Zoom lens and imaging device

Abstract

To provide a compact and lightweight zoom lens.SOLUTION: A zoom lens provided herein consists of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a rear group consisting of multiple groups and having positive refractive power as a whole, the second lens group G2 being movable while zooming. The second lens group G2 has a cemented lens consisting of a positive lens and a negative lens, and the rear group comprises a lens group Gf with negative refractive power configured to be movable while focusing, and a lens group Gn with negative refractive power disposed on the image side of the lens group Gf. The zoom lens satisfies given conditional expressions.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In imaging devices using solid-state imaging elements such as digital still cameras and digital video cameras, in recent years, with the progress of high pixel density of solid-state imaging elements, higher performance is required for the optical system compared to before. Also, with the miniaturization of cameras, a small zoom lens is required for the optical system.

[0003] However, a small zoom lens has not been well realized as a whole product.

[0004] Patent Document 1 discloses an invention related to an optical system for a telephoto zoom lens for a so-called mirrorless single-lens camera. In this zoom lens, by arranging a focus group on the image side of the aperture, miniaturization of the focus mechanism is achieved.

[0005] Patent Document 2 discloses an invention related to an optical system for a high-magnification zoom lens for a so-called mirrorless single-lens camera. In this zoom lens, by arranging the entire second lens group as a focus group, good optical performance is ensured throughout the zoom range.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the zoom lens described in Patent Document 1, the image-side lens group of the focusing group is large, resulting in insufficient miniaturization and weight reduction of the overall product. In the zoom lens described in Patent Document 2, the lens diameter of the second lens group is large, resulting in a large focusing mechanism, which also results in insufficient miniaturization and weight reduction in the radial direction.

[0008] Therefore, the objective of this invention is to provide a small and lightweight zoom lens. [Means for solving the problem]

[0009] To solve the above problems, the zoom lens according to the present invention comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear group consisting of multiple lens groups having positive refractive power as a whole, and is a zoom lens that performs magnification by changing the distance between adjacent lens groups, wherein at least the second lens group moves along the optical axis when magnification is performed, the second lens group has a cemented lens of a positive lens and a negative lens, the rear group has a Gf lens group having negative refractive power that moves along the optical axis when in focus, and a Gn lens group having negative refractive power on the image side of the Gf lens group, and the Gn lens group moves along the same trajectory as another lens group included in the rear group when magnification is performed from the wide-angle end to the telephoto end, and satisfies the following conditional expression. -5.5 < f1 / f2 < -1.0 (1) -18.0 < ffr / fw < -0.1 ·····(2) 0.1 < |fw / m2| < 2000 ·····(3) however, f1: Focal length of the first lens group f2: Focal length of the second lens group ffr: The combined focal length of all lenses positioned on the image side of the Gf lens group at the telephoto end. fw: Focal length at the wide-angle end of the zoom lens m2: Amount of movement of the second lens group along the optical axis when changing magnification from the wide-angle end to the telephoto end. Here, the moving amount is positive in the direction from the object side toward the image side.

[0010] Further, in order to solve the above problems, the imaging device according to the present invention is characterized by including the zoom lens and an imaging element that converts the optical image formed by the zoom lens into an electrical signal.

Effect of the Invention

[0011] According to the present invention, a small and lightweight zoom lens and an imaging device can be provided.

Brief Description of the Drawings

[0012] [Figure 1] It is a cross-sectional view at the wide-angle end of the zoom lens of Example 1 of the present invention. [Figure 2] It is a diagram of various aberrations at the wide-angle end of the zoom lens of Example 1. [Figure 3] It is a diagram of various aberrations in the state of the intermediate focal length of the zoom lens of Example 1. [Figure 4] It is a diagram of various aberrations at the telephoto end of the zoom lens of Example 1. [Figure 5] It is a cross-sectional view at the wide-angle end of the zoom lens of Example 2 of the present invention. [Figure 6] It is a diagram of various aberrations at the wide-angle end of the zoom lens of Example 2. [Figure 7] It is a diagram of various aberrations in the state of the intermediate focal length of the zoom lens of Example 2. [Figure 8] It is a diagram of various aberrations at the telephoto end of the zoom lens of Example 2. [Figure 9] It is a cross-sectional view at the wide-angle end of the zoom lens of Example 3 of the present invention. [Figure 10] It is a diagram of various aberrations at the wide-angle end of the zoom lens of Example 3. [Figure 11] It is a diagram of various aberrations in the state of the intermediate focal length of the zoom lens of Example 3. [Figure 12] It is a diagram of various aberrations at the telephoto end of the zoom lens of Example 3. [Figure 13] It is a cross-sectional view at the wide-angle end of the zoom lens of Example 4 of the present invention. [Figure 14] It is a diagram of various aberrations at the wide-angle end of the zoom lens of Example 4. [Figure 15] It is a diagram of various aberrations in the intermediate focal length state of the zoom lens of Example 4. [Figure 16] It is a diagram of various aberrations at the telephoto end of the zoom lens of Example 4. [Figure 17] It is a diagram schematically showing an example of the configuration of an imaging device according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the zoom lens and the imaging device according to the present invention will be described. However, the zoom lens and the imaging device described below are one aspect of the zoom lens and the imaging device according to the present invention, and the zoom lens and the imaging device according to the present invention are not limited to the following aspects.

[0014] 1. Zoom lens 1-1. Optical configuration The zoom lens is composed of, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a rear group having a positive refractive power as a whole composed of a plurality of lens groups. The rear group has a Gf lens group having a negative refractive power that moves along the optical axis during focusing, and has a Gn lens group having a negative refractive power on the image side of this Gf lens group. By adopting such a lens configuration, it is possible to make the whole small and light.

[0015] (1) First lens group The first lens group is a lens group having positive refractive power, and its specific configuration is not particularly limited as long as it has at least one positive lens. Furthermore, having at least one negative lens is preferable as it makes it easier to suppress chromatic aberration and obtain good optical performance. Furthermore, having a cemented lens of a positive lens and a negative lens is preferable as it makes it easier to suppress chromatic aberration and reduce the sensitivity of each lens.

[0016] Here, "lens group" refers to a group consisting of one or more adjacent lenses that move along the same trajectory and by the same amount along the optical axis during magnification. If a lens group consists of multiple lenses, the distance along the optical axis between each lens in that lens group shall not change during magnification. However, the distance along the optical axis between adjacent lens groups shall change during magnification.

[0017] (2) Second lens group The second lens group is a lens group with negative refractive power, and its specific configuration is not particularly limited as long as it has one or more negative lenses. Having a cemented lens of positive and negative lenses in the second lens group is preferable as it makes it easier to further suppress chromatic aberration and obtain good optical performance. Furthermore, by moving along the optical axis when changing magnification from the wide-angle end to the telephoto end, the second lens group enables miniaturization of the first lens group and a reduction in the amount of movement of other lens groups. To obtain the above effect, the second lens group moves towards the image side when changing magnification, which is effective in miniaturizing the subsequent lens groups and enables miniaturization of the entire product system.

[0018] (3) Rear group The rear group as a whole has a positive refractive power, and as long as it has three or more lens groups, its specific group configuration is not particularly limited. As long as it has at least one positive lens group and two negative lens groups, the other lens groups may have negative refractive power or positive refractive power.

[0019] By composing the rear group with three or more lens groups, the spacing between each lens group along the optical axis can be changed during zoom, thus increasing the design flexibility regarding the movable position of each lens group during zoom. As a result, it becomes easier to suppress aberration fluctuations, and a zoom lens with high optical performance can be obtained. Furthermore, by placing the aperture diaphragm within the rear group, the aperture diaphragm can be made smaller, making it easier to achieve radial miniaturization and weight reduction.

[0020] (4) Gf lens group The Gf lens group is a group of lenses with negative refractive power included in the rear group, and its specific configuration is not particularly limited as long as it contains one or more negative lenses. Furthermore, by including one or more positive lenses in the Gf lens group, it is possible to suppress the occurrence of axial chromatic aberration associated with movement during focusing and easily obtain good optical performance. In addition, it is preferable to use a cemented lens for the positive and negative lenses as it is easier to suppress sensitivity between lenses. Furthermore, it is preferable to have the positive lens and negative lens arranged from the object side as it is easier to suppress axial aberration. In addition, it is preferable to have a positive lens and a negative lens as it enables miniaturization of the entire product system. Furthermore, it is preferable that the lens on the image side of the Gf lens group has a concave shape on the image side.

[0021] (4) Gn lens group The Gn lens group is a group of lenses with negative refractive power and is positioned closer to the image than the Gf lens group. The specific configuration of the Gn lens group is not particularly limited. It is preferable that it moves along the optical axis when changing magnification from the wide-angle end to the telephoto end, and even more preferably moves toward the object. Moving toward the object allows for efficient magnification and facilitates miniaturization of the overall product length, which is preferable. Furthermore, it is preferable that the lens closest to the object in the Gn lens group has a concave shape toward the object.

[0022] 1-2.Operation (1) Multiplication The zoom lens employs the above configuration and achieves magnification by changing the distance along the optical axis between the first lens group, the second lens group, and the rear group. Preferably, the distance along the optical axis between the first and second lens groups is maximum at the telephoto end, and the distance along the optical axis between the second lens group and the rear group is minimum at the telephoto end. By moving each lens group in this way, it is easy to obtain good optical performance across the entire magnification range without having to unnecessarily increase the power.

[0023] Furthermore, it is preferable that the Gn lens group moves along the same trajectory as another lens group included in the rear group when changing magnification from the wide-angle end to the telephoto end, as this simplifies the mechanism for moving the Gn lens group and facilitates miniaturization and weight reduction of the entire product system.

[0024] (2)Focus In this zoom lens, the Gf lens group moves along the optical axis when focusing from infinity to close distance. By using the Gf lens group as the focusing group, it becomes easy to obtain a zoom lens with minimal field curvature variation across the entire range of object distances from infinity to close distance.

[0025] 1-3. Conditional expression The zoom lens should, in addition to adopting the configuration described above, satisfy at least one of the following conditional equations.

[0026] 1-3-1. Conditional expression (1) -5.5 < f1 / f2 < -1.0 (1) however, f1: Focal length of the first lens group f2: Focal length of the second lens group

[0027] The above condition (1) is a condition that defines the ratio of the combined focal length of the first lens group to the focal length of the second lens group. By satisfying condition (1), it is possible to shorten the overall optical length, and it becomes easier to miniaturize and lighten the first lens group and the second lens group, which have large outer diameters within the entire optical system.

[0028] Conversely, if the value of condition (1) falls below the lower limit, the focal length of the first lens group becomes longer than the appropriate value, making it difficult to shorten the overall optical length and reduce the extension amount of the first lens group during magnification, thus making it difficult to miniaturize and lighten the entire product system. On the other hand, if the value of condition (1) exceeds the upper limit, the combined focal length of the first lens group becomes shorter than the appropriate value, and the spherical aberration and coma aberration occurring at each surface become larger than the appropriate value. Furthermore, a large number of lenses are required for aberration correction, making it difficult to lighten the entire product system.

[0029] In order to obtain the above effect, the lower limit of conditional expression (1) is preferably -5.00, more preferably -4.75, and even more preferably -4.5. The upper limit of (1) is preferably -1.50, more preferably -2.00, and even more preferably -2.50. When adopting these preferred lower or upper limits, the equality sign (≦) may be replaced with an inequality sign (<). The same principle applies to other conditional expressions.

[0030] 1-3-2. Conditional expression (2) -18.0 < ffr / fw < -0.1 ·····(2) however, ffr: The combined focal length of all lenses in the Gf lens group positioned closer to the image side than the image side at the telephoto end. fw: Focal length at the wide-angle end of the zoom lens

[0031] Condition (2) is a condition that defines the ratio of the combined focal length of all lenses positioned on the image side of the Gf lens group at the telephoto end to the focal length of the zoom lens at the wide-angle end. By satisfying condition (2), it becomes possible to shorten the exit pupil at the telephoto end and reduce the outer diameter of the lens group close to the image plane, making it easier to miniaturize and lighten the entire product system.

[0032] Conversely, if the value of condition (2) falls below the lower limit, it indicates that the combined focal length of all lenses positioned on the image side of the Gf lens group is longer than the appropriate value. This results in a longer exit pupil at the telephoto end, making it difficult to reduce the outer diameter of the lens group close to the image plane, and thus making it difficult to miniaturize and lighten the entire product system. On the other hand, if the value of condition (2) is above the upper limit, it indicates that the combined focal length of all lenses positioned on the image side of the Gf lens group is shorter than the appropriate value. This makes it difficult to correct aberrations such as field curvature and distortion, requiring a large number of lenses for aberration correction, and thus making it difficult to lighten the entire product system.

[0033] To obtain the above effects, the lower limit of conditional equation (2) is preferably -10.0, more preferably -5.00, more preferably -4.00, and even more preferably -3.00. Furthermore, the upper limit of conditional equation (2) is preferably -0.50, and more preferably -1.00.

[0034] 1-3-3. Conditional expression (3) 0.1 < |fw / m2| < 2000.0 ·····(3) however, fw: Focal length at the wide-angle end of the zoom lens m2: Amount of movement of the second lens group along the optical axis when changing magnification from the wide-angle end to the telephoto end. However, the amount of movement is considered positive in the direction from the object to the image.

[0035] The above conditional equation (3) defines the ratio of the focal length at the wide-angle end of the zoom lens to the amount of movement of the second lens group on the optical axis when the zoom is changed from the wide-angle end to the telephoto end. The amount of movement is the difference between the position of the second lens group on the optical axis at the wide-angle end and the position of the second lens group on the optical axis at the telephoto end. The amount of movement is considered positive in the direction from the object side to the image side. Satisfying conditional equation (3) makes it easier to miniaturize the first lens group and reduce the amount of movement of each lens group.

[0036] Conversely, if the value of condition (3) falls below the lower limit, the amount of movement of the second lens group increases, making it difficult to miniaturize the entire product system. On the other hand, if the value of condition (3) exceeds the upper limit, the amount of movement of the second lens group decreases, and it becomes necessary to compensate for the change in magnification with other lens groups in order to obtain the predetermined zoom magnification. As a result, the amount of movement of other groups during magnification increases, making it difficult to miniaturize the entire product system.

[0037] To obtain the above effects, the lower limit of conditional expression (3) is preferably 1.0, more preferably 2.0, and even more preferably 3.0. Furthermore, the upper limit of conditional expression (3) is preferably 1000.0, more preferably 100.0, even more preferably 50.0, and even more preferably 20.0.

[0038] Furthermore, when changing magnification from the wide-angle end to the telephoto end, it is more preferable for the second lens group to move towards the image side. Moving the second lens group towards the image side is effective in miniaturizing the subsequent lens group, and makes it easier to miniaturize the entire product system. In this case, it is more preferable to change the above conditional equation (3) as follows. 0.1 < fw / m2 < 2000.0 (3)

[0039] 1-3-4. Conditional expression (4) -5.0 < β2t < -0.1 (4) however, β2t: Lateral magnification at the telephoto end of the second lens group

[0040] The above conditional equation (4) defines the lateral magnification at the telephoto end of the second lens group. By satisfying conditional equation (4), it is possible to shorten the overall optical length by optimizing the amount of movement of each lens group during magnification changes, and by facilitating aberration correction throughout the entire zoom range, the lens configuration can be simplified and the overall weight of the product can be reduced.

[0041] Conversely, if the value of condition (4) falls below the lower limit, it indicates that the lateral magnification of the second lens group is greater than the appropriate value. This amplifies the spherical aberration and coma aberration occurring in the first lens group beyond the appropriate value, requiring a large number of lenses for aberration correction, making it difficult to reduce the weight of the entire product. On the other hand, if the value of condition (4) is above the upper limit, it indicates that the lateral magnification of the second lens group is smaller than the appropriate value. To obtain a predetermined zoom magnification, it becomes necessary to compensate for the magnification change with lens groups other than the second lens group. This increases the amount of movement of each lens group during magnification, making it difficult to miniaturize the entire product.

[0042] To obtain the above effect, the lower limit of conditional equation (4) is preferably -4.0, more preferably -2.8, and even more preferably -2.0. Furthermore, the upper limit of conditional equation (4) is preferably -0.3, and more preferably -0.5.

[0043] 1-3-5. Conditional expression (5) 1.0 < β2t / β2w < 7.0 (5) however, β2w: Horizontal magnification at the wide-angle end of the second lens group β2t: Lateral magnification at the telephoto end of the second lens group

[0044] The above conditional equation (5) is a conditional equation for defining the ratio of the lateral magnification at the telephoto end of the second lens group to the lateral magnification at the wide-angle end of the second lens group. By satisfying conditional equation (5), the amount of movement of each lens group during magnification is optimized, making it possible to shorten the overall optical length. Furthermore, aberration correction becomes easier across the entire zoom range, simplifying the lens configuration and making it easier to reduce the weight of the entire product.

[0045] Conversely, if the value of condition (5) falls below the lower limit, the amount of movement of the second lens group during magnification becomes smaller than the appropriate value, and in order to obtain a predetermined magnification ratio, it becomes necessary to increase the amount of movement of lens groups other than the second lens group or to strengthen the refractive power. As a result, a large number of lenses are required for aberration correction, making it difficult to miniaturize and lighten the entire product system. On the other hand, if the value of condition (5) exceeds the upper limit, the amount of movement of the second lens group during magnification becomes larger than the appropriate value, making it difficult to miniaturize the entire product system.

[0046] To obtain the above effect, the lower limit of conditional expression (5) is preferably 1.50, more preferably 1.75, and even more preferably 2.00. Furthermore, the upper limit of conditional expression (5) is preferably 5.60, more preferably 4.5, and even more preferably 3.50.

[0047] 1-3-6. Conditional expression (6) -10.0 < (1-βf×βf)×βfr×βfr < -1.0·····(6) however, βf: Lateral magnification at the telephoto end of the Gf lens group βfr: The combined horizontal magnification of all lenses positioned closer to the image side than the image side of the Gf lens group at the telephoto end.

[0048] Conditional equation (6) defines the lateral magnification at the telephoto end of the Gf lens group and all lenses positioned on its image side, and the calculated value is a conditional equation for defining the so-called play magnification of the Gf lens group. By satisfying conditional equation (6), it becomes easier to optimize the amount of movement of the focus group when focusing, thereby reducing the size and weight of the entire optical system.

[0049] Conversely, if the value of condition (6) falls below the lower limit, the play ratio of the focus group becomes larger than the appropriate value, requiring the refractive power of each lens group to be increased beyond the appropriate value. As a result, a large number of lenses are required for aberration correction, making it difficult to reduce the weight of the entire product. On the other hand, if the value of condition (6) exceeds the upper limit, the play ratio of the focus group becomes smaller than the appropriate value, and the amount of movement of the focus group when focusing on an object at close range becomes large, resulting in a larger focusing mechanism and making it difficult to miniaturize the entire product.

[0050] To obtain the above effect, the lower limit of conditional equation (6) is preferably -9.30, more preferably -8.50, and even more preferably -8.00. Furthermore, the upper limit of conditional equation (6) is preferably -2.00.

[0051] 1-3-7. Conditional expression (7) 1.1 < f1 / fw < 10.0 (7)

[0052] The above conditional equation (7) is a conditional equation for defining the ratio between the focal length of the first lens group and the focal length at the wide-angle end of the zoom lens. By satisfying conditional equation (7), it becomes possible to shorten the overall optical length and easily reduce the weight of the first lens group, which has the largest outer diameter in the entire optical system.

[0053] Conversely, if the value of condition (7) falls below the lower limit, the focal length of the first lens group becomes shorter than the optimal value. While this is effective in reducing the overall optical length, the spherical aberration and coma aberration occurring at each surface become larger than the optimal value. As a result, a large number of lenses are required for aberration correction, making it difficult to reduce the weight of the entire product system. On the other hand, if the value of condition (7) exceeds the upper limit, the combined focal length of the first lens group becomes longer than the optimal value. This makes it difficult to shorten the overall optical length and reduce the extension amount of the first lens group during magnification, making it difficult to reduce the overall size of the product system.

[0054] To obtain the above effect, the lower limit of conditional equation (7) is preferably 1.50. Furthermore, the upper limit of conditional equation (7) is preferably 6.00, more preferably 5.00, and even more preferably 4.00.

[0055] 1-3-8. Conditional expression (8) 1.65 < Nd1n < 2.50 (8) however, Nd1n: The refractive index of the negative lens with the highest refractive index in the first lens group.

[0056] Condition (8) is a condition for defining the refractive index of the negative lens with the highest refractive index in the first lens group. By satisfying condition (8), it becomes easier to optimize the spherical aberration and coma aberration occurring in the first lens group, thereby reducing the size and weight of the entire product system.

[0057] Conversely, if the value of condition (8) falls below the lower limit, the over-correction of spherical aberration occurring in the negative lens becomes insufficient compared to the under-correction of spherical aberration occurring in the first lens group. As a result, a large number of lenses are required in subsequent lens groups to correct the aberrations, making it difficult to reduce the weight of the entire product. On the other hand, if the value of condition (8) exceeds the upper limit, the over-correction of spherical aberration occurring in the negative lens becomes insufficient compared to the under-correction of spherical aberration occurring in the first lens group. As a result, a large number of lenses are required in subsequent lens groups to correct the aberrations, making it difficult to reduce the weight of the entire product.

[0058] To obtain the above effect, the lower limit of conditional equation (8) is preferably 1.70, and more preferably 1.75. Furthermore, the upper limit of conditional equation (8) is preferably 2.10, more preferably 2.0, even more preferably 1.94, and even more preferably 1.90.

[0059] 2. Imaging device Next, the imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by comprising the zoom lens according to the present invention and an image sensor that converts the optical image formed by the zoom lens into an electrical signal. Preferably, the image sensor is provided on the image side of the zoom lens.

[0060] There are no particular limitations on the image sensor, and solid-state image sensors such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors can also be used. The imaging device according to the present invention is suitable for imaging devices using such solid-state image sensors, such as digital cameras and video cameras. Furthermore, the imaging device can be applied to various imaging devices such as single-lens reflex cameras, mirrorless cameras, digital still cameras, surveillance cameras, in-vehicle cameras, and drone cameras. These imaging devices may be interchangeable-lens imaging devices or fixed-lens imaging devices in which the lens is fixed to the housing. In particular, the zoom lens according to the present invention is suitable for zoom lenses in imaging devices equipped with large image sensors such as full-frame sensors. Since the zoom lens is generally small and lightweight and has high optical performance, high-quality images can be obtained even when used as a zoom lens for such imaging devices.

[0061] Figure 17 is a schematic diagram showing an example of the configuration of the imaging device 1. The camera 2 has a detachable zoom lens 3, an image sensor 21 positioned on the imaging plane IP of the zoom lens 3, and a cover glass 22 positioned on the object side of the image sensor 21. The zoom lens 3 has an aperture diaphragm 31.

[0062] Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples. [Examples]

[0063] (1) Optical configuration Figure 1 shows a cross-sectional view of the zoom lens of Example 1. As shown in Figure 1, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a rear group consisting of multiple groups that together have positive refractive power. The rear group is composed of, in order from the object side, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. The third lens group G3 has an aperture diaphragm S. Here, the fourth lens group G4 is a Gf lens group that moves along the optical axis when focused, and the fifth lens group is a Gn lens group.

[0064] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 each move toward the object along the optical axis. In addition, the third lens group G3 and the fifth lens group G5 move along the same trajectory. The configuration of each lens group is described below.

[0065] The first lens group G1 consists of a cemented lens formed by joining a negative meniscus lens L1 and a positive meniscus lens L2, with the convex surface facing the object, and a biconvex lens L3, in that order from the object side.

[0066] The second lens group G2 consists of, in order from the object side, a negative meniscus lens L4 and a positive meniscus lens L5, both with their convex surfaces facing the object, a cemented lens formed by joining a biconcave lens L6 and a biconvex lens L7, and a negative meniscus lens L8 with its concave surface facing the object.

[0067] The third lens group G3 consists of, in order from the object side, a biconvex lens L9, a biconvex lens L10, a bonded lens formed by joining a biconvex lens L11 and a biconcave lens L12, an aperture diaphragm S, a bonded lens formed by joining a negative meniscus lens L13 and a biconvex lens L14, a biconvex lens L15, a biconcave lens L16, and a biconvex lens L17.

[0068] The fourth lens group G4 consists of a cemented lens formed by joining a positive meniscus lens L18 and a negative meniscus lens L19 with its concave surface facing the image side, in order from the object side.

[0069] The fifth lens group G5 consists of a negative meniscus lens L20 with a concave surface on the object side. This lens L20 has a composite aspherical surface.

[0070] In Figure 1, "I" represents the image plane, specifically the imaging surface of a solid-state image sensor such as a CCD sensor or CMOS sensor, or the film surface of a silver halide film. Furthermore, a cover glass CG is provided on the object side of I. This is the same for the cross-sectional lens diagrams shown in other embodiments, so further explanation will be omitted.

[0071] (2) Numerical Examples Next, we will describe a numerical example in which the specific values ​​of the zoom lens are applied. Below, we show the "Lens Data," "Specifications Table," "Variable Interval," "Aspherical Coefficient," and "Lens Group Data." In addition, the values ​​of each conditional expression (Table 1) and the various numerical values ​​used to determine the values ​​of each conditional expression (Table 2) are shown together after Example 4.

[0072] In the "Lens Data" column, "Surface Number" indicates the order of the lens surfaces counted from the object side, "r" is the radius of curvature of the lens surface, "d" is the lens thickness or air gap on the optical axis, "nd" is the refractive index at the d line (wavelength λ=587.6nm), and "νd" is the Abbe number at the d line. In the "Surface Number" column, "ASPH" following the surface number indicates that the lens surface is aspherical, and "S" indicates that the surface is an aperture diaphragm. In the "d" column, "d(0)", "d(6)", etc., indicate that the spacing of the lens surfaces on the optical axis is a variable spacing that changes during magnification. In the radius of curvature column, "inf." means infinity, and indicates that the lens surface is planar.

[0073] In the "Specifications Table," "f" represents the focal length of the zoom lens, "FNo." is the F-number, and "ω" is the half-angle of view. The values ​​shown are for the wide-angle end, intermediate focal length, and telephoto end, respectively.

[0074] In the "Variable Interval" section, the values ​​for infinity focus at the wide-angle end, intermediate focal length, and telephoto end are shown, respectively. The same applies to other embodiments.

[0075] The "aspheric coefficient" indicates the aspheric coefficient when the aspheric shape is defined as follows: where x is the displacement from the reference plane in the direction of the optical axis, r is the radius of paraxial curvature, H is the height from the optical axis in the direction perpendicular to the optical axis, k is the conicity coefficient, and An is the nth-order aspheric coefficient. Also, in the table of "aspheric coefficients", "E±XX" represents exponential notation, and "×10 ±XX It means "...".

[0076]

number

[0077] The items in these tables are the same as those in the tables shown in other examples, so we will omit further explanation below.

[0078] Furthermore, Figures 2, 3, and 4 show the longitudinal aberration diagrams when the zoom lens is in focus on an object at infinity at its wide-angle end, intermediate focal length, and telephoto end. The longitudinal aberration diagrams shown in each figure, from left to right, represent spherical aberration (mm), astigmatism (mm), and distortion (%), respectively. In the spherical aberration diagram, the solid line represents spherical aberration at the d line (wavelength 587.56 nm), and the dashed line represents spherical aberration at the g line (wavelength 435.84 nm). In the astigmatism diagram, the vertical axis is half-angle of view (ω), and the horizontal axis is defocus, with the solid line representing the sagittal image plane (S) at the d line and the dashed line representing the meridional image plane (T) at the d line. In the distortion diagram, the vertical axis is half-angle of view (ω), and the horizontal axis is distortion. These matters are the same for the aberration diagrams shown in other embodiments, so further explanation is omitted below.

[0079] (Lens data) Face number RD Nd νd 1 140.280 1.000 1.83400 37.34 2 71.818 5.191 1.49700 81.61 3 1453.759 0.200 4 86.386 4.987 1.49700 81.61 5 -671.717 D(5) 6 279.897 0.800 1.87070 40.73 7 31.807 3.435 8 34.685 2.449 1.85478 24.80 9 48.743 3.732 10 -54.863 0.800 1.72916 54.67 11 52.358 3.920 1.85478 24.80 12 -122.362 0.937 13 -54.826 0.800 1.87070 40.73 14 -137.141 D(14) 15 88.192 3.216 1.63854 55.45 16 -126.808 0.200 17 61.272 2.938 1.56883 56.04 18 -1597.002 0.200 19 40.271 4.336 1.61800 63.39 20 -100.891 0.800 1.95375 32.32 21 76.735 12.860 22S inf. 5.980 23 78.059 0.800 1.95375 32.32 24 16.446 5.028 1.61800 63.39 25 -160.736 0.200 26 95.695 2.592 1.63930 44.87 27 -78.586 1.251 28 -27.998 0.800 1.72916 54.67 29 69.575 0.200 30 41.954 5.336 1.65412 39.68 31 -27.825 D(31) 32 45.168 2.181 1.84666 23.78 33 102.549 0.800 1.72916 54.67 34 21.310 D(34) 35ASPH -30.909 0.100 1.51460 49.96 36 -35.423 0.800 1.59349 67.00 37 -88.558 D(37) 38 inf. 2.500 1.51680 64.20 Image plane inf. 1.000

[0080] (Specifications table) Wide-angle end, Mid-range, Telephoto end f 51.552 122.4417 290.9854 FNo. 4.7089 6.4897 6.4952 ω 23.4944 9.7363 4.1286

[0081] (Variable interval) Wide-angle end, Mid-range, Telephoto end D(5) 1.0000 29.5878 60.1049 D(14) 40.7065 16.2511 1.0000 D(31) 0.9807 9.3356 8.9082 D(34) 30.4459 22.091 22.5184 D(37) 14.4999 32.4611 49.0997

[0082] (Aspherical coefficient) Surface number K A4 A6 A8 A10 A12 35 0.0000 7.03119E-06 9.43985E-09 7.14036E-12 7.39190E-15 1.72441E-17

[0083] (Lens group data) Group number Focal length G1 135.967 G2 -31.217 G3 41.088 G4 -64.284 G5 -82.605 [Examples]

[0084] (1) Optical configuration Figure 5 shows a cross-sectional view of the zoom lens of Example 2. As shown in Figure 5, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a rear group consisting of multiple groups having positive refractive power as a whole. The rear group is composed of, in order from the object side, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. The fourth lens group G4 has an aperture diaphragm S. Here, the fifth lens group G5 is a Gf lens group that moves along the optical axis when focused, and the sixth lens group is a Gn lens group.

[0085] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, and the third, fourth, fifth, and sixth lens groups G3, G4, G5, and G6 each move toward the object along the optical axis. In addition, the fourth lens group G4 and the sixth lens group G6 move along the same trajectory. The configuration of each lens group is described below.

[0086] The first lens group G1 consists of a bonded lens formed by joining a negative meniscus lens L1 and a biconvex lens L2, with the convex surface facing the object, and a biconvex lens L3, in that order from the object side.

[0087] The second lens group G2 consists of a bonded lens formed by joining a biconcave lens L4, a biconcave lens L5, and a biconvex lens L6, in that order from the object side, and a negative meniscus lens L7 with its concave surface facing the object side.

[0088] The third lens group G3 consists of a bonded lens formed by joining a biconvex lens L8, a biconvex lens L9, a biconvex lens L10, and a biconcave lens L11, in that order from the object side.

[0089] The fourth lens group G4 consists of an aperture diaphragm S, a cemented lens formed by joining a negative meniscus lens L12 and a biconvex lens L13, a negative meniscus lens L14, a cemented lens formed by joining a positive meniscus lens L15 and a biconcave lens L16, and a biconvex lens L17. These lenses L16 and L17 have an aspherical shape.

[0090] The fifth lens group G5 consists of a cemented lens formed by joining a positive meniscus lens L18 and a negative meniscus lens L19 with its concave surface facing the image side, in order from the object side.

[0091] The sixth lens group G6 consists of a negative meniscus lens L20 with a concave surface on the object side. This lens L20 has a composite aspherical surface.

[0092] (2) Numerical Examples Next, we will show examples of numerical implementations using the specific values ​​of the zoom lens. Figures 6, 7, and 8 also show longitudinal aberration diagrams when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens.

[0093] (Lens data) Face number RD Nd νd 1 217.1079 1.0000 1.87070 40.73 2 90.4950 7.4730 1.43700 95.10 3 -386.3192 0.2000 4 90.0885 6.9871 1.49700 81.61 5 -650.7101 D(5) 6 -603.1690 0.8000 1.91082 35.25 7 39.0857 4.6492 8 -62.4702 0.8000 1.59282 68.62 9 42.1177 5.6943 1.85478 24.80 10 -74.7101 1.3563 11 -44.7356 0.8000 1.91082 35.25 12 -102.6544 D(12) 13 90.6161 3.4091 1.61800 63.39 14 -280.4369 0.2000 15 47.1512 5.7492 1.49700 81.61 16 -506.8687 8.8446 17 32.8121 5.4460 1.61800 63.39 18 -118.0118 0.8000 2.00100 29.13 19 87.9349 D(19) 20S inf. 7.1522 21 67.4803 0.8000 2.00100 29.13 22 16.9646 6.6008 1.61340 44.27 23 -21.7845 0.8000 2.00100 29.13 24 -65.7583 1.0000 25 -77.4598 3.2111 1.85478 24.80 26 -21.8522 0.8000 1.77387 47.25 27ASPH 39.7020 1.2050 28ASPH 28.9875 5.8563 1.63930 44.87 29 -31.6072 D(29) 30 44.6723 2.5740 1.85478 24.80 31 195.7795 0.8000 1.72916 54.67 32 20.5423 D(32) 33ASPH -22.5854 0.1000 1.51460 49.96 34 -26.4686 0.8000 1.84263 42.59 35 -44.1143 D(35) 36 inf. 2.5000 1.51680 64.20 Image plane inf. 1.0000

[0094] (Specifications table) Wide-angle end, Mid-range, Telephoto end f 51.5451 141.3119 387.9155 FNo. 4.6040 6.0190 6.4986 ω 23.3081 8.4793 3.1194

[0095] (Variable interval) Wide-angle end, Mid-range, Telephoto end D(5) 1.0000 37.3753 75.6505 D(12) 51.0014 22.1315 1.0000 D(19) 1.5339 3.2464 6.7679 D(29) 0.9845 6.6961 3.0860 D(32) 26.5718 20.8603 24.4704 D(35) 14.4998 36.1300 49.7531

[0096] (Aspherical coefficient) Surface number K A4 A6 A8 A10 A12 27 0.0000 -5.50054E-06 6.48593E-09 -9.01927E-11 -4.13584E-15 1.99064E-15 28 0.0000 -1.59705E-05 6.66374E-09 1.16544E-11 -6.99629E-13 3.75875E-15 33 0.0000 1.43601E-05 2.28089E-08 2.57195E-11 -5.45627E-14 4.59464E-16

[0097] (Lens group data) Group number Focal length G1 150.777 G2 -35.087 G3 39.769 G4 99.715 G5 -63.536 G6 -63.392 [Examples]

[0098] (1) Optical configuration Figure 9 shows a cross-sectional view of the zoom lens of Example 3. As shown in Figure 9, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a rear group consisting of multiple groups that together have positive refractive power. The rear group is composed of, in order from the object side, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. The aperture diaphragm S is placed in the third lens group G3. Here, the fourth lens group G4 is a Gf lens group that moves along the optical axis when focused, and the fifth lens group is a Gn lens group.

[0099] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 each move toward the object along the optical axis. In addition, the third lens group G3 and the fifth lens group G5 move along the same trajectory. The configuration of each lens group is described below.

[0100] The first lens group G1 consists of a bonded lens formed by joining a negative meniscus lens L1 and a biconvex lens L2, with the convex surface facing the object side, in that order from the object side.

[0101] The second lens group G2 consists of, in order from the object side, a cemented lens formed by joining a biconvex lens L3 and a biconcave lens L4, and a negative meniscus lens L5 with its concave surface facing the object side.

[0102] The third lens group G3 consists of, in order from the object side, a biconvex lens L6, a bonded lens formed by joining a biconvex lens L7 and a biconcave lens L8, an aperture diaphragm S, a bonded lens formed by joining a negative meniscus lens L9 and a biconvex lens L10, a biconcave lens L11, and a biconvex lens L12.

[0103] The fourth lens group G4 consists of a bonded lens formed by joining a biconvex lens L13 and a biconcave lens L14 on the image side, in order from the object side.

[0104] The fifth lens group G5 consists of a negative meniscus lens L15 with a concave surface on the object side. This lens L15 has a composite aspherical surface.

[0105] (2) Numerical Examples Next, we will show examples of numerical implementations using the specific values ​​of the zoom lens. Figures 10, 11, and 12 also show longitudinal aberration diagrams when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens.

[0106] (Lens data) Face number RD Nd νd 1 97.3810 1.0000 1.83400 37.34 2 65.3564 6.0969 1.49700 81.61 3 -357.4593 D(3) 4 521.6104 3.6395 1.84666 23.78 5 -56.0589 0.8000 1.72916 54.67 6 71.2731 3.1101 7 -55.1365 0.8000 1.83481 42.72 8 -607.3141 D(8) 9 65.5883 3.8714 1.63854 55.45 10 -88.9316 0.2000 11 35.7714 4.9105 1.61997 63.88 12 -78.6426 0.8000 1.90366 31.34 13 91.4486 13.4138 14S inf. 5.9970 15 29.3555 0.8000 1.90366 31.34 16 12.8554 5.3881 1.61997 63.88 17 -1289.1248 1.0948 18 -39.1085 0.8000 1.80420 46.50 19 24.8823 0.2000 20 22.8459 7.0000 1.68893 31.16 21 -31.8355 D(21) 22 103.1500 2.2711 1.71736 29.50 23 -179.1975 0.8000 1.48749 70.44 24 19.2094 D(24) 25ASPH -59.7119 0.1000 1.51460 49.96 26 -84.0434 0.8000 1.83481 42.72 27 -210.1086 D(27) 28 inf. 2.5000 1.51680 64.20 Image plane inf. 1.0000

[0107] (Specifications table) Wide-angle end, Mid-range, Telephoto end f 72.1249 144.9063 290.9111 FNo. 4.5378 5.7122 6.6499 ω 17.0633 8.3186 4.1549

[0108] (Variable interval) Wide-angle end, Mid-range, Telephoto end D(3) 1.0000 43.9217 78.1773 D(8) 42.9273 20.097 1.0000 D(21) 0.9934 4.8635 6.9051 D(24) 33.1863 29.3162 27.2746 D(27) 14.4999 27.3721 44.2499

[0109] (Aspherical coefficient) Surface number K A4 A6 A8 A10 A12 25 0.0000 7.77961E-06 2.18096E-09 2.15496E-11 -5.60681E-14 8.26596E-17

[0110] (Lens group data) Group number Focal length G1 208.489 G2 -48.948 G3 41.843 G4 -59.501 G5 -118.579 [Examples]

[0111] (1) Optical configuration Figure 13 shows a cross-sectional view of the zoom lens of Example 4. As shown in Figure 13, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a rear group consisting of multiple groups having positive refractive power as a whole. The rear group is composed of, in order from the object side, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power. The third lens group G3 has an aperture diaphragm S. Here, the fifth lens group G5 is a Gf lens group that moves along the optical axis when focused, and the seventh lens group is a Gn lens group.

[0112] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, and the third, fourth, fifth, sixth, sixth, and seventh lens groups G3, G4, G5, G6, and G7 each move toward the object along the optical axis. The configuration of each lens group is described below.

[0113] The first lens group G1 consists of a bonded lens formed by joining a negative meniscus lens L1 and a biconvex lens L2, with the convex surface facing the object side, in that order from the object side.

[0114] The second lens group G2 consists of a bonded lens formed by joining a biconcave lens L3 and a positive meniscus lens L4, in that order from the object side.

[0115] The third lens group G3 consists of, in order from the object side, a biconvex lens L5, a biconvex lens L6, a bonded lens formed by joining a biconcave lens L7, and an aperture diaphragm S.

[0116] The fourth lens group G4 consists of a biconvex lens L8.

[0117] The fifth lens group G5 consists of a cemented lens formed by joining a positive meniscus lens L9 and a negative meniscus lens L10 with its concave surface facing the image side, in order from the object side.

[0118] The sixth lens group G6 consists of a positive meniscus lens L11 with a concave surface on the object side.

[0119] The seventh lens group G7 consists of, in order from the object side, a cemented lens formed by joining a positive meniscus lens L12 and a biconcave lens L13.

[0120] The lenses in the Gf lens group that are positioned closer to the image side than the image side are the sixth lens group G6 and the seventh lens group G7.

[0121] (2) Numerical Examples Next, we will show examples of numerical implementations using the specific values ​​of the zoom lens. Furthermore, Figures 14, 15, and 16 show longitudinal aberration diagrams when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens.

[0122] (Lens data) Face number RD Nd νd 1 80.2310 1.2000 1.65412 39.68 2 51.4611 6.9283 1.49700 81.61 3 -588.1180 D(3) 4 -83.1445 0.8000 1.77250 49.60 5 34.3555 3.1575 1.84666 23.78 6 93.2074 D(6) 7 42.4229 4.8058 1.48749 70.44 8 -75.5189 0.2000 9 36.3497 4.5183 1.48749 70.44 10 -98.8617 0.8000 1.90366 31.34 11 72.1939 2.0261 12S inf. D(12) 13ASPH 190.4294 2.6151 1.51680 64.20 14 -106.2288 D(14) 15 56.7162 1.5046 1.61340 44.27 16 61.3493 0.8000 1.49700 81.61 17 26.7503 D(17) 18 -167.6227 2.8673 1.51680 64.20 19 -35.1637 D(19) 20 -35.9906 3.1114 1.90200 25.26 21 -23.0202 0.8000 1.72916 54.67 22 157.9046 D(22) 23 inf. 2.5000 1.51680 64.20 Image plane inf. 1.0000

[0123] (Specifications table) Wide-angle end, Mid-range, Telephoto end f 73.0328 129.9833 289.7757 FNo. 4.2908 4.9963 6.4530 ω 16.5755 9.1923 4.1390

[0124] (Variable interval) Wide-angle end, Mid-range, Telephoto end D(3) 1.9648 38.6419 63.8017 D(6) 34.9313 23.3251 1.0000 D(12) 1.0000 4.1649 18.9593 D(14) 6.7538 1.0043 1.0187 D(17) 15.7987 23.2263 27.3620 D(19) 24.9698 20.1269 1.1823 D(22) 14.5000 26.7013 53.5073

[0125] (Aspherical coefficient) Surface number K A4 A6 A8 A10 A12 13 0.0000 -6.15279E-06 -8.73064E-10 -3.52033E-11 2.16752E-13 0.00000E+00

[0126] (Lens group data) Group number Focal length G1 168.411 G2 -61.141 G3 61.649 G4 132.344 G5 -48.792 G6 85.474 G7 -45.269

[0127] [Table 1] Example 1 Example 2 Example 3 Example 4 Conditional expression (1) f1 / f2 -4.356 -4.297 -4.259 -2.754 Conditional expression (2) ffr / fw -1.602 -1.230 -1.644 -1.337 Conditional expression (3)|fw / m2| 10.095 5.418 5.923 14.388 Conditional expression (4) β2t -0.859 -1.003 -0.673 -1.637 Conditional expression (5) β2t / β2w 2.627 3.134 2.061 2.656 Condition (6) (1-βf×βf)×βfr×βfr -6.152 -7.582 -5.996 -2.963 Conditional expression (7) f1 / fw 2.637 2.925 2.891 2.306 Conditional expression (8)Nd1n 1.834 1.871 1.834 1.654 [Industrial applicability]

[0128] The zoom lens according to the present invention can be used, for example, in film cameras, digital still cameras, and digital cameras. It can be suitably applied as an imaging optical system in imaging devices such as digital video cameras. [Explanation of symbols]

[0129] Gr...rear group Gff ···Gff lens group Gf ···Gf lens group (focusing group) Gfr ···Gfr lens group S ···Opening diaphragm CG ···Cover glass I...image plane G1 ···First lens group G2 ···Second lens group G3 ···Third lens group G4 ···4th lens group G5 ···5th lens group G6 ···6th lens group G7 ···7th lens group 1. Imaging device 2 ···Camera 3 ···Zoom lens 21 ···Image sensor 22 ···Cover glass 31 ···Aperture diaphragm IP...Image plane

Claims

1. A zoom lens comprising, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear group consisting of multiple lens groups having positive refractive power as a whole, wherein magnification is achieved by changing the distance between adjacent lens groups. During magnification, at least the second lens group moves along the optical axis. The first lens group has the negative lens closest to the object, The second lens group has a cemented lens consisting of a positive lens and a negative lens. The aforementioned group is, It has a group of Gf lenses that have a negative refractive force that moves along the optical axis when focused, The Gn lens group has a negative refractive power on the image side of the Gf lens group, The aforementioned Gn lens group moves along the same trajectory as another lens group included in the rear group when the magnification changes from the wide-angle end to the telephoto end. A zoom lens characterized by satisfying the following condition. -4.75 < f1 / f2 < -1.0 (1) -18.0 < ffr / fw < -0.1 (2) 0.1 < |fw / m2 | < 2000 (3) however, f1: Focal length of the first lens group f2: Focal length of the second lens group ffr: The combined focal length of all lenses positioned on the image side of the Gf lens group at the telephoto end. fw: Focal length at the wide-angle end of the zoom lens. m2: Amount of movement of the second lens group along the optical axis when changing magnification from the wide-angle end to the telephoto end. Here, the amount of movement is defined as positive in the direction from the object side to the image side.

2. A zoom lens comprising, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear group consisting of multiple lens groups having positive refractive power as a whole, wherein magnification is achieved by changing the distance between adjacent lens groups. During magnification, at least the second lens group moves along the optical axis. The first lens group has at least one negative lens, The second lens group has a cemented lens consisting of a positive lens and a negative lens. The aforementioned group is, It has a group of Gf lenses that have a negative refractive force that moves along the optical axis when focused, The Gn lens group has a negative refractive power on the image side of the Gf lens group, The aforementioned Gn lens group moves along the same trajectory as another lens group included in the rear group when the magnification changes from the wide-angle end to the telephoto end. A zoom lens characterized by satisfying the following condition. -4.75 < f1 / f2 < -1.0 (1) -18.0 < ffr / fw < -0.1 (2) 0.1 < |fw / m2 | < 2000 (3) 1.834 ≦ Nd1n < 2.50 (8) however, f1: Focal length of the first lens group f2: Focal length of the second lens group ffr: The combined focal length of all lenses positioned on the image side of the Gf lens group at the telephoto end. fw: Focal length at the wide-angle end of the zoom lens. m2: Amount of movement of the second lens group along the optical axis when changing magnification from the wide-angle end to the telephoto end. Here, the amount of movement is defined as positive in the direction from the object side to the image side. Nd1n: Refractive index of the negative lens with the highest refractive index in the first lens group.

3. A zoom lens according to claim 1 or claim 2 that satisfies the following conditional expression. -10.0 < (1 - βf × βf) × βfr × βfr < -1.0 .....(6) however, βf: Lateral magnification at the telephoto end of the Gf lens group. βfr: The combined horizontal magnification of all lenses positioned on the image side of the Gf lens group at the telephoto end.

4. The zoom lens according to any one of claims 1 to 3, wherein the Gf lens group includes at least one cemented lens.

5. The zoom lens according to any one of claims 1 to 4, wherein the Gf lens group comprises one negative lens and one positive lens.

6. The zoom lens according to any one of claims 1 to 5, wherein the Gf lens group has a positive lens and a negative lens in order from the object side.

7. The zoom lens according to any one of claims 1 to 6, wherein the aperture diaphragm is arranged within the rear group.

8. The zoom lens according to any one of claims 1 to 7, wherein the Gn lens group moves toward the object when the zoom is changed from the wide-angle end to the telephoto end.

9. An imaging device comprising a zoom lens according to any one of claims 1 to 8, and an image sensor that converts an optical image formed by the zoom lens into an electrical signal.

Images