Imaging optical system and imaging device equipped therewith

Abstract

To provide an image capturing optical system which offers good optical performance and an image capturing device having the mage capturing optical system.SOLUTION: An image capturing optical system is provided, consisting of a positive first lens group, an aperture stop, a positive second lens group, a negative third lens group, a positive fourth lens group, and a negative fifth lens group arranged in order from the most object side. When shifting focus from an object at infinity to a nearby object, the first lens group, third lens group, and fifth lens group are kept stationary relative to an image plane, and the second lens group and fourth lens group move along an optical axis to change the distances between the lens groups.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present disclosure relates to an imaging optical system in which various aberrations are satisfactorily corrected, and an imaging apparatus including the same. [Background Art]

[0002] Patent Literature 1 discloses an inner-focus imaging lens configured, in order from an object side to an image side, by a first lens group having positive power, a second lens group having positive power, a third lens group having negative power, a fourth lens group having positive power, and a fifth lens group having negative power. [Related Art] [Patent Literature]

[0003] [Patent Literature 1] Japanese Unexamined Patent Publication No. 2019-191502 [Summary of Invention] [Problem to be Solved by Invention]

[0004] An object of the present disclosure is to provide an imaging optical system in which various aberrations over the entire zoom range are satisfactorily corrected, and an imaging apparatus including the imaging optical system. [Means for Solving Problem]

[0005] The imaging optical system according to the present disclosure consists, in order from the most object side, of a first lens group having positive power, an aperture stop, a second lens group having positive power, a third lens group having negative power, a fourth lens group having positive power, and a fifth lens group having negative power. During focusing from an infinite focusing state to a close proximity focusing state, the first lens group, the third lens group, and the fifth lens group are fixed relative to an image plane, and the distance between each lens group is changed by moving the second lens group and the fourth lens group along an optical axis. The second lens group has, in order from the object side, a lens element with negative power and a lens element with positive power. And it satisfies the following condition (6).

[0006] 1.8 < nd2Gp ··· (6) Here, nd2Gp: Refractive index of the positive power lens element of the second lens group, That is the case.

[0007] Furthermore, the imaging optical system in this disclosure consists of, in order from the object side, a first lens group having positive power, an aperture diaphragm, a second lens group having positive power, a third lens group having negative power, a fourth lens group having positive power, and a fifth lens group having negative power. When focusing from infinity to near-focus, the first, third, and fifth lens groups are fixed with respect to the image plane, and the spacing between each lens group changes as the second and fourth lens groups move along the optical axis. The fifth lens group consists of a single lens element. And the following condition (8) is satisfied.

[0008] 50 < νd5G ··· (8) Here, νd5G: Abbe number of the lens element of the 5th lens group, That is the case.

[0009] Furthermore, the imaging optical system in this disclosure consists of, in order from the object side, a first lens group having positive power, an aperture diaphragm, a second lens group having positive power, a third lens group having negative power, a fourth lens group having positive power, and a fifth lens group having negative power. When focusing from infinity to near-focus, the first, third, and fifth lens groups are fixed with respect to the image plane, and the spacing between each lens group changes as the second and fourth lens groups move along the optical axis. The following condition (9) is satisfied.

[0010] 0.4< (1-β4×β4)×β4r×β4r < 1.0 (9) Here, β4: Horizontal magnification when the fourth lens group is focused at infinity. β4r: The combined lateral magnification of all lenses positioned on the image side from the fourth lens group when focused at infinity. That is the case.

[0011] Furthermore, the imaging optical system in this disclosure consists of, in order from the object side, a first lens group having positive power, an aperture diaphragm, a second lens group having positive power, a third lens group having negative power, a fourth lens group having positive power, and a fifth lens group having negative power. When focusing from infinity to near-focus, the first, third, and fifth lens groups are fixed with respect to the image plane, and the spacing between each lens group changes as the second and fourth lens groups move along the optical axis. The first lens group has, at the image side, a single image shake correction lens that moves perpendicular to the optical axis. And the following condition (10) is satisfied.

[0012] 0.2 ≦ |(1−β)×βr| ≦ 1.0 ···(10) Here, β: Lateral magnification of the image blur correction lens when focused at infinity. βr: The combined lateral magnification of all lenses positioned on the image side of the image stabilization lens when focused at infinity. That is the case.

[0013] Furthermore, the imaging optical system in this disclosure comprises, in order from the object side, a first lens group having positive power, an aperture diaphragm, a second lens group having positive power, a third lens group having negative power, a fourth lens group having positive power, and a fifth lens group having negative power. When focusing from infinity to near-focus, the first, third, and fifth lens groups are fixed with respect to the image plane, and the spacing between each lens group changes as the second and fourth lens groups move along the optical axis. The first lens group comprises, in order from the object side, a lens element having negative power, a lens element having positive power, a lens element having positive power, and a lens element having negative power.

[0014] Also, The image pickup apparatus according to the present disclosure is an image pickup apparatus capable of outputting an optical image of an object as an electrical image signal, and forms an optical image of the object As described in any of the above an image pickup optical system, and an image pickup device that converts the optical image formed by the image pickup optical system into an electrical image signal, It is equipped with.

Advantageous Effects of Invention

[0015] According to this disclosure, it is possible to provide an imaging optical system in which aberrations are well corrected and an imaging apparatus equipped therewith. [Brief explanation of the drawing]

[0016] [Figure 1A] Lens arrangement diagram showing the infinity focus state of the imaging optical system according to Embodiment 1 (Numerical Example 1) [Figure 1B] Longitudinal aberration diagram at each focus position of the imaging optical system according to numerical example 1 [Figure 1C] Transverse aberration diagrams in the basic state without image blur correction and with image blur correction applied, when the imaging optical system according to numerical example 1 is in focus on an object at infinity. [Figure 2A] Lens arrangement diagram showing the infinity focus state of the imaging optical system according to Embodiment 2 (Numerical Example 2) [Figure 2B] Longitudinal aberration diagrams at each focus position of the imaging optical system according to numerical example 2 [Figure 2C] Transverse aberration diagrams in the basic state without image blur correction and with image blur correction applied, in the state of infinity object focus of the imaging optical system according to numerical example 2. [Figure 3A] Lens arrangement diagram showing the infinity focus state of the imaging optical system according to Embodiment 3 (Numerical Example 3) [Figure 3B] Longitudinal aberration diagrams at each focus position of the imaging optical system according to numerical example 3 [Figure 3C] Transverse aberration diagrams in the basic state without image blur correction and with image blur correction applied, in the state of focusing on an object at infinity for the imaging optical system according to numerical example 3. [Figure 4A] Lens arrangement diagram showing the infinity focus state of the imaging optical system according to Embodiment 4 (Numerical Example 4) [Figure 4B] Longitudinal aberration diagram at each focus position of the imaging optical system according to numerical example 4 [Figure 4C] Transverse aberration diagrams in the basic state without image blur correction and with image blur correction applied, in the state of infinity object focus of the imaging optical system according to numerical example 4. [Figure 5A]Lens arrangement diagram showing the infinity focus state of the imaging optical system according to Embodiment 5 (Numerical Example 5) [Figure 5B] Longitudinal aberration diagram at each focus position of the imaging optical system according to numerical example 5 [Figure 5C] Lateral aberration diagrams in the basic state without image blur correction and with image blur correction applied, in the state of infinity object focus of the imaging optical system according to numerical example 5. [Figure 6] Schematic diagram of the imaging device according to Embodiment 1 [Figure 7] Schematic diagram of the camera system according to Embodiment 1 [Modes for carrying out the invention]

[0017] The embodiments will be described in detail below, with reference to the drawings as appropriate. However, unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.

[0018] The attached drawings and the following description are provided to enable a person skilled in the art to fully understand this disclosure, and are not intended to limit the subject matter described in the claims.

[0019] (Embodiments 1-5) The imaging optical systems according to Embodiments 1 to 5 will be described individually below with reference to the drawings.

[0020] Figures 1A, 2A, 3A, 4A, and 5A are lens arrangement diagrams of imaging optical systems according to embodiments 1 to 5, and all of them represent imaging optical systems in a state of point focus at infinity.

[0021] Figures 1A, 2A, 3A, 4A, and 5A (a) show the lens arrangement when the object is in point focus at infinity. Note that the aspect ratio is consistent in each figure (a).

[0022] In each figure (a), the asterisk * placed on the surface of a specific lens element indicates that the surface is aspherical.

[0023] Furthermore, the broken line arrows shown in (c) of each figure connect the positions of the lens group in the following states, from top to bottom: point focus on an object at infinity (Inf.), intermediate position (Mid.), and close-up object focus (CLO.). Note that the arrows simply connect the point focus state at infinity and the intermediate position, and the intermediate position and close-up object focus, and do not represent the actual movement of each lens group.

[0024] Furthermore, in (b) of each figure, the symbols G1 to G5 are indicated for each lens group, corresponding to the positions of each lens group shown in (a).

[0025] Furthermore, the symbols (+) and (-) attached to the signs of each lens group (G1 to G5) shown in (b) of each figure correspond to the power of each lens group. In other words, the symbol (+) indicates positive power, and the symbol (-) indicates negative power.

[0026] Furthermore, the arrows parallel to the optical axis attached to the lens groups shown in (b) of each figure represent focusing from the point-focus state for objects at infinity to the point-focus state for objects at close range. Note that in Figures 1A, 2A, 3A, 4A, and 5A, the reference numerals for each lens group are written below the position of each lens group in Figure (a). For convenience, arrows representing focusing are attached below these reference numerals for each lens group. The direction in which each lens group moves during focusing will be explained in detail later for each embodiment.

[0027] In each figure (a), the straight line on the far right indicates the position of the image plane S (the object-facing side of the image sensor). Therefore, the left side of the figure corresponds to the object side. Furthermore, a parallel plate P, such as a low-pass filter or cover glass, is placed between the last lens group facing the image plane S and the image plane S.

[0028] (Embodiment 1) Figure 1A shows the imaging optical system according to Embodiment 1.

[0029] The imaging optical system consists of, in order from the object side to the image side, a first lens group G1 with positive power, an aperture diaphragm A, a second lens group G2 with positive power, a third lens group G3 with negative power, a fourth lens group G4 with positive power, and a fifth lens group G5 with negative power.

[0030] The imaging optical system forms an image at the position of the image plane S.

[0031] The first lens group G1 consists 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 positive power, a fourth lens element L4 having negative power, and a fifth lens element L5 having positive power. The third lens element L3 and the fourth lens element L4 are bonded lenses joined together with an adhesive or the like.

[0032] The second lens group G2 consists of a sixth lens element L6 with negative power and a seventh lens element L7 with positive power, arranged in order from the object side to the image side. The sixth lens element L6 and the seventh lens element L7 are bonded together with an adhesive or the like.

[0033] The third lens group G3 consists of, in order from the object side to the image side, an eighth lens element L8 with positive power and a ninth lens element L9 with negative power. The eighth lens element L8 and the ninth lens element L9 are bonded together with an adhesive or the like.

[0034] The fourth lens group G4 consists of a tenth lens element L10 that has positive power.

[0035] The fifth lens group G5 consists of an eleventh lens element L11 that has negative power.

[0036] Each lens element will be explained.

[0037] The lens elements in the first lens group G1 are described below. The first lens element L1 is a biconcave lens. The second lens element L2 is a biconvex lens. The third lens element L3 is a biconvex lens. The fourth lens element L4 is a biconcave lens. The fifth lens element L5 is a biconvex lens. The surfaces on both sides of the fifth lens element L5 have an aspherical shape.

[0038] The lens elements in the second lens group G2 are described below. The sixth lens element L6 is a biconcave lens. The seventh lens element L7 is a biconvex lens. The object-facing surface of the sixth lens element L6 has an aspherical shape.

[0039] The lens elements in the third lens group G3 are described below. The eighth lens element L8 is a meniscus lens with a convex surface on the image side. The ninth lens element L9 is a biconcave lens.

[0040] The lens elements in the fourth lens group G4 are described below. The tenth lens element L10 is a biconvex lens. Both sides of the tenth lens element L10 have an aspherical shape.

[0041] The lens elements in the fifth lens group G5 are described below. The eleventh lens element L11 is a meniscus lens with a convex surface on the image side. Both sides of the eleventh lens element L11 have an aspherical shape.

[0042] In the imaging optical system according to Embodiment 1, when focusing from an infinity-focused object state to a close-up object state, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed to the image plane S. When focusing from an infinity-focused object state to a close-up object state during imaging, the second lens group G2 and the fourth lens group G4 move toward the object.

[0043] In detail, during focusing from a point-of-view state at infinity to a close-up object state, the second lens group G2 and the fourth lens group G4 move along the optical axis such 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, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 increases.

[0044] Furthermore, the fifth lens element L5 (image blur correction lens element), which is the image-side lens element within the first lens group G1, moves perpendicular to the optical axis to optically correct image blur. This image blur correction lens element allows the imaging optical system to correct image point movement caused by vibrations of the entire system. In other words, the imaging optical system can optically correct image blur caused by camera shake, vibrations, etc.

[0045] (Embodiment 2) Figure 2A shows the imaging optical system according to Embodiment 2.

[0046] The imaging optical system consists of, in order from the object side to the image side, a first lens group G1 with positive power, an aperture diaphragm A, a second lens group G2 with positive power, a third lens group G3 with negative power, a fourth lens group G4 with positive power, and a fifth lens group G5 with negative power.

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

[0048] The first lens group G1 consists 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 positive power, a fourth lens element L4 having negative power, and a fifth lens element L5 having positive power. The third lens element L3 and the fourth lens element L4 are bonded lenses joined together with an adhesive or the like.

[0049] The second lens group G2 consists of a sixth lens element L6 with negative power and a seventh lens element L7 with positive power, arranged in order from the object side to the image side. The sixth lens element L6 and the seventh lens element L7 are bonded together with an adhesive or the like.

[0050] The third lens group G3 consists of, in order from the object side to the image side, an eighth lens element L8 with positive power and a ninth lens element L9 with negative power. The eighth lens element L8 and the ninth lens element L9 are bonded together with an adhesive or the like.

[0051] The fourth lens group G4 consists of a tenth lens element L10 that has positive power.

[0052] The fifth lens group G5 consists of an eleventh lens element L11 that has negative power.

[0053] Each lens element will be explained.

[0054] The lens elements in the first lens group G1 are described below. The first lens element L1 is a biconcave lens. The second lens element L2 is a biconvex lens. The third lens element L3 is a biconvex lens. The fourth lens element L4 is a biconcave lens. The fifth lens element L5 is a biconvex lens. The surfaces on both sides of the fifth lens element L5 have an aspherical shape.

[0055] The lens elements in the second lens group G2 are described below. The sixth lens element L6 is a biconcave lens. The seventh lens element L7 is a biconvex lens. The object-facing surface of the sixth lens element L6 has an aspherical shape.

[0056] The lens elements in the third lens group G3 are described below. The eighth lens element L8 is a meniscus lens with a convex surface on the image side. The ninth lens element L9 is a biconcave lens.

[0057] The lens elements in the fourth lens group G4 are described below. The tenth lens element L10 is a biconvex lens. Both sides of the tenth lens element L10 have an aspherical shape.

[0058] The lens elements in the fifth lens group G5 are described below. The eleventh lens element L11 is a meniscus lens with a convex surface on the image side. Both sides of the eleventh lens element L11 have an aspherical shape.

[0059] In the imaging optical system according to Embodiment 1, when focusing from an infinity-focused object state to a close-up object state, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed to the image plane S. When focusing from an infinity-focused object state to a close-up object state during imaging, the second lens group G2 and the fourth lens group G4 move toward the object.

[0060] In detail, during focusing from a point-of-view state at infinity to a close-up object state, the second lens group G2 and the fourth lens group G4 move along the optical axis such 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, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 increases.

[0061] Furthermore, the fifth lens element L5 (image blur correction lens element), which is the image-side lens element within the first lens group G1, moves perpendicular to the optical axis to optically correct image blur. This image blur correction lens element allows the imaging optical system to correct image point movement caused by vibrations of the entire system. In other words, the imaging optical system can optically correct image blur caused by camera shake, vibrations, etc.

[0062] (Embodiment 3) Figure 3A shows the imaging optical system according to Embodiment 3.

[0063] The imaging optical system consists of, in order from the object side to the image side, a first lens group G1 with positive power, an aperture diaphragm A, a second lens group G2 with positive power, a third lens group G3 with negative power, a fourth lens group G4 with positive power, and a fifth lens group G5 with negative power.

[0064] The imaging optical system forms an image at the position of the image plane S.

[0065] The first lens group G1 consists 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 positive power, a fourth lens element L4 having negative power, and a fifth lens element L5 having positive power. The third lens element L3 and the fourth lens element L4 are bonded lenses joined together with an adhesive or the like.

[0066] The second lens group G2 consists of a sixth lens element L6 with negative power and a seventh lens element L7 with positive power, arranged in order from the object side to the image side. The sixth lens element L6 and the seventh lens element L7 are bonded together with an adhesive or the like.

[0067] The third lens group G3 consists of, in order from the object side to the image side, an eighth lens element L8 with positive power and a ninth lens element L9 with negative power. The eighth lens element L8 and the ninth lens element L9 are bonded together with an adhesive or the like.

[0068] The fourth lens group G4 consists of a tenth lens element L10 that has positive power.

[0069] The fifth lens group G5 consists of an eleventh lens element L11 that has negative power.

[0070] Each lens element will be explained.

[0071] The lens elements in the first lens group G1 are described below. The first lens element L1 is a biconcave lens. The second lens element L2 is a biconvex lens. The third lens element L3 is a biconvex lens. The fourth lens element L4 is a biconcave lens. The fifth lens element L5 is a biconvex lens. The surfaces on both sides of the fifth lens element L5 have an aspherical shape.

[0072] The lens elements in the second lens group G2 are described below. The sixth lens element L6 is a biconcave lens. The seventh lens element L7 is a biconvex lens. The object-facing surface of the sixth lens element L6 has an aspherical shape.

[0073] The lens elements in the third lens group G3 are described below. The eighth lens element L8 is a meniscus lens with a convex surface on the image side. The ninth lens element L9 is a biconcave lens.

[0074] The lens elements in the fourth lens group G4 are described below. The tenth lens element L10 is a biconvex lens. Both sides of the tenth lens element L10 have an aspherical shape.

[0075] The lens elements in the fifth lens group G5 are described below. The eleventh lens element L11 is a meniscus lens with a convex surface on the image side. Both sides of the eleventh lens element L11 have an aspherical shape.

[0076] In the imaging optical system according to Embodiment 1, when focusing from an infinity-focused object state to a close-up object state, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed to the image plane S. When focusing from an infinity-focused object state to a close-up object state during imaging, the second lens group G2 and the fourth lens group G4 move toward the object.

[0077] In detail, during focusing from a point-of-view state at infinity to a close-up object state, the second lens group G2 and the fourth lens group G4 move along the optical axis such 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, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 increases.

[0078] Furthermore, the fifth lens element L5 (image blur correction lens element), which is the image-side lens element within the first lens group G1, moves perpendicular to the optical axis to optically correct image blur. This image blur correction lens element allows the imaging optical system to correct image point movement caused by vibrations of the entire system. In other words, the imaging optical system can optically correct image blur caused by camera shake, vibrations, etc.

[0079] (Embodiment 4) Figure 4A shows the imaging optical system according to Embodiment 4.

[0080] The imaging optical system consists of, in order from the object side to the image side, a first lens group G1 with positive power, an aperture diaphragm A, a second lens group G2 with positive power, a third lens group G3 with negative power, a fourth lens group G4 with positive power, and a fifth lens group G5 with negative power.

[0081] The imaging optical system forms an image at the position of the image plane S.

[0082] The first lens group G1 consists 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 positive power, a fourth lens element L4 having negative power, and a fifth lens element L5 having positive power. The first lens element L1 and the second lens element L2 are bonded lenses joined together with an adhesive or the like. The third lens element L3 and the fourth lens element L4 are also bonded lenses joined together with an adhesive or the like.

[0083] The second lens group G2 consists of a sixth lens element L6 with negative power and a seventh lens element L7 with positive power, arranged in order from the object side to the image side. The sixth lens element L6 and the seventh lens element L7 are bonded together with an adhesive or the like.

[0084] The third lens group G3 consists of, in order from the object side to the image side, an eighth lens element L8 with positive power and a ninth lens element L9 with negative power. The eighth lens element L8 and the ninth lens element L9 are bonded together with an adhesive or the like.

[0085] The fourth lens group G4 consists of a tenth lens element L10 that has positive power.

[0086] The fifth lens group G5 consists of an eleventh lens element L11 that has negative power.

[0087] Each lens element will be explained.

[0088] The lens elements in the first lens group G1 are described below. The first lens element L1 is a biconcave lens. The second lens element L2 is a biconvex lens. The third lens element L3 is a biconvex lens. The fourth lens element L4 is a biconcave lens. The fifth lens element L5 is a biconvex lens. The surfaces on both sides of the fifth lens element L5 have an aspherical shape.

[0089] The lens elements in the second lens group G2 are described below. The sixth lens element L6 is a biconcave lens. The seventh lens element L7 is a biconvex lens. The object-facing surface of the sixth lens element L6 has an aspherical shape.

[0090] The lens elements in the third lens group G3 are described below. The eighth lens element L8 is a meniscus lens with a convex surface on the image side. The ninth lens element L9 is a plano-concave lens with a concave surface on the object side.

[0091] The lens elements in the fourth lens group G4 are described below. The tenth lens element L10 is a biconvex lens. Both sides of the tenth lens element L10 have an aspherical shape.

[0092] The lens elements in the fifth lens group G5 are described below. The eleventh lens element L11 is a meniscus lens with a convex surface on the image side. Both sides of the eleventh lens element L11 have an aspherical shape.

[0093] In the imaging optical system according to Embodiment 1, when focusing from an infinity-focused object state to a close-up object state, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed to the image plane S. When focusing from an infinity-focused object state to a close-up object state during imaging, the second lens group G2 and the fourth lens group G4 move toward the object.

[0094] In detail, during focusing from a point-of-view state at infinity to a close-up object state, the second lens group G2 and the fourth lens group G4 move along the optical axis such 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, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 increases.

[0095] Furthermore, the fifth lens element L5 (image blur correction lens element), which is the image-side lens element within the first lens group G1, moves perpendicular to the optical axis to optically correct image blur. This image blur correction lens element allows the imaging optical system to correct image point movement caused by vibrations of the entire system. In other words, the imaging optical system can optically correct image blur caused by camera shake, vibrations, etc.

[0096] (Embodiment 5) Figure 5A shows the imaging optical system according to Embodiment 5.

[0097] The imaging optical system consists of, in order from the object side to the image side, a first lens group G1 with positive power, an aperture diaphragm A, a second lens group G2 with positive power, a third lens group G3 with negative power, a fourth lens group G4 with positive power, and a fifth lens group G5 with negative power.

[0098] The imaging optical system forms an image at the position of the image plane S.

[0099] The first lens group G1 consists 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 positive power, a fourth lens element L4 having negative power, a fifth lens element having negative power, and a sixth lens element L6 having positive power. The third lens element L3 and the fourth lens element L4 are bonded lenses joined together with an adhesive or the like.

[0100] The second lens group G2 consists of a seventh lens element L7 with negative power and an eighth lens element L8 with positive power, arranged in order from the object side to the image side. The seventh lens element L7 and the eighth lens element L8 are bonded together with an adhesive or the like.

[0101] The third lens group G3 consists of a ninth lens element L9 with positive power and a tenth lens element L10 with negative power, arranged in order from the object side to the image side. The ninth lens element L9 and the tenth lens element L10 are bonded together with an adhesive or the like.

[0102] The fourth lens group G4 consists of an eleventh lens element L11 that has positive power.

[0103] The fifth lens group G5 consists of a twelfth lens element L12 that has negative power.

[0104] Each lens element will be explained.

[0105] The lens elements in the first lens group G1 are described below. The first lens element L1 is a biconcave lens. The second lens element L2 is a biconvex lens. The third lens element L3 is a biconvex lens. The fourth lens element L4 is a biconcave lens. The fifth lens element L5 is a biconcave lens. The sixth lens element L6 is a biconvex lens. The surfaces on both sides of the sixth lens element L6 have an aspherical shape.

[0106] The lens elements in the second lens group G2 are described below. The seventh lens element L7 is a biconcave lens. The eighth lens element L8 is a biconvex lens. The image-side surface of the eighth lens element L8 has an aspherical shape.

[0107] The lens elements in the third lens group G3 are described below. The ninth lens element L9 is a meniscus lens with a convex surface on the image side. The tenth lens element L10 is a biconcave lens.

[0108] The lens elements in the fourth lens group G4 are described below. The eleventh lens element L11 is a biconvex lens. Both sides of the eleventh lens element L11 have an aspherical shape.

[0109] The lens elements in the fifth lens group G5 are described below. The twelfth lens element L12 is a meniscus lens with a convex surface on the image side. Both sides of the twelfth lens element L12 have an aspherical shape.

[0110] In the imaging optical system according to Embodiment 1, when focusing from an infinity-focused object state to a close-up object state, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed to the image plane S. When focusing from an infinity-focused object state to a close-up object state during imaging, the second lens group G2 and the fourth lens group G4 move toward the object.

[0111] In detail, during focusing from a point-of-view state at infinity to a close-up object state, the second lens group G2 and the fourth lens group G4 move along the optical axis such 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, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 increases.

[0112] Furthermore, the sixth lens element L6 (image blur correction lens element), which is the image-side lens element within the first lens group G1, moves perpendicular to the optical axis to optically correct image blur. This image blur correction lens element allows the imaging optical system to correct image point movement caused by vibrations of the entire system. In other words, the imaging optical system can optically correct image blur caused by camera shake, vibrations, etc.

[0113] (Other embodiments) As described above, Embodiments 1 to 5 have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited thereto and can be applied to embodiments that are modified, replaced, added, or omitted as appropriate.

[0114] Furthermore, the number of lens groups and the number of lens elements within each lens group are actual numbers, and it is permissible to add lenses that do not actually possess any power.

[0115] Furthermore, while image blur correction is performed by moving the image blur correction lens element perpendicular to the optical axis, it is possible to correct image blur by moving it in a way that has a vertical component. For example, if the complexity of the lens barrel structure is acceptable, image blur correction may be performed by rotating the image blur correction lens element so that its center of rotation is on the optical axis.

[0116] (Conditions and effects, etc.) The following describes the conditions that can be satisfied by, for example, the imaging optical systems according to Embodiments 1 to 5. While multiple possible conditions are defined for the imaging optical systems according to Embodiments 1 to 5, the configuration that satisfies all of these conditions is the most effective. However, it is also possible to obtain an imaging optical system that produces corresponding effects by satisfying individual conditions.

[0117] The imaging optical system according to Embodiments 1 to 5 comprises, in order from the object side, a first lens group G1 having positive power, an aperture diaphragm A, a second lens group G2 having positive power, a third lens group G3 having negative power, a fourth lens group G4 having positive power, and a fifth lens group G5 having negative power. When focusing from an infinity focus state to a close-up focus state, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane S, and the spacing between each lens group changes as the second lens group G2 and the fourth lens group G4 move along the optical axis.

[0118] This makes it possible to provide an imaging optical system that is compact yet effectively corrects aberrations across the entire focus range.

[0119] Furthermore, for example, the imaging optical system should preferably satisfy the following condition (1).

[0120] 1.0 < f1 / f < 1.5 ···(1) Here, f1: Focal length of the first lens group G1, f: The total focal length of the system when focused at infinity. That is the case.

[0121] Condition (1) is a condition that defines the ratio of the focal length of the first lens group G1 to the focal length of the entire system when focused at infinity. By satisfying condition (1), an imaging optical system that can effectively correct various aberrations can be realized.

[0122] Conversely, if the value falls below the lower limit of condition (1), various aberrations, particularly field curvature, will occur, making it difficult to ensure good performance. Also, if the value exceeds the upper limit of condition (1), various aberrations, particularly coma aberration, will occur, making it difficult to ensure good performance.

[0123] Preferably, the above effects can be further enhanced by satisfying either or both of the following conditions (1a) and (1b).

[0124] 1.1 < f1 / f ···(1a) f1 / f < 1.4 ···(1b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (1c) and (1d).

[0125] 1.2 < f1 / f ···(1c) f1 / f < 1.35 ···(1d) Furthermore, for example, the imaging optical system should preferably satisfy the following condition (2).

[0126] 0.5 < |f5 / f| < 1.0 ···(2) Here, f5: Focal length of lens group G5, f: The total focal length of the system when focused at infinity. That is the case.

[0127] Condition (2) specifies the ratio of the focal length of the fifth lens group G5 to the total focal length of the entire system when focused at infinity. If the ratio falls below the lower limit of condition (2), various aberrations, especially coma and astigmatism, will occur, making it difficult to ensure good performance. Conversely, if the ratio exceeds the upper limit of condition (2), various aberrations, especially astigmatism, will occur, making it difficult to ensure good performance.

[0128] Preferably, the above effects can be further enhanced by satisfying either or both of the following conditions (2a) and (2b).

[0129] 0.55 < |f5 / f| ···(2a) |f5 / f| < 0.9 ···(2b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (2c) and (2d).

[0130] 0.6 < |f5 / f| ···(2c) |f5 / f| < 0.8 ···(2d) Furthermore, for example, the imaging optical system should preferably satisfy the following condition (3).

[0131] 1.8 ≦ f2 / f4 ≦ 3.4 (3) Here, f2: Focal length of the second lens group G2, f4: Focal length of the fourth lens group G4, That is the case.

[0132] Condition (3) specifies the ratio of the focal lengths of the second lens group G2 and the fourth lens group G4. By satisfying condition (3), a compact and effective aberration correction can be achieved.

[0133] Conversely, if the value falls below the lower limit of condition (3), various aberrations, especially spherical aberration and field curvature, will occur, making it difficult to ensure good performance. Also, if the value exceeds the upper limit of condition (3), various aberrations, especially spherical aberration and astigmatism, will occur, making it difficult to ensure good performance.

[0134] Preferably, the above effects can be further enhanced by satisfying either or both of the following conditions (3a) and (3b).

[0135] 2.0 ≤ f2 / f4 ···(3a) f2 / f4 ≤ 3.2 ···(3b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (3c) and (3d).

[0136] 2.2 ≤ f2 / f4 ···(3c) f2 / f4 ≤ 3.0 ···(3d) Furthermore, for example, the imaging optical system should preferably satisfy the following condition (4).

[0137] 0.1 < BF / Y < 0.5 ···(4) Here, BF: The distance along the optical axis from the lens surface with the strongest negative power on the image side to the image plane. Y: Maximum image height when focused at infinity. That is the case.

[0138] Condition (4) defines the ratio of the back focus to the maximum image height at infinity focus. If the value falls below the lower limit of condition (4), the back focus becomes too small, which is undesirable because it increases the likelihood of interference between the lens closest to the image sensor and the image sensor. Conversely, if the value exceeds the upper limit of condition (4), the back focus becomes too large, which is also undesirable because it increases the overall size of the lens.

[0139] Preferably, the above effects can be further enhanced by satisfying either or both of the following conditions (4a) and (4b).

[0140] 0.22 < BF / Y ···(4a) BF / Y < 0.38 ···(4b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (4c) and (4d).

[0141] 0.24 < BF / Y ···(4c) BF / Y < 0.36 ···(4d) Furthermore, for example, the imaging optical system should preferably satisfy the following condition (5).

[0142] 3.0 < TL / Y < 3.8 ···(5) Here, TL: Optical length when focused at infinity, Y: Maximum image height when focused at infinity. That is the case.

[0143] Condition (5) is a condition for defining the total optical length (the distance along the optical axis from the lens surface closest to the object to the image plane) and the maximum image height when the lens is focused at infinity.

[0144] If the value falls below the lower limit of condition (5), it becomes difficult to correct aberrations in the on-axis and off-axis light beams, which is undesirable. Conversely, if the value exceeds the upper limit of condition (5), miniaturization becomes difficult.

[0145] Preferably, the above effects can be further enhanced by satisfying either or both of the following conditions (5a) and (5b).

[0146] 3.1 < TL / Y ···(5a) TL / Y < 3.7 ···(5b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (5c) and (5d).

[0147] 3.3 < TL / Y ···(5c) TL / Y < 3.5 ···(5d) Furthermore, in an imaging optical system, for example, the second lens group G2 preferably has, in order from the object side, a lens element with negative power and a lens element with positive power, and satisfies the following condition (6).

[0148] 1.8 < nd2Gp ··· (6) Here, nd2Gp: Refractive index of the positive power lens element of the second lens group G2, That is the case.

[0149] Condition (6) specifies the preferred range of refractive index for the positive power lens element of the second lens group G2. Below the lower limit of condition (6), it becomes difficult to correct various aberrations, especially astigmatism and field curvature, in a balanced manner.

[0150] Preferably, the above effects can be further enhanced by satisfying the following condition (6a).

[0151] 1.82 < nd2Gp ···(6a) Furthermore, condition (6b) below specifies a preferred upper limit for condition (6). Exceeding the upper limit of condition (6b) may make it difficult to adequately correct the field curvature. In such cases, it is preferable to satisfy condition (6) or condition (6a) and then satisfy condition (6b).

[0152] nd2Gp < 2.1··· (6b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (6c) and (6d).

[0153] 1.84 < nd2Gp ···(6c) nd2Gp < 2.0··· (6d) Furthermore, for example, the imaging optical system should preferably satisfy the following condition (7).

[0154] 62 < νd4G ··· (7) Here, νd4G: Abbe number of the lens element of the fourth lens group G4, That is the case.

[0155] Condition (7) specifies the preferred range for the Abbe number of the lens element of the fourth lens group G4. If the Abbe number falls below the lower limit of condition (7), it becomes difficult to correct various aberrations, especially chromatic aberration, in a balanced manner.

[0156] Preferably, the above effects can be further enhanced by satisfying the following condition (7a).

[0157] 65 < νd4G ···(7a) Furthermore, condition (7b) below specifies a preferred upper limit for condition (7). Exceeding the upper limit of condition (7b) may make it difficult to adequately correct chromatic aberration. In such cases, it is preferable to satisfy condition (7) or condition (7a) and then satisfy condition (7b).

[0158] νd4G < 100···(7b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (7c) and (7d).

[0159] 70 < νd4G ···(7a) νd4G < 100···(7b) Furthermore, in an imaging optical system, for example, it is desirable that the fifth lens group consists of a single lens element and satisfies the following condition (8).

[0160] 50 < νd5G ··· (8) Here, νd5G: Abbe number of lens element G5 of lens group 5, That is the case.

[0161] Condition (8) specifies the preferred range for the Abbe number of the lens element of the fifth lens group G5. If the Abbe number falls below the lower limit of condition (8), it becomes difficult to correct various aberrations, especially chromatic aberration, in a balanced manner.

[0162] Preferably, the above effects can be further enhanced by satisfying the following condition (8a).

[0163] 54 < νd5G ···(8a) Furthermore, condition (8b) below specifies a preferred upper limit for condition (8). Exceeding the upper limit of condition (8b) may make it difficult to adequately correct chromatic aberration. In such cases, it is preferable to satisfy condition (8) or condition (8a) and then satisfy condition (8b).

[0164] νd5G < 80 ···(8b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (8c) and (8d).

[0165] 58 < νd5G ···(8a) νd5G < 64 ···(8b) Furthermore, for example, the imaging optical system should preferably satisfy the following condition (9).

[0166] 0.4< (1-β4×β4)×β4r×β4r < 1.0 (9) Here, β4: Horizontal magnification of the fourth lens group G4 when focused at infinity. β4r: The combined lateral magnification of all lenses positioned on the image side of the fourth lens group G4 when focused at infinity. That is the case.

[0167] Condition (9) defines the positional sensitivity of the fourth lens group G4. If the value falls below the lower limit of condition (9), the amount of movement of the fourth lens group G4 during focusing becomes large, making it difficult to miniaturize the lens system. Conversely, if the value exceeds the upper limit of condition (9), the positional sensitivity of the fourth lens group G4 becomes high, making it difficult to control during focusing, which is undesirable.

[0168] Preferably, the above effects can be further enhanced by satisfying either or both of the following conditions (9a) and (9b).

[0169] 0.5< (1-β4×β4)×β4r×β4r (9a) (1-β4×β4)×β4r×β4r< 0.9 (9b) More preferably, the aforementioned effects can be further enhanced by satisfying either or both of the following conditions (9c) and (9d).

[0170] 0.6 < (1 - β4 × β4) × β4r × β4r ... (9c) (1 - β4 × β4) × β4r × β4r < 0.8 ···(9d) Furthermore, in an imaging optical system, for example, the first lens group G1 preferably has a single image blur correction lens that moves perpendicular to the optical axis, located closest to the image, and satisfies the following condition (10).

[0171] 0.2 ≦ |(1−β)×βr| ≦ 1.0 ···(10) Here, β: Lateral magnification of the image blur correction lens when focused at infinity. βr: The combined lateral magnification of all lenses positioned on the image side of the image stabilization lens when focused at infinity. That is the case.

[0172] Condition (10) defines the ratio of image shift relative to the amount of movement of the image shake correction lens. Satisfying condition (10) enables compact and effective image shake correction.

[0173] If the value falls below the lower limit of condition (10), the amount of movement required for the image blur correction lens to shift the image by a predetermined amount becomes large, making miniaturization difficult. Conversely, if the value exceeds the upper limit of condition (10), the amount of movement required for the image blur correction lens to shift the image by a predetermined amount becomes small, requiring high-precision control. In addition, the increased power of the image blur correction lens makes good correction difficult.

[0174] Preferably, the above effects can be further enhanced by satisfying either or both of the following conditions (10a) and (10b).

[0175] 0.3 ≦ |(1−β)×βr| ···(10a) |(1−β)×βr| ≦ 0.95 ···(10b) More preferably, the above-mentioned effects can be further enhanced by satisfying either or both of the following conditions (10c) and (10d).

[0176] 0.4 ≦ |(1−β)×βr| ···(10c) |(1−β)×βr| ≦ 0.9 ···(10d) Furthermore, in an imaging optical system, for example, it is desirable that the first lens group G1 comprises, in order from the object side, a lens element with negative power, a lens element with positive power, a lens element with positive power, and a lens element with negative power.

[0177] This makes it possible to provide an imaging optical system that is compact yet effectively corrects aberrations across the entire focus range.

[0178] (Schematic configuration of the imaging device to which Embodiment 1 is applied) Figure 6 shows a schematic configuration of an imaging device to which the imaging optical system according to Embodiment 1 is applied. It is also possible to apply the imaging optical systems according to Embodiments 2 to 5 to the imaging device.

[0179] The imaging device 100 consists of a housing 104, an image sensor 102, and an imaging optical system 101 according to Embodiment 1. A specific example of the imaging device 100 is a digital camera.

[0180] The lens barrel 302 holds each lens group of the imaging optical system 101 and the aperture diaphragm A.

[0181] The image sensor 102 is positioned at the image plane S in the imaging optical system according to this embodiment 1.

[0182] The imaging optical system 101 is configured such that the second lens group G2 and the fourth lens group G4 move during focusing, and the lens frames included in the lens barrel 302 are attached to or engaged with them.

[0183] The imaging optical system 101 is configured with actuators and lens frames controlled by the imaging device 100 or a controller in the lens barrel 302 so that the second lens group G2 and the fourth lens group G4 move during focusing.

[0184] This makes it possible to realize an imaging device that can effectively correct various aberrations.

[0185] Although the image imaging optical system according to Embodiment 1 described above was shown as being applied to a digital camera, it can also be applied to surveillance cameras, smartphones, and the like.

[0186] (Schematic configuration of the camera system to which Embodiment 1 is applied) Figure 7 shows a schematic configuration of a camera system to which the imaging optical system according to Embodiment 1 is applied. It is also possible to apply the imaging optical systems according to Embodiments 2 to 5 to the camera system.

[0187] The camera system 200 comprises a camera body 201 and an interchangeable lens device 300 that is detachably connected to the camera body 201.

[0188] The camera body 201 includes an image sensor 202 that receives an optical image formed by the imaging optical system 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 (not shown) for storing the image signal, a camera mount section 204, and a viewfinder 205.

[0189] The imaging optical system of the interchangeable lens device 300 is the imaging optical system according to Embodiment 1.

[0190] The lens barrel 302 includes each lens group of the imaging optical system 301 and a lens mount portion 304 that holds the aperture diaphragm A and is connected to the camera mount portion 204 of the camera body 201.

[0191] The camera mount section 204 and the lens mount section 304 not only provide a physical connection, but also function as an interface that electrically connects the controller (not shown) in the camera body 201 and the controller (not shown) in the interchangeable lens device 300, enabling the exchange of signals between them.

[0192] The imaging optical system 301 is configured such that the lens barrel 302 can be attached to or engaged with the lens frames included in the lens barrel 302, so that the lens frames holding the second lens group G2 and the fourth lens group G4 can be moved during focusing.

[0193] The imaging optical system 301, which consists of lens groups held by the lens barrel 302 and the camera body 201, is configured with actuators and lens frames controlled by a controller in the interchangeable lens device 300 so that the second lens group G2 and the fourth lens group G4 move during focusing.

[0194] (Examples of numerical values) The following describes numerical examples of the imaging optical systems according to Embodiments 1 to 5. In each numerical example, the unit of length in the table is "mm" and the unit of field of view is "°". In each numerical example, r is the radius of curvature, d is the interplanar 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, the surface marked with an asterisk (*) is an aspherical surface, and the aspherical shape is defined by the following formula.

[0195]

number

[0196] Here, Z: The distance from a point on the aspherical surface at height h from the optical axis to the tangent plane of the aspherical surface's vertex. h: height from the optical axis, r: radius of curvature of the vertex, κ: cone constant, An: nth-order aspherical coefficient That is the case.

[0197] Figures 1B, 2B, 3B, 4B, and 5B are longitudinal aberration diagrams at each focus position of the imaging optical system according to Embodiments 1 to 5, respectively.

[0198] In each longitudinal aberration diagram, (a) shows the aberration at infinity focus, (b) shows the aberration at an intermediate position, and (c) shows the aberration at focus on a nearby object. Each longitudinal aberration diagram shows, from left to right, spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)). In the spherical aberration diagram, the vertical axis represents the F number (indicated as F in the diagram), the solid line represents the d-line, the short dashed line represents the F-line, and the long dashed line represents the C-line. In the astigmatism diagram, the vertical axis represents the image height (indicated as H in the diagram), the solid line represents the sagittal plane (indicated as s in the diagram), and the dashed line represents the meridional plane (indicated as m in the diagram). In the distortion diagram, the vertical axis represents the image height (indicated as H in the diagram).

[0199] Figures 1C, 2C, 3C, 4C, and 5C are lateral aberration diagrams of the imaging optical systems according to Embodiments 1 to 5 in the state of infinity object focus.

[0200] In each lateral aberration diagram, the top three diagrams correspond to the basic state without image blur correction at infinity focus, while the bottom three diagrams correspond to the image blur correction state at infinity focus with the image blur correction lens group moved by a predetermined amount in a direction perpendicular to the optical axis. In the basic state, the top diagram corresponds to the lateral aberration at the image point at 70% of the maximum image height, the middle diagram corresponds to the lateral aberration at the on-axis image point, and the bottom diagram corresponds to the lateral aberration at the image point at -70% of the maximum image height. In the image blur correction state, the top diagram corresponds to the lateral aberration at the image point at 70% of the maximum image height, the middle diagram corresponds to the lateral aberration at the on-axis image point, and the bottom diagram corresponds to the lateral aberration at the image point at -70% of the maximum image height. In each lateral aberration diagram, the horizontal axis represents the distance from the principal ray on the pupil plane, with solid lines representing the d-line, short dashed lines representing the F-line, and long dashed lines representing the C-line.

[0201] Furthermore, for each embodiment of the imaging optical system, the amount of movement of the image blur correction lens group in the direction perpendicular to the optical axis in the image blur correction state when the object at infinity is in focus is as follows.

[0202] Numerical Example 1: 0.401 mm Numerical example 2: 0.412 mm Numerical example 3: 0.410 mm Numerical example 4: 0.406 mm Numerical example 5: 0.270 mm In the state of point focus on an object at infinity, the amount of image eccentricity when the imaging optical system is tilted at a predetermined angle is equal to the amount of image eccentricity when the image blur correction lens group is translated by the above values ​​in a direction perpendicular to the optical axis.

[0203] As is clear from each lateral aberration diagram, the symmetry of lateral aberration at the on-axis image point is good. Furthermore, comparing the lateral aberration at the +70% image point and the lateral aberration at the -70% image point in the basic state, both show small curvature and nearly equal slopes of the aberration curves, indicating small eccentric coma and eccentric astigmatism. This means that sufficient imaging performance is obtained even in the image shake correction state. In addition, when the image shake correction angle of the imaging optical system is the same, the amount of parallel shift required for image shake correction decreases as the focal length of the entire imaging optical system decreases. Therefore, at any focus position, it is possible to perform sufficient image shake correction for a given image shake correction angle without degrading the imaging characteristics.

[0204] (Numerical Example 1) The imaging optical system of Numerical Example 1 corresponds to Embodiment 1 shown in Figure 1A. The surface data of the imaging optical system of Numerical Example 1 is shown in Table 1A, the aspherical data in Table 1B, and the various data in Tables 1C to 1E.

[0205] (Table 1A: Surface data) Face number rd nd vd Object surface ∞ variable 1 -48.24880 1.50000 1.64769 33.8 2 44.73430 0.72880 3 37.97200 5.00000 2.00069 25.5 4 -131.50720 0.90000 5 25.17960 6.60000 1.59282 68.6 6 -47.51790 0.01000 1.56732 42.8 7 -47.51790 1.10000 1.76182 26.6 8 30.77150 2.99140 9* 54.81860 2.80000 1.58660 59.0 10* -129.05710 1.34230 11 (aperture) ∞ Variable 12* -34.79670 1.40000 1.68948 31.0 13 27.95970 0.01000 1.56732 42.8 14 27.95970 4.00000 1.95375 32.3 15 -47.70420 Variable 16 -69.07570 3.10000 1.90366 31.3 17 -23.36060 0.01000 1.56732 42.8 18 -23.36060 1.00000 1.69895 30.1 19 306.94780 Variable 20* 202.64210 7.14970 1.55332 71.7 21* -24.51590 Variable 22* -17.16680 2.00000 1.58660 59.0 23* -295.00000 3.60000 24 ∞ 1.40000 1.51680 64.2 25 ∞ 1.00000 26 ∞ BF Image plane ∞ (Table 1B: Aspherical data) 9th page K= 0.00000E+00, A4=-1.30306E-05, A6=-5.62107E-08, A8=-3.60682E-10 A10= 8.61029E-14, A12=-7.87986E-14, A14= 5.22901E-17 Side 10 K= 0.00000E+00, A4=-9.82247E-06, A6=-9.90962E-09, A8=-2.51292E-09 A10= 3.89661E-11, A12=-4.70452E-13, A14= 1.70621E-15 Side 12 K=-4.20325E-01, A4=-2.20963E-05, A6=-1.90668E-08, A8=-1.28958E-09 A10= 1.02111E-11, A12= 0.00000E+00, A14= 0.00000E+00 Page 20 K= 0.00000E+00, A4=-1.18748E-05, A6= 6.25689E-08, A8=-1.36411E-10 A10= 7.15711E-14, A12=-3.29562E-17, A14=-1.87905E-18 Page 21 K= 0.00000E+00, A4= 3.35820E-06, A6= 1.04068E-07, A8=-6.34208E-10 A10= 4.09992E-12, A12=-1.28044E-14, A14= 1.19979E-17 Page 22 K=-2.75865E-01, A4= 7.31746E-05, A6=-2.58094E-07, A8= 7.84314E-10 A10= 2.62197E-13, A12=-3.52305E-15, A14= 0.00000E+00 Page 23 K= 0.00000E+00, A4= 3.22163E-05, A6=-2.53939E-07, A8= 7.10332E-10 A10=-8.86821E-13, A12= 0.00000E+00, A14= 0.00000E+00 (Various data) (Table 1C: Various data at each focus position) Infinity, Intermediate, Close Focal length 41.7102 39.5110 36.8281 F-numbers: 2.06002, 2.03508, 2.01362 Field of view: 27.4964 27.8222 28.1646 Image height 20.0000 20.0000 20.0000 Lens length 68.3749 68.3748 68.3749 BF 0.00000 0.00000 0.00000 d0 ∞ 1331.6250 531.6251 d11 8.5000 7.6379 6.4983 d15 2.3984 3.2604 4.4001 d19 4.5634 3.3774 1.8105 d21 5.2709 6.4569 8.0238 Entrance pupil position 18.4211 18.4211 18.4211 Exit pupil position -29.2267 -28.3987 -27.3813 Front principal point position 0.6174 0.5544 0.3280 Back principal point position 26.6705 27.6729 28.8610 (Table 1D: Single lens data) Lens starting plane, focal length 1 1 -35.6132 2 3 29.8849 3 5 28.7335 4 7 -24.3681 5 9 65.9620 6 12 -22.2820 7 14 18.9724 8 16 37.8430 9 18 -31.0201 10 20 39.9734 11 22 -31.1560 (Table 1E: Lens group data) Group First surface Focal length 1 1 51.98012 2 12 94.90715 3 16 -154.71471 4 20 39.97336 5 22 -31.15596 (Numerical Example 2) The image pickup optical system of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. 2A. Surface data of the image pickup optical system of Numerical Example 2 is shown in Table 2A, aspherical data is shown in Table 2B, and various kinds of data are shown in Tables 2C to 2E.

[0206] (Table 2A: Surface Data) Surface No. r d nd vd Object surface ∞ Variable 1 -47.27120 1.50000 1.64769 33.8 2 43.35010 1.13810 3 37.84250 5.13070 2.00069 25.5 4 -109.34490 0.30000 5 24.66250 6.33950 1.59282 68.6 6 -44.99310 0.01000 1.56732 42.8 7 -44.99310 1.10000 1.76182 26.6 8 29.03040 2.87540 9* 49.87530 2.80000 1.58660 59.0 10* -204.73780 1.74550 11(Aperture Stop) ∞ Variable 12* -29.49050 1.40000 1.68948 31.0 13 33.59850 0.01000 1.56732 42.8 14 33.59850 3.98870 1.95375 32.3 15 -39.48390 Variable 16 -121.42970 2.80000 1.90366 31.3 17 -30.03790 0.01000 1.56732 42.8 18 -30.03790 1.00000 1.69895 30.1 19 139.37220 Variable 20* 120.99910 7.84260 1.49710 81.6 21* -24.03830 Variable 22* -17.55440 2.00000 1.58660 59.0 23* -555.05190 3.60000 24 ∞ 1.40000 1.51680 64.2 25 ∞ 1.00000 26 ∞ BF Image plane ∞ (Table 2B: Aspherical data) 9th page K= 0.00000E+00, A4=-4.68166E-06, A6= 1.69614E-08, A8=-3.30307E-10 A10= 3.92522E-12, A12=-9.10972E-14, A14= 2.66210E-16 Side 10 K= 0.00000E+00, A4=-8.61855E-07, A6= 6.00961E-08, A8=-2.25834E-09 A10= 3.77021E-11, A12=-4.29350E-13, A14= 1.62997E-15 Side 12 K=-3.54281E-01, A4=-2.22970E-05, A6=-2.35367E-08, A8=-1.15351E-09 A10= 9.21922E-12, A12= 0.00000E+00, A14= 0.00000E+00 Page 20 K= 0.00000E+00, A4=-8.85815E-06, A6= 6.38274E-08, A8=-2.23000E-10 A10= 4.04212E-13, A12=-5.58470E-16, A14=-3.96775E-18 Page 21 K= 0.00000E+00, A4= 5.56661E-06, A6= 1.04165E-07, A8=-6.28585E-10 A10= 3.80047E-12, A12=-1.10689E-14, A14= 6.48773E-18 Page 22 K=-5.09328E-01, A4= 5.38576E-05, A6=-1.78278E-07, A8= 5.02684E-10 A10= 2.72567E-13, A12=-3.07869E-15, A14= 0.00000E+00 Page 23 K= 0.00000E+00, A4= 1.99308E-05, A6=-1.75668E-07, A8= 4.94739E-10 A10=-6.58493E-13, A12= 0.00000E+00, A14= 0.00000E+00 (Various Data) (Table 2C: Various Data at Each Focus Position) Infinity Middle Close-up Focal length 41.6884 39.4489 36.7360 F-number 2.06001 2.03372 2.01127 Angle of view 27.4897 27.8453 28.2094 Image height 20.0000 20.0000 20.0000 Total lens length 68.3449 68.3449 68.3448 BF 0.00000 0.00000 0.00000 d0 ∞ 1331.6550 531.6551 d11 8.8535 7.9489 6.7603 d15 1.7897 2.6943 3.8829 d19 4.6739 3.4427 1.8283 d21 5.0373 6.2685 7.8828 Entrance pupil position 18.1602 18.1602 18.1602 Exit pupil position -28.9682 -28.1366 -27.1231 Front principal point position -0.1313 -0.1364 -0.2992 Back principal point position 26.6634 27.7090 28.9358 (Table 2D: Single lens data) Lens starting plane, focal length 1 1 -34.6875 2 3 28.5920 3 5 27.8142 4 7 -23.0142 5 9 68.6481 6 12 -22.5741 7 14 19.5534 8 16 43.5324 9 18 -35.2702 10 20 41.0798 11 22 -30.9455 (Table 2E: Lens group data) Group starting plane focal length 1 1 51.60842 2 12 99.74965 3 16 -177.82625 4 20 41.07976 5 22 -30.94550 (Numerical Example 3) The imaging optical system of Numerical Example 3 corresponds to Embodiment 3 shown in Figure 3A. The surface data of the imaging optical system of Numerical Example 3 is shown in Table 3A, the aspherical data in Table 3B, and the various data in Tables 3C to 3E.

[0207] (Table 3A: Surface Data) Face number rd nd vd Object surface ∞ variable 1 -50.47670 1.50000 1.60342 38.0 2 35.30580 0.89820 3 32.54950 5.93800 2.00100 29.1 4 -140.64290 0.46440 5 26.05100 7.17530 1.49700 81.6 6 -43.26860 0.01000 1.56732 42.8 7 -43.26860 1.10000 1.76182 26.6 8 35.81630 1.81420 9* 60.99390 2.80000 1.58660 59.0 10* -108.35630 1.29580 11 (aperture) ∞ Variable 12* -34.42470 1.40000 1.68948 31.0 13 29.94870 0.01000 1.56732 42.8 14 29.94870 4.00000 1.95375 32.3 15 -46.62520 Variable 16 -97.21390 3.10000 1.90366 31.3 17 -25.97170 0.01000 1.56732 42.8 18 -25.97170 1.00000 1.69895 30.1 19 250.89340 Variable 20* 229.22650 6.93660 1.55332 71.7 21* -25.56050 Variable 22* -17.10980 2.00000 1.58660 59.0 23* -705.68610 3.60000 24 ∞ 1.40000 1.51680 64.2 25 ∞ 1.00000 26 ∞ BF Image plane ∞ (Table 3B: Aspheric data) 9th page K= 0.00000E+00, A4=-1.15917E-05, A6=-7.06701E-08, A8=-2.92537E-10 A10= 1.83000E-12, A12=-1.18168E-13, A14= 3.86396E-16 Page 10 K= 0.00000E+00, A4=-8.45388E-06, A6=-2.65783E-08, A8=-2.26254E-09 A10= 3.64884E-11, A12=-4.45535E-13, A14= 1.70602E-15 Page 12 K= 1.01706E-01, A4=-2.14456E-05, A6=-1.82712E-08, A8=-1.10860E-09 A10= 8.42294E-12, A12= 0.00000E+00, A14= 0.00000E+00 Page 20 K= 0.00000E+00, A4=-8.86483E-06, A6= 6.87803E-08, A8=-2.16144E-10 A10= 4.56678E-13, A12=-1.06364E-15, A14=-1.74491E-18 Page 21 K= 0.00000E+00, A4= 3.76656E-06, A6= 1.05629E-07, A8=-5.51680E-10 A10= 3.28466E-12, A12=-1.03646E-14, A14= 8.28818E-18 Page 22 K=-1.60121E-01, A4= 6.49077E-05, A6=-1.06703E-07, A8= 4.03786E-10 A10=-3.40656E-13, A12=-1.86476E-16, A14= 0.00000E+00 Page 23 K= 0.00000E+00, A4= 1.37251E-05, A6=-1.07707E-07, A8= 2.77280E-10 A10=-4.44651E-13, A12= 0.00000E+00, A14= 0.00000E+00 (Various data) (Table 3C: Various data at each focus position) Infinity, Intermediate, Close Focal length 41.6988 39.4777 36.7679 F-numbers: 2.06023, 2.03704, 2.01780 Field of view: 27.5190, 27.8220, 28.1322 Image height 20.0000 20.0000 20.0000 Lens length: 68.5662 68.5663 68.5663 BF 0.00000 0.00000 0.00000 d0 ∞ 1331.4336 531.4337 d11 8.7198 7.8237 6.6377 d15 2.1035 2.9997 4.1857 d19 4.6928 3.4822 1.8811 d21 5.5976 6.8082 8.4093 Entrance pupil position 17.9461 17.9461 17.9461 Exit pupil position -28.3712 -27.6190 -26.6923 Front principal point position -1.6480 -1.5595 -1.6057 Back principal point position 26.8648 27.8921 29.1098 (Table 3D: Single lens data) Lens starting plane, focal length 1 1 -34.2035 2 3 26.8665 3 5 33.8824 4 7 -25.5684 5 9 66.9382 6 12 -23.0241 7 14 19.6202 8 16 38.4245 9 18 -33.6226 10 20 41.9676 11 22 -29.9245 (Table 3E: Lens group data) Group starting plane focal length 1 1 54.23166 2 12 97.98983 3 16 -242.47228 4 20 41.96756 5 22 -29.92454 (Numerical Example 4) The imaging optical system of Numerical Example 4 corresponds to Embodiment 4 shown in Figure 4A. The surface data of the imaging optical system of Numerical Example 4 is shown in Table 4A, the aspherical data in Table 4B, and the various data in Tables 4C to 4E.

[0208] (Table 4A: Surface Data) Face number rd nd vd Object surface ∞ variable 1 -43.65260 1.40000 1.68893 31.2 2 26.65110 0.01000 1.56732 42.8 3 26.65110 6.53020 2.00069 25.5 4 -91.74250 0.30000 5 25.87580 7.09390 1.59282 68.6 6 -34.37440 0.01000 1.56732 42.8 7 -34.37440 1.00000 1.75520 27.5 8 31.69350 2.01070 9* 60.40430 2.80000 1.58660 59.0 10* -108.15820 1.26900 11 (aperture) ∞ Variable 12* -32.12080 1.30000 1.68948 31.0 13 29.82650 0.01000 1.56732 42.8 14 29.82650 4.44790 1.95375 32.3 15 -43.85400 Variable 16 -83.24220 2.80000 1.90366 31.3 17 -28.86210 0.01000 1.56732 42.8 18 -28.86210 1.00000 1.69895 30.1 19 ∞ Variable 20* 297.41410 6.63640 1.55332 71.7 21* -26.31260 Variable 22* -17.97840 2.00000 1.58660 59.0 23* -545.42630 3.60000 24 ∞ 1.40000 1.51680 64.2 25 ∞ 1.00000 26 ∞ BF Image plane ∞ (Table 4B: Aspheric data) 9th page K= 0.00000E+00, A4=-1.60858E-05, A6= 2.04423E-08, A8=-5.00399E-09 A10= 1.03452E-10, A12=-1.18145E-12, A14= 4.70808E-15 Side 10 K= 0.00000E+00, A4=-1.23340E-05, A6= 1.68062E-08, A8=-5.32458E-09 A10= 1.11190E-10, A12=-1.30069E-12, A14= 5.44695E-15 Side 12 K=-3.23019E-01, A4=-1.91896E-05, A6=-5.77786E-08, A8= 1.42084E-10 A10=-9.28101E-13, A12= 0.00000E+00, A14= 0.00000E+00 Page 20 K= 0.00000E+00, A4=-7.35139E-06, A6= 6.37903E-08, A8=-7.12465E-11 A10=-3.77501E-13, A12= 0.00000E+00, A14= 0.00000E+00 Page 21 K= 0.00000E+00, A4= 8.02250E-06, A6= 2.91337E-08, A8= 3.59713E-10 A10=-1.72914E-12, A12= 2.66920E-15, A14=-4.67029E-18 Page 22 K=-1.30292E-02, A4= 6.94180E-05, A6=-2.39958E-07, A8= 1.46294E-09 A10=-3.83909E-12, A12= 4.67719E-15, A14= 0.00000E+00 Page 23 K= 0.00000E+00, A4= 1.91303E-05, A6=-1.64342E-07, A8= 5.01200E-10 A10=-7.12839E-13, A12= 0.00000E+00, A14= 0.00000E+00 (Various data) (Table 4C: Various data at each focus position) Infinity, Intermediate, Close Focal length 41.7045 39.5377 36.8756 F-numbers: 2.06000, 2.03625, 2.01585 Field of view: 27.5564, 27.8536, 28.1546 Image height 20.0000 20.0000 20.0000 Lens length 68.3423 68.3423 68.3423 BF 0.00000 0.00000 0.00000 d0 ∞ 1331.6573 531.6573 d11 9.5705 8.4670 7.0370 d15 1.8806 2.9841 4.4141 d19 4.6412 3.4424 1.8361 d21 5.6219 6.8207 8.4270 Entrance pupil position 16.9086 16.9086 16.9086 Exit pupil position -29.5266 -28.6900 -27.6624 Front principal point position -0.2712 -0.3964 -0.6825 Back principal point position 26.6482 27.6156 28.7702 (Table 4D: Single lens data) Lens starting plane, focal length 1 1 -23.8264 2 3 21.2230 3 5 26.0439 4 7 -21.6937 5 9 66.4811 6 12 -22.2403 7 14 19.1786 8 16 47.7243 9 18 -41.2936 10 20 44.0103 11 22 -31.7375 (Table 4E: Lens group data) Group starting plane focal length 1 1 53.64266 2 12 97.35970 3 16 -273.98564 4 20 44.01029 5 22 -31.73754 (Numerical Example 5) The imaging optical system of Numerical Example 5 corresponds to Embodiment 5 shown in Figure 5A. The surface data of the imaging optical system of Numerical Example 5 is shown in Table 5A, the aspherical data in Table 5B, and the various data in Tables 5C to 5E.

[0209] (Table 5A: Surface Data) Face number rd nd vd Object surface ∞ variable 1 -48.02990 1.50000 1.75520 27.5 2 568.51760 1.07310 3 56.97520 4.20620 1.92286 20.9 4 -109.63940 0.30000 5 27.44170 5.18510 1.83481 42.7 6 -52.64140 0.01000 1.56732 42.8 7 -52.64140 1.20000 1.85451 25.2 8 25.72470 2.52950 9 -128.46330 1.40000 1.73037 32.2 10 137.75100 1.00000 11* 38.05700 3.20000 1.58660 59.0 12* -81.01800 1.30230 13 (aperture) ∞ variable 14 -30.99460 0.70000 1.60342 38.0 15 25.85030 0.01000 1.56732 42.8 16 25.85030 4.50000 1.85135 40.1 17* -47.12150 Variable 18 -103.05430 4.28320 1.90043 37.4 19 -20.33420 0.01000 1.56732 42.8 20 -20.33420 1.30000 1.72047 34.7 21 193.40840 Variable 22* 140.05110 6.90570 1.55332 71.7 23* -24.83730 Variable 24* -15.71470 2.20000 1.58660 59.0 25* -300.00000 3.60240 26 ∞ 1.40000 1.51680 64.2 27 ∞ 1.00000 28 ∞ BF Image plane ∞ (Table 5B: Aspherical data) Page 11 K= 0.00000E+00, A4=-1.00030E-05, A6=-1.33677E-07, A8= 1.11367E-09 A10=-2.04431E-11, A12= 0.00000E+00, A14= 0.00000E+00 Side 12 K= 0.00000E+00, A4=-3.88812E-06, A6=-1.03022E-07, A8= 1.95311E-10 A10=-1.40234E-11, A12= 0.00000E+00, A14= 0.00000E+00 Page 17 K= 0.00000E+00, A4= 1.59705E-05, A6=-4.79860E-08, A8= 1.66998E-09 A10=-2.49997E-11, A12= 1.92386E-13, A14=-5.99899E-16 Page 22 K= 0.00000E+00, A4=-8.93685E-06, A6= 1.76038E-08, A8= 2.45741E-10 A10=-3.19128E-12, A12= 1.42142E-14, A14=-2.40447E-17 Page 23 K= 0.00000E+00, A4= 9.76040E-06, A6=-4.21729E-08, A8= 1.10960E-09 A10=-8.18967E-12, A12= 2.93458E-14, A14=-4.23199E-17 Page 24 K=-3.25332E-01, A4= 8.52450E-05, A6=-2.84691E-07, A8= 9.42875E-10 A10=-3.38094E-13, A12=-1.90682E-15, A14= 0.00000E+00 Page 25 K= 0.00000E+00, A4= 2.91594E-05, A6=-2.12196E-07, A8= 5.51632E-10 A10=-6.90522E-13, A12= 0.00000E+00, A14= 0.00000E+00 (Various data) (Table 5C: Various data at each focus position) Infinity, Intermediate, Close Focal length 41.7098 39.4000 36.6012 F-numbers: 2.06022, 2.03133, 2.00429 Field of view: 27.3845 27.8040 28.2733 Image height 20.0000 20.0000 20.0000 Lens length 68.4029 68.4029 68.4030 BF 0.00000 0.00000 0.00000 d0 ∞ 1331.5970 531.5972 d13 9.2823 8.0963 6.6338 d17 1.9859 3.1718 4.6344 d21 4.1851 3.0379 1.5000 d23 4.1321 5.2794 6.8173 Entrance pupil position 18.3903 18.3903 18.3903 Exit pupil position -28.6850 -27.8765 -26.8846 Front principal point position -0.5433 -0.3956 -0.3516 Back principal point position 26.6956 27.8057 29.1234 (Table 5D: Single lens data) Lens starting plane, focal length 1 1 -58.5831 2 3 41.1242 3 5 22.2637 4 7 -20.0808 5 9 -90.8105 6 11 44.5850 7 14 -23.2505 8 16 20.1798 9 18 27.4604 10 20 -25.4737 11 22 38.7038 12 24 -28.3514 (Table 5E: Lens group data) Group starting plane focal length 1 1 51.16432 2 14 112.88568 3 18 -284.90279 4 22 38.70376 5 24 -28.35135 (Corresponding value for the condition) The corresponding values ​​for conditions (1) to (10) are shown in Table 1 below.

[0210] [Table 1] [Industrial applicability]

[0211] The imaging optical system described herein is applicable to digital still cameras, interchangeable lens digital cameras, digital video cameras, cameras in mobile phones, cameras in PDAs (Personal Digital Assistance), surveillance cameras in surveillance systems, webcams, in-vehicle cameras, etc., and is particularly suitable for imaging optical systems that require high image quality, such as digital still camera systems and digital video camera systems. [Explanation of Symbols]

[0212] G1 First Lens Group G2 Second Lens Group G3 3rd lens group G4 4th lens group G5 5th lens group L1 First lens element L2 Second lens element L3 Third lens element L4 4th lens element L5 Fifth lens element L6 6th lens element L7 7th lens element L8 8th lens element L9 9th lens element L10 10th lens element L11 11th lens element L12 12th lens element A aperture diaphragm P parallel plate S image plane 100 Imaging device 101 Imaging optical system 102 Image sensor 104 cabinets 200 Camera System 201 Camera body 202 Image sensor 203 Monitor 204 Camera mount section 205 Finder 300 interchangeable lens device 301 Imaging Optical System 302 Telescope Tube 304 Lens mount section

Claims

1. Starting from the object side, The first lens group has positive power, Aperture diaphragm and The second lens group has positive power, The third lens group possesses negative power, The fourth lens group possesses positive power, The fifth lens group possesses negative power, It consists of, When focusing from an infinity focus state to a near focus state, The first lens group, the third lens group, and the fifth lens group are fixed to the image plane. As the second and fourth lens groups move along the optical axis, the distance between each lens group changes. The aforementioned second lens group is arranged in order from the object side: A lens element with negative power, A lens element with positive power, It has, The following conditions (6) must be met: 1.8 < nd2Gp... (6) Here, nd2Gp: Refractive index of the positive power lens element of the second lens group, That is, Imaging optical system.

2. Starting from the object side, The first lens group has positive power, Aperture diaphragm and The second lens group has positive power, The third lens group possesses negative power, The fourth lens group possesses positive power, The fifth lens group possesses negative power, It consists of, When focusing from an infinity focus state to a near focus state, The first lens group, the third lens group, and the fifth lens group are fixed to the image plane. As the second and fourth lens groups move along the optical axis, the distance between each lens group changes. The fifth lens group consists of a single lens element, The following conditions (8) must be met, 50 < νd5G (8) Here, νd5G: Abbe number of the lens element of the fifth lens group, That is, Imaging optical system.

3. Starting from the object side, The first lens group has positive power, Aperture diaphragm and The second lens group has positive power, The third lens group possesses negative power, The fourth lens group possesses positive power, The fifth lens group possesses negative power, It consists of, When focusing from an infinity focus state to a near focus state, The first lens group, the third lens group, and the fifth lens group are fixed to the image plane. As the second and fourth lens groups move along the optical axis, the distance between each lens group changes. The following condition (9) is satisfied, 0.4<(1-β4×β4)×β4r×β4r<1.0...(9) Here, β4: Lateral magnification when the fourth lens group is focused at infinity, β4r: The combined lateral magnification of all lenses positioned on the image side of the fourth lens group when focused at infinity. That is, Imaging optical system.

4. Starting from the object side, The first lens group has positive power, Aperture diaphragm and The second lens group has positive power, The third lens group possesses negative power, The fourth lens group possesses positive power, The fifth lens group possesses negative power, It consists of, When focusing from an infinity focus state to a near focus state, The first lens group, the third lens group, and the fifth lens group are fixed to the image plane. As the second and fourth lens groups move along the optical axis, the distance between each lens group changes. The first lens group has, at the image side, one image shake correction lens that moves perpendicular to the optical axis, The following conditions (10) are satisfied, 0.2 ≦ | (1 - β) × βr | ≦ 1.0 ... (10) Here, β: Horizontal magnification of the image blur correction lens when focused at infinity. βr: The combined lateral magnification of all lenses positioned on the image side of the image stabilization lens when focused at infinity. That is, Imaging optical system.

5. Starting from the object side, The first lens group has positive power, Aperture diaphragm and The second lens group has positive power, The third lens group possesses negative power, The fourth lens group possesses positive power, The fifth lens group possesses negative power, It consists of, When focusing from an infinity focus state to a near focus state, The first lens group, the third lens group, and the fifth lens group are fixed to the image plane. As the second and fourth lens groups move along the optical axis, the distance between each lens group changes. The first lens group is arranged in the order from the object side: A lens element with negative power, A lens element with positive power, A lens element with positive power, A lens element with negative power, Equipped with, Imaging optical system.

6. The following conditions (1) must be met: 1.0 < f1 / f < 1.5 (1) Here, f1: Focal length of the first lens group, f: Total focal length of the system when focused at infinity. That is, The imaging optical system according to any one of claims 1 to 5.

7. The following conditions (2) must be met: 0.5 < |f5 / f| < 1.0...(2) Here, f5: Focal length of the fifth lens group, f: Total focal length of the system when focused at infinity. That is, The imaging optical system according to any one of claims 1 to 5.

8. The following condition (3) is satisfied, 1.8 ≦ f2 / f4 ≦ 3.4 (3) Here, f2: Focal length of the second lens group, f4: Focal length of the fourth lens group, That is, The imaging optical system according to any one of claims 1 to 5.

9. The following condition (4) is satisfied, 0.1 < BF / Y < 0.5...(4) Here, BF: The distance along the optical axis from the lens surface with the strongest negative power on the image side to the image plane. Y: Maximum image height when focused at infinity. That is, The imaging optical system according to any one of claims 1 to 5.

10. The following condition (5) is satisfied, 3.0 < TL / Y < 3.8...(5) Here, TL: Optical length when focused at infinity, Y: Maximum image height when focused at infinity. That is, The imaging optical system according to any one of claims 1 to 5.

11. The aforementioned second lens group is arranged in order from the object side: A lens element with negative power, A lens element with positive power, It has, The following conditions (6) must be met: 1.8 < nd2Gp... (6) Here, nd2Gp: Refractive index of the positive power lens element of the second lens group, That is, The imaging optical system according to any one of claims 2 to 5.

12. The fourth lens group consists of a single lens element, The following condition (7) is satisfied, 62 < νd4G... (7) Here, νd4G: Abbe number of the lens element of the fourth lens group, That is, The imaging optical system according to any one of claims 1 to 5.

13. The fifth lens group consists of a single lens element, The following conditions (8) must be met, 50 < νd5G (8) Here, νd5G: Abbe number of the lens element of the fifth lens group, That is, The imaging optical system according to claim 1, or any one of claims 3 to 5.

14. The following condition (9) is satisfied, 0.4<(1-β4×β4)×β4r×β4r<1.0...(9) Here, β4: Lateral magnification when the fourth lens group is focused at infinity, β4r: The combined lateral magnification of all lenses positioned on the image side of the fourth lens group when focused at infinity. That is, The imaging optical system according to any one of claims 1 to 2 or 4 to 5.

15. The first lens group has, at the image side, one image shake correction lens that moves perpendicular to the optical axis, The following conditions (10) are satisfied, 0.2 ≦ | (1 - β) × βr | ≦ 1.0 ... (10) Here, β: Lateral magnification of the image blur correction lens when focused at infinity. βr: The combined lateral magnification of all lenses positioned on the image side of the image blur correction lens when focused at infinity. That is, The imaging optical system according to any one of claims 1 to 3 or claim 4.

16. The first lens group is arranged in the order from the object side: A lens element with negative power, A lens element with positive power, A lens element with positive power, A lens element with negative power, Equipped with, The imaging optical system according to any one of claims 1 to 4.

17. An imaging device capable of outputting an optical image of an object as an electrical image signal, An imaging optical system according to any one of claims 1 to 5 that forms an optical image of an object, An image sensor that converts an optical image formed by the imaging optical system into an electrical image signal, Equipped with, Imaging device.

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