Zoom lens and imaging device

Abstract

To provide a zoom lens which has a high zoom ratio, allows for reducing the shortest shooting distance, and offers high optical performance, and to provide an image capturing device.SOLUTION: A zoom lens is provided, comprising, 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 having positive refractive power as a whole. The zoom lens has specific optical characteristics represented by three expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventional zoom lenses are known to have high magnifications for mirrorless single-lens cameras, digital still cameras, security cameras, and the like.

[0003] As for such zoom lenses, for example, a zoom lens system in which the signs of the refractive index of each lens group are positive, negative, positive, positive, in order from the object side is known (see, for example, Patent Document 1).

[0004] Also, an imaging lens is known in which the signs of the refractive index of each lens group, in order from the object side, are positive-negative-positive-positive or positive-negative-positive-positive (see, for example, Patent Document 2).

[0005] Also, a zoom lens is known in which the signs of the refractive index of each lens group are positive, negative, positive, negative, positive, in order from the object side (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-176229 [Patent Document 2] International Publication No. 2013-151153 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-195749 Summary of the Invention [Problem to be solved by the invention]

[0007] As the number of pixels in solid-state image sensors mounted on cameras has increased in recent years, zoom lenses are being required to have even higher performance than before, and particularly high-magnification zoom lenses are being required to have high performance that allows them to be used for multiple purposes.

[0008] The zoom lens system described in Patent Document 1 has a low zoom magnification, and as the magnification increases, it becomes more difficult to maintain the clearance between the lens groups, making it difficult to shoot at the shortest shooting distance and to achieve high optical performance at that time.

[0009] In the imaging lens described in Patent Document 2, the zoom ratio of the second lens group is small, so the movement amount of the second lens group is large, which reduces the movement range of the focus group accordingly, making it difficult to shoot at the shortest shooting distance and maintain performance at that time.

[0010] In the zoom lens described in Patent Document 3, the second lens group has a small variable magnification ratio, so the third lens group is also moved to achieve a high magnification of the zoom lens. However, this reduces the range of movement of the focus group, making it difficult to shoot at the shortest shooting distance and maintain performance at that distance.

[0011] As described above, as the magnification of a zoom lens increases, it becomes difficult to shorten the minimum shooting distance and correct aberrations to maintain performance.

[0012] One aspect of the present invention has been made in consideration of the above-described problems, and it is an object of the present invention to provide a zoom lens and an imaging device that have a high magnification, are capable of shortening the minimum shooting distance, and have high optical performance. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, a zoom lens according to one aspect of the present invention is a zoom lens that is composed of, 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 lens group having positive refractive power as a whole, and performs a magnification change operation by changing the spacing between adjacent lens groups, the rear group includes, in order from the object side, at least a third lens group, a fourth lens group, and a fifth lens group; the third lens group is composed of, in order from the object side, a positive lens, a negative lens, and a positive lens; The first lens group does not move during zooming, any one of the third lens group, the fourth lens group, and the fifth lens group is a focus group that performs focusing by moving on an optical axis, A zoom lens that satisfies the following formula: 0.3≦|ff| / M<0.8 (1) 6.0≦ft / f3≦15.0 (4)' 3.0≦|f1 / f2|≦6.72····(5)' however, M: Square root of the product of fw and ft ff: focal length of the focus group fw: focal length at the wide-angle end of the zoom lens when focused at infinity ft: focal length at the telephoto end of the zoom lens when focused at infinity f1: focal length of the first lens group f2: focal length of the second lens group f3: focal length of the third lens group

[0014] In order to solve the above-mentioned problem, an imaging device according to one aspect of the present invention includes the above-mentioned zoom lens and an imaging element provided on the image side of the zoom lens, which converts an optical image formed by the zoom lens into an electrical signal. [Effects of the Invention]

[0015] According to one aspect of the present invention, it is possible to provide a zoom lens and an imaging device that have a high magnification, can shorten the minimum shooting distance, and has high optical performance. [Brief explanation of the drawings]

[0016] [Figure 1]1A and 1B are diagrams illustrating the optical configuration of the zoom lens of Example 1 when focusing on infinity at the wide-angle end and the telephoto end. [Figure 2] FIG. 4 is a diagram showing longitudinal aberration when the zoom lens of Example 1 is focused on infinity at the wide-angle end. [Figure 3] FIG. 4 is a diagram showing longitudinal aberration when the zoom lens of Example 1 is in an intermediate focal length state and focused on infinity. [Figure 4] FIG. 4 is a diagram showing longitudinal aberration when the zoom lens of Example 1 is focused on infinity at the telephoto end. [Figure 5] 10A and 10B are diagrams illustrating the optical configuration of the zoom lens of Example 2 when focusing on infinity at the wide-angle end and the telephoto end. [Figure 6] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 2 is focused on infinity at the wide-angle end. [Figure 7] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 2 is in an intermediate focal length state and focused on infinity. [Figure 8] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 2 is focused on infinity at the telephoto end. [Figure 9] 10A and 10B are diagrams illustrating the optical configuration of a zoom lens according to a third embodiment when focused on infinity at the wide-angle end and the telephoto end. [Figure 10] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 3 is focused on infinity at the wide-angle end. [Figure 11] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 3 is in an intermediate focal length state and focused on infinity. [Figure 12] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 3 is focused on infinity at the telephoto end. [Figure 13] 10A and 10B are diagrams illustrating the optical configuration of the zoom lens of Example 4 when focusing on infinity at the wide-angle end and the telephoto end. [Figure 14] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 4 is focused on infinity at the wide-angle end. [Figure 15]FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 4 is in an intermediate focal length state and focused on infinity. [Figure 16] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 4 is focused on infinity at the telephoto end. [Figure 17] 10A and 10B are diagrams illustrating the optical configuration of the zoom lens of Example 5 when focusing on infinity at the wide-angle end and the telephoto end. [Figure 18] FIG. 11 is a diagram showing longitudinal aberration when the zoom lens of Example 5 is focused on infinity at the wide-angle end. [Figure 19] FIG. 10 is a diagram showing longitudinal aberration when the zoom lens of Example 5 is in an intermediate focal length state and focused on infinity. [Figure 20] FIG. 11 is a diagram showing longitudinal aberration when the zoom lens of Example 5 is focused on infinity at the telephoto end. [Figure 21] 1 is a diagram schematically illustrating an example of the configuration of an imaging device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A zoom lens and an imaging device according to an embodiment of the present invention will be described below. More specifically, this embodiment relates to a zoom lens suitable for use in the imaging optical system of digital input / output devices such as mirrorless single-lens cameras, security cameras, digital still cameras, and medical cameras that use solid-state imaging devices. However, the zoom lens and imaging device described below are merely one aspect of the zoom lens and imaging device according to the present invention, and the zoom lens and imaging device according to the present invention are not limited to the following aspects.

[0018] 1. Zoom Lens 1-1. Optical configuration A zoom lens according to an embodiment of the present invention is composed of, 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 lens group having positive refractive power. The rear lens group includes, in order from the object side, at least a third lens group, a fourth lens group, and a fifth lens group. Any one of the third lens group, the fourth lens group, and the fifth lens group is a focus group. The zoom lens performs a magnification change by changing the spacing between adjacent lens groups. By appropriately arranging the lenses and power distribution in the optical system, the zoom lens has a high magnification, is capable of shortening the minimum focusing distance, and has high optical performance.

[0019] In this specification, "shortening the minimum shooting distance" means shortening the distance from the lens surface of the lens closest to the object to which the object can be photographed when taking pictures at close range. The "shortest shooting distance" can also be called the shortest focusing distance.

[0020] In this specification, the term "lens group" refers to a collection of one or more lenses that work together during a magnification change. A lens group may consist of one lens, or may consist of multiple lenses. For example, a lens group may include a cemented lens in which multiple single lenses are integrated without an air gap, or a compound lens in which a single lens and resin are integrated without an air gap. The lenses in a lens group move while maintaining their relative positional relationship during a magnification change. The magnification change is performed by changing the spacing between lens groups, and the spacing between lenses belonging to the same lens group does not change during a magnification change.

[0021] Furthermore, in this specification, a "lens" does not only refer to a single lens, but may also refer to a cemented lens or a compound lens. For example, a cemented lens formed by cementing two single lenses together will be described as a single lens. Furthermore, a compound lens formed by compounding a single lens with resin will be described as a single lens.

[0022] (1) First lens group The first lens group is the lens group closest to the object in the zoom lens and has positive refractive power. The first lens group only needs to have positive refractive power as a whole, and it only needs to have at least one lens with positive refractive power. The configuration of the lenses in the first lens group can be determined appropriately within the range in which the first lens group has positive refractive power as a whole.

[0023] (2) Second lens group The second lens group is a lens group disposed on the image side of the first lens group and has negative refractive power. The second lens group only needs to have negative refractive power as a whole, and it only needs to have at least one lens with negative refractive power. The configuration of the lenses in the second lens group can be determined appropriately within the range in which the second lens group has negative refractive power as a whole.

[0024] (3) Rear group The rear group is a collection of lens groups arranged on the image side of the second lens group, and has positive refractive power as a whole. The rear group includes, in order from the object side, at least a third lens group, a fourth lens group, and a fifth lens group. The third lens group and the fourth lens group are arranged adjacent to each other, and the fourth lens group and the fifth lens group are arranged adjacent to each other. The rear group may further include one or more lens groups on the image side of the fifth lens group. For example, the rear group may include a sixth lens group arranged on the image side of the fifth lens group, or may include, in order from the object side, a sixth lens group and a seventh lens group arranged on the image side of the fifth lens group.

[0025] The rear group only needs to have positive refractive power as a whole, and it only needs to have at least one lens group with positive refractive power. The rear group may be composed of only one or more lens groups with positive refractive power. Furthermore, the rear group may also include a lens group with negative refractive power as long as it has positive refractive power as a whole, and it is preferable that the rear group include at least one lens group with positive refractive power and at least one lens group with negative refractive power.

[0026] In such a high-magnification zoom lens, it is preferable to vary the magnification by mainly moving the second lens group, which has a strong refractive power. Therefore, it is preferable to place a third lens group with positive refractive power on the image side of the second lens group, from the viewpoint of appropriately correcting aberration fluctuations, particularly spherical aberration fluctuations, that occur when the second lens group is varied in magnification. If a third lens group with negative refractive power is placed on the image side of the second lens group, it may be difficult to appropriately correct aberrations that occur when the second lens group is varied in magnification. Therefore, it is preferable to place a lens group with positive refractive power further on the image side than the third lens group with negative refractive power, which may make it difficult to shorten the overall length of the zoom lens. Therefore, it is preferable for the third lens group to have positive refractive power, from the viewpoint of realizing a high-magnification zoom lens.

[0027] From the viewpoint of canceling out aberrations occurring in each lens group, it is preferable that the rear group alternates between lens groups having positive refractive power and lens groups having negative refractive power. Therefore, as described above, it is preferable that the third lens group has positive refractive power, and therefore it is preferable that the fourth lens group has negative refractive power and the fifth lens group has positive refractive power.

[0028] (4) Focus group The zoom lens has a focus group. The focus group moves along the optical axis of the zoom lens to achieve focusing. In this case, the focus group may be moved along the optical axis. The focus group is any one of the third, fourth, and fifth lens groups, and it is preferable that the focus group be either the fourth or fifth lens group from the viewpoint of suppressing aberration fluctuations associated with focusing. Furthermore, it is preferable that the focus group has negative refractive power and that its movement trajectory from the wide-angle end to the telephoto end is a U-turn trajectory that is convex toward the image side, from the viewpoint of reducing the maximum movement amount of the lens group with positive refractive power, which occupies a large distance along the optical axis, and thus realizing a high-magnification, compact zoom lens.

[0029] The third lens group is usually highly effective against spherical aberration but not so much against curvature of field. For this reason, if the third lens group were to function as a focusing group, it would be easier to achieve on-axis focus, but resolution at the periphery would likely be insufficient. On the other hand, the fourth and fifth lens groups are usually equally effective against not only spherical aberration but also curvature of field. For this reason, it is preferable to use either the fourth or fifth lens group as a focusing group, from the perspective of achieving sufficient resolution on-axis and around the axis.

[0030] (5) Aperture The zoom lens may have an aperture. However, the aperture here refers to an aperture that determines the diameter of the light beam of the zoom lens, i.e., the F-number of the zoom lens. The arrangement of the aperture in the zoom lens is not limited.

[0031] (6) Lens group configuration The zoom lens is composed of, from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear lens group having positive refractive power. The rear lens group includes, from the object side, at least a third lens group, a fourth lens group, and a fifth lens group. No other lens groups are included between the first lens group and the second lens group, between the second lens group and the third lens group, between the third lens group and the fourth lens group, or between the fourth lens group and the fifth lens group, but this does not exclude optical elements other than lenses, such as filters, or apertures.

[0032] 1-2.Operation (1) Operation when changing magnification In this zoom lens, the air spacing between at least the lens groups is changed when changing magnification from the wide-angle end to the telephoto end. Furthermore, it is preferable that at least two lens groups in the rear group move on the optical axis when changing magnification from the wide-angle end to the telephoto end, from the viewpoint of reducing the amount of movement of the second lens group during magnification change and from the viewpoint of reducing aberration fluctuations caused by changing the magnification of the second lens group. This is suitable for realizing a zoom lens that is compact and has high optical performance despite its high magnification. Furthermore, it is preferable that at least one of the at least two lens groups that move in the rear group makes a U-turn at a single point from the wide-angle end to the telephoto end, as this makes effective use of limited space and realizes a high-magnification zoom lens.

[0033] From the viewpoint of realizing high performance, it is preferable that the movable lens groups in the rear group include at least one lens group having positive refractive power and at least one lens group having negative refractive power. By moving a lens group having positive refractive power and a lens group having negative refractive power in the rear group as a pair, it is possible to cancel out the aberrations generated by each lens group, and spherical aberration and curvature of field are further suppressed in the entire zoom lens. Therefore, from the viewpoint of realizing high performance, it is preferable.

[0034] Furthermore, keeping the third lens group fixed when changing magnification from the wide-angle end to the telephoto end is preferable from the viewpoints of ensuring a movement range for the focus group, shortening the minimum focusing distance, and realizing a zoom lens with high optical performance. Furthermore, the third lens group is usually highly susceptible to spherical aberration. Having a fixed third lens group is advantageous in that it makes it easy to adjust the optical characteristics within the third lens group. Therefore, it is preferable from the viewpoint of realizing high performance, especially at the wide-angle end where the F-number is small. Having a fixed third lens group means that the third lens group does not substantially move when changing magnification.

[0035] In order to achieve a high magnification, it is preferable to increase the air gap between the first and second lens groups when zooming from the wide-angle end to the telephoto end, and it is also preferable to decrease the air gap between the second and third lens groups.

[0036] (2) Focusing behavior In this zoom lens, focusing can be performed by the focus group described above. As described above, the focus group that moves when focusing from infinity to a close object is any one of the third, fourth, and fifth lens groups. Furthermore, the direction of movement of the focus group during focusing is not limited.

[0037] 1-3. Formulas that express the conditions of a zoom lens The zoom lens according to this embodiment employs the above-described configuration and preferably satisfies at least one of the following expressions.

[0038] 0.3≦|f f | / M<0.8 (1) however, M:f w and f t Square root of the product of f f :Focal length of the focus group f w : Focal length at the wide-angle end of a zoom lens when focused at infinity f t : The focal length at the telephoto end of a zoom lens when focused at infinity

[0039] As mentioned above, M is the square root of the product of the focal length of the zoom lens at the wide-angle end when focused at infinity and the focal length of the zoom lens at the telephoto end when focused at infinity. Specifically, M is defined by the following formula:

[0040]

number

[0041] Equation (1) defines the power of the focus group. Satisfying equation (1) is desirable from the perspective of achieving a high magnification of the zoom lens and shortening the imaging distance across the entire zoom range. On the other hand, if the lower limit of equation (1) is exceeded, the refractive power of the focus group may become too strong. While this is advantageous for increasing the magnification of the zoom lens, it may increase aberration fluctuations at each focusing distance, making it difficult to maintain optical performance even when shooting at the shortest focusing distance. Furthermore, if the upper limit of equation (1) is exceeded, the refractive power of the focus group may become too weak. While this makes it easier to suppress aberration fluctuations at each focusing distance, it may increase the amount of movement required for focusing across the entire zoom range, making it difficult to achieve a high magnification at the desired overall length of the zoom lens.

[0042] In order to maintain optical performance even when shooting at the minimum focusing distance, |f f | / M is more preferably 0.35 or more, and even more preferably 0.45 or more. From the viewpoint of realizing a high magnification of the zoom lens, |f f | / M is more preferably 0.7 or less, and even more preferably 0.6 or less.

[0043] It is preferable that the zoom lens according to this embodiment satisfies the following formula: 1.5≦β FW / β FT <7.0·····(2) however, β FW : Lateral magnification at the wide-angle end of the focus group β FT : Lateral magnification at the telephoto end of the focus group

[0044] Equation (2) defines the lateral magnification of the focus group. Satisfying equation (2) is preferable from the perspective of appropriately correcting aberrations associated with increasing the magnification of a zoom lens. On the other hand, if the lower limit of equation (2) is exceeded, aberration correction becomes easy when focusing across the entire zoom range, but the rate of magnification by the focus group may become too small. This may make it difficult to achieve a high magnification of the zoom lens. On the other hand, if the upper limit of equation (2) is exceeded, this is advantageous for increasing the magnification of the zoom lens, but it may make it difficult to correct aberrations within the focus group. This may make it difficult to appropriately correct aberrations when focusing across the entire zoom range.

[0045] From the perspective of achieving high magnification of the zoom lens, β FW / β FT is more preferably 1.8 or more, and even more preferably 2.0 or more. From the viewpoint of appropriately correcting aberrations during focusing in the entire zoom range, β FW / β FT is more preferably 6.0 or less, and even more preferably 5.0 or less.

[0046] It is preferable that the zoom lens according to this embodiment satisfies the following formula: 5.0≦β 2T / β 2W ≦40.0 (3) however, β 2T : Lateral magnification of the second lens group at the telephoto end β 2W : Lateral magnification of the second lens group at the wide-angle end

[0047] Equation (3) defines the zoom ratio achieved by the second lens group. Satisfying equation (3) is preferable from the perspective of achieving a balance between the zoom ratios of the second lens group and the other lens groups, achieving a high zoom ratio for the zoom lens, and appropriately correcting aberrations. On the other hand, if the lower limit of equation (3) is exceeded, the zoom ratio achieved by moving the second lens group may become too small. This increases the amount of movement of the second lens group, making it difficult to achieve a high zoom ratio within the desired overall length of the zoom lens. Furthermore, if the upper limit of equation (3) is exceeded, the refractive power of the second lens group becomes stronger. While increasing the amount of movement of the second lens group facilitates achieving a high zoom ratio for the zoom lens, this may result in excessive aberration fluctuations during zooming. This may make it difficult to achieve high optical performance across the entire zoom range.

[0048] From the viewpoint of correcting aberrations appropriately, β 2T / β 2W is more preferably 7.0 or more, and even more preferably 9.0 or more. From the viewpoint of realizing a high magnification of the zoom lens, β 2T / β 2W is more preferably 30.0 or less, and even more preferably 20.0 or less.

[0049] In the zoom lens according to this embodiment, when the third lens group has positive refractive power, it is preferable that the following expression be satisfied: 5.0≦f t / f3≦15.0 (4) however, f3: focal length of the third lens group f t : The focal length at the telephoto end of a zoom lens when focused at infinity

[0050] Equation (4) defines the ratio between the focal length of the third lens group and the focal length of the telephoto end of the zoom lens when focused at infinity. Satisfying equation (4) is preferable from the perspective of appropriately correcting aberrations at the telephoto end. On the other hand, if the ratio is below the lower limit of equation (4), aberrations in the third lens group are easily corrected, but the refractive power of the third lens group may become too weak. This may make it difficult to achieve a high magnification at the desired overall length of the zoom lens. Furthermore, if the ratio is above the upper limit of equation (4), the refractive power of the third lens group may become too strong. This may make it difficult to appropriately correct aberrations in the third lens group.

[0051] From the perspective of achieving high magnification of the zoom lens, f t / f3 is more preferably 6.0 or greater, and even more preferably 7.0 or greater. From the viewpoint of appropriately correcting aberrations in the third lens group, f t / f3 is more preferably 13.0 or less, and even more preferably 11.0 or less.

[0052] It is preferable that the zoom lens according to this embodiment satisfies the following formula: 3.0≦|f1 / f2|≦10.0····(5) however, f1: focal length of the first lens group f2: focal length of the second lens group

[0053] Equation (5) defines the ratio between the focal length of the first lens group and the focal length of the second lens group. Satisfying equation (5) is preferable from the perspective of achieving a high magnification of the zoom lens while appropriately correcting aberrations at the telephoto end. On the other hand, if the lower limit of equation (5) is exceeded, aberration fluctuations due to magnification changes of the second lens group are reduced, but it may be difficult to appropriately correct aberrations at the telephoto end. Furthermore, if the upper limit of equation (5) is exceeded, aberration fluctuations due to magnification changes of the second lens group may become too large, while it may be easy to correct aberrations at the telephoto end while achieving a high magnification of the zoom lens. This may make it difficult to appropriately correct aberrations across the entire zoom range.

[0054] From the viewpoint of appropriately correcting aberrations at the telephoto end, |f1 / f2| is more preferably equal to or greater than 4.0, and even more preferably equal to or greater than 5.0. Furthermore, from the viewpoint of appropriately correcting aberrations over the entire zoom range, |f1 / f2| is more preferably equal to or less than 9.0, and even more preferably equal to or less than 8.0.

[0055] It is preferable that the zoom lens according to this embodiment satisfies the following formula: -0.4≦β 2W ≦-0.1 (6) however, β 2W : Lateral magnification of the second lens group at the wide-angle end

[0056] Equation (6) defines the lateral magnification of the second lens group at the wide-angle end. Satisfying equation (6) is preferable from the viewpoint of appropriately correcting aberrations at the wide-angle end. On the other hand, if the lower limit of equation (6) is not reached, it becomes easy to correct aberrations at the wide-angle end, but it may be difficult to achieve a wider focal length at the wide-angle end. Furthermore, if the upper limit of equation (6) is reached, it becomes easy to widen the focal length at the wide-angle end, but it may be difficult to appropriately correct aberrations at the wide-angle end.

[0057] From the viewpoint of realizing a wider focal length at the wide-angle end, β 2Wis more preferably equal to or greater than -0.35, and even more preferably equal to or greater than -0.30. 2W is more preferably −0.16 or less, and even more preferably −0.18 or less.

[0058] It is preferable that the zoom lens according to this embodiment satisfies the following formula: 3.0≦D 2rw / f w ≦9.0 (7) however, D 2rw : The distance on the optical axis between the lens surface of the second lens group closest to the image and the lens surface of the third lens group closest to the object at the wide-angle end of a zoom lens when focused at infinity f w : Focal length at the wide-angle end of a zoom lens when focused at infinity

[0059] Equation (7) defines the ratio of the focal length of a zoom lens at the wide-angle end when focusing at infinity to the axial distance between the lens surface of the second lens group closest to the image and the lens surface of the third lens group closest to the object at the wide-angle end when focusing at infinity. Satisfying equation (7) is preferable from the viewpoint of achieving a more compact zoom lens while also widening the focal length at the wide-angle end. On the other hand, if the lower limit of equation (7) is not met, it becomes easier to achieve a more compact zoom lens, but it may be difficult to achieve a wider focal length at the wide-angle end. Furthermore, if the upper limit of equation (7) is exceeded, it becomes easier to achieve a more wide-angle focal length at the wide-angle end, but it may be difficult to achieve a more compact zoom lens.

[0060] In order to achieve a wider focal length at the wide-angle end, D 2rw / f w is more preferably 4.0 or more, and even more preferably 5.0 or more. From the viewpoint of realizing a compact zoom lens, D 2rw / f w is more preferably 8.0 or less, and even more preferably 7.5 or less.

[0061] It is preferable that the zoom lens according to this embodiment satisfies the following formula: 2.0≦|m2 / f2|≦6.0 (8) however, m2: Amount of movement of the second lens group when changing magnification from the wide-angle end to the telephoto end f2: focal length of the second lens group

[0062] Equation (8) defines the ratio between the amount of movement of the second lens group when changing magnification from the wide-angle end to the telephoto end and the focal length of the second lens group. Satisfying equation (8) is preferable from the perspective of achieving compactness of the zoom lens while properly correcting aberrations. On the other hand, if the lower limit of equation (8) is exceeded, it becomes easy to achieve compactness of the zoom lens, but it may become difficult to properly correct aberrations. Furthermore, if the upper limit of equation (8) is exceeded, it becomes easy to correct aberrations across the entire zoom range, but the amount of movement of the second lens group when changing magnification may become too large. This may make it difficult to achieve compactness of the zoom lens.

[0063] From the viewpoint of appropriately correcting aberrations, |m2 / f2| is more preferably equal to or greater than 2.5, and even more preferably equal to or greater than 3.0. Furthermore, from the viewpoint of realizing compact zoom lenses, |m2 / f2| is more preferably equal to or less than 5.5, and even more preferably equal to or less than 5.0.

[0064] It is preferable that the zoom lens according to this embodiment satisfies the following formula: 0.0<|f p / f n |<1.5·····(9) however, f p : The focal length of the lens group with the strongest positive refractive power among the moving lens groups in the rear group f n : The focal length of the lens group with the strongest negative refractive power among the moving lens groups in the rear group

[0065] Equation (9) defines the ratio between the focal length of the lens group having the strongest positive refractive power among the moving lens groups in the rear group and the focal length of the lens group having the strongest negative refractive power among the moving lens groups in the rear group. Satisfying equation (9) is preferable from the perspective of appropriately correcting aberrations at the wide-angle end. On the other hand, if the lower limit of equation (9) is exceeded, the range of movement of the lens group having positive refractive power, which is located at a long distance on the optical axis, is reduced, making it easier to miniaturize the zoom lens, but it may be difficult to appropriately correct spherical aberration, especially at the wide-angle end. Furthermore, if the upper limit of equation (9) is exceeded, it is easier to correct aberrations at the wide-angle end, but the range of movement of the lens group having positive refractive power may be too large. This may make it difficult to achieve a compact zoom lens.

[0066] From the perspective of properly correcting spherical aberration at the wide-angle end, |f p / f n is more preferably 0.4 or more, and even more preferably 0.6 or more. From the viewpoint of realizing a compact zoom lens, |f p / f n is more preferably 1.4 or less, and even more preferably 1.3 or less.

[0067] It is preferable that the zoom lens according to this embodiment satisfies the following formula: -2.0<(R b1 -R b2 ) / (R b1 +R b2 )≦2.0 (10) however, R b1 : Radius of curvature of the object-side surface of the lens located closest to the image R b2 : Radius of curvature of the image-side surface of the lens located closest to the image

[0068] Equation (10) defines the shape of the lens located closest to the image. Satisfying equation (10) is preferable from the perspective of reducing ghosting while appropriately correcting aberrations. On the other hand, if the lower limit of equation (10) is exceeded, it becomes easy to correct field curvature aberration, particularly at the wide-angle end, but it may be difficult to reduce ghosting. Furthermore, if the upper limit of equation (10) is exceeded, it becomes possible to reduce ghosting, but it may be difficult to appropriately correct field curvature aberration, particularly at the wide-angle end.

[0069] From the viewpoint of reducing ghosting, (R b1 -R b2 ) / (R b1 +R b2 ) is more preferably equal to or greater than −1.8, and even more preferably equal to or greater than −1.6. In addition, from the viewpoint of appropriately correcting the curvature of field at the wide-angle end, (R b1 -R b2 ) / (R b1 +R b2 ) is more preferably 1.8 or less, and even more preferably 1.6 or less.

[0070] 2. Imaging device Next, an image pickup device according to an embodiment of the present invention will be described, which includes a zoom lens according to the above embodiment and an image pickup element provided on the image plane side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal.

[0071] Here, the imaging element is not limited, and solid-state imaging elements such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors, silver halide film, etc. can also be used. The imaging device according to this embodiment is suitable for imaging devices using the above-mentioned solid-state imaging elements, such as digital cameras and video cameras. Furthermore, the imaging device may be a fixed-lens imaging device in which the lens is fixed to the housing, or an interchangeable-lens imaging device such as a single-lens reflex camera or a mirrorless single-lens camera. In particular, the zoom lens according to this embodiment can ensure a back focus suitable for an interchangeable lens system. Therefore, it is suitable for imaging devices such as single-lens reflex cameras equipped with an optical viewfinder, a phase difference sensor, and a reflex mirror for splitting light to these sensors.

[0072] Fig. 21 is a diagram schematically illustrating an example of the configuration of an imaging device according to this embodiment. As shown in Fig. 21, a mirrorless single-lens camera 1 has a main body 2 and a lens barrel 3 that is detachable from the main body 2. The mirrorless single-lens camera 1 is one form of an imaging device.

[0073] The lens barrel 3 has a zoom lens 30. The zoom lens 30 includes a first lens group 31, a second lens group 32, a third lens group 33, a fourth lens group 34, and a fifth lens group 35, and is configured to satisfy, for example, the above-mentioned expressions (1) and (2). An aperture 36 is disposed between the second lens group 32 and the third lens group 33.

[0074] The first lens group 31 has positive refractive power, the second lens group 32 has negative refractive power, the third lens group 33 has positive refractive power, the fourth lens group 34 has negative refractive power, and the fifth lens group 35 has positive refractive power. The third lens group 33, the fourth lens group 34, and the fifth lens group 35 correspond to the rear group described above.

[0075] The main body 2 has a CCD sensor 21 as an imaging element and a cover glass 22. The CCD sensor 21 is disposed in the main body 2 at a position where the optical axis OA of the zoom lens 30 in the lens barrel 3 attached to the main body 2 is the central axis. Instead of the cover glass 22, the main body 2 may have a parallel plate that has no substantial refractive power.

[0076] It is more preferable that the imaging device according to this embodiment has an image processing unit that electrically processes the captured image data acquired by the imaging element to change the shape of the captured image, and an image correction data storage unit that stores image correction data and an image correction program, etc., used to process the captured image data in the image processing unit.

[0077] When a zoom lens is made smaller, distortion of the captured image formed on the imaging plane is likely to occur. In this case, it is preferable to correct the distortion of the captured image. This correction can be performed, for example, by storing distortion correction data for correcting the distortion of the captured image in advance in an image correction data storage unit, and then using the distortion correction data stored in the image correction data storage unit in the image processing unit. This imaging device allows for even smaller zoom lenses, resulting in clearer captured images and a more compact imaging device overall.

[0078] Furthermore, in the imaging device according to this embodiment, it is preferable that the image correction data storage unit stores magnification chromatic aberration correction data in advance. It is also preferable that the image processing unit corrects the magnification chromatic aberration of the captured image using the magnification chromatic aberration correction data stored in the image correction data storage unit. By correcting the magnification chromatic aberration, i.e., chromatic distortion, using the image processing unit, it is possible to reduce the number of lenses constituting the optical system. Therefore, with this imaging device, it is possible to further miniaturize the zoom lens, thereby obtaining beautiful captured images and miniaturizing the entire imaging device.

[0079] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0080] An embodiment of the present invention will be described below. In the following tables, all lengths are in "mm" and all angles of view are in "°". Furthermore, "E+a" is expressed as "×10 a " indicates.

[0081] [Example 1] FIG. 1 is a cross-sectional view of the zoom lens of Example 1 at the wide-angle end and the telephoto end when focusing on infinity. The zoom lens of Example 1 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, 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 positive refractive power. An aperture stop S is disposed between the lens group G2 and the lens group G3. "IMG" in FIG. 1 denotes an image plane (image formation plane), and a cover glass CG is disposed between the fifth lens group G5 and the image plane IMG. "F" in FIG. 1 denotes a focus group, and in the zoom lens of Example 1, the fourth lens group G4 is the focus group. The third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group described above.

[0082] The zoom lens of Example 1 performs a magnification change operation by changing the air gap between each lens group. In the figure, the arrows below each lens group at the wide-angle end indicate the movement trajectory of each lens group when moving from the wide-angle end to the telephoto end. When changing magnification from the wide-angle end to the intermediate focal length state, the first lens group G1 and the third lens group G3 do not move, and the second lens group G2, the fourth lens group G4, and the fifth lens group G5 each move toward the image. When changing magnification from the intermediate focal length state to the telephoto end, the first lens group G1 and the third lens group G3 do not move, and the second lens group G2 and the fifth lens group G5 each move toward the image, and the fourth lens group G4 moves toward the object. Among the moving lens groups in the rear group, the lens group with the strongest positive refractive power is the fifth lens group G5, and the lens group with the strongest negative refractive power is the fourth lens group G4.

[0083] Next, an example in which specific numerical values of a zoom lens are applied will be described. Table 1 is a table of surface data of the zoom lens in Example 1.

[0084] In the surface data table, "No." indicates the order of the lens surface counted from the object side, "r" indicates the radius of curvature of the lens surface, "d" indicates the spacing of the lens surfaces on the optical axis, and "Nd" indicates the d line (wavelength λ=587. 56nm), "vd" is the Abbe number for the d-line, and "H" is the effective radius. In the surface number, an "*" indicates that the lens surface is aspherical, and an "S" indicates that it is an aperture. Furthermore, in the "d" column, indications such as "D(7)" and "D(14)" indicate that the distance on the optical axis of the lens surface is a variable distance that changes when changing magnification or focusing.

[0085] Note that "INF" in the radius of curvature indicates a flat surface. In Table 1, Nos. 1 to 7 are surface numbers of the first lens group G1, Nos. 8 to 14 are surface numbers of the second lens group G2, and No. 15 represents the aperture. Nos. 16 to 20 are surface numbers of the third lens group G3, and Nos. 21 to 23 are surface numbers of the fourth lens group G4. Nos. 24 to 28 are surface numbers of the fifth lens group G5, No. 26 is the object-side lens surface of the lens located closest to the image, and No. 28 is the image-side lens surface of the lens located closest to the image. Nos. 29 and 30 represent cover glasses CG, and No. 31 represents the image surface.

[0086] [Table 1] No. rd Nd vd H 1 112.1976 1.1000 1.84666 23.78 21.00 2 57.5905 6.3000 1.49700 81.61 19.90 3 -939.8475 0.1500 21.48 4 53.4899 5.0500 1.49700 81.61 19.56 5 402.8046 0.1500 18.07 6 43.5189 3.2000 1.69680 55.46 17.23 7 78.2228 D(7) 16.80 8 50.2170 0.7000 1.91082 35.25 9.90 9 12.1770 3.7117 8.08 10 -62.2615 0.7000 1.90043 37.37 8.02 11 14.0000 3.3000 1.98612 16.48 7.48 12 208.9337 1.1316 7.25 13 * -26.8364 0.8000 1.85370 40.60 7.23 14 * -500.0000 D(14) 7.18 15 S INF 0.6000 8.58 16 * 29.8008 3.8000 1.59201 67.02 8.90 17 * -36.0015 0.1500 8.88 18 19.0908 0.6000 1.92286 18.90 8.63 19 14.4921 6.0000 1.43700 95.10 8.32 20 -24.5409 D(20) 8.06 21 -53.4424 1.7000 1.95906 17.47 7.19 22 -25.6932 0.6000 1.69680 55.46 7.06 23 15.0753 D(23) 6.52 24 * 25.7320 4.0000 1.59201 67.02 6.92 25 * -13.5375 0.1000 6.95 26 -28.1420 0.6000 1.83481 42.72 6.73 27 11.9183 5.9500 1.55032 75.50 6.66 28 -14.2198 D(28) 6.88 29 INF 2.4000 1.51680 64.20 5.11 30 INF 1.6248 4.88 31 INF

[0087] Table 2 shows the specifications of the zoom lens of Example 1. Starting from the left, the specifications show the values for the wide-angle end, the mid-focal length state, and the telephoto end. In the specifications, "f" represents the focal length of the zoom lens when focused at infinity, "FNO" represents the F-number, and "ω" represents the half angle of view. Furthermore, in the specifications, "D(n)" (n is an integer) represents the variable spacing on the optical axis of the zoom lens when zooming.

[0088] [Table 2] f 6.7540 78.3064 155.8625 FNO 1.6473 4.3760 4.9900 ω 32.9390 3.2298 1.6576 D(7) 0.9550 32.2686 37.2483 D(14) 37.5933 6.2797 1.3000 D(20) 1.4290 13.7638 9.6363 D(23) 14.6550 5.7445 13.0704 D(28) 10.2223 6.7981 3.5999

[0089] Table 3 shows the aspherical coefficients of each aspherical surface in the zoom lens of Example 1. The aspherical coefficients in this table are values when each aspherical shape is defined by the following formula. [Formula]z=ch 2 / [1+{1-(1+K)c 2 h 2} 1 / 2 ]+A4h 4 +A6h 6 +A8h 8 +A10h 10 +A12h 12 +A14h 14 +A16h 16 +A18h 18 +A20h 20

[0090] In the above formula, "z" is the displacement of the aspherical surface in the optical axis direction from a reference plane perpendicular to the optical axis, "c" is the curvature (1 / r), "h" is the height from the optical axis, "K" is the conic coefficient, and "An" (n is an integer) is the nth-order aspherical coefficient. Note that the aspherical coefficient of surface numbers not shown is 0.

[0091] [Table 3] No. K A4 A6 A8 A10 13 -6.82425E+00 6.71059E-05 -1.28979E-06 -2.21950E-08 3.79256E-10 14 -10.00000E+00 9.90165E-05 -1.85285E-06 1.80642E-10 -2.47129E-11 16 7.23002E-02 -1.00114E-05 -1.73186E-07 2.06559E-09 -2.15916E-12 17 2.86949E+00 4.23935E-05 -1.39545E-07 2.20987E-09 -1.60939E-12 24 -1.53905E+00 -6.74771E-06 2.25878E-07 -2.25906E-09 7.72606E-11 25 -1.45478E+00 9.15364E-05 -2.36607E-07 -1.01907E-08 2.15078E-10 No. A12 A14 A16 A18 A20 13 -1.27271E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 14 1.69396E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 17 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 24 -3.53885E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 25 -4.16134E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0092] Table 4 shows the focal length of each lens group constituting the zoom lens of Example 1.

[0093] [Table 4] Lens group Surface number Focal length G1 1-7 58.1095 G2 8-14 -8.69447 G3 16-20 15.8525 G4 21-23 -18.3001 G5 24-28 20.8268

[0094] 2, 3, and 4 are diagrams showing longitudinal aberrations of the zoom lens of Example 1 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity, respectively. The longitudinal aberrations shown in each diagram are, from left to right as you face the drawing, spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)), respectively. The same applies to the other examples.

[0095] In the graph showing spherical aberration, the vertical axis represents the F-number and the horizontal axis represents the defocus. In the graph showing spherical aberration, the solid line represents the spherical aberration at the d-line (wavelength λ=587.56 nm), the short-dashed line represents the spherical aberration at the F-line (wavelength λ=486.13 nm), and the long-dashed line represents the spherical aberration at the C-line (wavelength λ=656.28 nm).

[0096] In the diagrams showing astigmatism, the vertical axis represents the half angle of view and the horizontal axis represents defocus. In the diagrams showing astigmatism, the solid line represents the astigmatism in the sagittal image plane (indicated by S in the diagrams) for the d-line, and the dashed line represents the astigmatism in the meridional plane (indicated by T in the diagrams) for the d-line.

[0097] In the diagram showing distortion, the vertical axis represents the half angle of view, and the horizontal axis represents %.

[0098] [Example 2] FIG. 5 is a diagram schematically illustrating the optical configuration of the zoom lens of Example 2 when focusing on infinity at the wide-angle end and the telephoto end. FIGS. 6, 7, and 8 are diagrams illustrating longitudinal aberrations of the zoom lens of Example 2 when focusing on infinity at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. The zoom lens of Example 2 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, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power. An aperture stop S is disposed between the lens group G2 and the lens group G3. In the zoom lens of Example 2, the fourth lens group G4 is a focus group. The third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the rear group described above.

[0099] The zoom lens of Example 2 performs a magnification change operation by changing the air gap between each lens group. When changing magnification from the wide-angle end to the intermediate focal length state, the first lens group G1, the third lens group G3, and the sixth lens group G6 do not move, and the second lens group G2, the fourth lens group G4, and the fifth lens group G5 move toward the image side. When changing magnification from the intermediate focal length state to the telephoto end, the first lens group G1, the third lens group G3, and the sixth lens group G6 do not move, and the second lens group G2 and the fifth lens group G5 move toward the image side, and the fourth lens group G4 moves toward the object side. Among the movable lens groups in the rear group, the lens group with the strongest positive refractive power is the fifth lens group G5, and the lens group with the strongest negative refractive power is the fourth lens group G4.

[0100] Table 5 is a table of surface data for the zoom lens of Example 2. In Table 2, Nos. 1 to 7 are surface numbers of the first lens group G1, Nos. 8 to 14 are surface numbers of the second lens group G2, and No. 15 represents the aperture. Nos. 16 to 20 are surface numbers of the third lens group G3, Nos. 21 to 23 are surface numbers of the fourth lens group G4, and Nos. 24 to 28 are surface numbers of the fifth lens group G5. Nos. 29 and 30 are surface numbers of the sixth lens group G6, No. 29 is the object-side lens surface of the lens located closest to the image, and No. 30 is the image-side lens surface of the lens located closest to the image. Nos. 31 and 32 represent cover glasses CG, and No. 33 represents the image surface.

[0101] [Table 5] No. rd Nd vd H 1 137.1778 1.1000 1.84666 23.78 22.01 2 63.3444 6.3000 1.49700 81.61 20.80 3 -545.3327 0.1500 21.48 4 55.7604 5.0500 1.49700 81.61 19.56 5 946.9574 0.1500 18.10 6 44.7580 3.2000 1.69680 55.46 17.23 7 83.8349 D(7) 16.82 8 76.4543 0.7000 1.91082 35.25 9.73 9 13.5628 4.0584 8.01 10 -28.0000 0.7000 1.90043 37.37 7.82 11 19.8770 3.3000 1.98612 16.48 7.48 12 -55.8236 0.7319 7.33 13 * -24.5384 0.8000 1.85370 40.60 7.26 14 * -337.3098 D(14) 7.18 15 S INF 0.6000 8.41 16 * 25.7945 3.8000 1.59201 67.02 8.72 17 * -47.3443 0.1500 8.72 18 21.5948 0.6000 1.92286 18.90 8.51 19 15.3800 6.0000 1.43700 95.10 8.21 20 -21.7919 D(20) 7.95 21 -50.6210 1.7000 1.95906 17.47 7.15 22 -25.0246 0.6000 1.69680 55.46 7.01 23 15.8232 D(23) 6.47 24 * 20.9644 4.0000 1.59201 67.02 6.92 25 * -25.0363 0.1000 6.91 26 439.1565 0.6000 1.83481 42.72 6.78 27 12.2911 5.9500 1.55032 75.50 6.58 28 -17.6631 D(28) 6.63 29 -32.1711 0.6000 2.00069 25.46 4.90 30 -30000.0000 2.0000 4.88 31 INF 2.4000 1.51680 64.20 4.79 32 INF 1.6256 4.72 33 INF

[0102] Table 6 shows the specifications of the zoom lens of Example 2. Table 7 shows the aspherical coefficients of each aspherical surface in the zoom lens of Example 2. Table 8 shows the focal lengths of each lens group constituting the zoom lens of Example 2.

[0103] [Table 6] f 6.7582 78.7812 156.0507 FNO 1.6473 4.3760 4.9900 ω 35.6868 3.2654 1.6611 D(7) 1.1343 32.1670 37.3748 D(14) 37.5405 6.5078 1.3000 D(20) 1.0191 14.4315 10.2661 D(23) 15.3822 5.7863 12.3669 D(28) 7.5316 3.7152 1.3000

[0104] [Table 7] No. K A4 A6 A8 A10 13 -8.95414E+00 2.76740E-05 -1.54642E-06 -4.20318E-09 2.73149E-10 14 10.00000E+00 8.98462E-05 -1.95127E-06 2.64909E-09 1.78506E-10 16 -2.60816E-01 -1.13471E-05 -2.03570E-07 3.86231E-09 -4.04436E-11 17 3.57107E+00 4.07381E-05 -1.63027E-07 3.66926E-09 -3.81222E-11 24 -1.72992E+00 1.24755E-05 6.97558E-08 -5.​​​​​​​14 -1.06947E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 17 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 24 -1.91639E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 25 -2.42908E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0105] [Table 8] Lens group Surface number Focal length G1 1-7 57.9427 G2 8-14 -9.04449 G3 16-20 16.5244 G4 21-23 -18.8028 G5 24-28 18.0092 G6 29-30 -32.1836

[0106] [Example 3] FIG. 9 is a diagram schematically illustrating the optical configuration of the zoom lens of Example 3 when focusing on infinity at the wide-angle end and the telephoto end. FIGS. 10, 11, and 12 are diagrams illustrating longitudinal aberrations of the zoom lens of Example 3 when focusing on infinity at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. The zoom lens of Example 3 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, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power. An aperture stop S is disposed between the lens group G2 and the lens group G3. In the zoom lens of Example 3, the fourth lens group G4 is a focus group. The third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the rear group described above.

[0107] The zoom lens of Example 3 performs a magnification change operation by changing the air gap between each lens group. When changing magnification from the wide-angle end to the intermediate focal length state, the first lens group G1 and the third lens group G3 do not move, and the second lens group G2, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 each move toward the image side. When changing magnification from the intermediate focal length state to the telephoto end, the first lens group G1 and the third lens group G3 do not move, and the second lens group G2, the fifth lens group G5, and the sixth lens group G6 each move toward the image side, and the fourth lens group G4 moves toward the object side. Of the movable lens groups in the rear group, the lens group with the strongest positive refractive power is the fifth lens group G5, and the lens group with the strongest negative refractive power is the fourth lens group G4.

[0108] Table 9 is a table of surface data for the zoom lens of Example 3. In Table 9, Nos. 1 to 7 are surface numbers for the first lens group G1, Nos. 8 to 14 are surface numbers for the second lens group G2, and No. 15 represents the aperture. Nos. 16 to 20 are surface numbers for the third lens group G3, Nos. 21 to 23 are surface numbers for the fourth lens group G4, and Nos. 24 and 25 are surface numbers for the fifth lens group G5. Nos. 26 to 28 are surface numbers for the sixth lens group G6, No. 26 is the object-side lens surface of the lens located closest to the image, and No. 28 is the image-side lens surface of the lens located closest to the image. Nos. 29 and 30 represent cover glasses CG, and No. 31 represents the image surface.

[0109] [Table 9] No. rd Nd vd H 1 110.8777 1.1000 1.84666 23.78 21.11 2 57.2759 6.3000 1.49700 81.61 20.00 3 -1000.0000 0.1500 21.54 4 53.5714 5.0500 1.49700 81.61 19.59 5 414.6051 0.1500 18.16 6 43.6276 3.2000 1.69680 55.46 17.31 7 78.0373 D(7) 16.88 8 49.8365 0.7000 1.91082 35.25 9.98 9 12.1159 3.8921 8.13 10 -62.7416 0.7000 1.90043 37.37 8.01 11 14.0000 3.3000 1.98612 16.48 7.47 12 230.7878 1.1841 7.25 13 * -26.6038 0.8000 1.85370 40.60 7.20 14 * -500.0000 D(14) 7.16 15 S INF 0.6000 8.62 16 * 29.9972 3.8000 1.59201 67.02 8.93 17 * -35.1871 0.1500 8.93 18 19.2664 0.6000 1.92286 18.90 8.62 19 14.5901 6.0000 1.43700 95.10 8.29 20 -24.5513 D(20) 7.96 21 -53.0433 1.7000 1.95906 17.47 6.97 22 -25.8545 0.6000 1.69680 55.46 6.80 23 15.1417 D(23) 6.23 24 * 25.6779 4.0000 1.59201 67.02 6.02 25 * -13.2002 D(25) 6.07 26 -26.2925 0.6000 1.83481 42.72 5.93 27 12.1482 5.9500 1.55032 75.50 5.92 28 -14.1970 D(28) 6.24 29 INF 2.4000 1.51680 64.20 5.04 30 INF 1.6809 4.84 31 INF

[0110] Table 10 shows the specifications of the zoom lens of Example 3. Table 11 shows the aspherical coefficients of each aspherical surface in the zoom lens of Example 3. Table 12 shows the focal length of each lens group constituting the zoom lens of Example 3.

[0111] [Table 10] f 6.7560 78.6762 155.8895 FNO 1.6473 4.3760 4.9900 ω 32.8557 3.2148 1.6566 D(7) 0.9550 32.3100 37.2374 D(14) 37.5827 6.2275 1.3000 D(20) 1.4206 13.7269 9.6969 D(23) 14.6753 5.7776 13.0033 D(25) 0.1219 0.1200 0.1237 D(28) 10.2161 6.8089 3.6095

[0112] [Table 11] No. K A4 A6 A8 A10 13 -7.28804E+00 7.13671E-05 -1.24806E-06 -2.35518E-08 3.61520E-10 14 1.00000E+01 1.07445E-04 -1.90718E-06 5.73782E-10 -3.95909E-11 16 -3.02312E-01 -1.17753E-05 -1.98743E-07 2.01342E-09 -1.78226E-12 17 3.34844E+00 4.05294E-05 -1.53849E-07 2.10931E-09 -1.10167E-12 24 -7.98700E-01 -1.27588E-05 2.64659E-07 -3.23247E-09 1.02160E-10 25 -1.47948E+00 9.04669E-05 -2.78129E-07 -1.15104E-08 3.25362E-10 No. A12 A14 A16 A18 A20 13 -1.13820E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 14 1.5s3642E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 It should be noted that there seems to be a small error in the transcription of "1.5s3642E-12" in the translation of line . It is likely supposed to be "1.53642E-12".16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 17 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 24 -2.46570E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 25 -4.29435E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0113] [Table 12] Lens group Surface number Focal length G1 1-7 58.1668 G2 8-14 -8.6581 G3 16-20 15.8453 G4 21-23 -18.2998 G5 24-25 15.3124 G6 26-28 -124.964

[0114] [Example 4] FIG. 13 is a diagram schematically illustrating the optical configuration of the zoom lens of Example 4 when focusing on infinity at the wide-angle end and the telephoto end. FIGS. 14, 15, and 16 are diagrams illustrating longitudinal aberrations of the zoom lens of Example 4 when focusing on infinity at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. The zoom lens of Example 4 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, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power. An aperture stop S is disposed between lens group G2 and lens group G3. In the zoom lens of Example 4, the fourth lens group G4 is a focus group. The third lens group G3, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 correspond to the rear group described above.

[0115] The zoom lens of Example 4 performs a magnification change operation by changing the air gap between each lens group. When changing magnification from the wide-angle end to the intermediate focal length state, the first lens group G1, the third lens group G3, and the seventh lens group G7 do not move, and the second lens group G2, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 move toward the image side. When changing magnification from the intermediate focal length state to the telephoto end, the first lens group G1, the third lens group G3, and the seventh lens group G7 do not move, and the second lens group G2, the fifth lens group G5, and the sixth lens group G6 move toward the image side, and the fourth lens group G4 moves toward the object side. Among the movable lens groups in the rear group, the lens group with the strongest positive refractive power is the fifth lens group G5, and the lens group with the strongest negative refractive power is the fourth lens group G4.

[0116] Table 13 is a table of surface data for the zoom lens of Example 4. In Table 2, Nos. 1 to 7 are surface numbers for the first lens group G1, Nos. 8 to 14 are surface numbers for the second lens group G2, and No. 15 represents the aperture. Nos. 16 to 20 are surface numbers for the third lens group G3, Nos. 21 to 23 are surface numbers for the fourth lens group G4, Nos. 24 and 25 are surface numbers for the fifth lens group G5, and Nos. 26 to 28 are surface numbers for the sixth lens group G6. Nos. 29 and 30 represent the seventh lens group G7, No. 29 is the object-side lens surface of the lens located closest to the image, and No. 30 is the image-side lens surface of the lens located closest to the image. Nos. 31 and 32 represent cover glasses CG, and No. 33 represents the image surface.

[0117] [Table 13] No. rd Nd vd H 1 134.1572 1.1000 1.84666 23.78 21.83 2 62.6441 6.3000 1.49700 81.61 20.63 3 -592.3774 0.1500 21.46 4 55.4996 5.0500 1.49700 81.61 19.57 5 864.2954 0.1500 18.09 6 44.6647 3.2000 1.69680 55.46 17.23 7 83.4755 D(7) 16.81 8 75.7835 0.7000 1.91082 35.25 9.73 9 13.3815 4.0392 8.00 10 -29.4609 0.7000 1.90043 37.37 7.82 11 19.5676 3.3000 1.98612 16.48 7.48 12 -57.7646 0.7546 7.32 13 * -24.4633 0.8000 1.85370 40.60 7.25 14 * -346.1876 D(14) 7.17 15 S INF 0.6000 8.40 16 * 25.9093 3.8000 1.59201 67.02 8.72 17 * -46.8441 0.1500 8.72 18 21.6811 0.6000 1.92286 18.90 8.51 19 15.4025 6.0000 1.43700 95.10 8.21 20 -21.6361 D(20) 7.96 21 -50.2621 1.7000 1.95906 17.47 7.16 22 -24.8423 0.6000 1.69680 55.46 7.02 23 15.8576 D(23) 6.48 24 * 21.5323 4.0000 1.59201 67.02 6.93 25 * -23.4435 D(25) 6.93 26 1641.7241 0.6000 1.83481 42.72 6.76 27 12.3201 5.9500 1.55032 75.50 6.57 28 -17.4104 D(28) 6.63 29 -32.1928 0.6000 2.00069 25.46 4.90 30 -30000.0000 2.0000 4.88 31 INF 2.4000 1.51680 64.20 4.79 32 INF 1.6255 4.72 33 INF

[0118] Table 14 shows the specifications of the zoom lens of Example 4. Table 15 shows the aspherical coefficients of each aspherical surface in the zoom lens of Example 4. Table 16 shows the focal length of each lens group constituting the zoom lens of Example 4.

[0119] [Table 14] f 6.7582 78.8393 156.0496 FNO 1.6473 4.3760 4.9900 ω 35.4566 3.2622 1.6617 D( 7) 1.1251 32.1702 37.3585 D(14) 37.5334 6.4883 1.3000 D(20) 0.9935 14.4336 10.3298 D(23) 15.3179 5.7809 12.3186 D(25) 0.2730 0.1151 0.0972 D(28) 7.4612 3.7161 1.3000

[0120] [Table 15] No. K A4 A6 A8 A10 13 -7.28949E+00 2.37103E-05 -1.39353E-06 -2.85038E-09 2.78197E-10 14 -1.00000E+01 7.33019E-05 -1.71815E-06 4.43017E-09 1.75819E-10 16 -3.01150E-01 -1.18100E-05 -1.85179E-07 3.67923E-09 -4.01292E-11 17 3.56817E+00 4.04548E-05 -1.39892E-07 3.48468E-09 -3.79760E-11 24 -2.34821E+00 9.18004E-06 1.20990E-07 -5.27601E-09 1.49508E-10 25 -2.41344E+00 4.89928E-05 5.61677E-08 -9.42465E-09 2.18601E-10 No. A12 A14 A16 A18 A20 13 -1.97442E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 14 -1.37632E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 17 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 24 -1.81625E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 25 -2.28290E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0121] [Table 16] Lens group Surface number Focal length G1 1-7 57.9741 G2 8-14 -9.04893 G3 16-20 16.5165 G4 21-23 -18.8153 G5 24-25 19.6069 G6 26-28 85.0052 G7 29-30 -32.2053

[0122] [Example 5] FIG. 17 is a diagram schematically illustrating the optical configuration of the zoom lens of Example 5 when focusing on infinity at the wide-angle end and the telephoto end. FIGS. 18, 19, and 20 are diagrams illustrating longitudinal aberrations of the zoom lens of Example 5 when focusing on infinity at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. The zoom lens of Example 5 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, 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 positive refractive power. An aperture stop S is disposed between the lens group G2 and the lens group G3. In the zoom lens of Example 5, the fifth lens group G5 is a focus group. The third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the rear group described above.

[0123] The zoom lens of Example 5 performs a magnification change operation by changing the air gap between each lens group. When changing magnification from the wide-angle end to the intermediate focal length state, the first lens group G1 and the third lens group G3 do not move, the second lens group G2, the fifth lens group G5, and the sixth lens group G6 each move toward the image side, and the fourth lens group G4 moves toward the object side. When changing magnification from the intermediate focal length state to the telephoto end, the first lens group G1 and the third lens group G3 do not move, the second lens group G2 and the sixth lens group G6 each move toward the image side, and the fourth lens group G4 and the fifth lens group G5 each move toward the object side. Of the movable lens groups in the rear group, the lens group with the strongest positive refractive power is the sixth lens group G6, and the lens group with the strongest negative refractive power is the fifth lens group G5.

[0124] Table 17 is a table of surface data for the zoom lens of Example 5. In Table 17, Nos. 1 to 7 are surface numbers for the first lens group G1, Nos. 8 to 14 are surface numbers for the second lens group G2, and No. 15 represents the aperture. Nos. 16 and 17 are surface numbers for the third lens group G3, Nos. 18 to 20 are surface numbers for the fourth lens group G4, and Nos. 21 to 23 are surface numbers for the fifth lens group G5. Nos. 24 to 28 are surface numbers for the sixth lens group G6, No. 26 is the object-side lens surface of the lens located closest to the image, and No. 28 is the image-side lens surface of the lens located closest to the image. Nos. 29 and 30 represent cover glasses CG, and No. 31 represents the image surface.

[0125] [Table 17] No. rd Nd vd H 1 109.1380 1.1000 1.84666 23.78 20.92 2 56.8734 6.3000 1.49700 81.61 19.83 3 -981.7909 0.1500 21.35 4 52.4880 5.0500 1.49700 81.61 19.46 5 335.5388 0.1500 18.15 6 42.7719 3.2000 1.69680 55.46 17.30 7 75.2835 D(7) 16.86 8 46.9493 0.7000 1.91082 35.25 9.89 9 11.6746 3.9499 8.02 10 -61.2362 0.7000 1.90043 37.37 7.91 11 14.0000 3.3000 1.98612 16.48 7.41 12 341.3233 1.1114 7.20 13 * -27.0050 0.8000 1.85370 40.60 7.15 14 * -500.0000 D(14) 7.12 15 S INF 0.6000 8.61 16 * 36.5250 3.8000 1.59201 67.02 9.02 17 * -28.5123 D(17) 9.05 18 15.9644 0.6000 1.92286 18.90 8.41 19 12.3100 6.0000 1.43700 95.10 8.02 20 -36.3815 D(20) 7.64 21 -41.3277 1.7000 1.95906 17.47 7.12 22 -22.9298 0.6000 1.69680 55.46 7.01 23 16.5718 D(23) 6.53 24 * 32.3580 4.0000 1.59201 67.02 6.87 25 * -13.2828 0.1000 6.94 26 -34.0709 0.6000 1.83481 42.72 6.71 27 12.7747 5.9500 1.55032 75.50 6.65 28 -14.9040 D(28) 6.87 29 INF 2.4000 1.51680 64.20 5.15 30 INF 1.6285 4.91 31 INF

[0126] Table 18 shows the specifications of the zoom lens of Example 5. Table 19 shows the aspherical coefficients of each aspherical surface in the zoom lens of Example 5. Table 20 shows the focal length of each lens group constituting the zoom lens of Example 5.

[0127] [Table 18] f 6.7543 78.2486 155.8677 FNO 1.6473 4.3760 4.9900 ω 32.5662 3.2253 1.6534 D(7) 0.9550 32.2390 37.1781 D(14) 37.5228 6.2388 1.3000 D(17) 0.6342 0.1461 0.1000 D(20) 1.3310 13.6460 9.5776 D(23) 14.7191 5.8101 13.1992 D(28) 9.9245 7.0067 3.7325[[ID=​​​​​​​​​​​​​​​​​​​​​​​​16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 17 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 24 -3.05431E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 25 -3.45085E-12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0129] [Table 20] Lens group Surface number Focal length G1 1-7 58.1288 G2 8-14 -8.66361 G3 16-17 27.6483 G4 18-20 33.4555 G5 21-23 -18.3136 G6 24-28 20.4381

[0130] Table 21 shows the values calculated by the above-mentioned formulas in Examples 1 to 5 and the numerical values used in the formulas.

[0131] [Table 21] Example 1 Example 2 Example 3 Example 4 Example 5 (1)|f f | / M 0.56 0.58 0.56 0.58 0.56 (2)β FW / β FT 2.04 3.26 2.03 3.30 1.96 (3)β 2T / β 2W 10.77 10.44 10.73 10.38 10.73 (4)f t / f39.83 9.44 9.84 9.45 5.64 (5)|f1 / f2| 6.68 6.41 6.72 6.41 6.71 (6)β 2W -0.22 -0.23 -0.22 -0.23 -0.22 (7)D 2rw / f w 5.65 5.64 5.65 5.64 5.64 (8)|m2 / f2| 4.17 4.00 4.19 4.00 4.18 (9)|f p / f n | 1.14 0.96 0.84 1.04 1.12 (10)(R b1 -R b2 ) / (R b1 +R b2 ) 0.33 -1.00 0.30 -1.00 0.39 f w 6.75 6.76 6.76 6.76 6.75 f t 155.86 156.05 155.89 156.05 155.87 f f -18.30 -18.80 -18.30 -18.82 -18.31 f158.11 57.94 58.17 57.97 58.13 f2-8.69 -9.04 -8.66 -9.05 -8.66 f315.85 16.52 15.85 16.52 27.65 β 2W -0.22 -0.23 -0.22 -0.23 -0.22 β 2T -2.34 -2.36 -2.32 -2.34 -2.33 β FW 6.03 9.88 6.02 9.93 5.85 β FT 2.96 3.03 2.97 3.01 2.99 D 2rw 38.19 38.14 38.18 38.13 38.12 m236.28 36.22 36.27 36.21 36.21 f p20.83 18.01 15.31 19.61 20.44 f n -18.30 -18.80 -18.30 -18.82 -18.31 R b1 -28.14 -32.17 -26.29 -32.19 -34.07 R b2 -14.22 -30000.00 -14.20 -30000.00 -14.90 [Explanation of symbols]

[0132] 1. Mirrorless camera 2 Main unit 3 Telescope tube 21 CCD sensors 22. CG cover glass 30 Zoom Lens 31, G1 First lens group 32, G2 second lens group 33, G3 third lens group 34, G4 4th lens group 35, G5 5th lens group 36, S aperture G6 6th lens group G7 7th lens group OA optical axis

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 lens group having positive refractive power as a whole, and performing a magnification change operation by changing the spacing between adjacent lens groups, the rear group includes, in order from the object side, at least a third lens group, a fourth lens group, and a fifth lens group; the third lens group is composed of, in order from the object side, two lenses: a positive lens and a cemented lens, and the cemented lens is composed of, in order from the object side, a negative lens and a positive lens, The first lens group does not move during zooming, any one of the third lens group, the fourth lens group, and the fifth lens group is a focus group that performs focusing by moving on an optical axis, A zoom lens that satisfies the following formula: 0.3≦|ff| / M<0.8 (1) 6.0≦ft / f3≦15.0 (4)' 3.0≦|f1 / f2|≦6.72...(5)' -1.0≦(Rb1-Rb2) / (Rb1+Rb2)≦2.0 (10) however, M: Square root of the product of fw and ft ff: focal length of the focus group fw: focal length at the wide-angle end of the zoom lens when focused at infinity ft: focal length at the telephoto end of the zoom lens when focused at infinity f1: focal length of the first lens group f2: focal length of the second lens group f3: focal length of the third lens group Rb1: radius of curvature of the object-side surface of the lens located closest to the image Rb2: Radius of curvature of the image-side surface of the lens located closest to the image

2. 2. The zoom lens according to claim 1, wherein at least two lens groups in the rear group move on the optical axis when zooming from the wide-angle end to the telephoto end.

3. the moving lens groups of the rear group include at least one lens group having positive refractive power and at least one lens group having negative refractive power; 3. The zoom lens according to claim 2, wherein the following formula is satisfied: 0.0<|fp / fn|<1.5 (9) however, fp: focal length of the lens group having the strongest positive refractive power among the moving lens groups in the rear group fn: focal length of the lens group having the strongest negative refractive power among the moving lens groups in the rear group

4. 4. The zoom lens according to claim 1, wherein the following formula is satisfied: 5.0≦β2T / β2W≦40.0 (3) however, β2T: lateral magnification at the telephoto end of the second lens group β2W: lateral magnification of the second lens group at the wide-angle end

5. 5. The zoom lens according to claim 1, wherein the following formula is satisfied: −0.4≦β2W≦−0.1 (6) however, β2W: lateral magnification of the second lens group at the wide-angle end

6. 6. The zoom lens according to claim 1, which satisfies the following formula: 3.0≦D2rw / fw≦9.0 (7) however, D2rw: the distance on the optical axis between the lens surface of the second lens group closest to the image side and the lens surface of the third lens group closest to the object side at the wide-angle end when the zoom lens is focused at infinity

7. 7. The zoom lens according to claim 1, which satisfies the following formula: 2.0≦|m2 / f2|≦6.0...(8) however, m2: the movement amount of the second lens group when changing magnification from the wide-angle end to the telephoto end f2: focal length of the second lens group

8. An imaging device comprising: the zoom lens according to any one of claims 1 to 7; and an imaging element provided on the image side of the zoom lens, which converts an optical image formed by the zoom lens into an electrical signal.

Images