JP2022182997A - Image capturing optical system, image capturing device, and camera system - Google Patents

Abstract

To provide an image capturing optical system capable of correcting well for aberrations, an image capturing device, and a camera system.SOLUTION: An image capturing optical system is provided, comprising a first lens group having positive refractive power, a second lens group, and a third lens group. The first lens group comprises a sub lens group G1A, an aperture stop, and a sub lens group G1B. The sub lens group G1A comprises a lens element L1A1 and a lens element L1A2. The lens element L1A1 has an object-side surface that is convex toward the object side. The third lens group comprises a lens element L3E having negative power and a lens element L3P located next to the lens element L3E on the object side.SELECTED DRAWING: Figure 1

Description

The present disclosure relates generally to imaging optics, imaging devices, and camera systems. More specifically, the present disclosure relates to an imaging optical system capable of satisfactorily correcting various aberrations, an imaging apparatus using the imaging optical system, and a camera system.

Patent Document 1 discloses an imaging optical system composed of, in order from the object side to the image side, a first lens group having positive power, a second lens group that moves during focusing, and a third lens group. there is

WO2016/194111

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

An imaging optical system according to one aspect of the present disclosure includes, in order from the object side, a first lens group having positive power, a second lens group having power, and a third lens group having power. When the imaging optical system is focused, the first lens group and the third lens group stop moving in the direction along the optical axis of the imaging optical system. so that the distance on the optical axis between the two lens groups closest to the object side and the distance on the optical axis between the second lens group closest to the image side and the third lens group closest to the object side, At least one negatively powered lens element LFN in the second lens group moves along the optical axis.

The first lens group includes, in order from the object side, a sub-lens group G1A, an aperture stop, and a sub-lens group G1B.

The sub-lens group G1A includes, in order from the most object side, a lens element L1A1 and a lens element L1A2 adjacent to the image side of the lens element L1A1.

The object side surface of the lens element L1A1 has a convex shape on the object side.

The third lens group includes, in order from the image side, a lens element L3E having negative power and a lens element L3P adjacent to the object side of the lens element L3E.

In addition, a camera system according to an aspect of the present disclosure includes an interchangeable lens device including the above-described imaging optical system, and an interchangeable lens device detachably connected to the interchangeable lens device via a camera mount section, and an optical system formed by the imaging optical system. a camera body including an imaging device that receives an image and converts it into an electrical image signal, wherein the interchangeable lens device forms an optical image of an object on the imaging device.

Also, an imaging device according to an aspect of the present disclosure 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 includes the imaging optical system described above and an imaging device. The imaging optical system forms an optical image of an object. The imaging device converts an optical image formed by the imaging optical system into an electrical image signal.

According to the present disclosure, it is possible to provide an imaging optical system capable of satisfactorily correcting various aberrations, an imaging apparatus using the imaging optical system, and a camera system.

FIG. 4 is a lens layout diagram showing an infinity focused state of an imaging optical system according to Embodiment 1 (Numerical Example 1). Longitudinal aberration diagram of the imaging optical system according to Numerical Example 1 FIG. 10 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to Embodiment 2 (Numerical Example 2). Longitudinal aberration diagram of the imaging optical system according to Numerical Example 2 FIG. 11 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to Embodiment 3 (Numerical Example 3) Longitudinal aberration diagram of the imaging optical system according to Numerical Example 3 FIG. 11 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to Embodiment 4 (Numerical Example 4). Longitudinal aberration diagram of the imaging optical system according to Numerical Example 4 FIG. 11 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to Embodiment 5 (Numerical Example 5). Longitudinal aberration diagram of the imaging optical system according to Numerical Example 5 Schematic configuration diagram of a digital camera according to Embodiment 1 1 is a schematic configuration diagram of a lens-interchangeable digital camera system according to Embodiment 1. FIG.

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art.

Applicants provide the accompanying drawings and the following description for a full understanding of the present disclosure by those skilled in the art, which are intended to limit the claimed subject matter. is not.

(Embodiments 1 to 5)
FIGS. 1, 3, 5, 7, and 9 show lens arrangement diagrams of imaging optical systems according to Embodiments 1 to 5 and operations thereof.

In the present disclosure, “focusing”, “focusing” or “focusing” refer to “focusing”, “focusing” or “focusing” of the imaging optical system, unless otherwise specified. In addition, in the present disclosure, unless otherwise specified, the term “optical axis” refers to the optical axis of the imaging optical system.

FIGS. 1, 3, 5, 7 and 9(a) all show lens layout diagrams in an infinity focused state. In (a) of each figure, the rightmost straight line represents the position of the image plane S (a plane facing the object side, which corresponds to a plane on which an imaging device is arranged, which will be described later). The left side of these drawings therefore corresponds to the object side. Further, between the last lens group facing the image plane S and the image plane S, for example, a low-pass filter or a cover glass CG is arranged. In addition, in (a) of each figure, the aspect ratio is the same.

An asterisk * attached to the surface of a particular lens element shown in (a) of each figure indicates that the surface is aspheric. If the object side or image side of each lens element is not marked with an asterisk *, the surface is spherical.

In addition, in the lower part of (b) of each figure, the reference numerals G1 to G3 are given to the respective lens groups corresponding to the positions of the respective lens groups shown in (a). The sign (+) and sign (-) attached to the sign of each lens group (G1 to G3) correspond to the sign of the power of each lens group. That is, the symbol (+) indicates positive power and the symbol (-) indicates negative power.

In addition, the upper part of each figure (b) shows sub-lens groups that subdivide the lens groups G1 to G3 shown in the lower part of (b), and each sub-lens group is denoted by a reference numeral. The sign (+) and sign (-) attached to the sign of each sub lens group (G1A, G1B, G2A, G2B) correspond to the sign of the power of each lens group. That is, the symbol (+) indicates positive power and the symbol (-) indicates negative power.

In addition, in the upper part of each figure (b) or the lower part of (b) in each figure, below the reference numerals of specific lens groups or specific sub-lens groups, the transition from the infinity focus state to the close focus state is shown. An arrow is attached to indicate the direction of movement associated with focusing.

(Embodiment 1)
An imaging optical system according to Embodiment 1 will be described below with reference to FIG.

FIG. 1 shows a lens arrangement diagram showing an infinity focused state of an imaging optical system according to Embodiment 1 and its operation.

As shown in FIG. 1, the imaging optical system of the present embodiment includes, 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, It is composed of a third lens group G3 having positive power, a cover glass CG, and the like.

The first lens group G1 is composed of, in order from the object side to the image side, a sub-lens group G1A having negative power, an aperture stop A, and a sub-lens group G1B having positive power.

The sub-lens group G1A includes, in order from the object side to the image side, a first lens element L1 having positive power, a second lens element L2 having negative power, and a third lens element L3 having negative power. , and a fourth lens element L4 having positive power.

The sub-lens group G1B is composed of, in order from the object side to the image side, a fifth lens element L5 having positive power and a sixth lens element L6 having positive power.

The third lens element L3 and the fourth lens element L4 are adhered to each other with an adhesive such as an ultraviolet curable resin to form a cemented lens. That is, the cemented lens includes the third lens element L3 and the fourth lens element L4.

The second lens group G2 is composed of a seventh lens element L7 having negative power.

The third lens group G3 is composed of an eighth lens element L8 having positive power and a ninth lens element L9 having negative power.

Each lens element constituting each lens group of the imaging optical system of the present embodiment will be described below.

First, each lens element in the sub-lens group G1A will be described.

The first lens element L1 is a meniscus lens having a convex surface on the object side. The second lens element L2 is a meniscus lens having a convex surface on the object side. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a biconvex lens. The first lens element L1 is an example of the lens element L1A1. Second lens element L2 is an example of lens element L1A2.

Next, each lens element in the sub-lens group G1B will be explained.

The fifth lens element L5 is a biconvex lens. The sixth lens element L6 is a biconvex lens, both surfaces of which are aspheric. The sixth lens element L6 is an example of lens element L1BE.

Next, lens elements in the second lens group G2 will be explained.

The seventh lens element L7 is a meniscus lens having a convex surface on the object side, both surfaces of which are aspheric. The seventh lens element L7 is an example of lens element LFN and lens element L2F.

Next, the lens elements in the third lens group G3 will be explained.

The eighth lens element L8 is a biconvex lens, both surfaces of which are aspheric. The ninth lens element L9 is a meniscus lens having a convex surface on the image side. The eighth lens element L8 is an example of lens element L3P. The ninth lens element L9 is an example of lens element L3E.

In the imaging optical system of the present embodiment, when focusing is performed from the infinity focused state to the near junction focused state, the first lens group G1 does not move, the aperture stop A does not move, and the second lens The group G2 moves along the optical axis toward the image side, and the third lens group G3 does not move.

Namely, the distance (d13) on the optical axis between the side closest to the image of the first lens group G1 and the side closest to the object of the second lens group G2, and the distance (d13) on the optical axis from the side closest to the image of the second lens group G2 to the side closest to the object of the third lens group G3. The imaging optical system performs focusing so that the distance (d15) on the optical axis from the side surface of the object changes.

More specifically, the seventh lens element L7 moves toward the image side during focusing from the infinity focus state to the near junction focus state.

In this embodiment, the image-side surface of the first lens group G1 is the image-side surface of the sixth lens element L6. The closest object side surface of the second lens group G2 is the object side surface of the seventh lens element L7. The image-side surface of the second lens group G2 is the image-side surface of the seventh lens element L7. The closest object side surface of the third lens group G3 is the object side surface of the eighth lens element L8.

(Embodiment 2)
An imaging optical system according to Embodiment 2 will be described below with reference to FIG.

FIG. 3 shows a lens arrangement diagram showing an infinity focused state of the imaging optical system according to Embodiment 2 and its operation.

As shown in FIG. 3, the imaging optical system of the present embodiment includes, 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, It is composed of a third lens group G3 having negative power, a cover glass CG, and the like.

The first lens group G1 is composed of, in order from the object side to the image side, a sub-lens group G1A having negative power, an aperture stop A, and a sub-lens group G1B having positive power.

The sub-lens group G1A includes, in order from the object side to the image side, a first lens element L1 having positive power, a second lens element L2 having negative power, and a third lens element L3 having negative power. , and a fourth lens element L4 having positive power.

The sub-lens group G1B is composed of, in order from the object side to the image side, a fifth lens element L5 having positive power and a sixth lens element L6 having positive power.

The third lens element L3 and the fourth lens element L4 are adhered to each other with an adhesive such as an ultraviolet curable resin to form a cemented lens. That is, the cemented lens includes the third lens element L3 and the fourth lens element L4.

The second lens group G2 is composed of a seventh lens element L7 having negative power.

The third lens group G3 is composed of an eighth lens element L8 having positive power and a ninth lens element L9 having negative power.

Each lens element constituting each lens group of the imaging optical system of the present embodiment will be described below.

First, each lens element in the sub-lens group G1A will be described.

The first lens element L1 is a meniscus lens having a convex surface on the object side. The second lens element L2 is a meniscus lens having a convex surface on the object side. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a biconvex lens. The first lens element L1 is an example of the lens element L1A1. Second lens element L2 is an example of lens element L1A2.

Next, each lens element in the sub-lens group G1B will be explained.

The fifth lens element L5 is a biconvex lens. The sixth lens element L6 is a biconvex lens, both surfaces of which are aspheric. The sixth lens element L6 is an example of lens element L1BE.

Next, lens elements in the second lens group G2 will be explained.

The seventh lens element L7 is a meniscus lens having a convex surface on the object side, both surfaces of which are aspheric. The seventh lens element L7 is an example of lens element LFN and lens element L2F.

Next, the lens elements in the third lens group G3 will be explained.

The eighth lens element L8 is a biconvex lens, both surfaces of which are aspheric. The ninth lens element L9 is a meniscus lens having a convex surface on the image side. The eighth lens element L8 is an example of lens element L3P. The ninth lens element L9 is an example of lens element L3E.

In the imaging optical system of the present embodiment, when focusing is performed from the infinity focused state to the near junction focused state, the first lens group G1 does not move, the aperture stop A does not move, and the second lens The group G2 moves along the optical axis toward the image side, and the third lens group G3 does not move.

Namely, the distance (d13) on the optical axis between the side closest to the image of the first lens group G1 and the side closest to the object of the second lens group G2, and the distance (d13) on the optical axis from the side closest to the image of the second lens group G2 to the side closest to the object of the third lens group G3. The imaging optical system performs focusing so that the distance (d15) on the optical axis from the side surface of the object changes.

More specifically, the seventh lens element L7 moves toward the image side during focusing from the infinity focus state to the near junction focus state.

In this embodiment, the image-side surface of the first lens group G1 is the image-side surface of the sixth lens element L6. The closest object side surface of the second lens group G2 is the object side surface of the seventh lens element L7. The image-side surface of the second lens group G2 is the image-side surface of the seventh lens element L7. The closest object side surface of the third lens group G3 is the object side surface of the eighth lens element L8.

(Embodiment 3)
An imaging optical system according to Embodiment 3 will be described below with reference to FIG.

FIG. 5 shows a lens arrangement diagram showing an infinity focused state of the imaging optical system according to Embodiment 3 and its operation.

As shown in FIG. 5, the imaging optical system of the present embodiment includes, 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, It is composed of a third lens group G3 having positive power, a cover glass CG, and the like.

The first lens group G1 is composed of, in order from the object side to the image side, a sub-lens group G1A having negative power, an aperture stop A, and a sub-lens group G1B having positive power.

The sub-lens group G1A includes, in order from the object side to the image side, a first lens element L1 having positive power, a second lens element L2 having negative power, and a third lens element L3 having negative power. , and a fourth lens element L4 having positive power.

The sub-lens group G1B is composed of, in order from the object side to the image side, a fifth lens element L5 having positive power and a sixth lens element L6 having positive power.

The third lens element L3 and the fourth lens element L4 are adhered to each other with an adhesive such as an ultraviolet curable resin to form a cemented lens. That is, the cemented lens includes the third lens element L3 and the fourth lens element L4.

The second lens group G2 is composed of a seventh lens element L7 having negative power.

The third lens group G3 is composed of an eighth lens element L8 having positive power, a ninth lens element L9 having positive power, and a tenth lens element L10 having negative power.

Each lens element constituting each lens group of the imaging optical system of the present embodiment will be described below.

First, each lens element in the sub-lens group G1A will be described.

The first lens element L1 is a meniscus lens having a convex surface on the object side. The second lens element L2 is a meniscus lens having a convex surface on the object side. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a biconvex lens. The first lens element L1 is an example of the lens element L1A1. Second lens element L2 is an example of lens element L1A2.

Next, each lens element in the sub-lens group G1B will be explained.

The fifth lens element L5 is a biconvex lens. The sixth lens element L6 is a biconvex lens, both surfaces of which are aspheric. The sixth lens element L6 is an example of lens element L1BE.

Next, lens elements in the second lens group G2 will be explained.

The seventh lens element L7 is a meniscus lens having a convex surface on the object side, both surfaces of which are aspheric. The seventh lens element L7 is an example of lens element LFN and lens element L2F.

Next, the lens elements in the third lens group G3 will be explained.

The eighth lens element L8 is a biconvex lens, both surfaces of which are aspheric. The ninth lens element L9 is a biconvex lens. A tenth lens element L10 is a meniscus lens having a convex surface on the image side. The ninth lens element L9 is an example of lens element L3P. The tenth lens element L10 is an example of lens element L3E.

In the imaging optical system of the present embodiment, when focusing is performed from the infinity focused state to the near junction focused state, the first lens group G1 does not move, the aperture stop A does not move, and the second lens The group G2 moves along the optical axis toward the image side, and the third lens group G3 does not move.

Namely, the distance (d13) on the optical axis between the side closest to the image of the first lens group G1 and the side closest to the object of the second lens group G2, and the distance (d13) on the optical axis from the side closest to the image of the second lens group G2 to the side closest to the object of the third lens group G3. The imaging optical system performs focusing so that the distance (d15) on the optical axis from the side surface of the object changes.

More specifically, the seventh lens element L7 moves toward the image side during focusing from the infinity focus state to the near junction focus state.

In this embodiment, the image-side surface of the first lens group G1 is the image-side surface of the sixth lens element L6. The closest object side surface of the second lens group G2 is the object side surface of the seventh lens element L7. The image-side surface of the second lens group G2 is the image-side surface of the seventh lens element L7. The closest object side surface of the third lens group G3 is the object side surface of the eighth lens element L8.

(Embodiment 4)
An imaging optical system according to Embodiment 4 will be described below with reference to FIG.

FIG. 7 shows a lens arrangement diagram showing the infinity focused state of the imaging optical system according to Embodiment 4 and its operation.

As shown in FIG. 7, the imaging optical system of the present embodiment includes, 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, It is composed of a third lens group G3 having positive power, a cover glass CG, and the like.

The first lens group G1 is composed of, in order from the object side to the image side, a sub-lens group G1A having negative power, an aperture stop A, and a sub-lens group G1B having positive power.

The sub-lens group G1A includes, in order from the object side to the image side, a first lens element L1 having positive power, a second lens element L2 having negative power, and a third lens element L3 having negative power. , and a fourth lens element L4 having positive power.

The sub-lens group G1B is composed of, in order from the object side to the image side, a fifth lens element L5 having positive power and a sixth lens element L6 having positive power.

The third lens element L3 and the fourth lens element L4 are adhered to each other with an adhesive such as an ultraviolet curable resin to form a cemented lens. That is, the cemented lens includes the third lens element L3 and the fourth lens element L4.

The second lens group G2 is composed of a seventh lens element L7 having positive power, an eighth lens element L8 having positive power, and a ninth lens element L9 having negative power.

The eighth lens element L8 and the ninth lens element L9 are adhered with an adhesive such as an ultraviolet curable resin, for example, to form a cemented lens. That is, the cemented lens includes the eighth lens element L8 and the ninth lens element L9.

The third lens group G3 is composed of a tenth lens element L10 having positive power and an eleventh lens element L11 having negative power.

Each lens element constituting each lens group of the imaging optical system of the present embodiment will be described below.

First, each lens element in the sub-lens group G1A will be described.

The first lens element L1 is a meniscus lens having a convex surface on the object side. The second lens element L2 is a meniscus lens having a convex surface on the object side. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a biconvex lens. The first lens element L1 is an example of the lens element L1A1. Second lens element L2 is an example of lens element L1A2.

Next, each lens element in the sub-lens group G1B will be explained.

The fifth lens element L5 is a biconvex lens. The sixth lens element L6 is a biconvex lens, both surfaces of which are aspheric. The sixth lens element L6 is an example of lens element L1BE.

Next, lens elements in the second lens group G2 will be explained.

The seventh lens element L7 is a meniscus lens having a convex surface on the image side, and its image side surface is aspheric. The eighth lens element L8 is a biconvex lens. The ninth lens element L9 is a biconcave lens. The seventh lens element L7 is an example of lens element L2F. The ninth lens element L9 is an example of the lens element LFN.

Next, the lens elements in the third lens group G3 will be explained.

The tenth lens element L10 is a biconvex lens, both surfaces of which are aspheric. The eleventh lens element L11 is a meniscus lens having a convex surface on the image side. The tenth lens element L10 is an example of the lens element L3P. The eleventh lens element L11 is an example of the lens element L3E.

In the imaging optical system of the present embodiment, when focusing is performed from the infinity focused state to the near junction focused state, the first lens group G1 does not move, the aperture stop A does not move, and the second lens The group G2 moves along the optical axis toward the image side, and the third lens group G3 does not move.

Namely, the distance (d13) on the optical axis between the side closest to the image of the first lens group G1 and the side closest to the object of the second lens group G2, and the distance (d13) on the optical axis from the side closest to the image of the second lens group G2 to the side closest to the object of the third lens group G3. The imaging optical system performs focusing so that the distance (d19) on the optical axis from the side surface of the object changes.

More specifically, the seventh lens element L7, the eighth lens element L8, and the ninth lens element L9 move together toward the image side during focusing from the infinity focus state to the near-conjugated focus state. do.

In this embodiment, the image-side surface of the first lens group G1 is the image-side surface of the sixth lens element L6. The closest object side surface of the second lens group G2 is the object side surface of the seventh lens element L7. The image-side surface of the second lens group G2 is the image-side surface of the ninth lens element L9. The closest object side surface of the third lens group G3 is the object side surface of the tenth lens element L10.

(Embodiment 5)
An imaging optical system according to Embodiment 5 will be described below with reference to FIG.

FIG. 9 shows a lens arrangement diagram showing the infinity focused state of the imaging optical system according to Embodiment 5 and its operation.

As shown in FIG. 9, the imaging optical system of the present embodiment includes, 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, It is composed of a third lens group G3 having negative power, a cover glass CG, and the like.

The first lens group G1 is composed of, in order from the object side to the image side, a sub-lens group G1A having negative power, an aperture stop A, and a sub-lens group G1B having positive power.

The sub-lens group G1A includes, in order from the object side to the image side, a first lens element L1 having positive power, a second lens element L2 having negative power, and a third lens element L3 having negative power. , and a fourth lens element L4 having positive power.

The first lens element L1 and the second lens element L2, and the third lens element L3 and the fourth lens element L4 are adhered with an adhesive such as an ultraviolet curable resin to form a cemented lens. That is, the first cemented lens includes the first lens element L1 and the second lens element L2, and the second cemented lens includes the third lens element L3 and the fourth lens element L4.

The sub-lens group G1B is composed of, in order from the object side to the image side, a fifth lens element L5 having positive power and a sixth lens element L6 having positive power.

The second lens group G2 is composed of, in order from the object side to the image side, a sub-lens group G2A having negative power and a sub-lens group G2B having positive power.

The sub-lens group G2A is composed of a seventh lens element L7 having negative power.

The sub-lens group G2B is composed of an eighth lens element L8 having positive power.

The third lens group G3 is composed of a ninth lens element L9 having positive power and a tenth lens element L10 having negative power.

Each lens element constituting each lens group of the imaging optical system of the present embodiment will be described below.

First, each lens element in the sub-lens group G1A will be described.

The first lens element L1 is a meniscus lens having a convex surface on the object side. The second lens element L2 is a meniscus lens having a convex surface on the object side. The third lens element L3 is a biconcave lens. The fourth lens element L4 is a biconvex lens. The first lens element L1 is an example of the lens element L1A1. Second lens element L2 is an example of lens element L1A2.

Next, each lens element in the sub-lens group G1B will be explained.

The fifth lens element L5 is a biconvex lens. The sixth lens element L6 is a biconvex lens, both surfaces of which are aspheric. The sixth lens element L6 is an example of lens element L1BE.

Next, lens elements in the sub-lens group G2A will be described.

The seventh lens element L7 is a biconcave lens, both surfaces of which are aspheric. The seventh lens element L7 is an example of lens element LFN and lens element L2F.

Next, lens elements in the sub-lens group G2B will be described.

The eighth lens element L8 is a meniscus lens having a convex surface on the image side, both surfaces of which are aspheric.

Next, the lens elements in the third lens group G3 will be explained.

The ninth lens element L9 is a meniscus lens having a convex surface on the image side. The tenth lens element L10 is a meniscus lens having a convex surface on the image side. The ninth lens element L9 is an example of lens element L3P. The tenth lens element L10 is an example of lens element L3E.

In the imaging optical system of the present embodiment, when focusing is performed from the infinity focused state to the near junction focused state, the first lens group G1 does not move, the aperture stop A does not move, and the second lens The sub-lens group G2A in the group G2 moves toward the image side along the optical axis, the sub-lens group G2B in the second lens group G2 moves toward the object side along the optical axis, and the third lens group G3 moves. do not do.

Namely, the distance (d13) on the optical axis between the side closest to the image of the first lens group G1 and the side closest to the object of the second lens group G2, and the distance (d13) on the optical axis from the side closest to the image of the second lens group G2 to the side closest to the object of the third lens group G3. The imaging optical system performs focusing so that the distance (d17) on the optical axis from the side surface of the object changes.

More specifically, the seventh lens element L7 moves to the image side and the eighth lens element L8 moves to the object side during focusing from the infinity focus state to the near junction focus state.

In this embodiment, the image-side surface of the first lens group G1 is the image-side surface of the sixth lens element L6. The closest object side surface of the second lens group G2 is the object side surface of the seventh lens element L7. The image-side surface of the second lens group G2 is the image-side surface of the eighth lens element L8. The closest object side surface of the third lens group G3 is the object side surface of the ninth lens element L9.

(Conditions and effects, etc.)
Conditions that can be satisfied by, for example, the imaging optical systems according to Embodiments 1 to 5 will be described below. Although a plurality of possible conditions are defined for the imaging optical systems according to Embodiments 1 to 5, the configuration of the imaging optical system that satisfies all of these multiple conditions is the most effective. However, by satisfying individual conditions, it is also possible to obtain an imaging optical system that produces corresponding effects.

For example, like the imaging optical systems according to Embodiments 1 to 5, the imaging optical system according to the present disclosure includes, in order from the most object side, a first lens group G1 having positive power and a second lens group G2 having power. and a third lens group G3 having power. During focusing of the imaging optical system, the first lens group G1 and the third lens group G3 do not move along the optical axis. In other words, when the imaging optical system is focused, the first lens group G1 and the third lens group G3 stop moving along the optical axis. Further, during focusing of the imaging optical system, the distance on the optical axis between the side closest to the image of the first lens group G1 and the side closest to the object of the second lens group G2, and the distance between the side closest to the image of the second lens group G2 and the third At least one negative power lens element LFN in the second lens group G2 moves along the optical axis so that the distance on the optical axis from the lens group G3 to the most object side surface changes.

The first lens group G1 includes, in order from the object side, a sub-lens group G1A, an aperture stop A, and a sub-lens group G1B.

The sub-lens group G1A includes, in order from the most object side, a lens element L1A1 and a lens element L1A2 adjacent to the image side of the lens element L1A1.

The object-side surface of lens element L1A1 has a convex shape on the object side.

The third lens group G3 includes, in order from the image side, a lens element L3E having negative power, and a lens element L3P adjacent to the object side of the lens element L3E.

With the basic configuration described above, an imaging optical system capable of satisfactorily correcting various aberrations can be realized.

Further, according to the basic configuration, even if the imaging optical system has an F number brighter than about 2.4, it is possible to achieve both high performance and miniaturization.

Moreover, it is desirable that the following condition (1) is satisfied in the imaging optical system of the basic configuration.

0.1 < L_STO/LL < 0.6 (1)
here,
L_STO: distance on the optical axis from the object side surface of lens element L1A1 to aperture stop A;
LL: distance on the optical axis from the object-side surface of lens element L1A1 to the image-side surface of lens element L3E;
is. Note that the units are the same (for example, the units of L_STO and LL are millimeters).

Condition (1) defines the relationship between the distance on the optical axis from the object side surface of lens element L1A1 to aperture stop A and the distance on the optical axis from the object side surface of lens element L1A1 to the image side surface of lens element L3E. It is the condition to be specified.

If the value is equal to or less than the lower limit of condition (1), the aperture stop A becomes too close to the object side of the imaging optical system and the exit pupil distance becomes large. becomes too large.

If the upper limit of the condition (1) is exceeded, the distance between the aperture stop A and the object side of the imaging optical system increases, so the lens diameter of the lens element L1A1 becomes too large.

Preferably, by satisfying at least one of the following conditions (1a) and (1b), the above effects can be further achieved.

0.15 < L_STO/LL (1a)
L_STO/LL<0.50 (1b)
More preferably, by satisfying at least one of the following conditions (1c) and (1d), the above effect can be further achieved.

0.20 < L_STO/LL (1c)
L_STO/LL<0.45 (1d)
Moreover, it is desirable that the following condition (2) is satisfied in the imaging optical system of the basic configuration.

2.0<LL/Y<10.0 (2)
here,
Y: image height when the imaging optical system is focused at infinity;
is. Note that the units are the same (for example, the units for LL and Y are millimeters).

Condition (2) defines the relationship between the distance on the optical axis from the object side surface of lens element L1A1 to the image side surface of lens element L3E and the image height when the imaging optical system is focused on infinity. .

If the lower limit of condition (2) is exceeded, the total length of the imaging optical system will be shortened, and lens elements and air gaps will not be able to be arranged appropriately, making it difficult to achieve high performance.

If the upper limit of condition (2) is exceeded, the total length of the imaging optical system becomes too large.

Preferably, by satisfying at least one of the following conditions (2a) and (2b), the above effects can be further achieved.

3.0<LL/Y (2a)
LL/Y<7.0 (2b)
More preferably, by satisfying at least one of the following conditions (2c) and (2d), the above effects can be further achieved.

3.5 <LL/Y (2c)
LL/Y<5.0 (2d)
Moreover, it is desirable that the following condition (3) is satisfied in the imaging optical system of the basic configuration.

0.1<TG3A/TL3E<20 (3)
here,
TG3A: the maximum value of the air gap on the optical axis in the third lens group G3;
TL3E: thickness on the optical axis of lens element L3E;
is.

Condition (3) is the maximum value of the air space on the optical axis in the third lens group G3 (the maximum air space between adjacent lens elements in the third lens group G3) and the lens element L3E thickness on the optical axis of .

Below the lower limit of condition (3), the maximum value of the air space in the third lens group G3 becomes narrower, so that the power of the lens elements in the third lens group G3 increases and the astigmatic difference increases. put away.

If the upper limit of the condition (3) is exceeded, the maximum value of the air space in the third lens group G3 becomes wide, and the overall length of the imaging optical system becomes large.

Preferably, by satisfying at least one of the following conditions (3a) and (3b), the above effect can be further achieved.

0.2 < TG3A/TL3E (3a)
TG3A/TL3E<15 (3b)
More preferably, by satisfying at least one of the following conditions (3c) and (3d), the above effects can be further achieved.

0.45<TG3A/TL3E (3c)
TG3A/TL3E<12 (3d)
Moreover, in the imaging optical system of the basic configuration, it is desirable that the lens element L1A1 has positive power.

This facilitates correction of excessive astigmatism.

Moreover, it is desirable that the following condition (4) is satisfied in the imaging optical system of the basic configuration.

|FL_L3E/FL| < 7 (4)
here,
FL_L3E: focal length of lens element L3E;
FL: focal length of the entire imaging optical system;
is. Note that the units are the same (for example, FL_L3E and FL are in millimeters).

Condition (4) is a condition that defines the relationship between the focal length of lens element L3E and the focal length of the entire imaging optical system.

If the upper limit of condition (4) is exceeded, the focal length of L3E will be too long, resulting in insufficient correction of curvature of field.

Preferably, at least one of the following conditions (4a) and (4b) is satisfied. By satisfying the condition (4b), the above effect can be further achieved. If the lower limit of condition (4a) is reached, the focal length of L3E becomes small, so correction of curvature of field becomes excessive.

0.50 < |FL_L3E/FL| (4a)
|FL_L3E/FL| < 6 (4b)
More preferably, by satisfying at least one of the following conditions (4c) and (4d), the above effect can be further achieved.

0.80 < |FL_L3E/FL| (4c)
|FL_L3E/FL| < 4 (4d)
Moreover, in the imaging optical system of the basic configuration, it is preferable that the object side surface of the lens element L3E has a concave shape and satisfy the following condition (5).

-1 < q < 4.5 (5)
here,
q: the form factor of lens element L3E,
q = (RrL3E + RfL3E) / (RrL3E - RfL3E),
RfL3E: the radius of curvature of the object-side surface of lens element L3E;
RrL3E: the radius of curvature of the image-side surface of lens element L3E;
is. Note that the units are the same (for example, the units for RfL3E and RrL3E are millimeters).

Condition (5) is a condition that defines the form factor of lens element L3E.

If the lower limit of condition (5) is exceeded, the effect of correcting field curvature of lens element L3E becomes large, so correction of field curvature becomes excessive.

If the upper limit of the condition (5) is exceeded, the correction effect of the curvature of field of the lens element L3E becomes small, so that the correction of the curvature of field becomes insufficient.

Preferably, by satisfying at least one of the following conditions (5a) and (5b), the above effects can be further achieved.

−0.8 < q (5a)
q < 4 (5b)
More preferably, by satisfying at least one of the following conditions (5c) and (5d), the above effects can be further achieved.

−0.6 < q (5c)
q < 3 (5d)
In the imaging optical system of the basic configuration, at least one of the image side surface of the lens element adjacent to the object side of the aperture diaphragm A and the object side surface of the lens element adjacent to the image side of the aperture diaphragm A faces the aperture diaphragm A. It is desirable to have a convex shape. As a result, the distance between the lens elements near the effective diameter can be widened. Therefore, it becomes easy to dispose the aperture stop A. In FIG. 1, the lens element adjacent to the object side of the aperture stop A is the fourth lens element L4. Also, in FIG. 1, the lens element adjacent to the image side of the aperture stop A is the fifth lens element L5.

Further, in the imaging optical system having the basic configuration, the positive lens element (lens element having positive power) and the negative lens element (lens element having negative power) in the third lens group G3 meet the following conditions (6): should be satisfied.

0.25<TG3P/TG3M<20 (6)
here,
TG3P: total thickness of the positive lens elements of the third lens group G3 on the optical axis;
TG3M: sum of thicknesses along the optical axis of the negative lens elements of the third lens group G3;
is. Note that the units are the same (for example, the units for TG3P and TG3M are millimeters).

Condition (6) defines the relationship between the total thickness of the positive lens elements in the third lens group G3 along the optical axis and the total thickness of the negative lens elements along the optical axis.

If the lower limit of condition (6) is exceeded, the thickness of the lens elements having positive power in the third lens group G3 will be small, resulting in excessive correction of curvature of field.

If the upper limit of condition (6) is exceeded, the thickness of the lens elements having positive power in the third lens group G3 will increase, and the image pickup optical system will become too large.

Preferably, by satisfying at least one of the following conditions (6a) and (6b), the above effect can be further achieved.

0.5<TG3P/TG3M (6a)
TG3P/TG3M<15 (6b)
More preferably, by satisfying at least one of the following conditions (6c) and (6d), the above effects can be further achieved.

0.8<TG3P/TG3M (6c)
TG3P/TG3M<13 (6d)
Moreover, it is desirable that the following condition (7) be satisfied in the imaging optical system of the basic configuration.

0.05<TSTO/Y<0.5 (7)
here,
TSTO: distance on the optical axis from the image-side surface of the lens element adjacent to the object side of the aperture stop A to the object-side surface of the lens element adjacent to the image side of the aperture stop A;
Y: image height when the imaging optical system is focused at infinity;
is. Note that the units are the same (for example, the units of TSTO and Y are millimeters).

Condition (7) is the distance on the optical axis from the image side surface of the lens element adjacent to the object side of the aperture diaphragm A to the object side surface of the lens element adjacent to the image side of the aperture diaphragm A, and image height.

If the lower limit of the condition (7) is exceeded, the distance between the aperture stop A and the optical axis becomes narrow, making it difficult to dispose the aperture stop A.

If the upper limit value of the condition (7) is exceeded, the distance on the optical axis before and after the aperture stop A increases, so that the imaging optical system becomes too large.

Preferably, by satisfying at least one of the following conditions (7a) and (7b), the above effect can be further achieved.

0.10<TSTO/Y (7a)
TSTO/Y<0.45 (7b)
More preferably, by satisfying at least one of the following conditions (7c) and (7d), the above effect can be further achieved.

0.15<TSTO/Y (7c)
TSTO/Y<0.40 (7d)
In the basic configuration of the imaging optical system, the third lens group G3 is composed of a lens element L3E and a lens element L3P in order from the image side, and the lens element L3P preferably has positive power.

This facilitates miniaturization of the third lens group G3.

Moreover, in the imaging optical system of the basic configuration, it is desirable that the object-side surface of the lens element L3E has a concave shape.

This makes it easy to suppress the occurrence of curvature of field.

Moreover, in the imaging optical system of the basic configuration, it is desirable that the sub-lens group G1B includes at least two lenses.

This facilitates correction of spherical aberration.

Moreover, in the imaging optical system of the basic configuration, it is desirable that the sub-lens group G1B includes a lens element L1BE having a positive power closest to the image side.

This facilitates correction of spherical aberration.

Moreover, it is desirable that the following condition (8) is satisfied in the imaging optical system of the basic configuration.

|NdL1BE−NdL2F| < 0.2 (8)
here,
NdL1BE: d-line refractive index of lens element L1BE;
NdL2F: d-line refractive index of the lens element L2F closest to the object side in the second lens group G2;
is.

Condition (8) defines the relationship between the d-line refractive index of the lens element L1BE and the d-line refractive index of the lens element L2F closest to the object side in the second lens group G2.

If the upper limit of condition (8) is exceeded, it becomes difficult to correct spherical aberration and coma aberration during focusing at infinity.

Preferably, by satisfying the following condition (8a), the above effects can be further achieved.

|NdL1BE−NdL2F| < 0.1 (8a)
More preferably, by satisfying the following condition (8b), the above effect can be further achieved.

|NdL1BE−NdL2F| < 0.01 (8b)
Moreover, it is desirable that the following condition (9) is satisfied in the imaging optical system of the basic configuration.

0.3<BF/Y<3 (9)
here,
BF: distance on the optical axis from the image side surface of the lens element L3E to the image surface S;
Y: image height when the imaging optical system is focused at infinity;
is. Note that the units are the same (for example, the units for BF and Y are millimeters).

The condition (9) defines the relationship between the distance on the optical axis from the image side surface of the lens element L3E to the image surface S and the image height when focusing on infinity.

If the lower limit of condition (9) is reached, the distance between the image side surface of the lens element L3E and the image plane S becomes narrow, making it difficult to arrange a member that fastens the image pickup optical system and the image pickup element arranged on the image plane S. becomes.

If the upper limit of the condition (9) is exceeded, the distance between the image side surface of the lens element L3E and the image surface S will be widened, resulting in an excessively large imaging optical system.

Preferably, by satisfying at least one of the following conditions (9a) and (9b), the above effect can be further achieved.

0.5<BF/Y (9a)
BF/Y<2.0 (9b)
More preferably, by satisfying at least one of the following conditions (9c) and (9d), the above effects can be further achieved.

0.7<BF/Y (9c)
BF/Y<1.2 (9d)
More preferably, by satisfying at least one of the following conditions (9e) and (9f), the above effects can be further achieved.

0.75<BF/Y (9e)
BF/Y<0.95 (9f)
Moreover, it is desirable that the following condition (10) be satisfied in the imaging optical system of the basic configuration.

0.3 < TFOC_L3E/FL < 3 (10)
here,
TFOC_L3E: Distance on the optical axis from the object side surface of the lens element L2F closest to the object side of the second lens group G2 to the image side surface of the lens element L3E when the imaging optical system is focused on infinity;
FL: focal length of the entire imaging optical system;
is. Note that the units are the same (for example, the units of TFOC_L3E and FL are millimeters).

Condition (10) is the distance on the optical axis from the object-side surface of the lens element L2F closest to the object side of the second lens group G2 to the image-side surface of the lens element L3E during focusing at infinity, and the total length of the imaging optical system. It is a condition that defines the relationship with the focal length.

If the lower limit of the condition (10) is reached, the amount of movement of the lens element that moves during focusing becomes small, and the focusing distance range becomes too narrow.

If the upper limit of condition (10) is exceeded, the amount of movement of the lens element that moves during focusing will increase, and the size of the imaging optical system will become too large.

Preferably, by satisfying at least one of the following conditions (10a) and (10b), the above effects can be further achieved.

0.5<TFOC_L3E/FL (10a)
TFOC_L3E/FL<2 (10b)
More preferably, by satisfying at least one of the following conditions (10c) and (10d), the above effects can be further achieved.

0.6 < TFOC_L3E/FL (10c)
TFOC_L3E/FL < 1 (10d)
Moreover, it is desirable that the following condition (11) be satisfied in the imaging optical system of the basic configuration.

0.5<TSTO_L3E/FL<6 (11)
here,
TSTO_L3E: distance on the optical axis from the aperture stop A to the image side surface of lens element L3E;
FL: focal length of the entire imaging optical system;
is. Note that the units are the same (for example, the units of TSTO_L3E and FL are millimeters).

Condition (11) defines the relationship between the distance on the optical axis from the aperture stop A to the image side surface of the lens element L3E and the focal length of the entire imaging optical system.

If the lower limit of condition (11) is exceeded, the distance between the aperture stop A and the third lens group G3 on the optical axis becomes narrow, and the amount of movement of the lens elements that can be moved during focusing becomes too small, making it impossible to achieve in-focus photography. The distance range becomes narrower.

If the distance between the aperture diaphragm A and the third lens group G3 on the optical axis becomes larger than the upper limit of the condition (11), the imaging optical system becomes too large.

Preferably, by satisfying at least one of the following conditions (11a) and (11b), the above effects can be further achieved.

0.9 < TSTO_L3E/FL (11a)
TSTO_L3E/FL < 5 (11b)
More preferably, by satisfying at least one of the following conditions (11c) and (11d), the above effects can be further achieved.

1.3 < TSTO_L3E/FL (11c)
TSTO_L3E/FL < 4 (11d)
Moreover, it is desirable that the following condition (12) is satisfied in the imaging optical system of the basic configuration.

0.2<FL_G1B/FL_G1<5 (12)
here,
FL_G1B: focal length of sub-lens group G1B;
FL_G1: focal length of the first lens group G1,
is. Note that the units are the same (for example, the units of FL_G1B and FL_G1 are millimeters).

Condition (12) defines the relationship between the focal length of the sub-lens group G1B and the focal length of the first lens group G1.

If the lower limit of condition (12) is exceeded, the focal length of the sub-lens group G1B will become short, resulting in insufficient correction of spherical aberration.

If the upper limit of condition (12) is exceeded, the focal length of the sub-lens group G1B will become too long, resulting in excessive correction of spherical aberration.

Preferably, by satisfying at least one of the following conditions (12a) and (12b), the above effects can be further achieved.

0.5<FL_G1B/FL_G1 (12a)
FL_G1B/FL_G1 < 4 (12b)
More preferably, by satisfying at least one of the following conditions (12c) and (12d), the above effect can be further achieved.

0.6 < FL_G1B/FL_G1 (12c)
FL_G1B/FL_G1 < 2 (12d)
Moreover, it is desirable that the following condition (13) is satisfied in the imaging optical system of the basic configuration.

0.1<TG3/FL<2 (13)
here,
TG3: distance on the optical axis from the object side surface to the image side surface of the third lens group G3;
FL: focal length of the entire imaging optical system;
is. Note that the units are the same (for example, the units for TG3 and FL are millimeters).

Condition (13) defines the relationship between the distance on the optical axis from the most object side surface to the most image side surface of the third lens group G3 and the focal length of the entire imaging optical system.

Below the lower limit of condition (13), the distance between the third lens group G3 on the optical axis becomes small, making it difficult to suppress the occurrence of curvature of field.

If the upper limit of the condition (13) is exceeded, the distance between the third lens group G3 on the optical axis increases, and the imaging optical system becomes too large.

Preferably, by satisfying at least one of the following conditions (13a) and (13b), the above effect can be further achieved.

0.15<TG3/FL (13a)
TG3/FL<1.4 (13b)
More preferably, by satisfying at least one of the following conditions (13c) and (13d), the above effects can be further achieved.

0.2<TG3/FL (13c)
TG3/FL<0.8 (13d)
Further, in the imaging optical system having the basic configuration, it is desirable that the most object side surface of the second lens group G2 moves toward the image side when focusing from the infinity focused state to the near junction focused state. For example, in FIG. 9, the closest object side surface of the second lens group G2 is the object side surface of the seventh lens element L7.

This facilitates the focusing operation when the shooting distance changes.

Also, the second lens group G2 preferably consists of three or less lenses including the lens element LFN.

As a result, the number of lens elements required for the focusing operation can be reduced, and the focusing mechanism can be simplified.

(Schematic configuration of imaging device to which Embodiment 1 is applied)
FIG. 11 shows a schematic configuration of an imaging device to which the imaging optical system according to the first embodiment is applied. Note that the imaging optical systems according to the second, third, fourth and fifth embodiments can also be applied to imaging apparatuses.

The imaging device 100 includes a housing 104, an imaging element 102, and an imaging optical system 101 according to the first embodiment. A specific example of the imaging device 100 is a digital camera.

The housing 104 has a lens barrel 302 . A lens barrel 302 holds each lens group of the imaging optical system 101 and an aperture stop A. FIG.

The imaging element 102 is arranged at the position of the image plane S in the imaging optical system 101 according to the first embodiment.

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 that displays image signals and a memory that stores image signals.

The imaging optical system 101 forms an optical image of an object. The imaging device 102 converts an optical image formed by the imaging optical system 101 into an electrical image signal.

The imaging optical system 101 has a distance on the optical axis between the most image side surface of the first lens group G1 and the most object side surface of the second lens group G2, and a distance between the most image side surface of the second lens group G2 and the third lens group G3. It is configured such that the distance on the optical axis from the side closest to the object changes. Specifically, the housing 104 is arranged so that at least one lens element having negative power (such as the seventh lens element L7) in the second lens group G2 moves during focusing of the imaging optical system 101. An included actuator and lens frame are attached or coupled to the at least one negatively powered lens element.

Accordingly, it is possible to realize the imaging apparatus 100 with good aberrations.

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.

(Schematic configuration of camera system to which Embodiment 1 is applied)
FIG. 12 shows a schematic configuration of a camera system to which the imaging optical system according to the first embodiment is applied. It is also possible to apply the imaging optical systems according to the second, third, fourth and fifth embodiments to a camera system.

A camera system 200 includes a camera body 201 and an interchangeable lens device 300 detachably connected to the camera body 201 .

The camera body 201 receives an optical image formed by the imaging optical system 301 of the interchangeable lens device 300, converts it into an electrical image signal, and displays the image signal converted by the imaging element 202. It includes a monitor 203 , a memory for storing image signals, a camera mount section 204 and a viewfinder 205 .

An imaging optical system 301 of the interchangeable lens device 300 is the imaging optical system according to the first embodiment. The interchangeable lens device 300 forms an optical image of an object on the imaging element 202 by the imaging optical system 301 .

The interchangeable lens device 300 includes an imaging optical system 301 , a lens barrel 302 and a lens mount section 304 . A lens barrel 302 holds each lens group of the imaging optical system 301 and an aperture stop A. FIG. The lens mount section 304 includes a lens mount section 304 detachably connected to the camera mount section 204 of the camera body 201 .

Thus, 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 electrically connect the controller in the camera body 201 and the controller in the interchangeable lens device 300, and function as an interface that enables mutual signal exchange.

The imaging optical system 301 includes 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 stop A, and a third lens group G3. The distance on the optical axis between the side closest to the image of the first lens group G1 and the side closest to the object of the second lens group G2, and the distance between the side closest to the image of the second lens group G2 and the side closest to the object of the third lens group G3. are configured such that the distance between them on the optical axis varies. Specifically, the interchangeable lens device 300 is arranged such that at least one lens element having negative power (such as the seventh lens element L7) in the second lens group G2 moves during focusing of the imaging optical system 301. Actuators and lens frames controlled by an internal controller are configured.

(Other embodiments)
As described above, Embodiments 1 to 5 have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. are made as appropriate.

In Embodiments 1 to 3, the seventh lens element L7, which is a single lens element, has been described as an example of the second lens group G2 and the lens element LFN. The second lens group G2 is located on the optical axis between the first lens group G1 and the second lens group G2, which are closest to the image side and the second lens group G2, respectively, with respect to the first lens group G1 and the third lens group G3, which do not move during focusing. and the distance on the optical axis between the second lens group G2 and the third lens group G3. can be configured to move along the optical axis. Therefore, the second lens group G2 and the lens element LFN are not limited to single lens elements.

For example, as described in Embodiment 4, the second lens group G2 includes the ninth lens element L9 having negative power as an example of the lens element LFN, and the second lens group G2 is a single lens element. A seventh lens element L7 and a cemented lens consisting of an eighth lens element L8 and a ninth lens element L9 may be provided, and the second lens group G2 may be configured to move integrally during focusing. . Alternatively, the second lens group G2 may be composed of only a cemented lens and configured to move during focusing. If an increase in the load on the focus actuator due to an increase in the weight of the lens element is allowed, by configuring the number of lens elements that move during focusing to be two or more, various aberrations of the imaging optical system, especially in the infinity focus state and near object, can be reduced. Curvature of field in an in-focus state can be suppressed.

Further, for example, as described in Embodiment 5, as an example of the second lens group G2, the sub-lens group G2A moves to the image side during focusing from the infinity focused state to the near junction focused state. , the sub-lens group G2B may move toward the object side. The sub-lens group G2A or sub-lens group G2B is not limited to a single lens element, and may be a cemented lens, or a group in which two or more single lens elements move together. Alternatively, it may be a group consisting of a combination of a single lens element and a cemented lens that move together. Alternatively, the second lens group G2 may include one or more lens elements between the sub-lens group G2A and the sub-lens group G2B that do not move during focusing. This makes it easier to suppress the amount of focus movement and changes in aberration during focusing. Also, by allowing an increase in the number of focus actuators in this way, it is possible to suppress various aberrations of the image pickup optical system, particularly curvature of field aberration in the infinity in-focus state and the close-object in-focus state.

Each lens group constituting the imaging optical system according to Embodiments 1 to 5 is a refractive lens element that deflects incident light by refraction (that is, a type in which deflection is performed at the interface between media having different refractive indices). lens element) only, but is not limited to this. For example, a diffractive lens element that deflects an incident light beam by diffraction, a refraction-diffraction hybrid lens element that deflects an incident light beam through a combination of diffraction and refraction, and a refractive index that deflects an incident light beam using the refractive index distribution in the medium. Each lens group may be composed of a distributed lens element or the like, or a combination of two or more of these elements. In particular, in a refractive/diffractive hybrid lens element, it is preferable to form a diffractive structure at the interface of media having different refractive indices because the wavelength dependency of the diffraction efficiency is improved. This makes it possible to realize a camera with good aberrations.

(Numerical example)
Numerical examples in which the imaging optical systems according to Embodiments 1 to 5 are specifically implemented will be described below. In each numerical example, the unit of length in the table is all "mm", and the unit of angle 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 referred to as vd) is the Abbe number for the d-line. In each numerical example, the surfaces marked with * are aspherical surfaces, and the aspherical surface shape is defined by the following equation.

here,
Z: the distance from a point on the aspherical surface whose height from the optical axis is h to the plane tangent to the apex of the aspherical surface;
h: height from the optical axis,
r: vertex curvature radius,
κ: conic constant,
An: An n-th order aspheric coefficient.

2, 4, 6, 8, and 10 are longitudinal aberration diagrams of imaging optical systems according to Numerical Examples 1 to 5, respectively.

In each longitudinal aberration diagram, (a) shows aberrations at infinity, and (b) shows each aberration at a close position. Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)) in order from the left. In the spherical aberration diagrams, the vertical axis represents the F-number (indicated by F in the figure), the solid line is the d-line, the short dashed line is the F-line, and the long dashed line is the C-line. line). In the astigmatism diagram, the vertical axis represents the image height (indicated by H in the figure), the solid line is the sagittal plane (indicated by s in the figure), and the broken line is the meridional plane (indicated by m in the figure). be. In the distortion diagrams, the vertical axis represents the image height (indicated by H in the diagrams).

(Numerical example 1)
The imaging optical system of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. Table 1A shows the surface data of the imaging optical system of Numerical Example 1, Table 1B shows the aspheric surface data, Table 1C shows various data in the infinity focus state and the close object focus state, and Table 1D shows the single lens data. Table 1E shows the lens group data in the infinity in-focus state, Table 1F shows the lens group magnification in the infinity in-focus state and the close object in-focus state, and Table 1G shows the sub-lens group data.

(Table 1A: surface data)
Face number rd nd vd
0 (object plane) ∞ variable
1 38.42740 5.52300 1.85996 30.5
2 94.19390 0.30000
3 43.21060 1.20000 1.49700 81.6
4 18.21170 15.51010
5 -25.82130 1.20000 1.65794 31.1
6 27.15660 0.01000 1.56732 42.8
7 27.15660 7.53000 1.59269 65.3
8 -56.61760 0.73800
9 (Aperture) ∞ 2.87000
10 48.08490 8.04450 1.59282 68.6
11 -47.17840 0.30000
12* 72.83460 5.11150 1.51570 55.8
13* -66.26290 variable
14* 33.70070 2.00000 1.51607 56.3
15* 16.81800 variable
16* 286.14730 6.26580 1.51570 55.8
17* -34.83520 12.50120
18 -20.12450 1.20000 1.54157 51.7
19 -54.83640 12.90000
20 ∞ 2.10000 1.51680 64.2
21 ∞ 1.00000
Image plane ∞

(Table 1B: Aspheric Data)
12th side
K= 0.00000E+00, A4=-4.36516E-06, A6= 4.27940E-09, A8=-1.31680E-11
A10=-1.14476E-15
13th side
K= 0.00000E+00, A4=8.55335E-06, A6=-3.38027E-09, A8= 0.00000E+00
A10= 0.00000E+00
14th side
K= 0.00000E+00, A4=-3.20814E-05, A6= 3.04040E-08, A8=-9.83934E-12
A10= 0.00000E+00
15th side
K=-1.42129E+00, A4=-2.12498E-08, A6= 8.60734E-09, A8= 2.95476E-11
A10= 0.00000E+00
16th side
K= 0.00000E+00, A4=3.35290E-05, A6=-1.49631E-08, A8=-2.39445E-12
A10= 0.00000E+00
17th side
K= 0.00000E+00, A4=1.74131E-05, A6=-1.58208E-08, A8= 3.47625E-11
A10=-1.23868E-13

(Table 1C: Various data in infinity focus state and close object focus state)
Infinity Close Focal Length 48.2535 43.6130
F number 1.86017 1.91036
Angle of view 24.1432 23.1170
Image height 21.3629 21.6300
Overall lens length 101.0000 101.0000
d0 ∞ 349.0000
d13 1.8000 6.6163
d15 12.8959 8.0795
Entrance pupil position 29.4626 29.4626
Exit pupil position -49.2742 -47.6344
Front principal point position 30.4699 27.7515
Rear principal point position 52.7546 51.7192

(Table 1D: single lens data)
lens starting surface focal length
1 1 72.1722
2 3 -64.3640
3 5 -19.9382
4 7 32.0381
5 10 41.4733
6 12 68.1328
7 14 -67.7858
8 16 60.6211
9 18 -59.4247

(Table 1E: Lens group data in infinity focused state)
Group Starting surface Focal length Lens length Position of front principal point Position of rear principal point
1 1 34.75504 48.33710 40.47156 49.68522
2 14 -67.78580 2.00000 2.74400 3.36936
3 16 318.80580 19.96700 -63.32946 -46.99420

(Table 1F: Lens group magnification in infinity focus state and close object focus state)
Group Start Infinity Proximity
1 1 0.00000 -0.09798
2 14 1.87116 1.80101
3 16 0.74199 0.74189

(Table 1G: Sub-lens group data)
Group Starting surface Focal length Lens construction length
1A 1 -67.64731 31.27312
1B 10 26.92788 13.45593

(Numerical example 2)
The imaging optical system of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. Table 2A shows surface data of the imaging optical system of Numerical Example 2, Table 2B shows aspheric surface data, Table 2C shows various data in infinity focus state and close object focus state, and Table 2D shows single lens data. Table 2E shows the lens group data when in focus at infinity, Table 2F shows lens group magnifications in infinity focus and close object focus, and Table 2G shows sub-lens group data.

(Table 2A: surface data)
Face number rd nd vd
0 (object plane) ∞ variable
1 57.56070 2.54360 1.99900 18.0
2 73.66890 0.30000
3 29.97440 1.20000 1.49700 81.6
4 20.75620 8.65050
5 -26.23400 1.20000 1.65166 30.6
6 35.19010 0.01000 1.56732 42.8
7 35.19010 5.35790 1.64068 60.6
8 -285.35080 0.73800
9 (Aperture) ∞ 2.87000
10 69.05930 9.80660 1.59788 64.7
11 -44.57610 0.99990
12* 43.16250 7.64130 1.51570 55.8
13* -65.81240 variable
14* 24.13330 2.18480 1.51607 56.3
15* 15.75700 variable
16* 532.37770 7.40260 1.51570 55.8
17* -34.64130 13.57170
18 -23.01700 1.88650 1.85057 20.8
19 -52.43680 13.34190
20 ∞ 2.10000 1.51680 64.2
21 ∞ 1.00000
Image plane ∞

(Table 2B: Aspheric Data)
12th side
K= 0.00000E+00, A4=-1.55697E-06, A6= 8.96331E-09, A8= 1.85826E-13
A10= 4.31685E-15
13th side
K= 0.00000E+00, A4=9.78416E-06, A6= 6.08302E-09, A8= 0.00000E+00
A10= 0.00000E+00
14th side
K= 0.00000E+00, A4=-3.15483E-05, A6=-2.40821E-09, A8=-7.41270E-12
A10= 0.00000E+00
15th side
K=-1.42129E+00, A4=4.29968E-06, A6=-1.56481E-08, A8= 2.83556E-11
A10= 0.00000E+00
16th side
K= 0.00000E+00, A4=2.68728E-05, A6=-7.77296E-09, A8= 9.37812E-12
A10= 0.00000E+00
17th side
K= 0.00000E+00, A4=1.45815E-05, A6=-9.83640E-09, A8= 2.93509E-11
A10=-2.74094E-14

(Table 2C: Various data in infinity focus state and close object focus state)
Infinity Close Focal length 48.8914 43.9759
F number 1.83100 1.85293
Angle of view 23.8296 22.9803
Image height 20.7445 21.0094
Total lens length 100.9999 100.9999
d0 ∞ 349.0010
d13 1.8000 8.2734
d15 16.3945 9.9211
Entrance pupil position 15.9492 15.9492
Exit pupil position -52.5306 -50.8265
Front principal point position 19.2618 16.8076
Rear principal point position 52.0226 51.0489

(Table 2D: single lens data)
lens starting surface focal length
1 1 244.2364
2 3 -141.9337
3 5 -22.8872
4 7 49.2173
5 10 46.8223
6 12 51.7818
7 14 -96.5405
8 16 63.3509
9 18 -49.6967

(Table 2E: Lens group data in infinity focused state)
Group Starting surface Focal length Lens length Position of front principal point Position of rear principal point
1 1 37.30850 41.31780 31.95023 48.16469
2 14 -96.54048 2.18480 4.55656 5.15985
3 16 -5207.58806 22.86080 1372.04384 1093.69861

(Table 2F: Lens group magnification in infinity focus state and close object focus state)
Group Start Infinity Proximity
1 1 0.00000 -0.10857
2 14 1.64348 1.57837
3 16 0.79737 0.79740

(Table 2G: Sub-lens group data)
Group Starting surface Focal length Lens construction length
1A 1 -39.98984 19.26200
1B 10 26.05053 18.44779

(Numerical example 3)
The imaging optical system of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. Table 3A shows the surface data of the imaging optical system of Numerical Example 3, Table 3B shows the aspheric surface data, Table 3C shows various data in the infinity focus state and the close object focus state, and Table 3D shows the single lens data. Table 3E shows the lens group data when in focus at infinity, Table 3F shows lens group magnifications in infinity focus and close object focus, and Table 3G shows sub-lens group data.

(Table 3A: surface data)
Face number rd nd vd

0 (object plane) ∞ variable
1 36.80330 5.54500 1.85825 30.8
2 86.39570 0.30000
3 46.92960 1.20000 1.49700 81.6
4 18.13980 15.57210
5 -25.78050 1.20000 1.63816 31.9
6 26.68960 0.01000 1.56732 42.8
7 26.68960 7.53000 1.60063 64.4
8 -49.63780 0.73800
9 (Aperture) ∞ 2.87000
10 40.93470 8.40880 1.59282 68.6
11 -49.08610 0.30000
12* 77.80870 4.05560 1.51570 55.8
13* -148.21700 variable
14* 51.39300 2.00000 1.51607 56.3
15* 21.93840 variable
16* 1484.47290 5.60210 1.51570 55.8
17* -39.64080 5.66730
18 237.74480 2.58230 1.81281 42.8
19 -511.55690 5.64460
20 -20.60640 1.20000 1.53265 55.5
21 -71.04900 12.90000
22 ∞ 2.10000 1.51680 64.2
23 ∞ 1.00000
Image plane ∞

(Table 3B: Aspheric Data)
12th side
K= 0.00000E+00, A4=8.30117E-06, A6= 3.75330E-08, A8= 6.41432E-11
A10=-2.10862E-13
13th side
K= 0.00000E+00, A4=2.22564E-05, A6= 5.27589E-08, A8= 0.00000E+00
A10= 0.00000E+00
14th side
K= 0.00000E+00, A4=5.65185E-06, A6=-9.83708E-08, A8= 2.08923E-10
A10= 0.00000E+00
15th side
K=-1.42129E+00, A4=2.96720E-05, A6=-1.28984E-07, A8= 2.84244E-10
A10= 0.00000E+00
16th side
K= 0.00000E+00, A4=3.66775E-05, A6=-1.59762E-08, A8=-6.65434E-12
A10= 0.00000E+00
17th side
K= 0.00000E+00, A4=1.83234E-05, A6=-1.96132E-08, A8= 4.85705E-11
A10=-1.88164E-13

(Table 3C: Various data in infinity focus state and close object focus state)
Infinity Close Focal length 48.2530 43.7094
F number 1.86015 1.91602
Angle of view 24.1429 23.0347
Image height 21.3216 21.6212
Total lens length 101.0001 101.0001
d0 ∞ 349.0010
d13 1.8000 7.4678
d15 12.7743 7.1064
Entrance pupil position 29.3679 29.3679
Exit pupil position -49.3899 -47.6162
Front principal point position 30.4966 27.5111
Rear principal point position 52.7660 51.6028

(Table 3D: single lens data)
lens starting surface focal length
1 1 71.0364
2 3 -60.3307
3 5 -20.3678
4 7 30.0087
5 10 39.0076
6 12 99.5476
7 14 -75.9282
8 16 74.9624
9 18 200.0001
10 20 -54.9451

(Table 3E: Lens group data in infinity focused state)
Group Starting surface Focal length Lens length Position of front principal point Position of rear principal point
1 1 36.49226 47.72950 39.44141 48.24180
2 14 -75.92820 2.00000 2.35623 3.00582
3 16 304.07442 20.69630 -55.10671 -39.94874

(Table 3F: Lens group magnification in infinity focus state and close object focus state)
Group Start Infinity Proximity
1 1 0.00000 -0.10369
2 14 1.76250 1.68865
3 16 0.75023 0.75012

(Table 3G: Sub-lens group data)
Group Starting surface Focal length Lens construction length
1A 1 -81.23 31.35700
1B 10 28.90376 12.76437

(Numerical example 4)
The imaging optical system of Numerical Example 4 corresponds to Embodiment 4 shown in FIG. Table 4A shows surface data of the imaging optical system of Numerical Example 4, Table 4B shows aspheric surface data, Table 4C shows various data in infinity focus state and close object focus state, and Table 4D shows single lens data. Table 4E shows the lens group data in the infinity in-focus state, Table 4F shows the lens group magnification in the infinity in-focus state and the close object in-focus state, and Table 4G shows the sub-lens group data.

(Table 4A: surface data)
Face number rd nd vd
0 (object plane) ∞ variable
1 29.39070 5.60400 1.89146 25.9
2 61.19300 0.30000
3 48.48210 1.20000 1.56786 43.5
4 17.04940 12.60990
5 -24.34420 1.22250 1.66002 29.8
6 24.60200 0.01000 1.56732 42.8
7 24.60200 7.53000 1.63367 61.2
8 -61.79990 0.73800
9 (Aperture) ∞ 2.87000
10 56.13210 6.84020 1.59282 68.6
11 -56.43950 0.30000
12* 94.09000 6.07110 1.51570 55.8
13* -41.15660 variable
14 -90.82290 2.80600 1.51570 55.8
15* -42.76750 0.30000
16 223.65230 2.54500 1.99900 18.0
17 -597.37760 0.01000 1.56732 42.8
18 -597.37760 1.20000 1.64193 48.1
19 26.63510 Variable
20* 395.20950 6.52110 1.51570 55.8
21* -34.09530 12.07120
22 -23.16360 1.20000 1.74373 24.5
23 -52.81980 12.91230
24 ∞ 2.10000 1.51680 64.2
25 ∞ 1.00000
Image plane ∞

(Table 4B: Aspheric Data)
12th side
K= 0.00000E+00, A4=-3.39428E-06, A6=-8.85129E-11, A8=-2.53310E-11
A10= 2.40292E-14
13th side
K= 0.00000E+00, A4=1.09393E-05, A6=-1.30330E-08, A8= 0.00000E+00
A10= 0.00000E+00
15th side
K=-1.42129E+00, A4=1.18141E-05, A6=-2.64056E-08, A8= 3.18637E-11
A10= 0.00000E+00
20th side
K= 0.00000E+00, A4=3.85717E-05, A6=-4.07250E-08, A8= 2.60220E-11
A10= 0.00000E+00
21st side
K= 0.00000E+00, A4=1.85614E-05, A6=-1.72363E-08, A8= 4.11325E-12
A10=-3.11109E-14

(Table 4C: various data in infinity focus state and close object focus state)
Infinity Close Focal length 48.2490 43.4014
F number 1.86007 1.90207
Angle of view 24.1355 22.9886
Image height 20.5383 20.9011
Overall lens length 101.0000 101.0000
d0 ∞ 349.0010
d13 1.8000 8.1183
d19 11.2386 4.9203
Entrance pupil position 26.6030 26.6030
Exit pupil position -49.0174 -47.0376
Front principal point position 27.3627 24.4842
Rear principal point position 52.7544 51.9422

(Table 4D: single lens data)
lens starting surface focal length
1 1 58.5734
2 3 -46.9589
3 5 -18.3568
4 7 28.7412
5 10 48.5707
6 12 56.3824
7 14 153.6832
8 16 163.1438
9 18 -39.6911
10 20 61.1800
11 22 -56.4459

(Table 4E: Lens group data in infinity focused state)
Group Starting surface Focal length Lens length Position of front principal point Position of rear principal point
1 1 37.35704 45.29570 38.62975 48.15623
2 14 -82.25802 6.86100 5.31688 8.01403
3 20 484.09358 19.79230 -97.79902 -75.35954

(Table 4F: Lens group magnification in infinity focus state and close object focus state)
Group Start Infinity Proximity
1 1 0.00000 -0.10665
2 14 1.67336 1.59751
3 20 0.77184 0.77174

(Table 4G: Sub-lens group data)
Group Starting surface Focal length Lens construction length
1A 1 -60.46558 28.47639
1B 10 27.48965 13.21128

(Numerical Example 5)
The imaging optical system of Numerical Example 5 corresponds to Embodiment 5 shown in FIG. Table 5A shows the surface data of the imaging optical system of Numerical Example 5, Table 5B shows the aspheric surface data, Table 5C shows various data in the infinity focus state and the close object focus state, and Table 5D shows the single lens data. Table 5E shows the lens group data in the infinity focused state, Table 5F shows the lens group magnification in the infinity focused state and the close object focused state, and Table 5G shows the sub lens group data.

(Table 5A: surface data)
Face number rd nd vd
0 (object plane) ∞ variable
1 30.66690 5.91450 1.87383 28.2
2 89.32480 0.01000 1.56732 42.8
3 89.32480 1.20000 1.56476 44.3
4 18.20210 12.11990
5 -24.35250 1.20000 1.63550 33.0
6 26.77550 0.01000 1.56732 42.8
7 26.77550 7.53000 1.61871 62.6
8 -48.93580 0.73800
9 (Aperture) ∞ 2.87000
10 44.13390 7.85270 1.59282 68.6
11 -49.05890 0.30000
12* 125.87800 4.61080 1.51570 55.8
13* -52.79440 variable
14* -158.77940 4.02260 1.51607 56.3
15* 53.80920 variable
16* -66.86380 5.00000 1.51570 55.8
17* -32.48830 variable
18 -74.07130 3.60690 1.79788 47.0
19 -38.64790 6.31040
20 -24.65900 1.20000 1.61615 34.6
21 -86.87210 12.90000
22 ∞ 2.10000 1.51680 64.2
23 ∞ 1.00000
Image plane ∞

(Table 5B: Aspheric Data)
12th side
K= 0.00000E+00, A4=-6.37727E-06, A6=-1.76312E-09, A8= 3.35755E-11
A10=-5.80543E-14
13th side
K= 0.00000E+00, A4=1.00000E-05, A6= 3.57664E-09, A8= 0.00000E+00
A10= 0.00000E+00
14th side
K= 0.00000E+00, A4=4.63373E-05, A6=-1.36197E-07, A8= 2.81755E-10
A10=-2.83756E-13
15th side
K=-1.42129E+00, A4=5.75463E-05, A6=-1.26605E-07, A8=2.08207E-10
A10= 0.00000E+00
16th side
K= 0.00000E+00, A4=4.02715E-05, A6=-1.74585E-08, A8=-6.66628E-11
A10= 0.00000E+00
17th side
K= 0.00000E+00, A4=2.94254E-05, A6=-8.09409E-09, A8=-2.80268E-11
A10=-1.55405E-13

(Table 5C: various data in infinity focus state and close object focus state)
Infinity Close Focal length 48.2513 43.8491
F number 1.86006 1.88829
Angle of view 24.1389 23.3778
Image height 21.0586 21.3409
Total lens length 100.9999 100.9999
d0 ∞ 349.0010
d13 1.8000 5.7339
d15 15.2361 8.2902
d17 3.4679 6.4799
Entrance pupil position 25.4248 25.4248
Exit pupil position -57.0352 -54.1634
Front principal point position 32.8540 29.6152
Rear principal point position 52.7460 51.4698

(Table 5D: single lens data)
lens starting surface focal length
1 1 51.0428
2 3 -40.7262
3 5 -19.8867
4 7 29.0767
5 10 40.4595
6 12 72.7634
7 14 -77.3773
8 16 116.7600
9 18 96.9061
10 20 -56.2981

(Table 5E: Lens group data in infinity focused state)
Group Starting surface Focal length Lens length Position of front principal point Position of rear principal point
1 1 33.88451 44.35590 36.06746 45.70752
2 14 -520.27206 24.25870 96.13860 -145.07039
3 18 -148.70233 11.11730 -14.36699 4.97024

(Table 5F: Lens group magnification in infinity focus state and close object focus state)
Group Start Infinity Proximity
1 1 0.00000 -0.09649
2 14 1.33164 1.26898
3 18 1.06934 1.06978

(Table 5G: Sub-lens group data)
Group Starting surface Focal length Lens construction length
1A 1 -74.63936 27.98445
1B 10 27.23843 12.76358
2A 14 -77.37733 4.02260
2B 16 116.76002 5.00000

(corresponding value of condition)
Table 6 shows the values corresponding to conditions (1) to (12).

The imaging optical system according to the present disclosure includes a digital still camera, an interchangeable lens digital camera, a digital video camera, a mobile phone camera, a PDA (Personal Digital Assistance) camera, a surveillance camera in a surveillance system, a web camera, and an in-vehicle camera. etc., and is particularly suitable for photographing optical systems that require high image quality, such as digital still camera systems and digital video camera systems.

G1 1st lens group G1A sub-lens group G1B sub-lens group G2 2nd lens group G2A sub-lens group G2B sub-lens group G3 3rd lens group L1 1st lens element L2 2nd lens element L3 3rd lens element L4 4th lens Element L5 Fifth lens element L6 Sixth lens element L7 Seventh lens element L8 Eighth lens element L9 Ninth lens element L10 Tenth lens element L11 Eleventh lens element A Aperture diaphragm CG Cover glass S Image surface 100 Imaging device 101 Imaging Optical system 102 Imaging element 104 Housing 200 Camera system 201 Camera body 202 Imaging element 203 Monitor 204 Camera mount section 205 Viewfinder 300 Interchangeable lens device 301 Imaging optical system 302 Lens barrel 304 Lens mount section

Claims (20)

In order from the object side,
a first lens group having positive power;
a second lens group having power;
a third lens group having power;
An imaging optical system consisting of
When the imaging optical system is focused, the first lens group and the third lens group stop moving in a direction along the optical axis of the imaging optical system,
During focusing of the imaging optical system, the distance on the optical axis between the most image side surface of the first lens group and the most object side surface of the second lens group and the distance between the most image side surface of the second lens group and the second lens group at least one lens element LFN having negative power in the second lens group moves along the optical axis such that a distance on the optical axis from the three lens groups closest to the object side surface changes;
The first lens group, in order from the most object side,
a sub-lens group G1A;
aperture diaphragm and
a sub-lens group G1B;
with
The sub-lens group G1A, in order from the most object side,
a lens element L1A1;
a lens element L1A2 adjacent to the image side of said lens element L1A1;
with
the object side surface of the lens element L1A1 has a convex shape on the object side;
The third lens group, in order from the most image side,
a lens element L3E having negative power;
a lens element L3P adjacent to the object side of the lens element L3E;
comprising
imaging optical system. the lens element L1A2 has a negative power, the image side surface of the lens element L1A2 has a concave shape,
satisfying the following conditions (1), (2), and (3),
0.1 < L_STO/LL < 0.6 (1)
2.0<LL/Y<10.0 (2)
0.1<TG3A/TL3E<20 (3)
here,
L_STO: distance on the optical axis from the object side surface of the lens element L1A1 to the aperture stop;
LL: the distance on the optical axis from the object side surface of the lens element L1A1 to the image side surface of the lens element L3E;
Y: image height when the imaging optical system is focused at infinity;
TG3A: the maximum value of the air gap on the optical axis in the third lens group TL3E: the thickness of the lens element L3E on the optical axis;
is
The imaging optical system according to claim 1. the lens element L1A1 has positive power;
The imaging optical system according to claim 1. satisfying the following condition (4),
|FL_L3E/FL| < 7 (4)
here,
FL_L3E: focal length of said lens element L3E;
FL: focal length of the entire imaging optical system;
is
The imaging optical system according to claim 1. The object side surface of the lens element L3E has a concave shape,
satisfying the following condition (5),
-1 < q < 4.5 (5)
here,
q: the form factor of the lens element L3E,
q = (RrL3E + RfL3E) / (RrL3E - RfL3E),
RfL3E: the radius of curvature of the object-side surface of the lens element L3E;
RrL3E: the radius of curvature of the image-side surface of said lens element L3E;
is
The imaging optical system according to claim 1. At least one of an image side surface of a lens element adjacent to the object side of the aperture diaphragm and an object side surface of a lens element adjacent to the image side of the aperture diaphragm has a convex shape toward the aperture diaphragm.
The imaging optical system according to claim 1. satisfying the following condition (6),
0.25<TG3P/TG3M<20 (6)
here,
TG3P: the total thickness of the positive lens elements of the third lens group along the optical axis;
TG3M: total thickness of the negative lens elements of the third lens group on the optical axis;
is
The imaging optical system according to claim 1. satisfying the following condition (7),
0.05<TSTO/Y<0.5 (7)
here,
TSTO: the distance on the optical axis from the image-side surface of the lens element adjacent to the object side of the aperture diaphragm to the object-side surface of the lens element adjacent to the image side of the aperture diaphragm;
Y: image height when the imaging optical system is focused at infinity;
is
The imaging optical system according to claim 1. the lens element L3P has positive power;
The imaging optical system according to claim 1. The object-side surface of the lens element L3E has a concave shape,
The imaging optical system according to claim 1. The sub-lens group G1B includes at least two lenses,
The imaging optical system according to claim 1. The sub-lens group G1B includes a lens element L1BE having a positive power closest to the image side,
The imaging optical system according to claim 1. satisfying the following condition (8),
|NdL1BE−NdL2F| < 0.2 (8)
here,
NdL1BE: refractive index of the d-line of the lens element L1BE;
NdL2F: d-line refractive index of the lens element L2F closest to the object side in the second lens group;
is
The imaging optical system according to claim 12. satisfying the following condition (9),
0.3<BF/Y<3 (9)
here,
BF: the distance on the optical axis from the image side surface of the lens element L3E to the image plane;
Y: image height when the imaging optical system is focused at infinity;
is
The imaging optical system according to claim 3. satisfying the following condition (10),
0.3 < TFOC_L3E/FL < 3 (10)
here,
TFOC_L3E: the distance on the optical axis from the object side surface of the lens element L2F closest to the object side of the second lens group to the image side surface of the lens element L3E when the imaging optical system is focused on infinity;
FL: focal length of the entire imaging optical system;
is
The imaging optical system according to claim 1. satisfy the following conditions,
0.2 < FL_G1B/FL_G1 < 5
here,
FL_G1B: the focal length of the sub-lens group G1B;
FL_G1: focal length of the first lens group;
is
The imaging optical system according to claim 1. satisfy the following conditions,
0.1 < TG3/FL < 2
here,
TG3: the distance on the optical axis from the object side surface to the image side surface of the third lens group,
FL: focal length of the entire imaging optical system;
is
The imaging optical system according to claim 1. When the imaging optical system is focused from an infinity focused state to a near junction focused state, the most object side surface of the second lens group moves toward the image side.
The imaging optical system according to claim 1. an interchangeable lens device including the imaging optical system according to claim 1;
a camera body detachably connected to the interchangeable lens device via a camera mount section and including an imaging device that receives an 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 imaging device,
camera system. An imaging device that converts an optical image of an object into an electrical image signal and at least one of displaying and storing the converted image signal,
an imaging optical system according to claim 1 that forms an optical image of an object;
an imaging device that converts an optical image formed by the imaging optical system into an electrical image signal;
comprising
Imaging device.

Images