Imaging optical system, imaging device, and camera system

Abstract

This disclosure aims to provide an imaging optical system, an imaging device, and a camera system that can effectively correct various aberrations. [Solution] The imaging optical system consists of a front group, an aperture diaphragm, and a rear group having positive power, in order from the object side. The front group has, in order from the object side to the image side, a negative meniscus lens element L1A1 with a convex surface toward the object, a negative meniscus lens element L1A2 with a convex surface toward the object, and a negative lens element L1A3 with a convex surface toward the object on the image side. And it satisfies conditions (1), (2) and (5).

Description

Technical Field

[0001] The present disclosure generally relates to an imaging optical system, an imaging apparatus, and a camera system. More specifically, the present disclosure relates to an imaging optical system capable of favorably correcting various aberrations, and an imaging apparatus and a camera system using the imaging optical system.

Background Art

[0002] Patent Document 1 discloses a wide-angle lens system that, in order from the object side, is composed of a first lens group G1 having negative refractive power, and a subsequent lens group GR that includes one or more lens groups and has positive refractive power as a whole, wherein during zooming or focusing, the air interval between the first lens group G1 and the subsequent lens group GR changes; the first lens group G1 has a lens with a first aspherical surface, and a lens with a second aspherical surface arranged on the image plane side relative to the lens with the first aspherical surface; the first lens group G1 has a lens with negative refractive power on the object side relative to the second aspherical surface; the first lens group G1 has a lens with positive refractive power; and the system satisfies a predetermined conditional expression.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide an imaging optical system capable of favorably correcting various aberrations, and an imaging apparatus and a camera system using the imaging optical system.

Means for Solving the Problems

[0005] An imaging optical system in one aspect of the present disclosure comprises, in order from the object side, a front group, an aperture diaphragm, and a rear group having positive power. The front group comprises, in order from the object side to the image side, a negative meniscus lens element L1A1 having a convex surface toward the object, a negative meniscus lens element L1A2 having a convex surface toward the object, and a negative lens element L1A3 having a convex surface toward the object on its image side.

[0006] And, the following conditions (3) and (5) are satisfied, 0.7 < DL1A2 / (DL1A1+DL1A3) ···(3) 0.3 < BF / Y < 2.0 ···(5) Here, DL1A1: Thickness of the negative meniscus lens element L1A1 along the optical axis, DL1A2: Thickness of the negative meniscus lens element L1A2 along the optical axis, DL1A3: Thickness of negative lens element L1A3 along the optical axis, BF: Back focus, Y: Image height when focused at infinity. That is the case.

[0007] Furthermore, an imaging optical system in one aspect of this disclosure comprises, in order from the object side, a front group, an aperture diaphragm, and a rear group having positive power. The front group comprises, in order from the object side to the image side, a negative meniscus lens element L1A1 having a convex surface toward the object, a negative meniscus lens element L1A2 having a convex surface toward the object, and a negative lens element L1A3 having a convex surface toward the object on its image side.

[0008] And, satisfying the following conditions (1), (2), and (5), 0.9 < DL1A2 / DL1A1 ···(1) 1.0 < DL1A2 / DL1A3 ···(2) 0.3 < BF / Y < 2.0 ···(5) Here, DL1A1: Thickness of the negative meniscus lens element L1A1 along the optical axis, DL1A2: Thickness of the negative meniscus lens element L1A2 along the optical axis, DL1A3: Thickness of negative lens element L1A3 along the optical axis, BF: Back focus, Y: Image height when focused at infinity. That is the case.

[0009] Furthermore, an imaging optical system in one aspect of this disclosure comprises, in order from the object side, a front group, an aperture diaphragm, and a rear group having positive power. When a single lens element or, in the case of a cemented lens, a cemented lens is used as the lens component, the front group comprises, in order from the object side to the image side, a negative lens component L1A1 having a convex surface toward the object, a negative lens component L1A2 having a convex surface toward the object, a negative lens component L1A3 having a convex surface toward the object on the image side, a lens component having positive power, and a lens component having positive power.

[0010] And, satisfying the following conditions (1), (2), and (5), 0.9 < DL1A2 / DL1A1 ···(1) 1.0 < DL1A2 / DL1A3 ···(2) 0.3 < BF / Y < 2.0 ···(5) Here, DL1A1: Thickness of the negative lens component L1A1 on the optical axis, DL1A2: The thickness of the negative lens component L1A2 on the optical axis. DL1A3: The thickness of the negative lens component L1A3 on the optical axis. BF: Back focus, Y: Image height when focused at infinity. That is the case.

[0011] Furthermore, a camera system according to one aspect of the present disclosure comprises an interchangeable lens device including any of the aforementioned imaging optical systems, and a camera body detachably connected to the interchangeable lens device via a camera mount, and including an image sensor that receives an optical image formed by the imaging optical system and converts it into an electrical image signal, wherein the interchangeable lens device forms an optical image of an object on the image sensor.

[0012] Further, an imaging apparatus according to one aspect of the present disclosure converts an optical image of an object into an electrical image signal, and performs at least one of display and storage of the converted image signal. The imaging apparatus includes any one of the aforementioned imaging optical systems and an imaging element. The imaging optical system forms the optical image of the object. The imaging element converts the optical image formed by the imaging optical system into an electrical image signal. Effects of the Invention

[0013] According to the present disclosure, it is possible to provide an imaging optical system capable of favorably correcting various aberrations, and an imaging apparatus and a camera system using the imaging optical system. Brief Description of the Drawings

[0014] [Figure 1A] Lens arrangement diagram showing the infinite focus state of the imaging optical system according to Embodiment 1 (Numerical Example 1) [Figure 1B] Longitudinal aberration diagram of the imaging optical system according to Numerical Example 1 [Figure 2A] Lens arrangement diagram showing the infinite focus state of the imaging optical system according to Embodiment 2 (Numerical Example 2) [Figure 2B] Longitudinal aberration diagram of the imaging optical system according to Numerical Example 2 [Figure 3A] Lens arrangement diagram showing the infinite focus state of the imaging optical system according to Embodiment 3 (Numerical Example 3) [Figure 3B] Longitudinal aberration diagram of the imaging optical system according to Numerical Example 3 [Figure 4A] Lens arrangement diagram showing the infinite focus state of the imaging optical system according to Embodiment 4 (Numerical Example 4) [Figure 4B] Longitudinal aberration diagram of the imaging optical system according to Numerical Example 4 [Figure 5] Schematic configuration diagram of the digital camera according to Embodiment 1 [Figure 6] Schematic configuration diagram of the interchangeable-lens digital camera system according to Embodiment 1 Modes for Carrying Out the Invention

[0015] 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.

[0016] The applicants provide the accompanying drawings and the following description so that a person skilled in the art can fully understand this disclosure, and not to limit the subject matter described in the claims.

[0017] (Embodiments 1 to 4) Figures 1A, 2A, 3A, and 4A show the lens arrangement diagrams and their operation for the imaging optical systems according to each of Embodiments 1 to 4.

[0018] In this disclosure, unless otherwise specified, "focusing," "in focus," or "focusing" refers to the imaging optical system achieving "focusing," "in focus," or "focusing." Also, in this disclosure, unless otherwise specified, "optical axis" refers to the optical axis of the imaging optical system.

[0019] Figures 1A, 2A, 3A, and 4A(a) all show lens configuration diagrams in the infinity focus state. In each figure (a), the straight line on the far right represents the position of the image plane S (corresponding to the plane on which the image sensor is placed, as described later, and facing the object). Therefore, the left side of these diagrams corresponds to the object side. Furthermore, between the last lens group facing the image plane S and the image plane S, for example, a low-pass filter or cover glass CG is placed. Note that the aspect ratio is consistent in each figure (a).

[0020] Furthermore, the asterisk * shown in (a) of each figure indicates that the surface of a specific lens element is aspherical. If no asterisk * is present on the object side or image side of each lens element, that surface is spherical.

[0021] Furthermore, in the lower section (b) of each figure, the symbols G1 to G3 are indicated for each lens group, corresponding to the position of each lens group shown in (a). The symbols (+) and (-) attached to the symbols of each lens group (G1 to G3) correspond to the sign of the power of each lens group. In other words, the symbol (+) indicates positive power, and the symbol (-) indicates negative power.

[0022] Furthermore, in the upper section (b) of each figure, the sub-lens groups that subdivide the lens groups G1 to G3 shown in the lower section (b) are indicated, and each sub-lens group is marked with a symbol. The symbols (+) and (-) attached to the symbols of each sub-lens group (G1A, G1B) correspond to the sign of the power of each sub-lens group. In other words, the symbol (+) indicates positive power, and the symbol (-) indicates negative power.

[0023] In addition, in the upper (b) section of each figure, or in the lower (b) section of each figure, an arrow is added below the symbol for a specific lens group or sub-lens group to indicate the direction of movement associated with focusing from infinity focus to near-focus.

[0024] (Embodiment 1) The imaging optical system according to Embodiment 1 will be described below with reference to Figure 1A.

[0025] Figure 1A shows a lens arrangement diagram illustrating the infinity focus state of the imaging optical system according to Embodiment 1, and its operation.

[0026] As shown in Figure 1A, the imaging optical system of this embodiment consists of, in order from the object side to the image side, a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power, and a cover glass CG, etc.

[0027] The first lens group G1 consists of, in order from the object side to the image side, the first sub-lens group G1A which has negative power, the aperture diaphragm A, and the first sub-lens group G1B which has positive power.

[0028] The first sub-lens group G1A 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 negative power, a third lens element L3 having negative power, a fourth lens element L4 having negative power, a fifth lens element L5 having positive power, and a sixth lens element L6 having positive power.

[0029] The fourth lens element L4 and the fifth lens element L5 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the fourth lens element L4 and the fifth lens element L5.

[0030] The first sub-lens group G1B consists of, in order from the object side to the image side, a seventh lens element L7 having negative power, an eighth lens element L8 having positive power, and a ninth lens element L9 having positive power.

[0031] The seventh lens element L7 and the eighth lens element L8 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the seventh lens element L7 and the eighth lens element L8.

[0032] The second lens group G2 consists of a tenth lens element L10 having positive power and an eleventh lens element L11 having negative power.

[0033] The 11th lens element L11 and the 12th lens element L12 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the 11th lens element L11 and the 12th lens element L12.

[0034] The third lens group G3 consists of a 12th lens element L12 that has positive power.

[0035] The following describes each lens element that constitutes each lens group in the imaging optical system of this embodiment.

[0036] First, I will explain each lens element within the first sub-lens group G1A.

[0037] The first lens element L1 is a meniscus lens with a convex surface on the object side. The second lens element L2 is a meniscus lens with a convex surface on the object side, and both of its surfaces are aspherical. The third lens element L3 is a meniscus lens with a convex surface on the object side. The fourth lens element L4 is a plano-concave lens with a concave surface on the image side. The fifth lens element L5 is a biconvex lens. The sixth lens element L6 is a biconvex lens.

[0038] The first lens element L1 is an example of lens element L1A1. The second lens element L2 is an example of lens element L1A2. The third lens element L3 is an example of lens element L1A3. The fourth lens element L4 is an example of lens element L1A4.

[0039] Next, we will explain each lens element within the first sub-lens group G1B.

[0040] The seventh lens element L7 is a meniscus lens with a convex surface on the object side. The eighth lens element L8 is a biconvex lens. The ninth lens element L9 is a biconvex lens with aspherical surfaces on both sides.

[0041] The fourth lens element L4 is an example of a negative lens element L1n. The fifth lens element L5 is an example of a positive lens element L1p.

[0042] Next, we will explain the lens elements within the second lens group G2.

[0043] The tenth lens element L10 is a biconvex lens. The eleventh lens element L11 is a biconcave lens.

[0044] The tenth lens element L10 is an example of a positive lens element L2p. The eleventh lens element L11 is an example of a negative lens element L2n.

[0045] Next, we will explain the lens elements within the third lens group G3.

[0046] The 12th lens element L12 is a biconvex lens.

[0047] In the imaging optical system of this embodiment, when focusing from infinity focus to near-focus state, the first lens group G1 does not move, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3 does not move. In other words, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane S.

[0048] More specifically, when focusing from infinity to near-focus, the 10th lens element L10 and the 11th lens element L11 move toward the image.

[0049] (Embodiment 2) The imaging optical system according to Embodiment 2 will be described below with reference to Figure 2A.

[0050] Figure 2A shows a lens arrangement diagram illustrating the infinity focus state of the imaging optical system according to Embodiment 2, and its operation.

[0051] As shown in Figure 2A, the imaging optical system of this embodiment consists of, in order from the object side to the image side, a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power, and a cover glass CG, etc.

[0052] The first lens group G1 consists of, in order from the object side to the image side, the first sub-lens group G1A which has negative power, the aperture diaphragm A, and the first sub-lens group G1B which has positive power.

[0053] The first sub-lens group G1A 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 negative power, a third lens element L3 having negative power, a fourth lens element L4 having negative power, a fifth lens element L5 having positive power, and a sixth lens element L6 having positive power.

[0054] The fourth lens element L4 and the fifth lens element L5 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the fourth lens element L4 and the fifth lens element L5.

[0055] The first sub-lens group G1B consists of, in order from the object side to the image side, a seventh lens element L7 having negative power, an eighth lens element L8 having positive power, and a ninth lens element L9 having positive power.

[0056] The seventh lens element L7 and the eighth lens element L8 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the seventh lens element L7 and the eighth lens element L8.

[0057] The second lens group G2 consists of a tenth lens element L10 having positive power and an eleventh lens element L11 having negative power.

[0058] The 11th lens element L11 and the 12th lens element L12 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the 11th lens element L11 and the 12th lens element L12.

[0059] The third lens group G3 consists of a 12th lens element L12 that has positive power.

[0060] The following describes each lens element that constitutes each lens group in the imaging optical system of this embodiment.

[0061] First, I will explain each lens element within the first sub-lens group G1A.

[0062] The first lens element L1 is a meniscus lens with a convex surface on the object side. The second lens element L2 is a meniscus lens with a convex surface on the object side, and both of its surfaces are aspherical. The third lens element L3 is a meniscus lens with a convex surface on the object side. The fourth lens element L4 is a plano-concave lens with a concave surface on the image side. The fifth lens element L5 is a biconvex lens. The sixth lens element L6 is a meniscus lens with a convex shape on the object side.

[0063] The first lens element L1 is an example of lens element L1A1. The second lens element L2 is an example of lens element L1A2. The third lens element L3 is an example of lens element L1A3. The fourth lens element L4 is an example of lens element L1A4.

[0064] Next, we will explain each lens element within the first sub-lens group G1B.

[0065] The seventh lens element L7 is a meniscus lens with a convex surface on the object side. The eighth lens element L8 is a biconvex lens. The ninth lens element L9 is a biconvex lens with aspherical surfaces on both sides.

[0066] The fourth lens element L4 is an example of a negative lens element L1n. The fifth lens element L5 is an example of a positive lens element L1p.

[0067] Next, we will explain the lens elements within the second lens group G2.

[0068] The tenth lens element L10 is a biconvex lens. The eleventh lens element L11 is a biconcave lens.

[0069] The tenth lens element L10 is an example of a positive lens element L2p. The eleventh lens element L11 is an example of a negative lens element L2n.

[0070] Next, we will explain the lens elements within the third lens group G3.

[0071] The 12th lens element L12 is a biconvex lens.

[0072] In the imaging optical system of this embodiment, when focusing from infinity focus to near-focus state, the first lens group G1 does not move, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3 does not move. In other words, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane S.

[0073] More specifically, when focusing from infinity to near-focus, the 10th lens element L10 and the 11th lens element L11 move toward the image.

[0074] (Embodiment 3) The imaging optical system according to Embodiment 3 will be described below with reference to Figure 3A.

[0075] Figure 3A shows a lens arrangement diagram illustrating the infinity focus state of the imaging optical system according to Embodiment 3, and its operation.

[0076] As shown in Figure 3A, the imaging optical system of this embodiment consists of, in order from the object side to the image side, a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power, and a cover glass CG, etc.

[0077] The first lens group G1 consists of, in order from the object side to the image side, the first sub-lens group G1A which has negative power, the aperture diaphragm A, and the first sub-lens group G1B which has positive power.

[0078] The first sub-lens group G1A 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 negative power, a third lens element L3 having negative power, a fourth lens element L4 having positive power, and a fifth lens element L5 having negative power.

[0079] The third lens element L3 and the fourth lens element L4 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the third lens element L3 and the fourth lens element L4.

[0080] The first sub-lens group G1B consists of, in order from the object side to the image side, a sixth lens element L6 having positive power, a seventh lens element L7 having negative power, an eighth lens element L8 having positive power, and a ninth lens element L9 having positive power.

[0081] The seventh lens element L7 and the eighth lens element L8 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the seventh lens element L7 and the eighth lens element L8.

[0082] The second lens group G2 consists of a tenth lens element L10 that has negative power.

[0083] The third lens group G3 consists of an eleventh lens element L11 that has positive power.

[0084] The following describes each lens element that constitutes each lens group in the imaging optical system of this embodiment.

[0085] First, I will explain each lens element within the first sub-lens group G1A.

[0086] The first lens element L1 is a meniscus lens with a convex surface on the object side. The second lens element L2 is a meniscus lens with a convex surface on the object side, and both of its surfaces are aspherical. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a biconvex lens. The fifth lens element L5 is a meniscus lens with a convex surface on the image side.

[0087] The first lens element L1 is an example of lens element L1A1. The second lens element L2 is an example of lens element L1A2. The third lens element L3 is an example of lens element L1A3.

[0088] Next, we will explain each lens element within the first sub-lens group G1B.

[0089] The sixth lens element L6 is a biconvex lens. The seventh lens element L7 is a plano-concave lens with a concave surface on the image side. The eighth lens element L8 is a biconvex lens. The ninth lens element L9 is a biconvex lens with aspherical surfaces on both sides.

[0090] The third lens element L3 is an example of a negative lens element L1n. The fourth lens element L4 is an example of a positive lens element L1p.

[0091] Next, we will explain the lens elements within the second lens group G2.

[0092] The tenth lens element L10 is a meniscus lens with a convex surface on the image side, and both of its surfaces are aspherical.

[0093] Next, we will explain the lens elements within the third lens group G3.

[0094] The 11th lens element L11 is a biconvex lens.

[0095] In the imaging optical system of this embodiment, when focusing from infinity focus to near-focus state, the first lens group G1 does not move, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3 does not move. In other words, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane S.

[0096] More specifically, when focusing from infinity to near-focus, the tenth lens element L10 moves toward the image.

[0097] (Embodiment 4) The imaging optical system according to Embodiment 4 will be described below with reference to Figure 4A.

[0098] Figure 4A shows a lens arrangement diagram illustrating the infinity focus state of the imaging optical system according to Embodiment 4, and its operation.

[0099] As shown in Figure 4A, the imaging optical system of this embodiment consists of, in order from the object side to the image side, a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power, and a cover glass CG, etc.

[0100] The first lens group G1 consists of, in order from the object side to the image side, the first sub-lens group G1A which has negative power, the aperture diaphragm A, and the first sub-lens group G1B which has positive power.

[0101] The first sub-lens group G1A 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 negative power, a third lens element L3 having negative power, a fourth lens element L4 having positive power, and a fifth lens element L5 having positive power.

[0102] The third lens element L3 and the fourth lens element L4 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the third lens element L3 and the fourth lens element L4.

[0103] The first sub-lens group G1B consists of, in order from the object side to the image side, a sixth lens element L6 having negative power, a seventh lens element L7 having positive power, and an eighth lens element L8 having positive power.

[0104] The sixth lens element L6 and the seventh lens element L7 are bonded together with an adhesive, such as an ultraviolet-curing resin, to form a bonded lens. In other words, the bonded lens includes the sixth lens element L6 and the seventh lens element L7.

[0105] The second lens group G2 consists of a ninth lens element L9 that has negative power.

[0106] The third lens group G3 consists of a tenth lens element L10 that has positive power.

[0107] The following describes each lens element that constitutes each lens group in the imaging optical system of this embodiment.

[0108] First, I will explain each lens element within the first sub-lens group G1A.

[0109] The first lens element L1 is a meniscus lens with a convex surface facing the object. The second lens element L2 is a meniscus lens with a convex surface facing the object, and both of its surfaces are aspherical. The third lens element L3 is a meniscus lens with a convex surface facing the object. The fourth lens element L4 is a meniscus lens with a convex surface facing the object. The fifth lens element L5 is a biconvex lens.

[0110] The first lens element L1 is an example of lens element L1A1. The second lens element L2 is an example of lens element L1A2. The third lens element L3 is an example of lens element L1A3.

[0111] Next, we will explain each lens element within the first sub-lens group G1B.

[0112] The sixth lens element L6 is a meniscus lens with a convex surface on the object side. The seventh lens element L7 is a biconvex lens. The eighth lens element L8 is a biconvex lens with aspherical surfaces on both sides.

[0113] The third lens element L3 is an example of a negative lens element L1n. The fourth lens element L4 is an example of a positive lens element L1p.

[0114] Next, we will explain the lens elements within the second lens group G2.

[0115] The ninth lens element L9 is a meniscus lens with a convex surface on the object side.

[0116] Next, we will explain the lens elements within the third lens group G3.

[0117] The tenth lens element L10 is a biconvex lens.

[0118] In the imaging optical system of this embodiment, when focusing from infinity focus to near-focus state, the first lens group G1 does not move, the second lens group G2 moves toward the image along the optical axis, and the third lens group G3 does not move. In other words, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane S.

[0119] More specifically, when focusing from infinity to near-focus, the ninth lens element L9 moves towards the image.

[0120] (Conditions and effects, etc.) The following describes the conditions that the imaging optical systems according to Embodiments 1 to 4 can satisfy. While multiple possible conditions are defined for the imaging optical systems according to Embodiments 1 to 4, the configuration that satisfies all of these conditions is the most effective. However, it is also possible to obtain an imaging optical system that achieves the corresponding effect by satisfying individual conditions.

[0121] For example, as in the imaging optical systems according to embodiments 1 to 4, the imaging optical system in this disclosure consists of, in order from the object side, a first lens group G1 having positive power, a second lens group G2 having negative power, and a third lens group G3 having positive power.

[0122] When focusing from infinity to near-focus, the first lens group G1 and the third lens group G3 are fixed relative to the image plane S, while the second lens group G2 moves along the optical axis.

[0123] The first lens group G1 consists of, in order from the object side, the first sub-lens group G1A, the aperture diaphragm A, and the first sub-lens group G1B.

[0124] The first sub-lens group G1A comprises, in order from the object side, a lens element L1A1 having negative power, a lens element L1A2 having negative power, and a lens element L1A3 having negative power.

[0125] In the basic configuration described above, the power configuration of the first lens group G1, the second lens group G2, and the third lens group G3 allows the third lens group G3 to effectively cancel out aberrations generated in the first lens group G1, particularly field curvature at the wide-angle end. This makes it possible to miniaturize the first lens group G1 by giving it strong power, while simultaneously canceling out the resulting aberrations with the third lens group G3. Furthermore, by providing an aperture diaphragm A within the first lens group G1, the distance from the aperture diaphragm to the image plane S is secured, allowing the lens on the image side to be made smaller than the aperture diaphragm A. This enables miniaturization of the imaging optical system. Moreover, by arranging at least three negative lens elements in succession from the object side in the first A sub-lens group G1A, it is possible to achieve a wide-angle view while maintaining a large aperture with an F-number of 2.0 or less, and effectively correcting various aberrations, especially distortion.

[0126] Furthermore, it is desirable to include a negative power lens element L1A4 adjacent to the image side of the lens element L1A3 in the basic imaging optical system configuration.

[0127] This allows for wider-angle lenses while correcting various aberrations, especially distortion.

[0128] Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (1).

[0129] 0.9 < DL1A2 / DL1A1 ···(1) Here, DL1A1: Thickness of lens element L1A1 along the optical axis, DL1A2: Thickness of lens element L1A2 along the optical axis, The units should be consistent (for example, the units for DL1A1 and DL1A3 are millimeters).

[0130] Condition (1) is a condition that defines the ratio of the thicknesses of lens element L1A1 and lens element L1A2 along the optical axis.

[0131] If the value falls below the lower limit of condition (1), the thickness of the lens element L1A1 becomes too large, and the outer diameter of the lens becomes too large. Therefore, miniaturization becomes difficult.

[0132] Furthermore, it is desirable that the following condition (1a) be satisfied within the scope of condition (1).

[0133] If the value exceeds the upper limit of condition (1a), the thickness of the lens element L1A1 becomes too small, making manufacturing difficult.

[0134] DL1A2 / DL1A1 < 6.0 ···(1a) Preferably, the aforementioned effects can be further enhanced by satisfying at least one of the following conditions (1b) and (1c).

[0135] 1.2 < DL1A2 / DL1A1 ···(1b) DL1A2 / DL1A1 < 5.0 ···(1c) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (1d) and (1e).

[0136] 1.5 < DL1A2 / DL1A1 ···(1d) DL1A2 / DL1A1 < 4.0 ···(1e) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (2).

[0137] 1.0 < DL1A2 / DL1A3 ···(2) Here, DL1A2: Thickness of lens element L1A2 along the optical axis, DL1A3: Thickness of lens element L1A3 along the optical axis, The units should be consistent (for example, the units for DL1A2 and DL1A3 are millimeters).

[0138] Condition (2) is a condition that defines the ratio of the thickness of lens element L1A2 and lens element L1A3 along the optical axis.

[0139] If the value falls below the lower limit of condition (2), the thickness of the lens element L1A3 becomes too large, and the overall length of the lens becomes too long. Therefore, miniaturization becomes difficult.

[0140] Furthermore, it is desirable that the following condition (2a) be satisfied within the scope of condition (2).

[0141] DL1A2 / DL1A3 < 6.0 ···(2a) If the value exceeds the upper limit of condition (2a), the thickness of the lens element L1A3 becomes too small, making manufacturing difficult.

[0142] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (2b) and (2c).

[0143] 1.5 < DL1A2 / DL1A3 ···(2b) DL1A2 / DL1A3 < 4.5 ···(2c) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (2d) and (2e).

[0144] 2.0 < DL1A2 / DL1A3 ···(2d) DL1A2 / DL1A3 < 3.5 ···(2e) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (3).

[0145] 0.7 < DL1A2 / (DL1A1+DL1A3) ···(3) Here, DL1A1: Thickness of lens element L1A1 along the optical axis, DL1A2: Thickness of lens element L1A2 along the optical axis, DL1A3: Thickness of lens element L1A3 along the optical axis, The units should be consistent (for example, the units for DL1A1, DL1A2, and DL1A3 are millimeters).

[0146] Condition (3) is a condition that defines the ratio of the thickness of lens element L1A2 on the optical axis to the sum of the thicknesses of lens elements L1A1 and L1A3 on the optical axis.

[0147] If the thickness falls below the lower limit of condition (3), the thickness of the lens element L1A2 becomes too small, and in order to properly correct aberrations, it becomes necessary to use a lens element with a large thickness difference ratio. As a result, the manufacturing of the lens element L1A2 becomes more complex, and surface accuracy tends to deteriorate.

[0148] Furthermore, it is desirable that the following condition (3a) be satisfied within the scope of condition (3).

[0149] (DL1A1+DL1A3) < 6.0 (3a) If the value exceeds the upper limit of condition (3a), the thickness of the lens element L1A2 becomes too large, and the overall length of the lens becomes too long. Therefore, miniaturization becomes difficult.

[0150] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (3b) and (3c).

[0151] 0.8 < DL1A2 / (DL1A1+DL1A3) (3b) (DL1A1+DL1A3) < 4.0 (3c) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (3d) and (3e).

[0152] 0.9 < DL1A2 / (DL1A1+DL1A3) ···(3d) (DL1A1+DL1A3) < 2.0 (3e) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (4).

[0153] 0.3 < f / D < 1.0 ···(4) Here, f: focal length when focusing at infinity. D: Distance along the optical axis from the outermost object side of the first lens group G1 to the image side of the fourth lens element from the object side of the first lens group G1 (distance along the optical axis from the object side of the first lens element L1 to the image side of the fourth lens element L4), The units should be consistent (for example, the units for f and D are millimeters).

[0154] Condition (4) is a condition that defines the ratio of the focal length at infinity focus to the distance on the optical axis from the outermost object-side of the first lens group G1 to the image-side of the fourth lens element from the object side of the first lens group G1.

[0155] If the value falls below the lower limit of condition (4), the distance along the optical axis from the outermost surface of the first lens group G1 to the image side of the fourth lens element from the object side of the first lens group G1 becomes too large, resulting in an excessively large overall lens length. Therefore, miniaturization becomes difficult.

[0156] If the value exceeds the upper limit of condition (4), the spacing between lens surfaces becomes too small, making it easier for the lens elements to interfere with each other. This makes it difficult to secure the space necessary for centering, which is undesirable as it increases the likelihood of product variations due to manufacturing errors.

[0157] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (4a) and (4b).

[0158] 0.4 < f / D ···(4a) f / D < 0.8 ···(4b) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (4c) and (4d).

[0159] 0.5 < f / D ···(4c) f / D < 0.6 ···(4d) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (5).

[0160] 0.3 < BF / Y < 2.0 ···(5) Here, BF: Back focus, Y: Image height when focused at infinity. The units should be consistent (for example, the units for BF and Y are millimeters).

[0161] Condition (5) is a condition that defines the ratio of the back focus to the image height when the image is in focus at infinity.

[0162] When the value falls below the lower limit of condition (5), the back focus and the image sensor interfere with each other.

[0163] If the value exceeds the upper limit of condition (5), the back focus becomes too long, and the entire imaging optical system becomes larger.

[0164] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (5a) and (5b).

[0165] 0.7 < BF / Y ···(5a) BF / Y < 1.8 ···(5b) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (5c) and (5d).

[0166] 1.3 < BF / Y ···(5c) BF / Y < 1.6 ···(5d) Furthermore, in the basic imaging optical system, it is desirable that at least one negative lens element in the first sub-lens group G1A satisfies the following condition (6).

[0167] νdL1An > 62 ···(6) Here, νdL1An: Abbe number on the d line of the negative lens element in the first sub-lens group G1A, That is the case.

[0168] Condition (6) is a condition that defines the Abbe number on the d line of the negative lens element in the first sub-lens group G1A.

[0169] When the value falls below the lower limit of condition (6), it becomes difficult to correct various aberrations, especially chromatic aberration.

[0170] Preferably, the above-mentioned effects can be further enhanced by satisfying the following condition (6a).

[0171] νdL1An > 65 ···(6a) More preferably, the above-mentioned effects can be further enhanced by satisfying the following condition (6b).

[0172] νdL1An > 67 ···(6b) Furthermore, in the basic imaging optical system, the first sub-lens group G1A preferably has a cemented lens consisting of a positive lens element L1p and a negative lens element L1n, and satisfies the following condition (7).

[0173] 1.4 < ndL1n < 1.65 ···(7) Here, ndL1n: Refractive index of the negative lens element L1n at the d line, That is the case.

[0174] Condition (7) is a condition that defines the refractive index of the negative lens element L1n at the d line.

[0175] If the value falls below the lower limit of condition (7), the absolute value of the Petzval sum becomes too large, making it difficult to correct for field curvature.

[0176] If the value exceeds the upper limit of condition (7), a highly dispersed material must be selected, making it difficult to correct chromatic aberration.

[0177] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (7a) and (7b).

[0178] 1.47 < ndL1n ···(7a) ndL1n < 1.61 ···(7b) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (7c) and (7d).

[0179] 1.49 < ndL1n ···(7c) ndL1n < 1.58 ···(7d) Furthermore, in the basic configuration of the imaging optical system, the second lens group G2 preferably has a cemented lens consisting of a positive lens element L2p and a negative lens element L2n, and satisfies the following condition (8).

[0180] 1.85 < ndL1p ···(8) Here, ndL2p: Refractive index of the positive lens element L2p at the d line, That is the case.

[0181] Condition (8) is a condition that defines the refractive index of the positive lens element L2p at the d line.

[0182] If the value falls below the lower limit of condition (8), chromatic aberration correction at the shortest focusing distance becomes impossible, and the close-up performance deteriorates.

[0183] Preferably, the above-mentioned effects can be further enhanced by satisfying the following condition (8a).

[0184] 1.90 < ndL2p ···(8a) More preferably, the above-mentioned effects can be further enhanced by satisfying the following condition (8b).

[0185] 1.94 < ndL2p ···(8b) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (9).

[0186] 0.5 < Ls / LL < ...(9) Here, Ls: Distance along the optical axis from aperture diaphragm A to image plane S. LL: Optical length when focused at infinity. The units should be consistent (for example, Ls and LL should be in millimeters).

[0187] Condition (9) is a condition that defines the ratio of the distance along the optical axis from the aperture diaphragm A to the image plane S to the total optical length when focused at infinity.

[0188] When the value falls below the lower limit of condition (9), the lens configuration on the image plane side becomes larger than the aperture A.

[0189] Furthermore, it is desirable that the following condition (9a) be satisfied within the scope of condition (9).

[0190] Ls / LL < 0.8 ···(9a) When the value exceeds the upper limit of condition (9a), the number of lenses on the object side is limited compared to the aperture A, making it difficult to correct chromatic aberration.

[0191] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (9b) and (9c).

[0192] 0.55 < Ls / LL ···(9b) Ls / LL < 0.7 ···(9c) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (9d) and (9e).

[0193] 0.57 < Ls / LL ···(9d) Ls / LL < 0.65 ···(9e) Furthermore, in the basic configuration of the imaging optical system, it is desirable that the first B sub-lens group G1B includes at least one positive lens element and satisfies the following condition (10).

[0194] νdL1Bp > 65 ···(10) Here, νdL1Bp: Abbe number on the d line of the positive lens element in the first sub-lens group G1B, That is the case.

[0195] Condition (10) is a condition that defines the Abbe number on the d line of the positive lens element in the first sub-lens group G1B.

[0196] When the value falls below the lower limit of condition (10), it becomes difficult to correct various aberrations, especially chromatic aberration.

[0197] Preferably, the above-mentioned effects can be further enhanced by satisfying the following condition (10a).

[0198] νdL1Bp > 70 ···(10a) More preferably, the above-mentioned effects can be further enhanced by satisfying the following condition (10b).

[0199] νdL1Bp > 80 ···(10b) Furthermore, in the basic configuration of the imaging optical system, it is desirable that the second lens group G2 be composed of two or fewer lens elements.

[0200] This configuration allows for a lighter focus group, enabling faster focusing.

[0201] Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (11).

[0202] 0.08 < |fG1 / fL1A2| < 0.3 (11) Here, fG1: Focal length of the first lens group G1, fL1A2: Focal length of the L1A2 lens element, The units should be consistent (for example, the units for fG1 and fL1A2 are millimeters).

[0203] Condition (11) is a condition that defines the ratio of the power of the first lens group G1 to the power of the L1A2 lens element.

[0204] If the value falls below the lower limit of condition (7), the power of the L1A2 lens element becomes too low, making it difficult to correct distortion.

[0205] If the value exceeds the upper limit of condition (7), the power of the L1A2 lens element becomes too large, and the inclination angle of the lens surface becomes too large, making manufacturing difficult.

[0206] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (11a) and (11b).

[0207] 0.1 < |fG1 / fL1A2| ···(11a) |fG1 / fL1A2| < 0.25 ···(11b) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (11c) and (11d).

[0208] 0.12 < |fG1 / fL1A2| ···(11c) |fG1 / fL1A2| < 0.2 ···(11d) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (12).

[0209] 1.45 < ndL1A2 < 1.60 (12) Here, ndL1A2: Refractive index of lens element L1A2 at the d line, That is the case.

[0210] Condition (12) is a condition that defines the refractive index of the lens element L1A2 at the d line.

[0211] If the value falls below the lower limit of condition (12), the absolute value of the Petzval sum becomes too large, making it difficult to correct for field curvature.

[0212] If the value exceeds the upper limit of condition (12), a highly dispersed material must be selected, which is undesirable because it makes it difficult to correct chromatic aberration.

[0213] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (12a) and (12b).

[0214] 1.48 < ndL1A2 ···(12a) ndL1A2 < 1.58 ···(12b) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (12c) and (12d).

[0215] 1.50 < ndL1A2 ···(12c) ndL1A2 < 1.55 ···(12d) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (13).

[0216] 50.0 < νdL1A2 < 65.0 (13) Here, νdL1A2: Abbe number on the d line of lens element L1A2, That is the case.

[0217] Condition (13) is a condition that defines the Abbe number of the lens element L1A2 on the d line.

[0218] When the value falls below the lower limit of condition (13), chromatic aberration correction becomes difficult.

[0219] If the value exceeds the upper limit of condition (13), chromatic aberration will be overcorrected, which is undesirable.

[0220] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (13a) and (13b).

[0221] 52.0 < νdL1A2 ···(13a) νdL1A2 < 62.0 ···(13b) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (13c) and (13d).

[0222] 55.0 < νdL1A2 ···(13c) νdL1A2 < 60.0 ···(13d) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (14).

[0223] 0.01 < DG3 / LL < 0.10 (14) Here, DG3: Distance along the optical axis from the outermost object side to the outermost image side of the third lens group G3, LL: Optical length when focused at infinity. The units should be consistent (for example, the units for DG3 and LL are millimeters).

[0224] Condition (14) specifies the distance along the optical axis from the outermost object side to the outermost image side of the third lens group G3, and the total optical length when focused at infinity.

[0225] If the value falls below the lower limit of condition (14), the distance along the optical axis from the outermost object side to the re-image side of the third lens group G3 becomes too small, making it difficult to manufacture the lens.

[0226] If the value exceeds the upper limit of condition (14), the distance along the optical axis from the outermost object side to the re-image side of the third lens group G3 becomes too large, and the overall length of the lens becomes too large. Therefore, miniaturization becomes difficult.

[0227] Preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (14a) and (14b).

[0228] 0.02 < DG3 / LL ···(14a) DG3 / LL < 0.08 ···(14b) More preferably, the above-mentioned effects can be further enhanced by satisfying at least one of the following conditions (14c) and (14d).

[0229] 0.03 < DG3 / LL ···(14c) DG3 / LL < 0.06 ···(14d) Furthermore, it is desirable that the basic imaging optical system satisfies the following condition (15).

[0230] 0.1 < DG2_S / LL < 1.0 (15) Here, DG2_S: the distance on the optical axis from the most object-side surface of the second lens group G2 to the image plane S, LL: the total optical length when focused at infinity, Herein, the units are unified (for example, the units of DG2_S and LL are millimeters).

[0231] Condition (15) is a condition that defines the distance on the optical axis from the most object-side surface of the second lens group G2 to the image plane S, and the total optical length when focused at infinity.

[0232] When the value is less than or equal to the lower limit of condition (15), the back focus becomes short, and the lens and the imaging surface are prone to interfere with each other, which is not preferable.

[0233] When the value is greater than or equal to the upper limit of condition (15), the lens diameter in the second lens group G2, which is the focus group, becomes large.

[0234] Preferably, by satisfying at least one of the following conditions (15a) and (15b), the aforementioned effects can be further enhanced.

[0235] 0.2 < DG2_S / LL ···(15a) DG2_S / LL < 0.7 ···(15b) More preferably, by satisfying at least one of the following conditions (15c) and (15d), the aforementioned effects can be further enhanced.

[0236] 0.3 < DG2_S / LL ···(15c) DG2_S / LL < 0.4 ···(15d) Further, in the imaging optical system of the basic configuration, it is desirable to satisfy the following condition (16).

[0237] 0.1 < DG1A1_A2 / D < 1.0 ···(16) Herein, DG1A1_A2: the distance on the optical axis from the image side surface of the lens element L1A1 to the object side surface of the lens element L1A2 (the air gap on the optical axis between the first lens element L1 and the second lens element L2), D: the distance on the optical axis from the most object-side surface of the first lens group G1 to the image side surface of the fourth lens element from the object side of the first lens group G1 (the distance on the optical axis from the object side surface of the first lens element L1 to the image side surface of the fourth lens element L4), It is to be noted that the units shall be unified (for example, the units of DG1A1_A2 and D are millimeters).

[0238] Condition (16) is a condition that defines the distance on the optical axis from the image side surface of the lens element L1A1 to the object side surface of the lens element L1A2, and the distance on the optical axis from the most object-side surface of the first lens group to the image side surface of the fourth lens element from the object side of the first lens group.

[0239] When the value is less than or equal to the lower limit of condition (16), the interval between the first lens element L1 and the second lens element L2 becomes too narrow, so the lenses are prone to interfere with each other. Therefore, it becomes difficult to secure the space required for alignment, and product variations due to manufacturing errors and the like are likely to occur, which is not preferable.

[0240] When the value is greater than or equal to the upper limit of condition (16), the interval between the first lens element L1 and the second lens element L2 becomes too wide, so the total lens length increases, making miniaturization difficult.

[0241] Preferably, by satisfying at least one of the following conditions (16a) and (16b), the aforementioned effects can be further achieved effectively.

[0242] 0.12 < DG1A1_A2 / D ···(16a) DG1A1_A2 / D < 0.8 ···(16b) More preferably, by satisfying at least one of the following conditions (16c) and (16d), the aforementioned effects can be further achieved effectively.

[0243] 0.15 < DG1A1_A2 / D ···(16c) DG1A1_A2 / D < 0.5 ···(16d) (Schematic configuration of the imaging device to which Embodiment 1 is applied) Figure 5 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, 3, and 4 to the imaging device.

[0244] The imaging device 100 comprises 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.

[0245] The housing 104 has a lens barrel 302. The lens barrel 302 holds each lens group of the imaging optical system 101 and the aperture diaphragm A.

[0246] The image sensor 102 is positioned at the image plane S in the imaging optical system 101 according to this embodiment 1.

[0247] The imaging device 100 converts an optical image of an object into an electrical image signal and performs at least one of displaying and storing the converted image signal. The imaging device 100 includes, for example, at least one of a monitor for displaying the image signal and a memory for storing the image signal.

[0248] The imaging optical system 101 forms an optical image of an object. The image sensor 102 converts the optical image formed by the imaging optical system 101 into an electrical image signal.

[0249] The imaging optical system 101 is configured such that the second lens group moves along the optical axis, while the first and third lens groups do not move along the optical axis. Specifically, the actuator and lens frame included in the housing 104 are attached or coupled so that the second lens group G2 moves when the imaging optical system 101 is focusing.

[0250] Thereby, it is possible to realize an imaging apparatus 100 with favorable various aberrations.

[0251] Note that although an example in which the imaging optical system 101 according to Embodiment 1 described above is applied to a digital camera has been shown, it can also be applied to surveillance cameras, smartphones, and the like.

[0252] (Schematic Configuration of Camera System to Which Embodiment 1 is Applied) Figure 6 shows a schematic configuration of a camera system to which the imaging optical system according to the present Embodiment 1 is applied. Note that it is also possible to apply the imaging optical systems according to Embodiments 2, 3, and 4 to the camera system.

[0253] The camera system 200 includes a camera body 201 and an interchangeable lens device 300 that is detachably connected to the camera body 201.

[0254] The camera body 201 includes an imaging element 202 that receives an optical image formed by the imaging optical system 301 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 imaging element 202, a memory that stores the image signal, a camera mount portion 204, and a viewfinder 205.

[0255] The imaging optical system 301 of the interchangeable lens device 300 is the imaging optical system according to Embodiment 1. The interchangeable lens device 300 forms an optical image of an object on the imaging element 202 by the imaging optical system 301.

[0256] The interchangeable lens device 300 includes a lens barrel 302 and a lens mount portion 304 in addition to the imaging optical system 301. The lens barrel 302 holds each lens group of the imaging optical system 301 and an aperture stop A. The lens mount portion 304 includes a lens mount portion 304 that is detachably connected to the camera mount portion 204 of the camera body 201.

[0257] In this way, the camera mount section 204 and the lens mount section 304 are physically connected. Furthermore, the camera mount section 204 and the lens mount section 304 also function as an interface that electrically connects the controller in the camera body 201 and the controller in the interchangeable lens device 300, enabling the exchange of signals between them.

[0258] The imaging optical system 301 comprises each lens group held by the lens barrel 302 and the cover glass CG of the camera body 201. The imaging optical system 301 includes a first lens group G1, a second lens group G2, an aperture diaphragm A, and a third lens group G3. The second lens group is configured to move along the optical axis, while the first and third lens groups do not move along the optical axis. Specifically, actuators and lens frames controlled by a controller in the interchangeable lens device 300 are configured so that the second lens group G2 moves when the imaging optical system 301 is focusing.

[0259] (Other embodiments) As described above, Embodiments 1 to 4 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.

[0260] Each lens group constituting the imaging optical system according to Embodiments 1 to 4 is composed only of refractive lens elements that deflect incident light rays by refraction (i.e., lens elements of the type in which deflection occurs at the interface between media having different refractive indices), but is not limited thereto. For example, each lens group may be composed of a diffractive lens element that deflects incident light rays by diffraction, a refractive-diffractive hybrid lens element that deflects incident light rays by a combination of diffraction and refraction, a refractive index distribution lens element that deflects incident light rays by the refractive index distribution in the medium, or a combination of two or more of these. In particular, in the refractive-diffractive hybrid lens element, forming a diffractive structure at the interface between media with different refractive indices is preferable because it improves the wavelength dependence of the diffraction efficiency. This makes it possible to realize a camera with good aberrations.

[0261] (Examples of numerical values) The following describes numerical examples of the imaging optical systems according to Embodiments 1 to 4. 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.

[0262]

number

[0263] 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.

[0264] Figures 1B, 2B, 3B, and 4B are longitudinal aberration diagrams of the imaging optical systems for numerical examples 1 to 4, respectively.

[0265] In each longitudinal aberration diagram, (a) shows the aberration at infinity, and (b) shows the aberration at close range. 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 is the d-line, the short dashed line is the F-line, and the long dashed line is the C-line. In the astigmatism diagram, the vertical axis represents the image height (indicated as H in the diagram), the solid line is the sagittal plane (indicated as s in the diagram), and the dashed line is 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).

[0266] (Numerical Example 1) The imaging optical system of Numerical Example 1 corresponds to Embodiment 1 shown in Figure 1A. Table 1A shows the surface data of the imaging optical system of Numerical Example 1, Table 1B shows the aspherical data, Table 1C shows various data in the infinity focus state and the close-up object focus state, Table 1D shows the single lens data, Table 1E shows the lens group data, and Table 1F shows the lens group magnification data.

[0267] (Table 1A: Surface data) Face number rd nd vd Object surface ∞ variable 1 21.52410 1.30000 1.80420 46.5 2 11.49510 2.88980 3* 10.18310 2.50000 1.53380 55.6 4* 6.66670 4.61720 5 20.35660 0.80000 1.49700 81.6 6 9.32960 3.37550 7 ∞ 0.70000 1.59349 67.0 8 8.61960 0.01000 1.56732 42.8 9 8.61960 6.00000 1.59270 35.4 10 -96.21750 1.34820 11 52.54740 2.65930 1.75211 25.0 12 -144.26600 2.80000 13 (aperture) ∞ 1.97430 14 27.94310 1.00000 2.00100 29.1 15 10.53080 0.01000 1.56732 42.8 16 10.53080 6.11210 1.49700 81.6 17 -20.10960 0.20000 18* 26.30440 5.22090 1.58575 59.5 19* -15.68690 Variable 20 41.50130 2.21190 1.94595 18.0 21 -187.39040 0.01000 1.56732 42.8 22 -187.39040 0.60000 1.84666 23.8 23 12.64740 Variable 24 157.21840 2.72520 1.62299 58.1 25 -29.57090 10.43000 26 ∞ 4.20000 1.51680 64.2 27 ∞ 1.00000 Image plane ∞ (Table 1B: Aspherical data) 3rd page K=-4.13601E-01, A4=-4.83155E-05, A6= 9.17529E-08, A8=-1.33747E-08 A10= 1.42533E-10, A12=-5.26229E-13 Side 4 K=-7.48255E-01, A4=-2.83442E-05, A6= 9.67121E-07, A8=-8.90069E-08 A10= 1.25287E-09, A12=-6.87122E-12 Side 18 K= 0.00000E+00, A4=-4.21347E-05, A6= 1.05188E-08, A8=-1.99866E-09 A10=-8.71399E-12, A12= 9.90029E-14 Page 19 K= 0.00000E+00, A4= 2.64024E-05, A6=-4.74134E-07, A8=-1.82935E-10 A10=-5.27974E-12, A12=-8.61303E-14 (Table 1C: Various data under infinity focus and near object focus conditions) Infinity Close Focal length 9.3466 9.2278 F-number 1.76816 1.77089 Field of view 49.8179 49.8620 Image height 10.0000 10.0000 Lens length 70.9975 70.9922 d0 ∞ 129.0009 d19 1.2010 1.6129 d23 5.1035 4.6917 Entrance pupil position 12.9734 12.9734 Exit pupil position -49.3881 -48.2726 Front principal point position 20.5511 20.4144 Back principal point position 61.6509 61.1570 (Table 1D: Single lens data) Lens starting plane, focal length 1 1 -32.5585 2 3 -48.0580 3 5 -35.5096 4 7 -14.5235 5 9 13.6376 6 11 51.5117 7 14 -17.3822 8 16 14.8927 9 18 17.5837 10 20 36.0876 11 22 -13.9743 12 24 40.1764 (Table 1E: Lens group data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 6.72504 43.51730 18.59635 53.39115 2 20 -24.16495 2.82190 2.36005 3.63480 3 24 40.17638 17.35520 1.42125 3.88889 (Table 1F: Lens group magnification) Group starting surface, infinity, proximity 1 1 0.00000 -0.04774 2 20 2.17172 2.15413 3 24 0.63996 0.64010 (Numerical Example 2) The imaging optical system of Numerical Example 2 corresponds to Embodiment 2 shown in Figure 2A. The surface data of the imaging optical system of Numerical Example 2 is shown in Table 2A, the aspherical data in Table 2B, the various data in the infinity focus state and the close-up object focus state in Table 2C, the single lens data in Table 2D, the lens group data in Table 2E, and the sub-lens group data in Table 2F.

[0268] (Table 2A: Surface data) Face number rd nd vd Object surface ∞ variable 1 20.26490 1.30000 1.80420 46.5 2 11.14650 3.49600 3* 10.32020 2.60000 1.53380 55.6 4* 6.66670 3.94670 5 16.29720 0.80000 1.59283 68.6 6 9.82920 3.34380 7 ∞ 0.70000 1.59349 67.0 8 9.09440 0.01000 1.56732 42.8 9 9.09440 6.00000 1.59605 30.4 10 -69.98070 0.97710 11 34.56000 3.50000 1.75211 25.0 12 92.70240 2.40000 13 (aperture) ∞ 1.50000 14 37.07980 1.00000 2.00100 29.1 15 11.07800 0.01000 1.56732 42.8 16 11.07800 6.35180 1.55032 75.5 17 -17.71270 0.20000 18* 27.23670 6.61100 1.55332 71.7 19* -15.07250 Variable 20 64.59400 2.53230 1.94595 18.0 21 -29.26310 0.01000 1.56732 42.8 22 -29.26310 0.60000 1.84666 23.8 23 13.46920 Variable 24 41.76420 2.37190 1.84810 47.1 25 -171.18090 10.43000 26 ∞ 4.20000 1.51680 64.2 27 ∞ 1.00000 Image plane ∞ (Table 2B: Aspherical data) 3rd page K=-6.39282E-01, A4=-6.33076E-05, A6= 6.46097E-07, A8=-1.37477E-08 A10= 1.58888E-10, A12=-5.96355E-13 Side 4 K=-7.16748E-01, A4=-9.64329E-05, A6= 7.99780E-07, A8=-6.15563E-08 A10=9.76937E-10, A12=-6.64285E-12 Side 18 K= 0.00000E+00, A4=-5.72968E-05, A6= 2.40616E-07, A8=-1.28042E-08 A10= 1.77443E-10, A12=-1.16431E-12 Page 19 K= 0.00000E+00, A4= 1.13409E-05, A6=-1.79265E-09, A8=-1.08680E-08 A10= 1.43512E-10, A12=-8.96872E-13 (Table 2C: Various data under infinity focus and near-field focus conditions) Infinity Close Focal length 10.1013 9.9451 F-number 1.76831 1.77096 Field of view 47.5937 47.6586 Image height 10.0000 10.0000 Lens length 72.3039 72.3025 d0 ∞ 127.7000 d19 1.1964 1.6543 d23 5.2129 4.7550 Entrance pupil position 13.3007 13.3007 Exit pupil position -47.3561 -46.1700 Front principal point position 21.2475 21.0702 Back principal point position 62.2026 61.6450 (Table 2D: Single lens data) Lens starting plane, focal length 1 1 -32.8939 2 3 -46.8923 3 5 -43.7926 4 7 -15.3235 5 9 13.8968 6 11 71.4185 7 14 -16.0915 8 16 13.4367 9 18 18.5695 10 20 21.5731 11 22 -10.8245 12 24 39.7897 (Table 2E: Lens group data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 7.17626 44.74640 19.25453 54.00238 2 20 -23.08986 3.14230 2.26682 3.72120 3 24 39.78967 17.00190 0.25301 2.76590 (Table 2F: Lens group magnification) Group starting surface, infinity, proximity 1 1 0.00000 -0.05134 2 20 2.28142 2.26143 3 24 0.61699 0.61702 (Numerical Example 3) The imaging optical system of Numerical Example 3 corresponds to Embodiment 3 shown in Figure 3A. Table 3A shows the surface data of the imaging optical system of Numerical Example 3, Table 3B shows the aspherical data, Table 3C shows various data in the infinity focus state and the close-up object focus state, Table 3D shows the single lens data, Table 3E shows the lens group data, and Table 3F shows the lens group magnification data.

[0269] (Table 3A: Surface Data) Face number rd nd vd Object surface ∞ variable 1 22.90590 1.20000 1.95375 32.3 2 10.54100 2.96720 3* 12.49070 2.50000 1.51602 56.5 4* 7.28590 11.90120 5 -14.87290 0.80000 1.49700 81.6 6 73.91550 0.01000 1.56732 42.8 7 73.91550 2.34500 2.00100 29.1 8 -18.53010 2.27660 9 -12.01440 1.00000 1.49700 81.6 10 -17.34100 1.00000 11 (aperture) ∞ 4.32870 12 15.28340 4.08300 1.53775 74.7 13 -42.62420 0.51720 14 ∞ 0.80000 1.95375 32.3 15 13.23620 0.01000 1.56732 42.8 16 13.23620 3.67650 1.49700 81.6 17 -24.73100 0.93490 18* 106.13890 4.04380 1.51602 56.5 19* -19.80650 Variable 20* -11.11910 2.26810 1.64190 22.5 21* -21.69420 Variable 22 30.83590 3.67810 1.48749 70.4 23 -42.59340 10.80220 24 ∞ 4.20000 1.51680 64.2 25 ∞ 1.00000 Image plane ∞ (Table 3B: Aspheric data) 3rd page K=-2.70512E-01, A4= 8.23955E-05, A6=-1.41872E-06, A8= 1.25669E-08 A10 = -6.48285E-11 Side 4 K=-9.98814E-01, A4= 1.52609E-04, A6=-2.63666E-06, A8= 7.17647E-09 A10 = -1.52969E-10 Side 18 K= 0.00000E+00, A4=-2.28763E-04, A6=-4.54975E-06, A8= 1.65888E-08 A10 = -4.77889E-10 Page 19 K= 0.00000E+00, A4=-8.38116E-05, A6=-5.31109E-06, A8= 5.08478E-08 A10 = -3.19373E-10 Page 20 K= 0.00000E+00, A4= 1.02640E-03, A6=-1.11239E-05, A8= 8.24437E-08 A10 = -1.66997E-10 Page 21 K= 0.00000E+00, A4= 7.73439E-04, A6=-4.36622E-06, A8=-1.82425E-08 A10 = 2.65100E-10 (Table 3C: Various data under infinity focus and near object focus conditions) Infinity Close Focal length 9.3150 9.2532 F-number 1.76801 1.77534 Field of view 49.7611 49.7613 Image height 10.0000 10.0000 Lens length 71.0341 71.0109 d0 ∞ 128.9978 d19 1.2000 1.9460 d21 3.4597 2.7137 Entrance pupil position 10.9738 10.9738 Exit pupil position -83.0404 -79.2775 Front principal point position 19.2443 19.1387 Back principal point position 61.7191 61.1412 (Table 3D: Single lens data) Lens starting plane, focal length 1 1 -21.4923 2 3 -40.5069 3 5 -24.8384 4 7 14.9913 5 9 -83.9308 6 12 21.4488 7 14 -13.8781 8 16 17.9239 9 18 32.7044 10 20 -38.7877 11 22 37.3038 (Table 3E: Lens group data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 8.50508 44.39410 17.93650 54.12445 2 20 -38.78773 2.26810 -1.58538 -0.82510 3 22 37.30377 18.68030 1.05571 3.65086 (Table 3F: Lens group magnification data) Group starting surface, infinity, proximity 1 1 0.00000 -0.06144 2 20 1.92333 1.90226 3 22 0.56944 0.57007 (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, the various data in the infinity focus state and the close-up object focus state in Table 4C, the single lens data in Table 4D, the lens group data in Table 4E, and the lens group magnification data in Table 4F.

[0270] (Table 4A: Surface Data) Face number rd nd vd Object surface ∞ variable 1 25.16230 1.50000 1.87071 40.7 2 10.68800 2.83920 3* 21.74520 2.30000 1.51602 56.5 4* 11.34520 5.52880 5 146.90700 1.00000 1.49700 81.6 6 12.04680 0.01000 1.56732 42.8 7 12.04680 4.00000 1.84666 23.8 8 14.36270 6.81020 9 39.18250 2.69240 1.90366 31.3 10 -39.18250 4.86680 11 (aperture) ∞ 1.70000 12 33.31680 0.80000 2.00100 29.1 13 10.64360 0.01000 1.56732 42.8 14 10.64360 4.43550 1.55032 75.5 15 -37.83430 2.57030 16* 21.17880 4.33020 1.61881 63.9 17* -18.56740 Variable 18 34.06230 0.80000 1.91082 35.2 19 12.85710 Variable 20 168.50900 2.45310 1.59283 68.6 21 -28.25740 10.80000 22 ∞ 4.20000 1.51680 64.2 23 ∞ 1.00000 Image plane ∞ (Table 4B: Aspheric data) 3rd page K= 0.00000E+00, A4= 3.34480E-04, A6=-2.40675E-06, A8= 1.77608E-08 A10=-7.00153E-11, A12= 0.00000E+00, A14= 0.00000E+00 Side 4 K= 0.00000E+00, A4= 3.78767E-04, A6=-3.23045E-06, A8= 2.23521E-08 A10=-3.15635E-10, A12= 0.00000E+00, A14= 0.00000E+00 Page 16 K= 0.00000E+00, A4=-3.85694E-05, A6= 3.29081E-07, A8=-8.57234E-09 A10= 5.88995E-11, A12= 1.09634E-13, A14= 1.89390E-21 Page 17 K= 0.00000E+00, A4= 3.48156E-05, A6=-9.85426E-08, A8=-5.80609E-09 A10= 3.59244E-11, A12= 2.12753E-13, A14=-1.80773E-21 (Table 4C: Various data under infinity focus and near-field focus conditions) Infinity Close Focal length 9.3145 9.1995 F-number 1.76860 1.77124 Field of view: 49.9380 50.0104 Image height 10.0000 10.0000 Lens length 70.9977 70.9961 d0 ∞ 129.0001 d17 1.2015 1.5681 d19 5.1519 4.7853 Entrance pupil position 11.9476 11.9476 Exit pupil position -46.9921 -46.1107 Front principal point position 19.4157 19.2870 Back principal point position 61.6832 61.1881 (Table 4D: Single lens data) Lens starting plane, focal length 1 1 -22.4207 2 3 -49.7123 3 5 -26.4696 4 7 49.2455 5 9 22.0394 6 12 -15.9051 7 14 15.6010 8 16 16.6831 9 18 -23.0899 10 20 41.0107 (Table 4E: Lens group data) Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 6.41458 45.39340 17.25418 53.78799 2 18 -23.08988 0.80000 0.68483 1.05849 3 20 41.01069 17.45310 1.32507 3.66191 (Table 4G: Lens group magnification data) Group starting surface, infinity, proximity 1 1 0.00000 -0.04587 2 18 2.27105 2.25501 3 20 0.63939 0.63943 (Corresponding value for the condition) The corresponding values ​​for conditions (1) to (14) are shown in Table 1 below.

[0271] [Table 1] [Industrial applicability]

[0272] 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, and in-vehicle cameras, 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]

[0273] G1 First Lens Group G1A 1A Sub-lens group G1B 1B Sub-lens group G2 Second Lens Group G3 3rd 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 S image plane CG cover glass 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. It consists of, in order from the object side, a front group, an aperture diaphragm, and a rear group with positive power. The aforementioned group is arranged in order from the object side to the image side, A negative meniscus lens element L1A1 having a convex surface on the object side, A negative meniscus lens element L1A2 having a convex surface on the object side, A negative lens element L1A3 having a convex surface on the image side toward the object, It has, The following conditions (1), (2), and (5) must be satisfied, 0.9 < DL1A2 / DL1A1...(1) 1.0 < DL1A2 / DL1A3...(2) 0.3 < BF / Y < 2.0...(5) Here, DL1A1: Thickness of the negative meniscus lens element L1A1 along the optical axis, DL1A2: Thickness of the negative meniscus lens element L1A2 along the optical axis, DL1A3: Thickness of the negative lens element L1A3 on the optical axis, BF: Back focus, Y: Image height when focused at infinity. That is, Imaging optical system.

2. It consists of, in order from the object side, a front group, an aperture diaphragm, and a rear group with positive power. When a single lens element is used as the lens component in the case of a non-bonding lens, and a bonding lens is used in the case of a bonding lens, the front group is arranged in order from the object side to the image side, A negative lens component L1A1 having a convex surface on the object side, A negative lens component L1A2 having a convex surface on the object side, A negative lens component L1A3 has a convex surface on the image side toward the object, Lens components that possess positive power, Lens components that possess positive power, It has, The following conditions (1), (2), and (5) must be satisfied, 0.9 < DL1A2 / DL1A1...(1) 1.0 < DL1A2 / DL1A3...(2) 0.3 < BF / Y < 2.0...(5) Here, DL1A1: Thickness of the negative lens component L1A1 on the optical axis, DL1A2: Thickness of the negative lens component L1A2 on the optical axis, DL1A3: Thickness of the negative lens component L1A3 on the optical axis, BF: Back focus, Y: Image height when focused at infinity. That is, Imaging optical system.

3. Starting from the object side, it consists of a front group, an aperture diaphragm, and a rear group with positive power. The aforementioned group is arranged in order from the object side to the image side, A negative meniscus lens element L1A1 having a convex surface on the object side, A negative meniscus lens element L1A2 having a convex surface on the object side, A negative lens element L1A3 having a convex surface on the image side toward the object, It has, The following conditions (3) and (5) are satisfied, 0.7 < DL1A2 / (DL1A1+DL1A3)...(3) 0.3 < BF / Y < 2.0...(5) Here, DL1A1: Thickness of the negative meniscus lens element L1A1 along the optical axis, DL1A2: Thickness of the negative meniscus lens element L1A2 along the optical axis, DL1A3: Thickness of the negative lens element L1A3 on the optical axis, BF: Back focus, Y: Image height when focused at infinity. That is, Imaging optical system.

4. The following condition (4) is satisfied, 0.3 < f / D < 1.0...(4) Here, f: focal length when focused at infinity. D: Distance along the optical axis from the outermost object side of the front group to the image side of the fourth lens element from the object side of the front group, The imaging optical system according to any one of claims 1 to 3.

5. At least one negative lens element in the aforementioned front group satisfies the following condition (6): νdL1An > 62 (6) Here, νdL1An: Abbe number in the d line of the negative lens element in the front group, The imaging optical system according to any one of claims 1 to 3.

6. The following condition (9) is satisfied, 0.5 < Ls / LL...(9) Here, Ls: Distance along the optical axis from the aperture diaphragm to the image plane, LL: Optical length when focused at infinity. The imaging optical system according to any one of claims 1 to 3.

7. The following conditions (12) and (13) are satisfied, 1.45 < ndL1A2 < 1.60 (12) 50.0 < νdL1A2 < 65.0 (13) Here, ndL1A2: The refractive index of the negative meniscus lens element L1A2 at the d line, νdL1A2: Abbe number on the d line of the negative meniscus lens element L1A2, The imaging optical system according to claim 1 or 2.

8. The following conditions (16) must be met: 0.1 < DG1A1_A2 / D < 1.0 (16) Here, DG1A1_A2: Distance along the optical axis from the image side of the negative meniscus lens element L1A1 to the object side of the negative meniscus lens element L1A2, D: Distance along the optical axis from the outermost object side of the front group to the image side of the fourth lens element from the object side of the front group. The imaging optical system according to claim 1 or 2.

9. An interchangeable lens device including an imaging optical system according to any one of claims 1 to 3, A camera body that includes an image sensor which is detachably connected to the interchangeable lens device via a camera mount and receives the optical image formed by the imaging optical system and converts it into an electrical image signal, A camera system comprising, The interchangeable lens device forms an optical image of an object on the image sensor. Camera system.

10. An imaging device that converts an optical image of an object into an electrical image signal, and performs at least one of displaying and storing the converted image signal, An imaging optical system according to any one of claims 1 to 3 that forms an optical image of an object, An image sensor that converts an optical image formed by the aforementioned imaging optical system into an electrical image signal, Equipped with, Imaging device.

Images