Zoom lens and imaging device

Abstract

To provide a zoom lens that is compact, lightweight, and has good optical performance. [Solution] The system consists of, in order from the object side to the image side, a first lens group having positive refractive power that does not move for magnification, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power, wherein the spacing between adjacent lens groups changes during magnification, the first lens group has at least two lenses, the fourth lens group consists of one single lens, and the fifth lens group consists of one single lens, and the focal length of the second lens group, the focal length of the third lens group, and the distance on the optical axis from the object-side surface to the image-side surface of the third 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 recent years, high-definition display has become possible using high-pixel imaging devices and monitors. When combined with a telephoto lens, detailed information on a distant subject can be displayed. However, since the telephoto lens has a narrow shooting range and may lose sight of the subject when it moves, a zoom lens that can change the shooting range is desirable for the lens.

[0003] In order to obtain high-definition display, the need for the zoom lens to perform good aberration correction has been increasing. However, even when performing good aberration correction, it is desired that the zoom lens is small and lightweight. Conventionally, as a zoom lens that is small and can efficiently secure a magnification ratio, a zoom lens including five lens groups having positive, negative, positive, negative, and positive refractive powers in order from the object side is known.

[0004] For example, in Patent Document 1, five lens groups having positive, negative, positive, negative, and positive refractive powers in order from the object side are arranged, and the second lens group, the third lens group, and the fourth lens group move during zooming, and a zoom lens having a magnification ratio of about 1.8 times is disclosed. In Patent Document 2, five lens groups having positive, negative, positive, negative, and positive refractive powers in order from the object side are arranged, and the second lens group, the third lens group, and the fourth lens group move during zooming, and a zoom lens having a magnification ratio of about 2.6 times is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] Patent Document 1 describes a first lens group consisting of a single lens, which makes it difficult to correct axial chromatic aberration at the telephoto end when the focal length is increased. Patent Document 2 describes a design with a large number of lenses, which presents challenges in reducing weight. Therefore, the present invention aims to provide a zoom lens that is small, lightweight, and has good optical performance. [Means for solving the problem]

[0007] To achieve the above objective, a zoom lens according to one aspect of the present invention comprises, in order from the object side to the image side, a first lens group having positive refractive power that does not move for magnification, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power, wherein the distance between adjacent lens groups changes during magnification, the first lens group has at least two lenses, the fourth lens group consists of one single lens, the fifth lens group consists of one single lens, and when the focal length of the second lens group is f2, the focal length of the third lens group is f3, and the distance on the optical axis from the object-side surface to the image-side surface of the third lens group is B3L, -2.00 ≤ f2 / f3 ≤ -0.95 0.87 ≤ B3L / f3 ≤ 1.40 It is characterized by satisfying the following conditions.

[0008] Another embodiment of the present invention is a zoom lens comprising, in order from the object side to the image side, a first lens group having a positive refractive power that does not move for magnification, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power, characterized in that the spacing between adjacent lens groups changes during magnification. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a zoom lens that is small, lightweight, and has good optical performance. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view of the zoom lens of Example 1 at its wide-angle end when focused at infinity. [Figure 2] This is an aberration diagram of the zoom lens of Example 1 at the wide-angle end when focused at infinity. [Figure 3] This is an aberration diagram of the zoom lens of Example 1 at an intermediate focal length when focused at infinity. [Figure 4] This is an aberration diagram of the zoom lens of Example 1 at the telephoto end when focused at infinity. [Figure 5] This is a cross-sectional view of the zoom lens of Example 2 at its wide-angle end when focused at infinity. [Figure 6] This is an aberration diagram of the zoom lens of Example 2 at the wide-angle end when focused at infinity. [Figure 7] This is an aberration diagram of the zoom lens of Example 2 at an intermediate focal length when focused at infinity. [Figure 8] This is an aberration diagram of the zoom lens of Example 2 at the telephoto end when focused at infinity. [Figure 9] This is a cross-sectional view of the zoom lens of Example 3 at its wide-angle end when focused at infinity. [Figure 10] This is an aberration diagram of the zoom lens of Example 3 at the wide-angle end when focused at infinity. [Figure 11] This is an aberration diagram of the zoom lens of Example 3 at an intermediate focal length when focused at infinity. [Figure 12] This is an aberration diagram of the zoom lens of Example 3 at the telephoto end when focused at infinity. [Figure 13] This is a cross-sectional view of the zoom lens of Example 4 at its wide-angle end when focused at infinity. [Figure 14] This is an aberration diagram of the zoom lens of Example 4 at the wide-angle end when focused at infinity. [Figure 15] This is an aberration diagram of the zoom lens of Example 4 at an intermediate focal length when focused at infinity. [Figure 16] It is an aberration diagram at infinity focus at the telephoto end of the zoom lens of Example 4. [Figure 17] It is a cross-sectional view at infinity focus at the wide-angle end of the zoom lens of Example 5. [Figure 18] It is an aberration diagram at infinity focus at the wide-angle end of the zoom lens of Example 5. [Figure 19] It is an aberration diagram at infinity focus at the intermediate focal length of the zoom lens of Example 5. [Figure 20] It is an aberration diagram at infinity focus at the telephoto end of the zoom lens of Example 5. [Figure 21] It is a cross-sectional view at infinity focus at the wide-angle end of the zoom lens of Example 6. [Figure 22] It is an aberration diagram at infinity focus at the wide-angle end of the zoom lens of Example 6. [Figure 23] It is an aberration diagram at infinity focus at the intermediate focal length of the zoom lens of Example 6. [Figure 24] It is an aberration diagram at infinity focus at the telephoto end of the zoom lens of Example 6. [Figure 25] It is a diagram for explaining an embodiment of the imaging device of the present invention.

Mode for Carrying Out the Invention

[0011] The zoom lens of the present invention is composed of, in order from the object side to the image side, a first lens group L1 with a positive refractive power, a second lens group L2 with a negative refractive power, a third lens group L3 with a positive refractive power, a fourth lens group L4 with a negative refractive power, and a fifth lens group L5 with a positive refractive power, and is a configuration suitable for a compact zoom lens. The first lens group L1 does not move for zooming, and therefore, the zoom lens of the present invention does not need to constitute a mechanism for moving the heavy first lens group L1. The first lens group L1 has at least two lenses and is configured to be able to correct chromatic aberration. In the examples described later, the fourth lens group L4 consists of a single lens, and the fifth lens group L5 consists of a single lens, aiming to reduce the weight.

[0012] Furthermore, in the zoom lens of the present invention, when the focal length of the second lens group L2 is f2, the focal length of the third lens group L3 is f3, and the distance on the optical axis from the object-side surface to the image-side surface of the third lens group L3 is B3L, -2.00 ≤ f2 / f3 ≤ -0.95 ···(1) 0.87 ≤ B3L / f3 ≤ 1.40 ···(2) The following conditions are met.

[0013] Conditional equation (1) defines the ratio of the focal length of the second lens group L2 to the focal length of the third lens group L3. If the upper limit of conditional equation (1) is exceeded, it becomes difficult to suppress the variation in coma aberration during magnification. Conversely, if the lower limit of conditional equation (1) is exceeded, the amount of movement of the second lens group L2 becomes large in order to secure the desired magnification ratio, which is undesirable from the perspective of the movement mechanism.

[0014] Conditional equation (2) defines the ratio of the distance along the optical axis from the object-side surface to the image-side surface of the third lens group L3 to the focal length of the third lens group L3. If the upper limit of conditional equation (2) is exceeded, it becomes difficult to secure the amount of movement of the lens group that moves during magnification, and thus difficult to secure the magnification ratio. Conversely, if the lower limit of conditional equation (2) is exceeded, it becomes difficult to correct coma aberration and chromatic aberration.

[0015] The objective of the present invention is achieved with the above configuration, but the zoom lens of the present invention, when the focal length of the fifth lens group L5 is set to f5, -1.46 ≤ f2 / f5 ≤ -0.64 ···(3) It is desirable to satisfy the following conditions. Conditional equation (3) is an equation that defines the ratio of the focal length of the second lens group L2 to the focal length of the fifth lens group L5. If the upper limit of conditional equation (3) is exceeded, it becomes difficult to suppress the fluctuation of coma aberration during magnification. Conversely, if the lower limit of conditional equation (3) is exceeded, the amount of movement of the second lens group L2 becomes large in order to secure the desired magnification ratio, which is undesirable from the perspective of the movement mechanism.

[0016] Furthermore, in the zoom lens of the present invention, when the focal length of the first lens group L1 is f1, 2.98 ≤ f1 / f3 ≤ 4.89 ···(4) It is desirable to satisfy the following conditions. Conditional equation (4) is an equation that defines the ratio of the focal length of the first lens group L1 to the focal length of the third lens group L3. If the upper limit of conditional equation (4) is exceeded, the overall length tends to increase when telephotoping, which is undesirable. Conversely, if the lower limit of conditional equation (4) is exceeded, it becomes difficult to correct axial chromatic aberration at the telephoto end.

[0017] Furthermore, the zoom lens of the present invention is 2.18 ≤ f1 / f5 ≤ 4.14 ···(5) It is desirable to satisfy the following conditions. Conditional equation (5) is an equation that defines the ratio of the focal length of the first lens group L1 to the focal length of the fifth lens group L5. If the upper limit of conditional equation (5) is exceeded, the overall length tends to increase when telephotoping, which is undesirable. Conversely, if the lower limit of conditional equation (5) is exceeded, the back focus tends to become shorter, which is undesirable when placing filters.

[0018] Furthermore, in the zoom lens of the present invention, when the focal length of the fourth lens group L4 is set to f4, -1.35 ≤ f3 / f4 ≤ -0.77 ···(6) It is desirable to satisfy the following conditions. Conditional equation (6) is an equation that specifies the ratio of the focal length of the third lens group L3 to the focal length of the fourth lens group L4. If the upper limit of conditional equation (6) is exceeded, it becomes difficult to correct coma aberration. Conversely, if the lower limit of conditional equation (6) is exceeded, it becomes difficult to correct chromatic aberration.

[0019] Furthermore, it is desirable that the third lens group L3 has at least five lenses. In the embodiments described later, a configuration in which the third lens group L3 consists of 5 to 7 lenses is shown as an example. The third lens group L3 plays a significant role in correcting aberrations across the entire range from the wide-angle end to the telephoto end. Having at least five lenses in the third lens group L3 makes it possible to arrange lenses over a wide range on the optical axis, which is effective in correcting both on-axial and off-axial aberrations.

[0020] Furthermore, in the zoom lens of the present invention, when B1L is the distance along the optical axis from the object-side surface to the image-side surface of the first lens group L1, 0.36 ≤ B1L / B3L ≤ 0.94 ···(7) It is desirable to satisfy the following conditions. Equation (7) defines the ratio of the distance along the optical axis from the object-side surface to the image-side surface of the first lens group L1 to the distance along the optical axis from the object-side surface to the image-side surface of the third lens group L3. If the upper limit of equation (7) is exceeded, the aberration correction effect of the third lens group L3 becomes difficult to obtain, and it becomes difficult to properly correct aberrations across the entire range from the wide-angle end to the telephoto end. Conversely, if the lower limit of equation (7) is exceeded, the diameter of the lens closer to the image side within the first lens group L1 tends to increase, leading to an increase in weight, which is undesirable.

[0021] Furthermore, the zoom lens of the present invention is 0.74 ≤ f² / f⁴ ≤ 1.95 ···(8) It is desirable to satisfy the following conditions. Conditional equation (8) is an equation that defines the ratio of the focal length of the second lens group L2 to the focal length of the fourth lens group L4. If the upper limit of conditional equation (8) is exceeded, the amount of movement of the second lens group L2 becomes large in order to secure the desired magnification ratio, which is undesirable from the perspective of the movement mechanism. Conversely, if the lower limit of conditional equation (8) is exceeded, it becomes difficult to suppress the fluctuation of coma aberration during magnification.

[0022] Furthermore, the zoom lens of the present invention is -6.02 ≤ f1 / f4 ≤ -2.54 ···(9) It is desirable to satisfy the following conditions. Conditional equation (9) is an equation that defines the ratio of the focal length of the first lens group L1 to the focal length of the fourth lens group L4. If the upper limit of conditional equation (9) is exceeded, it becomes difficult to correct axial chromatic aberration at the telephoto end. Conversely, if the lower limit of conditional equation (9) is exceeded, the overall length tends to increase when telephotoping, which is undesirable.

[0023] Furthermore, in the zoom lens of the present invention, when focusing from an object at infinity to an object at close range, it is desirable that the fourth lens group L4 moves from the object side to the image side. The fourth lens group L4 has a narrower light beam diameter than the third lens group L3 and a lower ray height than the fifth lens group L5, so its lens diameter tends to be small. Also, the fourth lens group L4 consists of a single lens. Because the fourth lens group L4 has a small diameter and fewer elements, it is easy to reduce its weight, and by making the fourth lens group L4 the focusing lens group, the focusing mechanism can be miniaturized.

[0024] Furthermore, it is desirable that the zoom lens of the present invention has at least two negative lenses in the third lens group L3. Having at least two negative lenses in the third lens group L3 makes it possible to correct both axial chromatic aberration and lateral chromatic aberration.

[0025] Furthermore, in the zoom lens of the present invention, when VNmax is the largest Abbe number among the negative lenses included in the third lens group L3, and VNmin is the smallest Abbe number among the negative lenses included in the third lens group L3, 1.11 ≤ VNmax / VNmin ≤ 2.00 ···(10) It is desirable to satisfy the following conditions. Note that the Abbe numbers shown in this invention are values ​​based on the d line. Conditional equation (10) is an equation that defines the ratio of the largest Abbe number among the negative lenses included in the third lens group L3 to the smallest Abbe number among the negative lenses included in the third lens group L3. If the upper limit of conditional equation (10) is exceeded, the correction of axial chromatic aberration tends to become excessive. Conversely, if the lower limit of conditional equation (10) is exceeded, it becomes difficult to suppress the fluctuation of magnification chromatic aberration during magnification.

[0026] Furthermore, it is even more desirable to specify the numerical ranges for conditional expressions (1) to (10) as follows. -1.51≦f2 / f3≦-0.95 (1a) 0.88≦B3L / f3≦1.21 (2a) -1.40≦f2 / f5≦-0.67 (3a) 3.14≦f1 / f3≦4.67 (4a) 2.31≦f1 / f5≦3.96 (5a) -1.29≦f3 / f4≦-0.81 (6a) 0.38≦B1L / B3L≦0.90 (7a) 0.78≦f2 / f4≦1.86 (8a) -5.74≦f1 / f4≦-2.68 (9a) 1.17≦VNmax / VNmin≦1.91 (10a) Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. [Examples]

[0027] Figure 1 shows a cross-sectional view of the zoom lens of Embodiment 1 (Numerical Embodiment 1) of the present invention when it is focused at infinity at its wide-angle end. Figures 2-4 show the aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lens of Embodiment 1 when it is focused at infinity at its wide-angle end, intermediate focal length, and telephoto end, respectively. In the aberration diagrams, d and g are represented by the d and g lines, M and S are represented by the meridional and sagittal image planes, and chromatic aberration is represented by the g line. In the cross-sectional view of the lens in Figure 1, L1-L5 represent the first to fifth lens groups, SP is the aperture diaphragm, P is a glass block such as the faceplate or low-pass filter of the CCD, and I is the image plane. The solid and dashed arrows represent the movement trajectories when zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a close-up object, respectively. The same applies to the following embodiments.

[0028] The zoom lens of Example 1 has, in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power. When the magnification is changed, the distance between adjacent lens groups changes.

[0029] During magnification from the wide-angle end to the telephoto end, the second lens group L2 moves toward the image side, and the fourth lens group L4 moves toward the image side along a convex trajectory. The first lens group L1, the third lens group L3, and the fifth lens group L5 do not move for magnification. For focusing from infinity to the close distance, the fourth lens group L4 moves toward the image side. The aperture diaphragm SP is positioned between the second lens group L2 and the third lens group L3.

[0030] The first lens group L1 consists of a positive lens and a cemented lens of a positive and negative lens, in order from the object side to the image side. The second lens group L2 consists of a negative lens and a cemented lens of a negative and positive lens, in order from the object side to the image side. The third lens group L3 consists of a positive lens, a cemented lens of a positive and negative lens, a positive lens, a positive lens, and a negative lens, in order from the object side to the image side. The fourth lens group L4 consists of one negative lens. The fifth lens group L5 consists of one positive lens. Numerical values ​​corresponding to Example 1. Table 1 shows the values ​​for conditional equations (1) to (10) of Example 1. The zoom lens of Example 1 satisfies conditional equations (1) to (10). [Examples]

[0031] Figure 5 shows a cross-sectional view of the zoom lens of Embodiment 2 (Numerical Embodiment 2) of the present invention at the wide-angle end when focused at infinity. Figures 6 to 8 show the aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lens of Embodiment 2 at the wide-angle end, intermediate focal length, and telephoto end when focused at infinity. The zoom lens of Example 2 has, in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power. When the magnification is changed, the distance between adjacent lens groups changes.

[0032] During magnification from the wide-angle end to the telephoto end, the second lens group L2 moves toward the image side, and the fourth lens group L4 moves toward the image side along a convex trajectory. The first lens group L1, the third lens group L3, and the fifth lens group L5 do not move for magnification. For focusing from infinity to the close distance, the fourth lens group L4 moves toward the image side. The aperture diaphragm SP is positioned between the second lens group L2 and the third lens group L3.

[0033] The first lens group L1 consists of a positive lens and a cemented lens of a positive and negative lens, in order from the object side to the image side. The second lens group L2 consists of a negative lens and a cemented lens of a negative and positive lens, in order from the object side to the image side. The third lens group L3 consists of a positive lens, a cemented lens of a positive and negative lens, a cemented lens of a positive and negative lens, a positive lens, and a negative lens, in order from the object side to the image side. The fourth lens group L4 consists of one negative lens. The fifth lens group L5 consists of one positive lens. Numerical values ​​corresponding to Example 2. The values ​​for conditional equations (1) to (10) in Example 2 are shown in Table 1. The zoom lens of Example 2 satisfies conditional equations (1) to (10). [Examples]

[0034] Figure 9 shows a cross-sectional view of the zoom lens of Embodiment 3 (Numerical Embodiment 3) of the present invention when it is focused at infinity at its wide-angle end. Figures 10 to 12 show the aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lens of Embodiment 3 when it is focused at infinity at its wide-angle end, intermediate focal length, and telephoto end, respectively. The zoom lens of Example 3 has, in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power. When the zoom is changed, the distance between adjacent lens groups changes.

[0035] During magnification from the wide-angle end to the telephoto end, the second lens group L2 moves toward the image side, and the fourth lens group L4 moves toward the image side along a convex trajectory. The first lens group L1, the third lens group L3, and the fifth lens group L5 do not move for magnification. For focusing from infinity to the close distance, the fourth lens group L4 moves toward the image side. The aperture diaphragm SP is positioned between the second lens group L2 and the third lens group L3.

[0036] The first lens group L1 consists of a positive lens and a negative lens, arranged from the object side to the image side. The second lens group L2 consists of a negative lens and a cemented lens of a negative lens and a positive lens, arranged from the object side to the image side. The third lens group L3 consists of a positive lens, a cemented lens of a positive lens and a negative lens, a positive lens, a positive lens, and a negative lens, arranged from the object side to the image side. The fourth lens group L4 consists of one negative lens. The fifth lens group L5 consists of one positive lens. Numerical values ​​corresponding to Example 3: Table 1 shows the values ​​for conditional equations (1) to (10) in Example 3. The zoom lens of Example 3 satisfies conditional equations (1) to (10). [Examples]

[0037] Figure 13 shows a cross-sectional view of the zoom lens of Embodiment 4 (Numerical Embodiment 4) of the present invention when it is focused at infinity at its wide-angle end. Figures 14 to 16 show the aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lens of Embodiment 4 when it is focused at infinity at its wide-angle end, intermediate focal length, and telephoto end, respectively. The zoom lens of Example 4 has, in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power. When the magnification is changed, the distance between adjacent lens groups changes.

[0038] During magnification from the wide-angle end to the telephoto end, the second lens group L2 moves toward the image side, and the fourth lens group L4 moves toward the image side along a convex trajectory. The first lens group L1, the third lens group L3, and the fifth lens group L5 do not move for magnification. For focusing from infinity to the close distance, the fourth lens group L4 moves toward the image side. The aperture diaphragm SP is positioned between the second lens group L2 and the third lens group L3.

[0039] The first lens group L1 consists of a positive lens and a cemented lens (a positive lens and a negative lens), arranged from the object side to the image side. The second lens group L2 consists of a cemented lens (a negative lens and a positive lens), arranged from the object side to the image side. The third lens group L3 consists of a positive lens, a negative lens, a positive lens, a positive lens, and a negative lens, arranged from the object side to the image side. The fourth lens group L4 consists of one negative lens. The fifth lens group L5 consists of one positive lens.

[0040] The sixth surface in the second lens group L2, the tenth and eleventh surfaces in the third lens group L3, and the twenty-two and twenty-one surfaces in the fourth lens group L4 are composed of aspherical surfaces. Numerical values ​​corresponding to Example 4. The values ​​for conditional equations (1) to (10) of Example 4 are shown in Table 1. The zoom lens of Example 4 satisfies conditional equations (1) to (10). [Examples]

[0041] Figure 17 shows a cross-sectional view of the zoom lens of Embodiment 5 (Numerical Embodiment 5) of the present invention when it is focused at infinity at its wide-angle end. Figures 18 to 20 show the aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lens of Embodiment 5 when it is focused at infinity at its wide-angle end, intermediate focal length, and telephoto end, respectively. The zoom lens of Example 5 has, in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power. When the magnification is changed, the distance between adjacent lens groups changes.

[0042] During magnification from the wide-angle end to the telephoto end, the second lens group L2 moves towards the image, the third lens group L3 moves towards the object, the fourth lens group L4 moves towards the object, and the fifth lens group L5 moves towards the image. The first lens group L1 does not move for magnification. For focusing from infinity to the close distance, the fourth lens group L4 moves towards the image. The aperture diaphragm SP is positioned between the second lens group L2 and the third lens group L3.

[0043] The first lens group L1 consists of a positive lens and a cemented lens (a positive lens and a negative lens), arranged from the object side to the image side. The second lens group consists of a cemented lens (a negative lens and a positive lens), arranged from the object side to the image side. The third lens group L3 consists of a positive lens, a negative lens, a positive lens, a positive lens, and a negative lens, arranged from the object side to the image side. The fourth lens group L4 consists of one negative lens. The fifth lens group L5 consists of one positive lens.

[0044] The sixth surface in the second lens group L2, the tenth and eleventh surfaces in the third lens group L3, and the twenty-two and twenty-one surfaces in the fourth lens group L4 are composed of aspherical surfaces. Numerical values ​​corresponding to Example 5. Table 1 shows the values ​​for conditional equations (1) to (10) in Example 5. The zoom lens of Example 5 satisfies conditional equations (1) to (10). [Examples]

[0045] Figure 21 shows a cross-sectional view of the zoom lens of Embodiment 6 (Numerical Embodiment 6) of the present invention when it is focused at infinity at its wide-angle end. Figures 22 to 24 show the aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lens of Embodiment 6 when it is focused at infinity at its wide-angle end, intermediate focal length, and telephoto end, respectively. The zoom lens of Example 6 has, in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with negative refractive power, and a fifth lens group L5 with positive refractive power. When the magnification is changed, the distance between adjacent lens groups changes.

[0046] During magnification from the wide-angle end to the telephoto end, the second lens group L2 moves toward the image side, and the fourth lens group moves toward the image side along a convex trajectory. The first lens group L1, the third lens group L3, and the fifth lens group L5 do not move for magnification. For focusing from infinity to the close distance, the fourth lens group L4 moves toward the image side. The aperture diaphragm SP is positioned between the second lens group L2 and the third lens group L3.

[0047] The first lens group L1 consists of a positive lens and a cemented lens of a positive and negative lens, in order from the object side to the image side. The second lens group L2 consists of a negative lens and a cemented lens of a negative and positive lens, in order from the object side to the image side. The third lens group L3 consists of a positive lens, a cemented lens of a positive and negative lens, a positive lens, a positive lens, and a negative lens, in order from the object side to the image side. The fourth lens group L4 consists of one negative lens. The fifth lens group L5 consists of one positive lens. Numerical values ​​corresponding to Example 6. Table 1 shows the values ​​for conditional equations (1) to (10) of Example 6. The zoom lens of Example 6 satisfies conditional equations (1) to (10).

[0048] The following shows numerical examples 1 to 6 corresponding to Examples 1 to 6. In the numerical examples, ri is the radius of curvature of the i-th surface in order from the object side, di is the distance between the i-th surface and the (i+1)-th surface (lens thickness or air gap), and ndi and νdi are the refractive index and Abbe number of the optical element (optical medium) between the i-th surface and the (i+1)-th surface, respectively. Note that the Abbe number νd is given by nF, nd, and nC, where the refractive indices for the F line (wavelength 486.1 nm), d line (wavelength 587.6 nm), and C line (wavelength 656.3 nm) are nF, nd, and nC, respectively. νd=(nd-1) / (nF-nC) ···(A) It is defined by equation (A).

[0049] Furthermore, the asterisk (*) to the right of the surface number indicates that the surface is aspherical. The aspherical shape is defined as follows: the X-axis is in the direction of the optical axis, the h-axis is perpendicular to the optical axis, the direction of light propagation is positive, the paraaxial radius of curvature is R, and the aspheric coefficients are K, A4, and A6.

number

[0050] [Numerical Example 1] Unit: mm Surface data Face number rd nd vd 1 51.755 5.50 1.49700 81.5 2 -155.895 8.25 3 60.305 4.83 1.49700 81.5 4 -67.958 1.22 1.77250 49.6 5 74.682 (variable) 6 -2110.150 0.83 1.59522 67.7 7 35.551 3.03 8 -34.844 0.84 1.49700 81.5 9 63.310 1.49 1.85478 24.8 10 619.177 (variable) 11 (aperture) ∞ 1.95 12 100.079 2.69 1.49700 81.5 13 -51.510 0.17 14 66.843 4.25 1.49700 81.5 15 -28.233 0.88 1.67300 38.3 16 161.083 0.17 17 20.255 3.88 1.49700 81.5 18 181.380 19.35 19 126.398 1.18 1.95375 32.3 20 -102.074 1.73 21 -17.270 0.60 1.74320 49.3 22 -50.748 (variable) 23 -55.624 0.62 1.49700 81.5 24 21.460 (Variable) 25 24.878 5.19 1.59522 67.7 26 -148.115 11.57 27 ∞ 1.20 1.51633 64.1 28 ∞ 1.00 Image plane ∞ Various data Zoom ratio 2.00 Wide-angle, Medium, Telephoto Focal length 59.45 89.79 118.90 F-number 3.30 3.30 3.30 Half-angle 10.39 6.80 5.13 Image height 10.75 10.75 10.75 Lens length 127.62 127.62 127.62 BF 13.36 13.36 13.36 d 5 2.46 17.91 28.21 d10 27.80 12.35 2.05 d22 1.93 3.99 2.66 d24 13.42 11.36 12.69 Zoom lens group data Group starting plane focal length 1 1 118.77 2 6 -36.38 3 11 31.06 4 23 -31.08 5 25 36.19

[0051] [Numerical Example 2] Unit: mm Surface data Face number rd nd vd 1 53.094 5.46 1.49700 81.5 2 -171.656 10.18 3 64.162 4.55 1.49700 81.5 4 -68.091 1.20 1.77250 49.6 5 79.441 (variable) 6 420.203 0.81 1.59522 67.7 7 36.320 2.83 8 -35.705 0.82 1.49700 81.5 9 64.685 1.39 1.85478 24.8 10 472.426 (variable) 11 (aperture) ∞ 1.94 12 39.105 3.08 1.59522 67.7 13 -92.745 0.17 14 30.703 4.43 1.59522 67.7 15 -38.079 0.82 1.89286 20.4 16 142.794 0.17 17 31.353 4.58 1.92286 18.9 18 -25.670 0.74 1.85896 22.7 19 23.484 17.37 20 82.142 1.28 2.05090 26.9 21 -122.698 1.00 22 -23.961 0.61 1.95375 32.3 23 -49.091 (variable) 24 -62.671 0.64 1.49700 81.5 25 20.861 (Variable) 26 21.525 5.29 1.49700 81.5 27 -206.760 11.90 28 ∞ 1.20 1.51633 64.1 29 ∞ 1.00 Image plane ∞ Various data Zoom ratio 2.00 Wide-angle, Medium, Telephoto Focal length 59.45 89.59 118.89 F-number 3.30 3.30 3.30 Half-angle 10.47 6.87 5.17 Image height 10.75 10.75 10.75 Lens length 127.66 127.66 127.66 BF 13.69 13.69 13.69 d 5 2.23 18.79 29.83 d10 29.66 13.10 2.06 d23 2.34 3.73 1.84 d25 10.37 8.98 10.88 Zoom lens group data Group starting plane focal length 1 1 125.50 2 6 -39.13 3 11 32.94 4 24 -31.41 5 26 39.53

[0052] [Numerical Example 3] Unit: mm Surface data Face number rd nd vd 1 62.136 5.22 1.49700 81.5 2 -108.707 8.09 3 -85.770 1.25 1.95375 32.3 4 -183.887 (variable) 5 350.182 0.88 1.61772 49.8 6 41.052 3.04 7 -38.621 0.89 1.49700 81.5 8 85.733 1.52 1.85478 24.8 9 -563.243 (variable) 10 (aperture) ∞ 2.00 11 312.573 2.32 1.49700 81.5 12 -51.682 0.17 13 96.642 4.16 1.49700 81.5 14 -28.437 0.92 1.67300 38.3 15 1195.998 0.17 16 19.933 3.90 1.49700 81.5 17 91.786 19.16 18 87.603 2.86 1.88300 40.8 19 -101.802 1.81 20 -17.181 0.65 1.54072 47.2 21 -85.846 (variable) 22 -56.307 0.67 1.49700 81.5 23 20.104 (Variable) 24 23.036 5.16 1.53775 74.7 25 -124.686 12.70 26 ∞ 1.20 1.51633 64.1 27 ∞ 1.00 Image plane ∞ Various data Zoom ratio 2.00 Wide-angle, Medium, Telephoto Focal length 49.29 74.29 98.58 F-number 2.88 2.88 2.88 Half-angle 12.63 8.25 6.21 Image height 10.75 10.75 10.75 Lens length 127.60 127.60 127.60 BF 14.49 14.49 14.49 d 4 1.20 21.78 35.51 d 9 36.31 15.72 2.00 d21 2.17 3.37 2.17 d23 8.59 7.38 8.59 Zoom lens group data Group starting plane focal length 1 1 137.68 2 5 -48.52 3 10 34.38 4 22 -29.72 5 24 36.61

[0053] [Numerical Example 4] Unit: mm Surface data Face number rd nd vd 1 60.130 5.57 1.49700 81.5 2 -159.917 13.01 3 102.771 3.77 1.49700 81.5 4 -64.719 1.19 1.80400 46.5 5 158.970 (variable) 6* -49.217 0.81 1.59201 67.0 7 29.426 1.19 1.89286 20.4 8 41.444 (variable) 9 (aperture) ∞ 1.95 10* 20.709 4.49 1.49700 81.5 11* -105.304 3.83 12 -103.908 0.79 1.73800 32.3 13 46.472 0.17 14 26.528 4.32 1.49700 81.5 15 -34.952 10.59 16 119.595 0.97 1.69680 55.5 17 -250.245 1.68 18 -15.443 0.60 1.51823 58.9 19 -29.024 (variable) 20* -56.809 0.60 1.49700 81.5 21* 15.171 (variable) 22 23.737 4.34 1.70154 41.2 23 199.919 11.29 24 ∞ 1.20 1.51633 64.1 25 ∞ 1.00 Image plane ∞ Aspherical data Page 6 K =-8.18405e+00 A 4=-4.85224e-06 A 6= 8.10925e-09 Side 10 K =-7.17032e-01 A 4= 8.67192e-06 A 6= 3.04649e-08 Page 11 K =-2.07362e+01 A 4= 1.86370e-05 A 6= 1.84865e-08 Page 20 K =-5.24145e+01 A 4=-6.68490e-05 A 6= 1.64677e-07 Page 21 K = 4.53772e-01 A 4=-7.76392e-05 A 6=-1.81357e-07 Various data Zoom ratio 2.00 Wide-angle, Medium, Telephoto Focal length 59.50 90.02 119.00 F-number 3.30 3.30 3.30 Half-angle 10.32 6.75 5.09 Image height 10.75 10.75 10.75 Lens length 127.61 127.61 127.61 BF 13.08 13.08 13.08 d 5 3.04 21.00 32.97 d 8 33.20 15.23 3.26 d19 2.94 3.30 1.77 d21 15.48 15.12 16.65 Zoom lens group data Group starting plane focal length 1 1 131.42 2 6 -42.66 3 9 29.57 4 20 -24.02 5 22 38.01

[0054] [Numerical Example 5] Unit: mm Surface data Face number rd nd vd 1 71.671 4.93 1.49700 81.5 2 -149.571 10.52 3 88.546 4.02 1.49700 81.5 4 -75.190 1.26 1.71999 50.2 5 115.406 (variable) 6* -56.716 0.93 1.59201 67.0 7 27.820 1.47 2.00069 25.5 8 39.301 (variable) 9 (aperture) ∞ 2.00 10* 21.168 5.43 1.49700 81.5 11* -125.386 0.60 12 -86.016 1.68 1.73800 32.3 13 64.198 0.17 14 26.921 5.23 1.49700 81.5 15 -53.578 14.93 16 -108.579 2.17 1.95906 17.5 17 -69.467 1.54 18 -14.758 0.60 1.71300 53.9 19 -28.341 (variable) 20* -63.243 0.62 1.49700 81.5 21 * 19.432 (variable) 22 29.533 4.87 1.60738 56.8 23 -74.577 (variable) 24 ∞ 1.20 1.51633 64.1 25 ∞ 1.00 Image plane ∞ Aspherical data Page 6 K =-8.57185e+00 A 4=-3.71396e-06 A 6= 3.46895e-09 Side 10 K =-4.64388e-01 A 4= 2.49093e-06 A 6= 1.57132e-08 Page 11 K = 1.54625e-01 A 4= 1.15581e-05 A 6= 1.10570e-08 Page 20 K =-2.06697e+01 A 4=-2.05880e-05 A 6= 1.66808e-08 Page 21 K=-1.45802e-01 A 4=-5.90326e-06 A 6= 2.46646e-09 Various data Zoom ratio 2.00 Wide-angle, Medium, Telephoto Focal length 59.45 87.20 118.90 F-number 3.30 3.30 3.30 Half-angle 10.18 6.92 5.07 Image height 10.75 10.75 10.75 Lens length 127.57 127.57 127.57 BF 20.96 18.96 15.09 d 5 3.47 18.03 27.74 d 8 34.13 16.62 3.83 d19 1.79 3.92 5.07 d21 4.25 7.06 12.87 d23 19.16 17.17 13.30 Zoom lens group data Group starting plane focal length 1 1 133.58 2 6 -47.18 3 9 34.86 4 20 -29.83 5 22 35.46

[0055] [Numerical Example 6] Unit: mm Surface data Face number rd nd vd 1 50.887 5.29 1.49700 81.5 2 -188.749 11.69 3 60.930 3.98 1.49700 81.5 4 -65.082 1.08 1.74400 44.8 5 93.895 (variable) 6 -403.784 0.75 1.60300 65.4 7 30.044 5.31 8 -32.027 1.34 1.49700 81.5 9 46.256 1.50 1.85478 24.8 10 219.707 (variable) 11 (aperture) ∞ 2.19 12 -273.347 1.94 1.49700 81.5 13 -38.865 0.17 14 49.508 4.26 1.49700 81.5 15 -26.393 0.82 1.67300 38.3 16 234.907 0.17 17 20.741 3.49 1.49700 81.5 18 239.394 20.04 19 97.215 1.50 1.88300 40.8 20 -90.957 1.58 21 -17.544 0.65 1.66672 48.3 22 -46.116 (variable) 23 -72.328 0.67 1.49700 81.5 24 23.153 (variable) 25 23.102 4.63 1.59522 67.7 26 405.101 13.62 27 ∞ 1.20 1.51633 64.1 28 ∞ 1.00 Image plane ∞ Various data Zoom ratio 2.00 Wide-angle, Medium, Telephoto Focal length 54.41 81.86 108.83 F-number 3.30 3.30 3.30 Half-angle 11.50 7.56 5.67 Image height 10.75 10.75 10.75 Lens length 127.59 127.59 127.59 BF 15.41 15.41 15.41 d 5 2.27 14.60 22.82 d10 22.88 10.55 2.33 d22 1.80 4.07 2.72 d24 12.17 9.90 11.24 Zoom lens group data Group starting plane focal length 1 1 99.46 2 6 -28.94 3 11 30.07 4 23 -35.21 5 25 40.97

[0056] Table 1 shows the relationship between conditional equations (1) to (10) and the various numerical values ​​in numerical examples 1 to 6. [Table 1]

[0057] In the illustrated embodiment, the fourth lens group L4 is composed of a single lens having negative refractive power, but the present invention is not limited thereto. The fourth lens group L4 may be composed of multiple lenses, so that the refractive power of the entire fourth lens group L4 is negative. Furthermore, in the illustrated embodiment, the fifth lens group L5 is composed of a single lens having positive refractive power, but the present invention is not limited thereto. The fifth lens group L5 may be composed of multiple lenses so that the refractive power of the entire fifth lens group L5 is positive. Furthermore, although the first lens group L1 is composed of two or three lenses in the illustrated embodiment, the present invention is not limited thereto. The first lens group L1 may be composed of four or more lenses. As described above, each embodiment makes it possible to realize a zoom lens that is small, lightweight, and has good optical performance.

[0058] [Imaging device] Next, an embodiment of an imaging device (surveillance camera) using the zoom lens of the present invention as the imaging optical system will be described with reference to Figure 25. In Figure 25(A), 11 is the surveillance camera body, and 12 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor built into the camera body that receives the subject image formed by the lens unit 16. 13 is a memory unit that records information corresponding to the subject image photoelectrically converted by the solid-state image sensor 12. 14 is a network cable for transferring the subject image photoelectrically converted by the solid-state image sensor 12.

[0059] Figure 25(B) shows an example of the imaging device being used with a dome-shaped cover 15 attached and mounted on the ceiling. 10 is the part not covered by the dome-shaped cover 15. By applying an imaging device using the zoom lens of the present invention as the imaging optical system to optical equipment such as surveillance cameras, it is possible to realize compact optical equipment with high optical performance. The imaging device is not limited to surveillance cameras; it can also be used with video cameras, digital cameras, TV cameras, and the like. Furthermore, by using an electronic image sensor such as a CCD, the output image quality can be further improved by electronically correcting aberrations. 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.

[0060] This embodiment includes the following configuration. (Composition 1) The lens system consists of, in order from the object side to the image side, a first lens group with positive refractive power that does not move for magnification, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with negative refractive power, and a fifth lens group with positive refractive power. The spacing between adjacent lens groups changes during magnification. The first lens group has at least two lenses, the fourth lens group consists of one single lens, and the fifth lens group consists of one single lens. When the focal length of the second lens group is f2, the focal length of the third lens group is f3, and the distance along the optical axis from the object-side surface to the image-side surface of the third lens group is B3L, -2.00 ≤ f2 / f3 ≤ -0.95 0.87 ≤ B3L / f3 ≤ 1.40 A zoom lens characterized by meeting certain conditions. (Configuration 2) When the focal length of the fifth lens group is f5, -1.46 ≤ f2 / f5 ≤ -0.64 A zoom lens according to configuration 1, characterized in that it satisfies the following conditions. (Composition 3) When the focal length of the first lens group is f1, 2.98 ≤ f1 / f3 ≤ 4.89 A zoom lens according to configuration 1 or 2, characterized in that it satisfies the following conditions. (Composition 4) When the focal length of the first lens group is f1 and the focal length of the fifth lens group is f5, 2.18 ≤ f1 / f5 ≤ 4.14 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 fourth lens group is f4, -1.35 ≤ f3 / f4 ≤ -0.77 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 has at least five lenses. (Composition 7) When B1L is the distance along the optical axis from the object-side surface to the image-side surface of the first lens group, 0.36 ≤ B1L / B3L ≤ 0.94 A zoom lens described in any of configurations 1 to 6, characterized by satisfying the following conditions. (Composition 8) When the focal length of the fourth lens group is f4, 0.74 ≤ f2 / f4 ≤ 1.95 A zoom lens described in any of configurations 1 to 7, characterized by satisfying the following conditions. (Composition 9) When the focal length of the first lens group is f1 and the focal length of the fourth lens group is f4, -6.02 ≤ f1 / f4 ≤ -2.54 A zoom lens described in any of configurations 1 to 8, characterized by satisfying the following conditions. (Composition 10) A zoom lens according to any one of configurations 1 to 9, characterized in that when focusing from infinity to close distance, the fourth lens group moves from the object side to the image side. (Composition 11) The zoom lens according to any one of configurations 1 to 10, characterized in that the third lens group has at least two negative lenses. (Composition 12) When the largest Abbe number among the negative lenses included in the third lens group is VNmax, and the smallest Abbe number among the negative lenses included in the third lens group is VNmin, 1.11 ≤ VNmax / VNmin ≤ 2.00 A zoom lens described in any of configurations 1 to 11, characterized by satisfying the following conditions. (Composition 13) A zoom lens according to any one of configurations 1 to 12, characterized in that when changing magnification from the wide-angle end to the telephoto end, the second lens group moves toward the image side and the fourth lens group moves. (Composition 14) The zoom lens according to any one of claims 1 to 13, characterized in that the first lens group consists of two or three lenses. (Composition 15) The zoom lens according to configuration 6, characterized in that the third lens group consists of 5 to 7 lenses. (Composition 16) The zoom lens according to configuration 11, characterized in that the third lens group includes two or three negative lenses. (Composition 17) A zoom lens characterized by comprising, in order from the object side to the image side, a first lens group having positive refractive power that does not move for magnification, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power, wherein the spacing between adjacent lens groups changes during magnification. (Composition 18) An imaging device having a zoom lens as described in any of configurations 1 to 17, and an image sensor that receives the image formed by the zoom lens. [Explanation of Symbols]

[0061] L1 First lens group L2 Second lens group L3 Third lens group L4 4th lens group L5 5th lens group

Claims

1. The lens system consists of, in order from the object side to the image side, a first lens group with positive refractive power that does not move for magnification, a second lens group with negative refractive power, a third lens group with positive refractive power, a fourth lens group with negative refractive power, and a fifth lens group with positive refractive power. The spacing between adjacent lens groups changes during magnification. The first lens group has at least two lenses, the fourth lens group consists of one single lens, and the fifth lens group consists of one single lens. When the focal length of the second lens group is f2, the focal length of the third lens group is f3, and the distance on the optical axis from the object-side surface to the image-side surface of the third lens group is B3L, -2.00 ≤ f² / f³ ≤ -0.95 0.87 ≤ B3L / f3 ≤ 1.40 A zoom lens characterized by meeting certain conditions.

2. When the focal length of the fifth lens group is f5, -1.46 ≤ f² / f⁵ ≤ -0.64 A zoom lens according to claim 1, characterized by satisfying the following conditions.

3. When the focal length of the first lens group is f1, 2.98 ≤ f1 / f3 ≤ 4.89 A zoom lens according to claim 1, characterized by satisfying the following conditions.

4. When the focal length of the first lens group is f1 and the focal length of the fifth lens group is f5, 2.18 ≤ f1 / f5 ≤ 4.14 A zoom lens according to claim 1, characterized by satisfying the following conditions.

5. When the focal length of the fourth lens group is f4, -1.35 ≤ f3 / f4 ≤ -0.77 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 has at least five lenses.

7. When B1L is the distance along the optical axis from the object-side surface to the image-side surface of the first lens group, 0.36 ≤ B1L / B3L ≤ 0.94 A zoom lens according to claim 1, characterized by satisfying the following conditions.

8. When the focal length of the fourth lens group is f4, 0.74 ≤ f² / f⁴ ≤ 1.95 A zoom lens according to claim 1, characterized by satisfying the following conditions.

9. When the focal length of the first lens group is f1 and the focal length of the fourth lens group is f4, -6.02 ≤ f1 / f4 ≤ -2.54 A zoom lens according to claim 1, characterized by satisfying the following conditions.

10. The zoom lens according to claim 1, characterized in that when focusing from infinity to close distance, the fourth lens group moves from the object side to the image side.

11. The zoom lens according to claim 1, characterized in that the third lens group has at least two negative lenses.

12. When the largest Abbe number among the negative lenses included in the third lens group is VNmax, and the smallest Abbe number among the negative lenses included in the third lens group is VNmin, 1.11 ≤ VNmax / VNmin ≤ 2.00 A zoom lens according to claim 1, characterized by satisfying the following conditions.

13. The zoom lens according to claim 1, characterized in that when the zoom is changed from the wide-angle end to the telephoto end, the second lens group moves toward the image side and the fourth lens group moves.

14. The zoom lens according to claim 1, characterized in that the first lens group consists of two or three lenses.

15. The zoom lens according to claim 6, characterized in that the third lens group consists of 5 to 7 lenses.

16. The zoom lens according to claim 11, characterized in that the third lens group includes two or three negative lenses.

17. A zoom lens characterized by comprising, in order from the object side to the image side, a first lens group having positive refractive power that does not move for magnification, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power, wherein the spacing between adjacent lens groups changes during magnification.

18. An imaging device having a zoom lens according to any one of claims 1 to 17 and an image sensor for receiving an image formed by the zoom lens.

Images