Imaging optical system, imaging device having the same, and camera system

Abstract

To provide a zoom lens which offers good optical performance over an entire zoom range, an imaging device having the same, and an interchangeable lens device.SOLUTION: An imaging optical system is composed of, in order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, and a third lens group having power. When zooming from a wide-angle end to a telephoto end, the first, second, and third lens groups move along an optical axis of the imaging optical system, changing a distance between adjacent lens groups. The imaging optical system satisfies a condition (1) represented by the following expression: 1.85<L1nd, ...(1), where L1nd represents a refractive index of a negative lens element located on the most object side.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present disclosure relates to an imaging optical system in which various aberrations are well corrected across the entire zoom range, and an imaging device and camera system including the same. [Background technology]

[0002] Patent Document 1 discloses a zoom lens that is composed of, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group with negative refractive power, and in which each lens group moves during zooming so that the spacing between adjacent lens groups changes, and is characterized by the ratios of β2t to β2w and β3t to β3w, where β2w is the lateral magnification of the second lens group at the wide-angle end, β2t is the lateral magnification of the second lens group at the telephoto end, β3w is the lateral magnification of the third lens group at the wide-angle end, and β3t is the lateral magnification of the third lens group at the telephoto end. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-062053 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide an imaging optical system in which various aberrations are well corrected across the entire zoom range, and an imaging device and camera system including the same. [Means for solving the problem]

[0005] An imaging optical system according to one aspect of the present disclosure includes, in order from the object side to the image side, a first lens group having negative power, a second lens group having positive power, and a third lens group having positive power. During zooming of the imaging optical system from the wide-angle end to the telephoto end, the first lens group, the second lens group, and the third lens group move along the optical axis of the imaging optical system so that the spacing between adjacent lens groups changes. The imaging optical system satisfies the following condition (1): 1.85 < L1nd (1) where L1nd is the refractive index of the negative lens element located closest to the object, is.

[0006] A camera system according to one aspect of the present disclosure includes an interchangeable lens device including the imaging optical system described above, and a camera body including an image sensor that is detachably connected to the interchangeable lens device via a camera mount and that receives an optical image formed by the imaging optical system and converts it into an electrical image signal. The interchangeable lens device then forms the optical image of the object on the image sensor.

[0007] An imaging device according to the present disclosure converts an optical image of an object into an electrical image signal and at least one of displays and stores the converted image signal, and includes the imaging optical system that forms the optical image of the object, and an imaging element that converts the optical image formed by the imaging optical system into the electrical image signal. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an imaging optical system in which various aberrations are well corrected across the entire zoom range, and an imaging device and an interchangeable lens device that include the imaging optical system. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to a first embodiment (numerical example 1); [Figure 1B]1 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 1 in a state of focusing at infinity. [Figure 2A] FIG. 10 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to a second embodiment (Numerical Example 2). [Figure 2B] 10A and 10B are longitudinal aberration diagrams of the imaging optical system according to Numerical Example 2 in a state of focusing at infinity. [Figure 3A] FIG. 10 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to a third embodiment (Numerical Example 3). [Figure 3B] 10A and 10B are longitudinal aberration diagrams of the imaging optical system according to Numerical Example 3 in a state of focusing at infinity. [Figure 4A] FIG. 10 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to a fourth embodiment (numerical example 4); [Figure 4B] FIG. 10 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 4 in a state where the imaging optical system is focused at infinity. [Figure 5A] FIG. 10 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to a fifth embodiment (numerical example 5). [Figure 5B] FIG. 10 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 5 in a state of focusing at infinity. [Figure 6] 1 is a schematic diagram of an imaging device according to a first embodiment; [Figure 7] 1 is a schematic diagram of a camera system according to a first embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0011] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] (Embodiments 1 to 5) The imaging optical systems according to the first to fifth embodiments will be individually described below with reference to the drawings.

[0013] 1A, 2A, 3A, 4A, and 5A are lens layout diagrams of imaging optical systems according to first to fifth embodiments, respectively, and all show imaging optical systems in an infinity focused state.

[0014] (a) of Figures 1A, 2A, 3A, 4A, and 5A shows the lens arrangement at the wide-angle end (shortest focal length state: focal length fw). (d) of each figure shows the lens arrangement at the intermediate position (intermediate focal length state: focal length fM = √(fw * fT)). (e) of each figure shows the lens arrangement at the telephoto end (longest focal length state: focal length fT). Note that the aspect ratio is the same in (a), (d), and (e) of each figure.

[0015] An asterisk * on the surface of a particular lens element shown in (a) of each figure indicates that the surface is aspherical. If an asterisk * is not marked on the object-side or image-side surface of each lens element in (a), the surface is spherical.

[0016] The broken arrows in (c) of each figure show, from top to bottom, the positions of the lens groups in each state: wide-angle end (WIDE), middle position (MID), and telephoto end (TELE). Note that the arrows simply connect the wide-angle end and middle position, and the middle position and telephoto end, and do not show the actual movement of each lens group.

[0017] In (b) of each figure, the lens groups are labeled G1 to G3 in accordance with the positions of the lens groups shown in (a).

[0018] The symbols (+) and (-) attached to the reference numerals (G1 to G3) of each lens group shown in (b) of each figure correspond to the power of each lens group. That is, the symbol (+) indicates positive power, and the symbol (-) indicates negative power.

[0019] The arrows attached to the lens groups shown in (b) of each figure represent focusing from an infinity-focused state to a close-focused state. In Figures 1A, 2A, 3A, 4A, and 5A, the reference numerals of each lens group are written below the positions of the lens groups in (a), and therefore, for convenience, arrows representing focusing are attached below the reference numerals of each lens group. However, the direction in which each lens group moves during focusing in each zoom state will be specifically explained later for each embodiment.

[0020] In each of (a), (d), and (e) of the figures, the line drawn on the far right indicates the position of the image plane S (the object-side surface of the image sensor). Therefore, the left side of the figure corresponds to the object side. Furthermore, a parallel plate such as a low-pass filter or cover glass CG is disposed between the image plane S and the final lens group of the imaging optical system that faces the image plane S.

[0021] (Embodiment 1) FIG. 1A shows an imaging optical system according to the first embodiment.

[0022] The imaging optical system is composed of, in order from the object side to the image side, a first lens group G1 having negative power, a second lens group G2 having positive power, and a third lens group G3 having negative power.

[0023] The imaging optical system forms an image at the position of an image plane S.

[0024] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having negative power, a third lens element L3 having negative power, and a fourth lens element L4 having positive power.

[0025] The second lens group G2 is composed of, in order from the object side to the image side, an aperture stop A, a fifth lens element L5 having positive power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The sixth lens element L6 and the seventh lens element L7 are a cemented lens bonded together with an adhesive or the like.

[0026] The third lens group G3 is composed of an eighth lens element L8 having negative power.

[0027] Each lens element will now be described.

[0028] The lens elements in the first lens group G1 will be described. The first lens element L1 is a meniscus lens having a convex surface facing the object side. The second lens element L2 is a meniscus lens having a convex surface facing the object side. Both surfaces of the second lens element L2 have aspheric shapes. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a meniscus lens having a convex surface facing the object side.

[0029] The lens elements in the second lens group G2 will be described. The fifth lens element L5 is a biconvex lens. Both surfaces of the fifth lens element L5 are aspherical. The sixth lens element L6 is a meniscus lens with a convex surface facing the object side. The seventh lens element L7 is a biconvex lens.

[0030] The lens elements in the third lens group G3 will now be described. The eighth lens element L8 is a biconcave lens. Both surfaces of the eighth lens element L8 have aspherical shapes.

[0031] In the imaging optical system according to Embodiment 1, when zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1, the second lens group G2, and the third lens group G3 move relative to the image plane S. Then, when zooming from the wide-angle end to the telephoto end during imaging, each lens group moves along the optical axis so that the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the distance between the third lens group G3 and the image plane S increases.

[0032] In the imaging optical system according to the first embodiment, the third lens group G3 moves toward the image side along the optical axis during focusing from an infinity focused state to a close focused state.

[0033] (Embodiment 2) FIG. 2A shows an imaging optical system according to the second embodiment.

[0034] The imaging optical system is composed of, in order from the object side to the image side, a first lens group G1 having negative power, a second lens group G2 having positive power, and a third lens group G3 having negative power.

[0035] The imaging optical system forms an image at the position of an image plane S.

[0036] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having positive power, a third lens element L3 having negative power, and a fourth lens element L4 having positive power.

[0037] The second lens group G2 is composed of, in order from the object side to the image side, an aperture stop A, a fifth lens element L5 having positive power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The sixth lens element L6 and the seventh lens element L7 are a cemented lens bonded together with an adhesive or the like.

[0038] The third lens group G3 is composed of an eighth lens element L8 having negative power.

[0039] Each lens element will now be described.

[0040] The lens elements in the first lens group G1 will be described. The first lens element L1 is a meniscus lens having a convex surface facing the object side. The second lens element L2 is a meniscus lens having a convex surface facing the object side. Both surfaces of the second lens element L2 have aspheric shapes. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a meniscus lens having a convex surface facing the object side.

[0041] The lens elements in the second lens group G2 will be described. The fifth lens element L5 is a biconvex lens. Both surfaces of the fifth lens element L5 are aspherical. The sixth lens element L6 is a meniscus lens with a convex surface facing the object side. The seventh lens element L7 is a biconvex lens.

[0042] The lens elements in the third lens group G3 will now be described. The eighth lens element L8 is a biconcave lens. Both surfaces of the eighth lens element L8 have aspherical shapes.

[0043] In the imaging optical system according to Embodiment 2, when zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1, the second lens group G2, and the third lens group G3 move relative to the image plane S. Then, when zooming from the wide-angle end to the telephoto end during imaging, each lens group moves along the optical axis so that the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the distance between the third lens group G3 and the image plane S increases.

[0044] In the imaging optical system according to the second embodiment, the third lens group G3 moves along the optical axis toward the image side during focusing from an infinity focused state to a close focused state.

[0045] (Embodiment 3) FIG. 3A shows an imaging optical system according to the third embodiment.

[0046] The imaging optical system is composed of, in order from the object side to the image side, a first lens group G1 having negative power, a second lens group G2 having positive power, and a third lens group G3 having negative power.

[0047] The imaging optical system forms an image at the position of an image plane S.

[0048] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having negative power, a third lens element L3 having negative power, and a fourth lens element L4 having positive power.

[0049] The second lens group G2 is composed of, in order from the object side to the image side, an aperture stop A, a fifth lens element L5 having positive power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The sixth lens element L6 and the seventh lens element L7 are a cemented lens bonded together with an adhesive or the like.

[0050] The third lens group G3 is composed of an eighth lens element L8 having negative power.

[0051] Each lens element will now be described.

[0052] The lens elements in the first lens group G1 will be described. The first lens element L1 is a meniscus lens having a convex surface facing the object side. The second lens element L2 is a meniscus lens having a convex surface facing the object side. Both surfaces of the second lens element L2 have aspheric shapes. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a meniscus lens having a convex surface facing the object side.

[0053] The lens elements in the second lens group G2 will be described. The fifth lens element L5 is a biconvex lens. Both surfaces of the fifth lens element L5 have aspherical shapes. The sixth lens element L6 is a biconcave lens. The seventh lens element L7 is a biconvex lens.

[0054] The lens elements in the third lens group G3 will now be described. The eighth lens element L8 is a biconcave lens. Both surfaces of the eighth lens element L8 have aspherical shapes.

[0055] In the imaging optical system according to Embodiment 3, when zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1, the second lens group G2, and the third lens group G3 move relative to the image plane S. Then, when zooming from the wide-angle end to the telephoto end during imaging, each lens group moves along the optical axis so that the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the distance between the third lens group G3 and the image plane S increases.

[0056] In the imaging optical system according to the third embodiment, the third lens group G3 moves along the optical axis toward the image side during focusing from an infinity focused state to a close focused state.

[0057] (Fourth embodiment) FIG. 4A shows an imaging optical system according to the fourth embodiment.

[0058] The imaging optical system is composed of, in order from the object side to the image side, a first lens group G1 having negative power, a second lens group G2 having positive power, and a third lens group G3 having negative power.

[0059] The imaging optical system forms an image at the position of an image plane S.

[0060] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having positive power, a second lens element L2 having negative power, a third lens element L3 having negative power, and a fourth lens element L4 having positive power.

[0061] The second lens group G2 is composed of, in order from the object side to the image side, an aperture stop A, a fifth lens element L5 having positive power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The sixth lens element L6 and the seventh lens element L7 are a cemented lens bonded together with an adhesive or the like.

[0062] The third lens group G3 is composed of an eighth lens element L8 having negative power.

[0063] Each lens element will now be described.

[0064] The lens elements in the first lens group G1 will be described. The first lens element L1 is a meniscus lens having a convex surface on the object side. The second lens element L2 is a meniscus lens having a convex surface on the object side. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a meniscus lens having a convex surface on the object side.

[0065] The lens elements in the second lens group G2 will be described. The fifth lens element L5 is a biconvex lens. Both surfaces of the fifth lens element L5 are aspherical. The sixth lens element L6 is a meniscus lens with a convex surface facing the object side. The seventh lens element L7 is a biconvex lens.

[0066] The lens elements in the third lens group G3 will now be described. The eighth lens element L8 is a biconcave lens. Both surfaces of the eighth lens element L8 have aspherical shapes.

[0067] In the imaging optical system according to embodiment 4, when zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1, the second lens group G2, and the third lens group G3 move relative to the image plane S. Then, when zooming from the wide-angle end to the telephoto end during imaging, each lens group moves along the optical axis so that the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the distance between the third lens group G3 and the image plane S increases.

[0068] In the imaging optical system according to the fourth embodiment, the third lens group G3 moves along the optical axis toward the image side during focusing from an infinity focused state to a close focused state.

[0069] (Embodiment 5) FIG. 5A shows an imaging optical system according to the fifth embodiment.

[0070] The imaging optical system is composed of, in order from the object side to the image side, a first lens group G1 having negative power, a second lens group G2 having positive power, and a third lens group G3 having positive power.

[0071] The imaging optical system forms an image at the position of an image plane S.

[0072] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having negative power, a third lens element L3 having negative power, and a fourth lens element L4 having positive power.

[0073] The second lens group G2 is composed of, in order from the object side to the image side, an aperture stop A, a fifth lens element L5 having positive power, a sixth lens element L6 having negative power, a seventh lens element L7 having positive power, and an eighth lens element L8 having negative power. The sixth lens element L6 and the seventh lens element L7 are a cemented lens bonded together with an adhesive or the like.

[0074] The third lens group G3 is composed of a ninth lens element L9 having positive power.

[0075] Each lens element will now be described.

[0076] The lens elements in the first lens group G1 will be described. The first lens element L1 is a meniscus lens having a convex surface facing the object side. The second lens element L2 is a meniscus lens having a convex surface facing the object side. Both surfaces of the second lens element L2 have aspheric shapes. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a meniscus lens having a convex surface facing the object side.

[0077] The lens elements in the second lens group G2 will be described. The fifth lens element L5 is a biconvex lens. Both surfaces of the fifth lens element L5 have aspherical shapes. The sixth lens element L6 is a meniscus lens with a convex surface facing the object side. The seventh lens element L7 is a biconvex lens. The eighth lens element L8 is a meniscus lens with a convex surface facing the object side. Both surfaces of the eighth lens element L8 have aspherical shapes.

[0078] The lens elements in the third lens group G3 will now be described. The ninth lens element L9 is a meniscus lens having a convex surface facing the object side. The object side surface of the ninth lens element L9 has an aspherical shape.

[0079] In the imaging optical system according to embodiment 5, when zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1, the second lens group G2, and the third lens group G3 move relative to the image plane S. Then, when zooming from the wide-angle end to the telephoto end during imaging, each lens group moves along the optical axis so that the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the image plane S increases.

[0080] In the imaging optical system according to the fifth embodiment, the third lens group G3 moves along the optical axis toward the image side during focusing from an infinity focused state to a close focused state.

[0081] (Other embodiments) As described above, the first to fifth embodiments have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate.

[0082] Although the imaging optical systems according to the first to fifth embodiments have been described above as examples in which the entire zoom range from the wide-angle end to the telephoto end is used, it is not necessary to use the entire zoom range. For example, a range in which optical performance is ensured may be selected according to a desired zoom range and used as an imaging optical system. In other words, it may be used as an imaging optical system with a lower magnification than the imaging optical systems described below in Numerical Examples 1 to 5 corresponding to the first to fifth embodiments. Furthermore, a focal length in which optical performance is ensured according to a desired zoom position may be selected and used as a single focal length lens system.

[0083] Furthermore, the number of lens groups and the number of lens elements in each lens group are substantial, and lenses with substantially no power may be added.

[0084] (Conditions and effects, etc.) Below, we will explain conditions that can be satisfied by the imaging optical systems according to, for example, Embodiments 1 to 5. Note that, although multiple possible conditions are defined for the imaging optical systems according to Embodiments 1 to 5, the most effective imaging optical system configuration is one that satisfies all of these multiple conditions. However, it is also possible to obtain imaging optical systems that achieve the respective corresponding effects by satisfying individual conditions.

[0085] The imaging optical systems according to Embodiments 1 to 5 are composed of, in order from the object side to the image side, a first lens group G1 having negative power, a second lens group G2 having positive power, and a third lens group G3 having positive power. When zooming the imaging optical system from the wide-angle end to the telephoto end, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis so that the spacing between adjacent lens groups changes. This configuration is the basic configuration.

[0086] The imaging optical system with the basic configuration is configured to realize a zoom lens system that can obtain a wide angle of view at the wide-angle end and can effectively correct various aberrations throughout the entire zoom range. This allows for effective correction of various aberrations that occur in each lens group during zooming. As a result, it is possible to provide an imaging optical system in which various aberrations are effectively corrected throughout the entire zoom range.

[0087] Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (1).

[0088] 1.85 < L1nd (1) where: L1nd: refractive index of the negative lens element located closest to the object, is.

[0089] Condition (1) is a condition for defining the refractive index of the negative lens element located closest to the object side in the imaging optical system.

[0090] By satisfying the condition (1), the imaging optical system can be made compact.

[0091] Conversely, if the lower limit of the condition (1) is not met, a low refractive index material must be selected, which is undesirable because it makes it difficult to correct various aberrations, particularly curvature of field.

[0092] Preferably, the above-mentioned effect can be further enhanced by satisfying the following condition (1a):

[0093] 1.90 < L1nd (1a) More preferably, the above-mentioned effect can be further enhanced by satisfying the following condition (1b):

[0094] 2.00 < L1nd (1b) Furthermore, in an imaging optical system with a basic configuration, for example, it is desirable that the third lens group has negative power.

[0095] This allows for even smaller size than the imaging optical system of the basic configuration.

[0096] Furthermore, for example, in an imaging optical system with a basic configuration, it is desirable that the first lens group G1 be made up of three or more lens elements.

[0097] This allows for excellent correction of various aberrations, particularly distortion and curvature of field at the wide-angle end.

[0098] Furthermore, for example, in an imaging optical system having a basic configuration, it is desirable to satisfy the following condition (2):

[0099] 0.5 < R11 / fw <8.0 (2) where: R11: the radius of curvature of the object-side surface of the negative lens element located closest to the object, fw: focal length at the wide-angle end of the imaging optical system, is.

[0100] Condition (2) sets forth the ratio between the radius of curvature of the object-side surface of the negative lens element located closest to the object in the imaging optical system and the focal length of the imaging optical system at the wide-angle end.

[0101] By satisfying the condition (2), a wide angle of view can be obtained at the wide-angle end, and curvature of field at the wide-angle end can be corrected satisfactorily.

[0102] Conversely, if the lower limit of condition (2) is exceeded, the radius of curvature becomes too small, which is undesirable because it becomes difficult to effectively correct curvature of field, and if the upper limit of condition (2) is exceeded, the radius of curvature becomes too large, which is undesirable because it increases the overall size of the lens.

[0103] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (2a) and (2b).

[0104] 1.0 < R11 / fw (2a) R11 / fw <5.0 (2b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (2c) and (2d):

[0105] 1.5 < R11 / fw (2c) R11 / fw <2.0 (2d) Furthermore, for example, in the basic configuration of the imaging optical system, it is desirable that the first lens group G1 has two or more negative lens elements and that the following condition (3) is satisfied.

[0106] 60 < L1νd < 100 (3) where: L1νd: Abbe number of one of the two or more negative lens elements in the first lens group G1, is.

[0107] Condition (3) sets forth the Abbe number of one of the two or more negative lens elements in the first lens group G1 in the imaging optical system.

[0108] By satisfying the condition (3), various aberrations, particularly lateral chromatic aberration, can be effectively corrected.

[0109] Conversely, if the lower limit of condition (3) is exceeded, a high-dispersion glass must be selected as the material for the negative lens element in the first lens group G1, which makes it difficult to correct chromatic aberration, and if the upper limit of condition (3) is exceeded, a low-refractive index material must be selected as the material for the negative lens element in the first lens group G1, which makes it difficult to correct field curvature, which is undesirable.

[0110] Preferably, the above-mentioned effects can be further enhanced by satisfying either one or both of the following conditions (3a) and (3b):

[0111] 70 < L1νd (3a) L1νd < 90 (3b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (3c) and (3d):

[0112] 75 < L1νd (3c) L1νd < 80 (3d) Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (4):

[0113] 0.1 < G1L / Lt < 0.4 (4) where: G1L: total thickness of the first lens group G1, Lt: total optical length at the telephoto end of the imaging optical system, is.

[0114] Condition (4) is a condition for specifying the ratio of the total thickness of the first lens group G1 (the distance on the optical axis between the object-side surface of the lens element that is located closest to the object and the image-side surface of the lens element that is located closest to the image, among the lens elements that constitute the first lens group G1) to the total optical length at the telephoto end of the imaging optical system (the distance on the optical axis between the object-side surface of the lens element that is located closest to the object and the image plane S).

[0115] By satisfying condition (4), the length of the lens barrel when retracted can be reduced.

[0116] Conversely, if the lower limit of condition (4) is exceeded, the total thickness of the first lens group G1 becomes too thin, making it difficult to correct various aberrations, which is undesirable, and if the upper limit of condition (4) is exceeded, the length of the lens barrel when retracted becomes too long, which is undesirable.

[0117] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (4a) and (4b):

[0118] 0.15 < G1L / Lt (4a) G1L / Lt < 0.35 (4b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (4c) and (4d):

[0119] 0.20 < G1L / Lt (4c) G1L / Lt < 0.25 (4d) Furthermore, for example, in an imaging optical system with a basic configuration, it is desirable that the first lens group moves along a locus that is convex toward the image side when zooming from the wide-angle end to the telephoto end of the imaging optical system.

[0120] This shortens the dimension of the zoom cam in the optical axis direction, and makes it possible to shorten the length of the lens barrel when retracted.

[0121] Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (5):

[0122] 0.5 < | f1 / fw | < 3.0 ···(5) where: f1: focal length of the first lens group G1, fw: focal length at the wide-angle end of the imaging optical system, is.

[0123] Condition (5) sets forth the ratio of the focal length of the first lens group G1 to the focal length of the imaging optical system at the wide-angle end.

[0124] By satisfying the condition (5), a wide angle of view can be obtained at the wide-angle end, and various aberrations can be corrected satisfactorily.

[0125] Conversely, if the lower limit of condition (5) is exceeded, the refractive power of the first lens group G1 becomes too high, making it difficult to correct various aberrations, which is undesirable, and if the upper limit of condition (5) is exceeded, the refractive power of the first lens group G1 becomes too low, which undesirably increases the size of the lens barrel.

[0126] Preferably, the above-mentioned effects can be further enhanced by satisfying either one or both of the following conditions (5a) and (5b):

[0127] 1.0 < | f1 / fw | (5a) | f1 / fw | < 2.0 (5b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (5c) and (5d):

[0128] 1.3 < | f1 / fw | (5c) | f1 / fw | < 1.5 (5d) Furthermore, for example, in the basic configuration of the imaging optical system, it is desirable that the second lens group G2 has one or more positive lens elements and satisfies the following condition (6):

[0129] 65 < L2νd < 100 (6) where: L2νd: Abbe number of at least one positive lens element among the one or more positive lens elements constituting the second lens group G2, is.

[0130] Condition (6) sets forth the Abbe number of at least one positive lens element among the one or more positive lens elements constituting second lens group G2 in the imaging optical system.

[0131] By satisfying the condition (6), various aberrations, particularly lateral chromatic aberration, can be effectively corrected.

[0132] Conversely, if the lower limit of condition (6) is exceeded, a high-dispersion glass must be selected as the material for the positive lens element in the second lens group G2, which makes it difficult to correct chromatic aberration, and if the upper limit of condition (6) is exceeded, a low-refractive index material must be selected as the material for the positive lens element in the second lens group G2, which makes it difficult to correct spherical aberration, and this is also undesirable.

[0133] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (6a) and (6b):

[0134] 70 < L2νd (6a) L2νd < 90 (6b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (6c) and (6d):

[0135] 80 < L2νd (6c) L2νd < 85 (6d) Furthermore, for example, in an imaging optical system, it is desirable that the second lens group G2 has an aperture stop A closest to the object side and satisfies the following condition (7):

[0136] 0.05 < G2L / Lt < 0.25 (7) where: G2L: total thickness of the second lens group G2, Lt: total optical length at the telephoto end of the imaging optical system, is.

[0137] Condition (7) is a condition for specifying the ratio in the imaging optical system between the total thickness of the second lens group G2 (the distance on the optical axis from the aperture stop A to the image-side surface of the lens element located closest to the image) and the total optical length at the telephoto end of the imaging optical system (the distance on the optical axis between the object-side surface of the lens element located closest to the object in the imaging optical system and the image plane S).

[0138] By satisfying condition (7), the length of the lens barrel when retracted can be reduced.

[0139] Conversely, if the lower limit of condition (7) is exceeded, the total thickness of the second lens group G2 becomes too thin, making it difficult to correct various aberrations, which is undesirable, and if the upper limit of condition (7) is exceeded, the length of the lens barrel when retracted becomes too long, which is undesirable.

[0140] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (7a) and (7b):

[0141] 0.10 < G2L / Lt (7a) G2L / Lt < 0.20 (7b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (7c) and (7d):

[0142] 0.12 < G2L / Lt (7c) G2L / Lt < 0.15 (7d) Furthermore, for example, in an imaging optical system with a basic configuration, it is desirable that the second lens group G2 has, in order from the object side, a lens element having positive power, a lens element having negative power, and a lens element having positive power.

[0143] This allows various aberrations to be corrected effectively.

[0144] Also, for example, in an imaging optical system, it is desirable that the second lens group G2 has an aperture stop A that is disposed closest to the object and moves integrally with the other elements of the second lens group G2.

[0145] This allows the lens diameter of the first lens group G1 to be reduced and the number of cam grooves to be reduced, thereby enabling the lens barrel to be made more compact.

[0146] Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (8):

[0147] 0.05 < G2m / Lt < 0.4 (8) where: G2m: the movement amount of the second lens group G2 when zooming from the wide-angle end to the telephoto end of the imaging optical system, Lt: total optical length at the telephoto end of the imaging optical system, is.

[0148] Condition (8) is a condition for specifying the ratio of the amount of movement of the second lens group G2 during zooming from the wide-angle end to the telephoto end in an imaging optical system to the total optical length at the telephoto end (the distance on the optical axis between the object-side surface of the lens element located closest to the object in the imaging optical system and the image plane S).

[0149] By satisfying condition (8), the cam barrel can be shortened, thereby reducing the length of the lens barrel when retracted.

[0150] Conversely, if the lower limit of condition (8) is exceeded, the refractive power of the second lens group G2 becomes too high, making it impossible to correct various aberrations, which is undesirable, and if the upper limit of condition (8) is exceeded, the length of the lens barrel when retracted becomes too long, which is undesirable.

[0151] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (8a) and (8b):

[0152] 0.10 < G2m / Lt (8a) G2m / Lt < 0.30 (8b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (8c) and (8d):

[0153] 0.14 < G2m / Lt (8c) G2m / Lt < 0.20 (8d) Furthermore, for example, in the basic configuration of the imaging optical system, it is desirable that the third lens group G3 is made up of a single lens element.

[0154] By configuring the third lens group G3 with a single lens element, it is possible to reduce the weight of the third lens group G3, and it becomes easier to achieve high-speed focusing.

[0155] Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (9):

[0156] L3nd < 1.65 (9) where: L3nd: refractive index of a single lens element in the third lens group G3, is.

[0157] The condition (9) sets forth the refractive index of the single lens element in the third lens group G3 in the imaging optical system.

[0158] By satisfying the condition (9), it is possible to reduce the weight of the third lens group G3, and it becomes easier to achieve high-speed focusing.

[0159] Conversely, if the upper limit of the condition (9) is exceeded, a glass material must be selected as the material for the single lens element of the third lens group G3, and the weight of the focus lens increases.

[0160] Preferably, the above effect can be further enhanced by satisfying the following condition (9a):

[0161] L3nd < 1.60 (9a) More preferably, the above-mentioned effect can be further enhanced by satisfying the following condition (9b):

[0162] L3nd < 1.55 (9b) It is also desirable that the imaging optical system, for example, satisfy the following condition (10) simultaneously with any one of the above-mentioned conditions (9), (9a), and (9b):

[0163] L3νd < 65 (10) where: L3νd: Abbe number of a single lens element in the third lens group G3, is.

[0164] The condition (10) sets forth the Abbe number of the single lens element in the third lens group G3 in the imaging optical system.

[0165] By satisfying the condition (10), it is possible to reduce the weight of the third lens group G3, and high-speed focusing becomes easier.

[0166] Conversely, if the upper limit of the condition (10) is exceeded, a glass material must be selected as the material for the single lens element of the third lens group G3, and the weight of the focus lens increases.

[0167] Preferably, the above effect can be further enhanced by satisfying the following condition (10a):

[0168] L3νd < 60 (10a) More preferably, the above-mentioned effect can be further enhanced by satisfying the following condition (10b):

[0169] L3νd < 56 (10b) Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (11):

[0170] 0.3 < | f3 / fw | < 2.5 ···(11) where: f3: focal length of the third lens group G3, fw: focal length at the wide-angle end of the imaging optical system, is.

[0171] The condition (11) sets forth the ratio of the focal length of the third lens group G3 to the focal length of the imaging optical system at the wide-angle end.

[0172] By satisfying the condition (11), the balance between the focusing speed and the stopping accuracy can be optimized.

[0173] Conversely, if the lower limit of condition (11) is exceeded, the power of the focus group will be too strong, which will degrade stopping accuracy, and if the upper limit of condition (11) is exceeded, the power of the focus group will be too weak, which will reduce speed, which is also undesirable.

[0174] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (11a) and (11b).

[0175] 0.7 < | f3 / fw | (11a) | f3 / fw | < 1.7 (11b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (11c) and (11d):

[0176] 1.0 < | f3 / fw | (11c) | f3 / fw | < 1.5 (11d) Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (12):

[0177] 0.2 < LTt / Lt < 0.8 (12) where: LTt: total lens length at the telephoto end of the imaging optical system, Lt: total optical length at the telephoto end of the imaging optical system, is.

[0178] Condition (12) is a condition for specifying the ratio of the total lens length at the telephoto end of the imaging optical system (the distance on the optical axis between the object-side surface of the lens element located closest to the object and the image-side surface of the lens element located closest to the image) to the total optical length at the telephoto end of the imaging optical system (the distance on the optical axis between the object-side surface of the lens element located closest to the object and the image plane S).

[0179] By satisfying condition (12), the length of the lens barrel when retracted can be reduced.

[0180] Conversely, if the lower limit of condition (12) is exceeded, the overall lens length at the telephoto end becomes too short, which is undesirable because sufficient resolution performance cannot be obtained, and if the upper limit of condition (12) is exceeded, the length of the lens barrel when retracted becomes too long, which is undesirable.

[0181] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (12a) and (12b):

[0182] 0.3 < Lt / Lt (12a) LTt / Lt < 0.7 (12b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (11c) and (11d):

[0183] 0.4 < Lt / Lt (12c) LTt / Lt < 0.5 (12d) Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (13):

[0184] 0.5 < BFw / Yw < 2.5 (13) where: BFw: back focus at the wide-angle end of the imaging optical system, Yw: image height at the wide-angle end of the imaging optical system, is.

[0185] Condition (13) specifies the ratio of the back focus (the distance on the optical axis from the image-side surface of the lens element closest to the image side to the image plane S) at the wide-angle end of the imaging optical system to the image height at the wide-angle end of the imaging optical system.

[0186] By satisfying condition (13), miniaturization becomes possible.

[0187] Conversely, if the lower limit of condition (13) is exceeded, the back focal length becomes too short, which is undesirable because the lens and the imaging surface tend to interfere with each other, while if the upper limit of condition (13) is exceeded, the back focal length becomes too long, which is undesirable because the entire lens system becomes large.

[0188] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (13a) and (13b):

[0189] 1.0 < BFw / Yw (13a) BFw / Yw < 2.0 (13b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (13c) and (13d):

[0190] 1.4 < BFw / Yw (13c) BFw / Yw < 1.6 (13d) Furthermore, for example, it is desirable that the imaging optical system satisfy the following condition (14):

[0191] 0.6 < Lt / Lw < 1.2 (14) where: Lt: total optical length at the telephoto end of the imaging optical system, Lw: total optical length at the wide-angle end of the imaging optical system, is.

[0192] Condition (14) is a condition for specifying the ratio of the total optical length of the imaging optical system at the telephoto end (the distance on the optical axis between the object-side surface of the lens element located closest to the object in the imaging optical system and the image plane S) to the total optical length of the imaging optical system at the wide-angle end (the distance on the optical axis between the object-side surface of the lens element located closest to the object in the imaging optical system and the image plane S).

[0193] By satisfying the condition (14), the dimension of the zoom cam in the optical axis direction becomes smaller, and the length of the lens barrel when retracted can be reduced.

[0194] Conversely, if the lower limit of condition (14) is exceeded, the overall lens length at the telephoto end of the imaging optical system becomes too short, making it difficult to increase the zoom ratio, which is undesirable. Also, if the upper limit of condition (14) is exceeded, the dimension of the zoom cam in the optical axis direction becomes too long, making the entire lens system large, which is undesirable.

[0195] Preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (14a) and (14b):

[0196] 0.8 < Lt / Lw (14a) Lt / Lw < 1.1 (14b) More preferably, the above-mentioned effect can be further enhanced by satisfying either one or both of the following conditions (14c) and (14d):

[0197] 0.9 < Lt / Lw (14c) Lt / Lw < 1.0 (14d) (Schematic configuration of an imaging device to which the first embodiment is applied) 6 shows a schematic configuration of an imaging device to which the imaging optical system according to Embodiment 1 is applied. Note that the imaging optical systems according to Embodiments 2 to 5 can also be applied to imaging devices.

[0198] The imaging device 100 is made up of a housing 104, an imaging element 102, and an imaging optical system 101 according to Embodiment 1. A specific example of the imaging device 100 is a digital camera.

[0199] The housing 104 has a lens barrel 302. The lens barrel 302 holds each lens group of the imaging optical system 101 (including the aperture stop A).

[0200] The image pickup element 102 is disposed at the position of the image plane S in the image pickup optical system according to the first embodiment.

[0201] The imaging optical system 101 is configured such that the lens frames included in the lens barrel 302 are attached to or engaged with each of the first lens group G1, the second lens group G2, and the third lens group G3 so that the first lens group G1, the second lens group G2, and the third lens group G3 move during zooming. In an imaging device 100 equipped with an imaging optical system 101 having each lens group held by a lens barrel 302, an actuator and a lens frame controlled by a controller within the imaging device 100 are configured so that the third lens group G3 moves during focusing.

[0202] This makes it possible to realize an imaging device that can effectively correct various aberrations.

[0203] Although the imaging optical system according to the first embodiment described above is applied to a digital camera, it can also be applied to a digital video camera, a surveillance camera, a smartphone, and the like.

[0204] (Schematic configuration of a camera system to which the first embodiment is applied) 7 shows a schematic configuration of a camera system to which the imaging optical system according to Embodiment 1 is applied. Note that the imaging optical systems according to Embodiments 2 to 5 can also be applied to a camera system.

[0205] The camera system 200 includes a camera body 201 and an interchangeable lens device 300 that is detachably connected to the camera body 201 .

[0206] The camera body 201 includes an image sensor 202 that receives an optical image formed by the imaging optical system 101 of the interchangeable lens device 300 and converts it into an electrical image signal, a monitor 203 that displays the image signal converted by the image sensor 202, a memory that stores the image signal, a camera mount unit 204, and a viewfinder 205.

[0207] The imaging optical system 101 of the interchangeable lens device 300 is the imaging optical system according to the first embodiment.

[0208] The interchangeable lens device 300 includes, in addition to the imaging optical system 101, a lens barrel 302 and a lens mount unit 304. The lens barrel 302 holds each lens group of the imaging optical system 101 and an aperture diaphragm A. The lens mount unit 304 is connected to the camera mount unit 204 of the camera body 201.

[0209] The camera mount unit 204 and the lens mount unit 304 are physically connected to each other. Furthermore, the camera mount unit 204 and the lens mount unit 304 electrically connect the controller in the camera body 201 and the controller in the interchangeable lens device 300, and also function as an interface that enables the exchange of signals between them.

[0210] The imaging optical system 101 is configured so that the lens frames included in the lens barrel 302 can be attached or engaged with each other so that the lens barrel 302 can move each of the lens frames holding the first lens group G1, the second lens group G2, and the third lens group G3 during zooming.

[0211] In a camera system 200 comprising a camera body 201 and each lens group held by a lens barrel 302, an actuator and a lens frame controlled by a controller within the interchangeable lens device 300 are configured so that the third lens group G3 moves when focusing the imaging optical system 101.

[0212] This makes it possible to realize an imaging device that can effectively correct various aberrations.

[0213] Although the imaging optical system according to the first embodiment described above is applied to a digital camera, it can also be applied to a digital video camera, a surveillance camera, a smartphone, and the like.

[0214] (Numerical example) Numerical examples that specifically implement the imaging optical systems according to Embodiments 1 to 5 will be described below. In each numerical example, all lengths in the tables are in "mm" and all angles of view are in "°". In each numerical example, r is the radius of curvature, d is the surface spacing, nd is the refractive index for the d-line, and νd (also written as vd) is the Abbe number for the d-line. In each numerical example, surfaces marked with an * are aspherical, and the aspherical shape is defined by the following equation:

[0215]

number

[0216] where: Z: The distance from a point on the aspheric surface at a height h from the optical axis to the tangent plane of the vertex of the aspheric surface. h: height from the optical axis, r: apex curvature radius, κ: conic constant, An: n-th order aspheric coefficient is.

[0217] 1B, 2B, 3B, 4B, and 5B are longitudinal aberration diagrams of the imaging optical systems according to the first to fifth embodiments in the infinity focused state.

[0218] In each longitudinal aberration diagram, (a) shows the aberrations at the wide-angle end, (b) shows the aberrations at the intermediate position, and (c) shows the aberrations at the telephoto end. Each longitudinal aberration diagram, from left to right, shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)). In each spherical aberration diagram, the vertical axis represents the F-number (denoted by F in the diagram), with the solid line representing the d-line, the short-dashed line representing the F-line, and the long-dashed line representing the C-line characteristics. In each astigmatism diagram, the vertical axis represents the image height (denoted by H in the diagram), with the solid line representing the sagittal plane (denoted by s) and the dashed line representing the meridional plane (denoted by m). In each distortion diagram, the vertical axis represents the image height (denoted by H in the diagram).

[0219] (Numerical Example 1) The imaging optical system of Numerical Example 1 corresponds to Embodiment 1 shown in Fig. 1A. Surface data of the imaging optical system of Numerical Example 1 is shown in Table 1A, aspherical surface data is shown in Table 1B, and various data in an infinity focused state are shown in Tables 1C to 1F.

[0220] (Table 1A: Surface data) Surface number rd nd vd object surface ∞ 1 29.72970 1.20000 2.00100 29.1 2 14.05380 6.07960 3* 320.00000 2.80000 1.53380 55.6 4* 92.08330 3.78540 5 -52.34240 0.90000 1.59283 68.6 6 45.03730 0.49090 7 28.48860 4.24410 1.80809 22.8 8 258.32790 Variable 9 (Aperture) ∞ 1.50000 10* 13.20250 3.90000 1.80610 40.7 11* -300.00000 1.82520 12 93.04890 0.50000 1.80610 33.3 13 7.23310 0.01000 1.56732 42.8 14 7.23310 2.70400 1.49700 81.6 15 -20.30710 Variable 16* -25.79700 1.90000 1.53380 55.6 17* 120.00000 variable 18 ∞ 2.10000 1.51680 64.2 19∞1.00000 Image plane ∞ (Table 1B: Aspheric Data) 3rd page K= 8.62779E-01, A4= 8.76762E-05, A6= 1.80523E-07, A8=-4.82966E-09 A10= 5.06456E-11, A12=-2.26364E-13, A14= 3.77768E-16 Side 4 K= 9.94897E-01, A4= 8.50255E-05, A6= 4.36081E-07, A8=-1.18646E-08 A10= 1.41878E-10, A12=-7.94806E-13, A14= 1.58526E-15 Side 10 K= 0.00000E+00, A4=-6.53783E-05, A6=-2.36530E-07, A8=-7.14212E-08 A10= 1.77714E-09, A12=-3.27660E-11, A14= 0.00000E+00 Page 11 K= 0.00000E+00, A4=-3.40712E-05, A6=-2.20996E-06, A8= 2.63690E-08 A10=-1.42969E-09, A12=8.16354E-12, A14= 0.00000E+00 Page 16 K= 0.00000E+00, A4= 4.09073E-04, A6=-2.52089E-05, A8= 1.70938E-06 A10=-6.51792E-08, A12=9.89011E-10, A14= 0.00000E+00 Page 17 K= 0.00000E+00, A4= 4.31564E-04,A6=-1.95480E-05, A8= 1.19295E-06 A10=-4.78744E-08, A12=9.90203E-10, A14=-8.03075E-12 (Various data when focused at infinity) (Table 1C: Various data) Zoom ratio 2.04640 Wide-angle Mid-range Telephoto Focal length 18.8119 26.9018 38.4968 F-number 4.51734 5.38496 6.54366 Angle of view 49.9560 38.6973 29.0433 Image height 20.0000 21.0000 21.6330 Optical total length 85.8995 83.0618 84.4826 d8 20.9499 10.6965 2.9333 d15 1.7994 2.0527 3.0078 d17 28.2110 35.3734 43.6023 Entrance pupil position 16.1941 14.0397 11.7232 Exit pupil position -39.6525 -46.9749 -55.7930 Front principal point position 26.0812 25.5164 23.6520 Back principal point position 67.0870 56.1028 45.9745 (Table 1D: Single lens data) Lens starting surface focal length 1 1 -27.6869 2 3 -243.2401 3 5 -40.6948 4 7 39.2998 5 10 15.7755 6 12 -9.7546 7 14 11.0929 8 16 -39.5965 (Table 1E: Zoom lens group data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -25.45755 19.50000 1.37841 5.00755 2 9 18.24439 10.43920 1.74368 4.29311 3 16 -39.59645 1.90000 0.21819 0.88503 (Table 1F: Zoom lens group magnification) Group Starting plane Wide angle Intermediate Telephoto 1 1 0.00000 0.00000 0.00000 2 9 -0.41092 -0.53431 -0.69153 3 16 1.79830 1.97775 2.18673

[0221] (Numerical Example 2) The imaging optical system of Numerical Example 2 corresponds to Embodiment 2 shown in Fig. 2A. Surface data of the imaging optical system of Numerical Example 2 is shown in Table 2A, aspherical surface data is shown in Table 2B, and various data in an infinity focused state are shown in Tables 2C to 2F.

[0222] (Table 2A: Surface data) Surface number rd nd vd object surface ∞ 1 37.24840 1.20000 1.90366 31.3 2 15.67780 4.81900 3* 325.00000 2.80000 1.53380 55.6 4* 483.93620 3.57370 5 -52.60720 0.90000 1.59283 68.6 6 35.97690 1.03590 7 28.18300 3.57480 1.80518 25.5 8 182.25580 Variable 9 (Aperture) ∞ 1.50000 10* 12.92780 3.70000 1.80998 40.9 11* -300.00000 1.53260 12 93.97250 0.50000 1.80610 33.3 13 7.49460 0.01000 1.56732 42.8 14 7.49460 3.85740 1.49700 81.6 15 -21.39470 Variable 16* -22.86130 1.80000 1.58313 59.5 17* 120.00000 variable 18 ∞ 2.10000 1.51680 64.2 19∞1.00000 Image plane ∞ (Table 2B: Aspheric Data) 3rd page K= 1.00000E+00, A4= 6.62444E-05,A6= 1.98979E-09, A8= 2.28777E-10 A10= 4.77023E-12, A12=-3.65710E-14, A14= 1.15964E-16 Side 4 K=-1.00000E+00, A4= 7.32903E-05, A6=-1.07423E-07, A8= 2.39063E-09 A10=-1.19083E-11, A12=2.97383E-14, A14= 3.73967E-17 Side 10 K= 0.00000E+00, A4=-3.37865E-05, A6=-5.39579E-07, A8=-1.33018E-08 A10= 2.05327E-10, A12=-9.96535E-12, A14= 0.00000E+00 Page 11 K= 0.00000E+00, A4= 9.56450E-06,A6=-1.44964E-06, A8= 2.65402E-08 A10=-1.18038E-09, A12=6.46899E-12, A14= 0.00000E+00 Page 16 K= 0.00000E+00, A4= 4.17495E-04, A6=-1.14683E-05, A8= 4.42428E-07 A10=-1.40695E-08, A12=1.94878E-10, A14= 0.00000E+00 Page 17 K= 0.00000E+00, A4= 4.33760E-04, A6=-6.14512E-06, A8=-5.96226E-08 A10= 1.07752E-08, A12=-3.95163E-10, A14= 4.98466E-12 (Various data when focused at infinity) (Table 2C: Various data) Zoom ratio 2.07060 Wide-angle Mid-range Telephoto Focal length 20.9036 30.0642 43.2831 F-number 4.51841 5.39313 6.53084 Angle of view 46.9719 35.3839 26.0549 Image height 20.0000 21.0000 21.6330 Optical total length 87.3161 83.8167 84.2164 d8 22.6993 11.6053 3.0000 d15 1.8337 2.1380 3.2000 d17 28.8797 36.1700 44.1130 Entrance pupil position 17.2260 14.6026 11.6746 Exit pupil position -40.3090 -47.7706 -56.2935 Front principal point position 27.2919 25.7154 21.6555 Back principal point position 66.4219 53.6754 40.8952 (Table 2D: Single lens data) Lens starting surface focal length 1 1 -30.7715 2 3 1842.5264 3 5 -35.9043 4 7 40.9805 5 10 15.3827 6 12 -10.1293 7 14 11.6857 8 16 -32.7787 (Table 2E: Zoom lens group data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -28.58421 17.90340 1.29204 4.59848 2 9 17.97139 11.10000 2.11654 4.76569 3 16 -32.77867 1.80000 0.18111 0.84937 (Table 2F: Zoom lens group magnification) Group Starting plane Wide angle Intermediate Telephoto 1 1 0.00000 0.00000 0.00000 2 9 -0.36877 -0.47746 -0.61897 3 16 1.98309 2.20286 2.44637

[0223] (Numerical Example 3) The imaging optical system of Numerical Example 3 corresponds to Embodiment 3 shown in Fig. 3A. Surface data of the imaging optical system of Numerical Example 3 is shown in Table 3A, aspherical surface data is shown in Table 3B, and various data in an infinity focused state are shown in Tables 3C to 3F.

[0224] (Table 3A: Surface data) Surface number rd nd vd object surface ∞ 1 30.00000 1.20000 2.05090 26.9 2 14.53720 4.64780 3* 82.00780 2.80000 1.53380 55.6 4* 32.36190 5.10450 5 -53.84480 0.90000 1.59283 68.6 6 39.91180 0.53270 7 26.47820 4.20000 1.80809 22.8 8 632.98110 Variable 9 (Aperture) ∞ 1.50000 10* 13.21070 3.10940 1.80998 40.9 11* -300.00000 2.44910 12 -940.69830 0.50000 1.80610 33.3 13 7.36220 0.01000 1.56732 42.8 14 7.36220 3.53150 1.49700 81.6 15 -15.99550 variable 16* -33.26220 1.10000 1.53380 55.6 17* 120.00000 variable 18 ∞ 2.10000 1.51680 64.2 19∞1.00000 Image plane ∞ (Table 3B: Aspheric data) 3rd page K= 9.44891E-01, A4= 1.10925E-04, A6=-2.09561E-07, A8= 1.38825E-10 A10= 8.72661E-12, A12=-2.21577E-14, A14=-3.60858E-17 Side 4 K= 8.98781E-01, A4= 1.16756E-04, A6= 7.36789E-08, A8=-5.70612E-09 A10= 7.93221E-11, A12=-3.52468E-13, A14= 1.72808E-16 Side 10 K= 0.00000E+00, A4=-7.39091E-05,A6= 2.30028E-07, A8=-1.80242E-07 A10= 6.01341E-09, A12=-1.10169E-10, A14= 0.00000E+00 Page 11 K= 0.00000E+00, A4=-5.54399E-05, A6=-3.58977E-07, A8=-1.65689E-07 A10= 5.42608E-09, A12=-1.00718E-10, A14= 0.00000E+00 Page 16 K= 0.00000E+00, A4= 2.29263E-04, A6=-5.60094E-06, A8= 1.47830E-07 A10=-8.19708E-10, A12=-1.60641E-11, A14= 0.00000E+00 Page 17 K= 0.00000E+00, A4= 3.10661E-04, A6=-1.06217E-05, A8= 5.80641E-07 A10=-2.43922E-08, A12=6.04793E-10, A14=-6.44696E-12 (Various data when focused at infinity) (Table 3C: Various data) Zoom ratio 1.69617 Wide-angle Mid-range Telephoto Focal length 17.7305 23.0874 30.0739 F-number 4.51792 5.11820 5.88089 Angle of view 51.6270 43.6457 36.0494 Image height 20.0000 21.0000 21.6330 Optical total length 83.7824 81.2177 81.4574 d8 19.6505 11.9326 5.8252 d15 1.7864 1.9521 2.3794 d17 27.6605 32.6480 38.5678 Entrance pupil position 15.4681 13.9642 12.4068 Exit pupil position -39.7422 -44.8387 -51.0369 Front principal point position 25.2871 25.1555 24.7477 Back principal point position 66.0453 58.0986 51.3498 (Table 3D: Single Lens Data) Lens starting surface focal length 1 1 -27.9496 2 3 -102.1492 3 5 -38.5272 4 7 34.0915 5 10 15.6917 6 12 -9.0601 7 14 10.6804 8 16 -48.6669 (Table 3E: Zoom Lens Group Data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -24.12219 19.38500 1.26901 4.51850 2 9 18.93457 11.10000 2.25218 4.34883 3 16 -48.66687 1.10000 0.15526 0.53987 (Table 3F: Zoom lens group magnification) Group Starting plane Wide angle Intermediate Telephoto 1 1 0.00000 0.00000 0.00000 2 9 -0.45129 -0.55301 -0.67307 3 16 1.62873 1.73070 1.85230

[0225] (Numerical Example 4) The imaging optical system of Numerical Example 4 corresponds to Embodiment 4 shown in Fig. 4A. Surface data of the imaging optical system of Numerical Example 4 is shown in Table 4A, aspherical surface data is shown in Table 4B, and various data in an infinity focused state are shown in Tables 4C to 4F.

[0226] (Table 4A: Surface data) Surface number rd nd vd object surface ∞ 1 111.24910 2.49900 1.62299 58.1 2 344.85050 0.20000 3 39.04740 1.10000 2.00100 29.1 4 13.60580 8.08670 5 -85.84330 1.10000 1.59283 68.6 6 20.97500 0.20790 7 19.43880 5.80610 1.75211 25.0 8 296.49490 Variable 9 (Aperture) ∞ 1.40000 10* 13.08320 3.70000 1.80998 40.9 11* -1000.00000 1.03400 12 45.19980 0.60000 1.80610 33.3 13 7.36490 0.01000 1.56732 42.8 14 7.36490 3.56190 1.49700 81.6 15 -26.41290 Variable 16* -19.77570 1.53070 1.53380 55.6 17* 900.00000 variable 18 ∞ 2.10000 1.51680 64.2 19∞1.00000 Image plane ∞ (Table 4B: Aspheric data) Side 10 K= 0.00000E+00, A4=-6.05193E-05,A6= 1.89592E-06, A8=-2.34889E-07 A10= 8.33876E-09, A12=-1.25507E-10, A14= 0.00000E+00 Page 11 K= 0.00000E+00, A4=-3.07142E-05,A6= 2.32034E-06, A8=-3.32646E-07 A10= 1.29001E-08, A12=-2.04486E-10, A14= 0.00000E+00 Page 16 K= 0.00000E+00, A4= 7.16225E-04, A6=-1.54379E-05, A8= 3.61808E-07 A10=-8.98837E-09, A12=1.17515E-10, A14= 1.29606E-14 Page 17 K= 0.00000E+00, A4= 7.16071E-04, A6=-9.10540E-06, A8=-9.24790E-08 A10= 7.83931E-09, A12=-1.27323E-10, A14=-3.37398E-14 (Various data when focused at infinity) (Table 4C: Various data) Zoom ratio 2.04650 Wide-angle Mid-range Telephoto Focal length 18.8124 26.9065 38.4995 F-number 4.60834 5.51242 6.59329 Angle of view 50.2618 39.1674 28.9957 Image height 20.0000 21.0000 21.6330 Optical total length 87.3125 85.2965 84.9847 d8 22.5135 12.7150 4.5000 d15 1.8239 1.9853 3.5708 d17 29.0388 36.6599 42.9776 Entrance pupil position 16.9939 14.9688 12.5313 Exit pupil position -39.9879 -47.7095 -54.9784 Front principal point position 26.9727 26.6902 24.0887 Back principal point position 68.5760 58.3561 46.5215 (Table 4D: Single Lens Data) Lens starting surface focal length 1 1 262.5355 2 3 -21.3222 3 5 -28.3253 4 7 27.4125 5 10 15.9700 6 12 -10.9928 7 14 12.0081 8 16 -36.2294 (Table 4E: Zoom Lens Group Data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -24.66096 18.99970 2.57731 6.80868 2 9 17.56620 10.30590 1.86920 4.64365 3 16 -36.22936 1.53070 0.02144 0.55474 (Table 4F: Zoom lens group magnification) Group Starting plane Wide angle Intermediate Telephoto 1 1 0.00000 0.00000 0.00000 2 9 -0.40226 -0.51864 -0.68471 3 16 1.89638 2.10371 2.28002

[0227] (Numerical Example 5) The imaging optical system of Numerical Example 5 corresponds to Embodiment 5 shown in Fig. 5A. Surface data of the imaging optical system of Numerical Example 5 is shown in Table 5A, aspherical surface data is shown in Table 5B, and various data in an infinity focused state are shown in Tables 5C to 5F.

[0228] (Table 5A: Surface data) Surface number rd nd vd object surface ∞ 1 145.51400 1.20000 1.90366 31.3 2 21.04080 0.99100 3* 56.75240 2.80000 1.53380 55.6 4* 44.06560 5.24990 5 -113.36270 0.90000 1.59283 68.6 6 72.81750 0.37410 7 29.72110 4.20000 1.80518 25.5 8 234.01010 Variable 9 (Aperture) ∞ 1.50000 10* 12.81670 3.69990 1.80998 40.9 11* -300.00000 2.22200 12 40.60520 0.50000 1.80610 33.3 13 6.22290 0.01000 1.56732 42.8 14 6.22290 4.17640 1.49700 81.6 15 -55.72170 1.05330 16* 94.71780 1.00000 1.58313 59.5 17* 13.29960 variable 18* 41.32870 3.90310 1.53380 55.6 19 344.47730 Variable 20 ∞ 2.10000 1.51680 64.2 21∞1.00000 Image plane ∞ (Table 5B: Aspheric Data) 3rd page K=-3.03205E-01, A4= 9.12291E-05, A6=-1.70317E-07, A8= 4.80458E-10 A10= 2.48935E-12, A12=-2.56896E-14, A14= 5.56985E-17 Side 4 K= 2.74714E-01, A4= 9.56179E-05, A6=-1.56448E-07, A8= 2.16577E-10 A10= 9.00574E-12, A12=-7.74235E-14, A14= 1.84046E-16 Side 10 K= 0.00000E+00, A4=-4.53962E-06,A6=-8.04827E-07, A8= 3.43337E-08 A10=-7.38922E-10, A12=6.20957E-12, A14= 0.00000E+00 Page 11 K= 0.00000E+00, A4= 4.95748E-05, A6=-8.50097E-07, A8= 3.80261E-08 A10=-8.91011E-10, A12=8.42035E-12, A14= 0.00000E+00 Page 16 K= 0.00000E+00, A4=-1.48070E-04,A6= 1.25291E-05, A8=-5.58940E-07 A10= 1.81660E-08, A12=-1.82258E-10, A14= 0.00000E+00 Page 17 K= 0.00000E+00, A4=-2.36783E-04, A6= 6.93683E-06, A8=-1.76554E-07 A10=-8.48798E-10, A12=1.90643E-10, A14=-2.93084E-12 Page 18 K= 0.00000E+00, A4=-7.41983E-06,A6= 2.96220E-08, A8=-6.23047E-11 A10= 1.65405E-13, A12=-2.12472E-16, A14= 0.00000E+00 (Various data when focused at infinity) (Table 5C: Various data) Zoom ratio 1.92306 Wide-angle Mid-range Telephoto Focal length 24.9597 34.6116 47.9991 F-number 4.67546 5.30328 6.30592 Angle of view 41.9670 32.0865 24.4016 Image height 20.0000 21.0000 21.6330 Optical total length 95.3496 87.0631 87.5201 d8 27.4297 12.5662 3.0000 d17 17.0402 12.6982 11.6711 d19 14.0000 24.9190 35.9693 Entrance pupil position 18.1978 14.0683 10.2619 Exit pupil position -52.4765 -55.6647 -65.0288 Front principal point position 31.2875 27.1393 22.8040 Back principal point position 70.3977 52.4010 39.4699 (Table 5D: Single Lens Data) Lens starting surface focal length 1 1 -27.3451 2 3 -400.0003 3 5 -74.6560 4 7 41.8983 5 10 15.2559 6 12 -9.1765 7 14 11.5210 8 16 -26.6534 9 18 87.5860 (Table 5E: Zoom Lens Group Data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 -38.55272 15.71500 -1.99425 0.74662 2 9 31.35226 14.16160 -11.82696 -1.81248 3 18 87.58602 3.90310 -0.34538 1.02435 (Table 5F: Zoom lens group magnification) Group Starting plane Wide angle Intermediate Telephoto 1 1 0.00000 0.00000 0.00000 2 9 -0.83005 -1.36861 -2.34991 3 18 0.77998 0.65597 0.52982

[0229] (Condition's corresponding value) Table 1 below shows the corresponding values ​​for conditions (1) to (14).

[0230] [Table 1] [Industrial Applicability]

[0231] The imaging optical system according to the present disclosure is applicable to digital still cameras, digital cameras with interchangeable lenses, digital video cameras, cameras in mobile phone devices such as smartphones, cameras in PDAs (Personal Digital Assistances), surveillance cameras in surveillance systems, web cameras, in-vehicle cameras, and the like, and is particularly suitable for imaging optical systems that require high image quality, such as digital still camera systems and digital video camera systems.

Claims

1. From the object side to the image side, a first lens group having negative power; a second lens group having positive power; a third lens group having power; and An imaging optical system comprising: the first lens group, the second lens group, and the third lens group move along an optical axis of the imaging optical system so that intervals between adjacent lens groups change during zooming from a wide-angle end to a telephoto end of the imaging optical system; The imaging optical system satisfies the following condition (1): 1.85 < L1nd...(1) where: L1nd: the refractive index of the negative lens element located closest to the object, That is, Imaging optical system.

2. the third lens group has negative power; The imaging optical system according to claim 1 .

3. the first lens group is composed of three or more lens elements; The imaging optical system according to claim 1 .

4. The imaging optical system satisfies the following condition (2): 0.5<R11 / fw<8.0...(2) where: R11: the radius of curvature of the object-side surface of the negative lens element located closest to the object, fw: focal length of the imaging optical system at the wide-angle end, That is, The imaging optical system according to claim 1 .

5. the first lens group has two or more negative lens elements; The imaging optical system satisfies the following condition (3): 60 < L1νd < 100 (3) where: L1νd: Abbe number of one of the two or more negative lens elements, That is, The imaging optical system according to claim 1 .

6. The imaging optical system satisfies the following condition (4): 0.1 < G1L / Lt < 0.4 ... (4) where: G1L: total thickness of the first lens group, Lt: total optical length of the imaging optical system at the telephoto end, That is, The imaging optical system according to claim 1 .

7. During zooming of the imaging optical system from the wide-angle end to the telephoto end, the first lens group moves along a locus convex toward the image side. The imaging optical system according to claim 1 .

8. The imaging optical system satisfies the following condition (5): 0.5 < | f1 / fw | < 3.0...(5) where: f1: focal length of the first lens group, fw: focal length of the imaging optical system at the wide-angle end, That is, The imaging optical system according to claim 1 .

9. the second lens group has one or more positive lens elements, The imaging optical system satisfies the following condition (6): 65 < L2νd < 100 (6) where: L2νd: Abbe number of at least one positive lens element among the one or more positive lens elements, That is, The imaging optical system according to claim 1 .

10. the second lens group includes an aperture stop closest to the object, The imaging optical system satisfies the following condition (7): 0.05<G2L / Lt<0.25...(7) where: G2L: total thickness of the second lens group, Lt: total optical length of the imaging optical system at the telephoto end, That is, The imaging optical system according to claim 1 .

11. The second lens group includes, in order from the object side, a lens element having a positive power; a lens element having negative power; a lens element having a positive power; having The imaging optical system according to claim 1 .

12. the second lens group has an aperture stop that is disposed closest to the object and moves integrally with other elements of the second lens group; The imaging optical system according to claim 1 .

13. The imaging optical system satisfies the following condition (8): 0.05 < G2m / Lt < 0.4 ... (8) where: G2m: the movement amount of the second lens group during zooming of the imaging optical system from the wide-angle end to the telephoto end, Lt: total optical length of the imaging optical system at the telephoto end, That is, The imaging optical system according to claim 1 .

14. the third lens group is composed of a single lens element; The imaging optical system satisfies the following conditions (9) and (10): L3nd < 1.65...(9) L3νd < 65...(10) where: L3nd: the refractive index of the single lens element in the third lens group, L3νd: Abbe number of the single lens element in the third lens group, That is, The imaging optical system according to claim 1 .

15. The imaging optical system satisfies the following condition (11): 0.3 < | f3 / fw | < 2.5 ... (11) where: f3: the focal length of the third lens group, fw: focal length of the imaging optical system at the wide-angle end, That is, The imaging optical system according to claim 1 .

16. The imaging optical system satisfies the following condition (12): 0.2 < LTt / Lt < 0.8 (12) where: LTt: total lens length of the imaging optical system at the telephoto end, Lt: total optical length of the imaging optical system at the telephoto end, That is, The imaging optical system according to claim 1 .

17. The imaging optical system satisfies the following condition (13): 0.5 < BFw / Yw < 2.5 (13) where: BFw: back focus at the wide-angle end of the imaging optical system, Yw: image height at the wide-angle end of the imaging optical system, That is, The imaging optical system according to claim 1 .

18. The imaging optical system satisfies the following condition (14): 0.6 < Lt / Lw < 1.2 (14) where: Lt: total optical length of the imaging optical system at the telephoto end, Lw: total optical length of the imaging optical system at the wide-angle end, That is, The imaging optical system according to claim 1 .

19. an interchangeable lens device including the imaging optical system according to any one of claims 1 to 18; a camera body that is detachably connected to the interchangeable lens device via a camera mount and includes an image sensor that receives an optical image of an object formed by the image pickup optical system and converts the image into an electrical image signal; Equipped with the interchangeable lens device forms the optical image of the object on the imaging element; Camera system.

20. 1. An imaging device that converts an optical image of an object into an electrical image signal and at least one of displays and stores the converted image signal, an imaging optical system according to any one of claims 1 to 18, which forms the optical image of the object; an imaging element that converts the optical image formed by the imaging optical system into the electrical image signal; Equipped with Imaging device.

Images