2, the spacing between adjacent lens groups changes during zooming or focusing.

[0057] The first lens group U1 consists of a biconvex positive lens G11, a meniscus positive lens G12 with a convex shape on the object side, and a biconvex positive lens G13 and a biconcave negative lens G14, arranged in order from the object side to the image side. The second lens group U2 consists of a double concave negative lens G21, a double concave negative lens G22, and a meniscus positive lens G23 with a convex shape on the object side, arranged in order from the object side to the image side.

[0058] The third lens group U3 consists of a biconvex positive lens G31, a biconvex positive lens G32, and a biconcave negative lens G33, arranged in order from the object side to the image side. Adjacent to the object side of the third lens group U3 is an aperture diaphragm SP that does not move for zooming. The fourth lens group U4 is composed of a biconvex positive lens G41.

[0059] The fifth lens group U5 consists of a meniscus positive lens G51 with a convex shape on the object side, a meniscus negative lens G52 with a convex shape on the object side, a biconvex positive lens G53, a biconcave negative lens G54, a meniscus negative lens G55 with a convex shape on the image side, and a meniscus positive lens G56 with a convex shape on the object side, arranged in order from the object side to the image side.

[0060] G13 and G14, G22 and G23, G32 and G33, and G53 and G54 each constitute a cemented lens. These cemented lenses effectively correct chromatic aberration by creating an Abbe number difference and refractive index difference between the two constituent lenses.

[0061] Figure 5 shows the aberration diagrams for the zoom lens of Example 2 at an object distance of infinity: at the wide-angle end (A), at an intermediate focal length (B), and at the telephoto end (C). Figure 6 shows the aberration diagrams for the zoom lens of Example 2 at an object distance of 5m: wide-angle end (A), intermediate focal length (B), and telephoto end (C).

[0062] As shown in the aberration diagrams of Figures 5 and 6, the aberrations are well corrected at object distances of infinity and 5m. Table 1 shows the numerical values ​​in Example 2 corresponding to conditional equations (1) to (6). The zoom lens in Example 2 satisfies conditional equations (1) to (6). Thus, the zoom lens of Example 2 achieves high optical performance by reducing aberration fluctuations in field curvature during focusing, despite its compact size. [Examples]

[0063] Figure 7 shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens at the wide-angle end when the object distance is infinity in Example 3. The zoom lens of Example 3 has, in order from the object side to the image side, a first lens group U1 with positive refractive power, a second lens group U2 with negative refractive power, a third lens group U3 with positive refractive power, a fourth lens group U4 with positive refractive power, and a fifth lens group U5 with negative refractive power.

[0064] When zooming from the wide-angle end to the telephoto end, the second lens group moves towards the image, the fourth lens group moves, while the first, third, and fifth lens groups remain stationary. Also, when focusing from infinity to close range, the fourth lens group moves towards the object. In the zoom lens of Example 3, the spacing between adjacent lens groups changes during zooming or focusing.

[0065] The first lens group U1 consists of a biconvex positive lens G11, a meniscus positive lens G12 with a convex shape on the object side, and a biconvex positive lens G13 and a biconcave negative lens G14, arranged in order from the object side to the image side. The second lens group U2 consists of a double concave negative lens G21, a double concave negative lens G22, and a meniscus positive lens G23 with a convex shape on the object side, arranged in order from the object side to the image side.

[0066] The third lens group U3 consists of a biconvex positive lens G31, a biconvex positive lens G32, and a biconcave negative lens G33, arranged in order from the object side to the image side. Adjacent to the object side of the third lens group U3 is an aperture diaphragm SP that does not move for zooming. The fourth lens group U4 consists of biconvex positive lenses G41 arranged sequentially from the object side to the image side.

[0067] The fifth lens group U5 consists of a meniscus positive lens G51 with a convex shape on the object side, a meniscus negative lens G52 with a convex shape on the object side, a biconvex positive lens G53, a biconcave negative lens G54, a meniscus negative lens G55 with a convex shape on the image side, and a meniscus positive lens G56 with a convex shape on the object side, arranged in order from the object side to the image side.

[0068] G13 and G14, G22 and G23, G32 and G33, and G53 and G54 each constitute a cemented lens. These cemented lenses effectively correct chromatic aberration by creating an Abbe number difference and refractive index difference between the two constituent lenses.

[0069] Figure 8 shows the aberration diagrams for the zoom lens of Example 3 at the wide-angle end (A), the intermediate focal length (B), and the telephoto end (C) when the object distance is infinity. Figure 9 shows the aberration diagrams for the zoom lens of Example 3 at an object distance of 5m: wide-angle end (A), intermediate focal length (B), and telephoto end (C).

[0070] As shown in the aberration diagrams in Figures 8 and 9, each aberration is well corrected at object distances of infinity and 5m. Table 1 shows the numerical values ​​in Example 3 corresponding to conditional equations (1) to (6). The zoom lens in Example 3 satisfies conditional equations (1) to (6). Thus, the zoom lens of Example 3 achieves high optical performance by reducing aberration fluctuations in field curvature during focusing, despite its compact size. [Examples]

[0071] Figure 10 shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens at the wide-angle end when the object distance is infinity in Example 4. The zoom lens of Example 4 has, in order from the object side to the image side, a first lens group U1 having positive refractive power, a second lens group U2 having negative refractive power, a third lens group U3 having positive refractive power, a fourth lens group U4 having positive refractive power, and a fifth lens group U5 having positive refractive power.

[0072] When zooming from the wide-angle end to the telephoto end, the second lens group moves towards the image, the fourth lens group moves, while the first, third, and fifth lens groups remain stationary. Also, when focusing from infinity to close range, the fourth lens group moves towards the object. In the zoom lens of Example 4, the spacing between adjacent lens groups changes during zooming or focusing.

[0073] The first lens group U1 consists of a biconvex positive lens G11, a meniscus positive lens G12 with a convex shape on the object side, and a biconvex positive lens G13 and a biconcave negative lens G14, arranged in order from the object side to the image side. The second lens group U2 consists of a double concave negative lens G21, a double concave negative lens G22, and a meniscus positive lens G23 with a convex shape on the object side, arranged in order from the object side to the image side.

[0074] The third lens group U3 consists of a biconvex positive lens G31, a biconvex positive lens G32, and a meniscus negative lens G33 with a convex shape on the image side, arranged in order from the object side to the image side. Adjacent to the object side of the third lens group U3 is an aperture diaphragm SP that does not move for zooming. The fourth lens group U4 consists of a biconvex positive lens G41, a meniscus positive lens G42 with a convex shape on the object side, and a biconcave negative lens G43, arranged in order from the object side to the image side.

[0075] The fifth lens group U5 consists of a biconvex positive lens G51, a biconcave negative lens G52, a meniscus negative lens G53 with a convex shape on the image side, and a biconvex positive lens G54, arranged in order from the object side to the image side. G13 and G14, G22 and G23, G32 and G33, and G51 and G52 each constitute a cemented lens. These cemented lenses effectively correct chromatic aberration by creating an Abbe number difference and refractive index difference between the two constituent lenses.

[0076] Figure 11 shows the aberration diagrams for the zoom lens of Example 4 at the wide-angle end (A), the intermediate focal length (B), and the telephoto end (C) when the object distance is infinity. Figure 12 shows the aberration diagrams for the zoom lens of Example 4 at an object distance of 5m: wide-angle end (A), intermediate focal length (B), and telephoto end (C).

[0077] As shown in the aberration diagrams in Figures 11 and 12, each aberration is well corrected at object distances of infinity and 5m. Table 1 shows the numerical values ​​in Example 4 corresponding to conditional equations (1) to (6). The zoom lens in Example 4 satisfies conditional equations (1) to (6). Thus, the zoom lens of Example 4 achieves high optical performance by reducing aberration fluctuations in field curvature during focusing, despite its compact size. [Examples]

[0078] Figure 13 shows a cross-sectional view and a diagram of the movement trajectory of the zoom lens at the wide-angle end when the object distance is infinity in Example 5. The zoom lens of Example 5 has, in order from the object side to the image side, a first lens group U1 having positive refractive power, a second lens group U2 having negative refractive power, a third lens group U3 having positive refractive power, a fourth lens group U4 having positive refractive power, and a fifth lens group U5 having positive refractive power.

[0079] When zooming from the wide-angle end to the telephoto end, the second lens group moves towards the image, the fourth lens group moves, while the first, third, and fifth lens groups remain stationary. Also, when focusing from infinity to close range, the fourth lens group moves towards the object. In the zoom lens of Example 5, the spacing between adjacent lens groups changes during zooming or focusing.

[0080] The first lens group U1 consists of a biconvex positive lens G11, a meniscus positive lens G12 with a convex shape on the object side, and a biconvex positive lens G13 and a biconcave negative lens G14, arranged in order from the object side to the image side. The second lens group U2 consists of a double concave negative lens G21, a double concave negative lens G22, and a meniscus positive lens G23 with a convex shape on the object side, arranged in order from the object side to the image side.

[0081] The third lens group U3 consists of a biconvex positive lens G31, a biconvex positive lens G32, and a meniscus negative lens G33 with a convex shape on the image side, arranged in order from the object side to the image side. Adjacent to the object side of the third lens group U3 is an aperture diaphragm SP that does not move for zooming. The fourth lens group U4 is composed of a biconvex positive lens G41.

[0082] The fifth lens group U5 consists of a biconvex positive lens G51, a biconcave negative lens G52, a meniscus negative lens G53 with a convex shape on the image side, and a biconvex positive lens G54, arranged in order from the object side to the image side. G13 and G14, G22 and G23, and G32 and G33 each constitute a cemented lens. These cemented lenses effectively correct chromatic aberration by creating an Abbe number difference and refractive index difference between the two constituent lenses.

[0083] Figure 14 shows the aberration diagrams for the zoom lens of Example 5 at the wide-angle end (A), the intermediate focal length (B), and the telephoto end (C) when the object distance is infinity. Figure 15 shows the aberration diagrams for the zoom lens of Example 5 at an object distance of 5m: wide-angle end (A), intermediate focal length (B), and telephoto end (C).

[0084] As shown in the aberration diagrams in Figures 14 and 15, each aberration is well corrected at object distances of infinity and 5m. Table 1 shows the numerical values ​​in Example 5 corresponding to conditional equations (1) to (6). The zoom lens in Example 5 satisfies conditional equations (1) to (6). Thus, the zoom lens of Example 5 achieves high optical performance by reducing aberration fluctuations in field curvature during focusing, despite its compact size.

[0085] In each embodiment, the shape or number of lenses constituting the zoom lens is not limited and may be changed as appropriate. Furthermore, some lenses or lens groups may be moved to have a component perpendicular to the optical axis, thereby correcting image blur caused by vibrations such as camera shake.

[0086] [Numerical Example 1] Unit: mm Surface data Face number rd nd vd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.50 3 43.346 4.50 1.49700 81.5 4 204.347 6.65 5 55.572 6.08 1.49700 81.5 6 -264.580 1.50 1.83481 42.7 7 43.471 (variable) 8 -166.795 0.99 1.43875 94.7 9 27.879 2.85 10 -38.408 0.98 1.66672 48.3 11 35.500 2.07 1.96300 24.1 12 178.184 (variable) 13 (aperture) ∞ 0.00 14 169.876 2.49 2.00100 29.1 15 -56.525 0.28 16 34.491 4.34 1.43875 94.7 17 -33.086 0.99 2.00100 29.1 18 247.697 (variable) 19 41.766 4.34 1.43875 94.7 20 -53.773 (variable) 21 17.444 4.73 1.59522 67.7 22 254.346 0.81 23 43.510 0.99 1.96300 24.1 24 14.976 3.31 25 7773.645 3.19 1.77830 23.9 26 -19.186 1.14 1.72916 54.7 27 61.983 9.25 28 -11.230 0.99 1.43875 94.7 29 -25.311 7.14 30 25.098 4.44 1.74400 44.8 31 231.512 6.28 32 ∞ 0.50 1.51633 64.1 33 ∞ 4.09 34 ∞ 0.70 1.51633 64.1 35 ∞ 1.26 36 ∞ 0.03 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.51 82.52 116.48 F-number 3.20 3.20 3.20 Half-angle 10.41 7.42 5.27 Image height 10.75 10.75 10.75 Lens length 128.05 128.05 128.05 BF 12.45 12.45 12.45 d 7 3.18 13.28 23.39 d12 22.69 12.59 2.48 d18 8.27 5.72 5.08 d20 2.50 5.05 5.69 Zoom lens group data Group starting plane focal length 1 1 114.73 2 8 -29.68 3 13 56.83 4 19 54.33 5 21 1023.45

[0087] [Numerical Example 2] Unit: mm Surface data Face number rd nd vd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.50 3 43.346 4.50 1.49700 81.5 4 204.347 6.27 5 51.328 4.72 1.49700 81.5 6 -398.102 2.01 1.83481 42.7 7 42.808 (variable) 8 -134.607 0.98 1.49700 81.5 9 28.689 2.81 10 -38.228 0.95 1.66672 48.3 11 36.108 2.17 1.96300 24.1 12 253.565 (variable) 13 (aperture) ∞ 1.00 14 177.032 2.50 2.00100 29.1 15 -57.882 0.29 16 37.721 4.67 1.49700 81.5 17 -31.815 0.99 2.00100 29.1 18 233.163 (variable) 19 44.339 4.51 1.49700 81.5 20 -59.320 (variable) 21 17.456 4.87 1.59522 67.7 22 451.817 0.29 23 52.788 0.97 1.96300 24.1 24 15.760 3.04 25 197.852 3.31 1.77830 23.9 26 -20.529 1.00 1.72916 54.7 27 42.507 10.15 28 -11.466 0.97 1.49700 81.5 29 -22.309 7.35 30 24.892 4.30 1.74400 44.8 31 168.554 6.19 32 ∞ 0.50 1.51633 64.1 33 ∞ 4.09 34 ∞ 0.70 1.51633 64.1 35 ∞ 1.26 36 ∞ 0.03 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.51 82.47 116.47 F-number 3.20 3.20 3.20 Half-angle 10.41 7.43 5.27 Image height 10.75 10.75 10.75 Lens length 127.65 127.65 127.65 BF 12.36 12.36 12.36 d 7 4.67 14.47 24.27 d12 21.05 11.25 1.45 d18 7.95 5.61 5.10 d20 2.50 4.83 5.35 Zoom lens group data Group starting plane focal length 1 1 109.68 2 8 -28.63 3 13 54.76 4 19 51.80 5 21 -1844.07

[0088] [Numerical Example 3] Unit: mm Surface data Face number rd nd vd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.50 3 43.346 4.50 1.49700 81.5 4 204.347 5.60 5 49.213 3.52 1.49700 81.5 6 -719.246 1.47 1.83481 42.7 7 43.230 (Variable) 8 -113.697 0.94 1.49700 81.5 9 29.886 3.01 10 -41.028 0.89 1.66672 48.3 11 35.787 2.31 1.96300 24.1 12 217.815 (variable) 13 (aperture) ∞ 1.00 14 208.098 2.70 2.00100 29.1 15 -55.858 0.26 16 37.238 4.96 1.49700 81.5 17 -32.503 0.97 2.00100 29.1 18 199.431 (variable) 19 43.531 4.44 1.49700 81.5 20 -60.232 (variable) 21 18.474 4.93 1.59522 67.7 22 515.246 0.30 23 55.180 0.97 1.96300 24.1 24 16.568 3.11 25 200.701 3.40 1.77830 23.9 26 -21.295 0.99 1.72916 54.7 27 42.193 10.57 28 -11.908 0.96 1.49700 81.5 29 -22.629 8.22 30 27.243 3.63 1.74400 44.8 31 171.671 7.45 32 ∞ 0.50 1.51633 64.1 33 ∞ 4.09 34 ∞ 0.70 1.51633 64.1 35 ∞ 1.26 36 ∞ 0.03 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.53 82.20 116.42 F-number 3.20 3.20 3.20 Half-angle 10.41 7.45 5.28 Image height 10.75 10.75 10.75 Lens length 127.66 127.66 127.66 BF 13.62 13.62 13.62 d 7 3.54 13.39 23.25 d12 21.06 11.20 1.35 d18 8.76 6.11 4.89 d20 2.51 5.15 6.37 Zoom lens group data Group starting plane focal length 1 1 107.48 2 8 -29.13 3 13 55.51 4 19 51.58 5 21 -428.95

[0089] [Numerical Example 4] Unit: mm Surface data Face number rd nd vd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.50 3 43.346 4.50 1.49700 81.5 4 204.347 5.29 5 55.787 3.48 1.49700 81.5 6 -300.996 1.46 1.80400 46.5 7 43.186 (variable) 8 -167.507 0.88 1.59522 67.7 9 39.001 2.62 10 -40.969 0.62 1.49700 81.5 11 43.045 1.71 1.84666 23.8 12 139.859 (variable) 13 (aperture) ∞ 1.10 14 76.998 3.06 1.59522 67.7 15 -67.258 0.09 16 59.866 4.72 1.49700 81.5 17 -29.390 0.83 1.88300 40.8 18 -294.796 (variable) 19 28.693 5.70 1.59522 67.7 20 -69.932 0.26 21 25.990 3.96 1.59522 67.7 22 1319.715 1.37 23 -75.225 0.99 1.74400 44.8 24 18.863 (Variable) 25 63.812 3.48 1.70154 41.2 26 -28.231 1.00 1.56732 42.8 27 25.322 19.23 28 -16.432 0.96 1.49700 81.5 29 -42.467 3.28 30 28.390 4.35 1.63980 34.5 31 -194.735 4.71 32 ∞ 0.50 1.51633 64.1 33 ∞ 4.09 34 ∞ 0.70 1.51633 64.1 35 ∞ 1.26 36 ∞ 0.03 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.53 82.69 116.32 F-number 3.20 3.20 3.20 Half-angle 10.41 7.41 5.28 Image height 10.75 10.75 10.75 Lens length 127.80 127.80 127.80 BF 10.88 10.88 10.88 d 7 3.47 14.40 25.33 d12 24.03 13.09 2.16 d18 7.50 4.35 2.87 d24 2.49 5.64 7.12 Zoom lens group data Group starting plane focal length 1 1 120.89 2 8 -33.87 3 13 64.89 4 19 69.68 5 25 201.35

[0090] [Numerical Example 5] Unit: mm Surface data Face number rd nd vd 1 143.301 4.00 1.49700 81.5 2 -143.301 0.74 3 43.346 4.50 1.49700 81.5 4 204.347 7.13 5 54.905 3.27 1.49700 81.5 6 -353.303 1.47 1.83481 42.7 7 45.991 (variable) 8 -268.317 0.92 1.59522 67.7 9 33.122 2.87 10 -36.436 0.85 1.59522 67.7 11 47.668 1.84 1.96300 24.1 12 324.216 (variable) 13 (aperture) ∞ 2.09 14 210.492 2.67 1.53775 74.7 15 -49.978 0.07 16 64.907 4.37 1.49700 81.5 17 -28.900 0.90 1.80610 40.9 18 -535.858 (variable) 19 56.476 4.02 1.49700 81.5 20 -65.366 (variable) 21 18.321 7.47 1.49700 81.5 22 -250.972 2.29 23 -248.870 2.03 1.71999 50.2 24 17.937 19.29 25 -12.502 0.99 1.49700 81.5 26 -30.083 4.75 27 26.876 4.44 1.67300 38.3 28 -544.024 4.71 29 ∞ 0.50 1.51633 64.1 30 ∞ 4.09 31 ∞ 0.70 1.51633 64.1 32 ∞ 1.26 33 ∞ 0.03 Image plane ∞ Various data Zoom ratio 1.99 Wide-angle, Medium, Telephoto Focal length 58.55 83.35 116.33 F-number 3.20 3.20 3.20 Half-angle 10.40 7.35 5.28 Image height 10.75 10.75 10.75 Lens length 127.73 127.73 127.73 BF 10.88 10.88 10.88 d 7 3.11 13.18 23.25 d12 20.36 10.29 0.22 d18 7.94 4.12 3.45 d20 2.48 6.30 6.97 Zoom lens group data Group starting plane focal length 1 1 110.81 2 8 -30.79 3 13 81.34 4 19 61.64 5 21 427.26

[0091] [Table 1]

[0092] (Imaging device) Next, with reference to Figure 16, we will describe the imaging device (surveillance camera) 100 that uses the zoom lens of each embodiment as the imaging optical system.

[0093] Figure 16 is a diagram of the configuration of the imaging device 100. 11 is the surveillance camera body. 15 is the imaging optical system, which is composed of a zoom lens from any of Examples 1 to 5. 12 is an image sensor (photoelectric conversion element) built into the surveillance camera body 11 that receives the subject image formed by the imaging optical system 15 (captures the image formed by the zoom lens). The image sensor is composed of a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor, etc.

[0094] 13 is a memory (recording unit) that records information corresponding to the subject image converted photoelectrically by the image sensor 12. 14 is a network cable (transfer unit) for transferring the subject image converted photoelectrically by the image sensor 12. The imaging device may also be configured with a dome attached when used as a surveillance camera, for example. Note that the imaging device in each embodiment is not limited to a surveillance camera, but can also be used as other imaging devices such as a video camera or a digital camera.

[0095] 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 the unit so that each lens group moves as described above when zooming or focusing. 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.

[0096] For example, a control unit (control device) located far from the drive unit that drives each lens of a zoom lens may be configured to include a transmission unit that sends control signals (commands) to control the zoom lens. With such a control unit, the zoom lens can be operated remotely.

[0097] Furthermore, in the imaging device equipped with the zoom lens of each embodiment, an electrical correction means may be configured to correct distortion, chromatic aberration, and the like for the image signal acquired by the image sensor. Furthermore, the angle of view and FNO (F-number) of the zoom lens in each embodiment are not limited and can be changed as appropriate. Furthermore, focusing in an imaging device equipped with the zoom lens of the present invention is not limited to moving the lens group in the optical axis direction, but may also be performed by moving the image sensor in the optical axis direction.

[0098] According to each embodiment, for example, it is possible to provide a zoom lens, imaging device, and system that are compact and have advantages in terms of high optical performance with suppressed aberration fluctuations of field curvature during focusing. 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.

[0099] This embodiment includes the following configuration. (Composition 1) The lens system has, in order from the object side to the image side, a first lens group that does not move for zooming and has positive refractive power, a second lens group that moves during zooming and has negative refractive power, a third lens group that does not move for zooming and has positive refractive power, a fourth lens group that moves during zooming and has positive refractive power, and a fifth lens group that does not move for zooming. During zooming, the distance between adjacent lens groups changes. When the focal length of the first lens group is f1, the focal length of the fourth lens group is f4, the distance along the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fourth lens group at the wide-angle end with the object distance at infinity is L34w, and the distance along the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fifth lens group is L35, 0.07 <f4 / f1<0.65 0.00 <L34w / L35<0.39 A zoom lens characterized by meeting certain conditions. (Configuration 2) When L34t 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 fourth lens group at the telephoto end when the object distance is infinity, 0.00 <L34t / L35<0.39 A zoom lens according to configuration 1, characterized in that it satisfies the following conditions. (Composition 3) When the combined focal length of the first lens group, the second lens group, and the third lens group at the wide-angle end is f13w, 0.00 < |f1 / f13w| < 0.55 A zoom lens according to configuration 1 or 2, characterized in that it satisfies the following conditions. (Composition 4) When the combined focal length of the first lens group, the second lens group, and the third lens group at the telephoto end is f13t, 0.00 < |f1 / f13t| < 0.25 A zoom lens described in any of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) When the focal length of the fifth lens group is set to f5, 0.00 < |f4 / f5| < 0.38 A zoom lens described in any of configurations 1 to 4, characterized by satisfying the following conditions. (Composition 6) The zoom lens according to any one of configurations 1 to 5, characterized in that the third lens group includes a positive lens and a negative lens. (Composition 7) A zoom lens according to any one of configurations 1 to 6, characterized in that when focusing from an object distance of infinity to a close distance, the fourth lens group moves toward the object. (Composition 8) A zoom lens according to any one of configurations 1 to 7, characterized in that when zooming from the wide-angle end to the telephoto end, the second lens group moves toward the image side, and the fourth lens group moves along a different trajectory from the second lens group. (Composition 9) A zoom lens according to any one of configurations 1 to 8, characterized by having an aperture diaphragm positioned adjacent to the object side of the third lens group. (Composition 10) The lens system has, in order from the object side to the image side, a first lens group that does not move for zooming and has positive refractive power, a second lens group that moves during zooming and has negative refractive power, a third lens group that does not move for zooming and has positive refractive power, a fourth lens group that moves during zooming and has positive refractive power, and a fifth lens group that does not move for zooming. During zooming, the distance between adjacent lens groups changes. When the focal length of the first lens group is f1 and the focal length of the fourth lens group is f4, 0.07 <f4 / f1<0.65 A zoom lens characterized by meeting certain conditions. (Composition 11) An imaging device characterized by having a zoom lens as described in any of configurations 1 to 10, and an image sensor that receives an image formed by the zoom lens. [Explanation of symbols]

[0100] U1 First Lens Group U2 Second Lens Group U3 Third Lens Group U4 4th lens group U5 5th lens group

Claims

1. The lens system has, in order from the object side to the image side, a first lens group that does not move for zooming and has positive refractive power, a second lens group that moves during zooming and has negative refractive power, a third lens group that does not move for zooming and has positive refractive power, a fourth lens group that moves during zooming and has positive refractive power, and a fifth lens group that does not move for zooming. During zooming, the distance between adjacent lens groups changes. When the focal length of the first lens group is f1, the focal length of the fourth lens group is f4, the distance along the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fourth lens group at the wide-angle end when the object distance is infinity is L34w, and the distance along the optical axis from the lens surface closest to the object of the third lens group to the lens surface closest to the image of the fifth lens group is L35, 0.07<f4 / f1<0.65 0.00<L34w / L35<0.39 A zoom lens characterized by meeting certain conditions.

2. When L34t 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 fourth lens group at the telephoto end when the object distance is infinity, 0.00<L34t / L35<0.39 A zoom lens according to claim 1, characterized by satisfying the following conditions.

3. When the combined focal length of the first lens group, the second lens group, and the third lens group at the wide-angle end is f13w, 0.00<|f1 / f13w|<0.55 A zoom lens according to claim 1, characterized by satisfying the following conditions.

4. When the combined focal length of the first lens group, the second lens group, and the third lens group at the telephoto end is f13t, 0.00<|f1 / f13t|<0.25 A zoom lens according to claim 1, characterized by satisfying the following conditions.

5. When the focal length of the fifth lens group is set to f5, 0.00<|f4 / f5|<0.38 A zoom lens according to claim 1, characterized by satisfying the following conditions.

6. The zoom lens according to claim 1, characterized in that the third lens group includes a positive lens and a negative lens.

7. The zoom lens according to claim 1, characterized in that the fourth lens group moves toward the object when focusing from an object distance of infinity to a close distance.

8. The zoom lens according to claim 1, characterized in that when zooming from the wide-angle end to the telephoto end, the second lens group moves toward the image side, and the fourth lens group moves along a different trajectory from the second lens group.

9. The zoom lens according to claim 1, characterized in that it has an aperture diaphragm positioned adjacent to the object side of the third lens group.

10. The lens system has, in order from the object side to the image side, a first lens group that does not move for zooming and has positive refractive power, a second lens group that moves during zooming and has negative refractive power, a third lens group that does not move for zooming and has positive refractive power, a fourth lens group that moves during zooming and has positive refractive power, and a fifth lens group that does not move for zooming. During zooming, the distance between adjacent lens groups changes. When the focal length of the first lens group is f1 and the focal length of the fourth lens group is f4, 0.07<f4 / f1<0.65 A zoom lens characterized by meeting certain conditions.

11. An imaging device characterized by having a zoom lens according to any one of claims 1 to 10 and an image sensor that receives an image formed by the zoom lens.

Images