Image capturing optical system, image capturing device having the same, and camera system

Abstract

To provide an image capturing optical system with good aberrations including spherical aberration, astigmatism, and distortion aberration.SOLUTION: An image capturing optical system provided herein is configured such that distances between adjacent lens groups change while zooming and comprises a lens group Gm located on the most object side among lens groups having negative power. The lens group Gm comprises, in order from the object side to the image side, a lens element LGmF1 with negative power, a bi-aspheric lens element LGmF2 with negative power, and two or more lens elements with power.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an imaging optical system with reduced aberrations, and an imaging device and a camera system including the same. [Background technology]

[0002] Patent Document 1 discloses a zoom lens including, in order from the object side to the image side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power. The zoom lens is configured to change magnification by fixing the fifth lens group and moving the first lens group, the second lens group, the third lens group, and the fourth lens group in the optical axis direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-71179 A Summary of the Invention

[0004] In the imaging optical system of the present disclosure, the spacing between each lens group changes during zooming, and among the lens groups having negative power, the lens group Gm closest to the object side includes, in order from the object side to the image side, a lens element LGmF1 having negative power, a lens element LGmF2 having an aspheric shape on both sides and having negative power, and two or more lens elements having power.

[0005] The imaging optical system according to the present disclosure includes a lens group Gm having negative power, which includes, in order from the lens element LGmF1 having the strongest negative power among the lens elements located closer to the object side than the aperture stop to the image side, a lens element LGmF2 having a negative power and an aspheric shape on both sides, and two or more lens elements having power. The lens element closest to the image side of the lens group Gm is adjacent to the object side of the aperture stop, or adjacent to the further object side of the positive lens element adjacent to the object side of the aperture stop.

[0006] According to the present disclosure, it is possible to provide an imaging optical system with good correction of various aberrations, and an imaging device and a camera system including the same. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a lens arrangement diagram showing an infinity focused state of an imaging optical system according to a first embodiment. [Diagram 2] FIG. 2 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 1 of the embodiment in a state focused on an object at infinity. [Diagram 3] FIG. 3 is a lateral aberration diagram in a basic state in which image blurring correction is not performed and in a state in which image blurring correction is performed at the telephoto end of the imaging optical system according to this numerical example. [Figure 4] FIG. 4 is a lens arrangement diagram showing an infinity focused state of the imaging optical system according to the second embodiment. [Diagram 5] FIG. 5 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 2 of the embodiment in a state focused on an object at infinity. [Figure 6] FIG. 6 is a lateral aberration diagram in a basic state in which image blurring correction is not performed and in a state in which image blurring correction is performed at the telephoto end of the imaging optical system according to this numerical example. [Figure 7] FIG. 7 is a lens arrangement diagram showing an infinity focused state of the imaging optical system according to the third embodiment. [Figure 8] FIG. 8 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 3 of the embodiment in a state focused on an object at infinity. [Figure 9] FIG. 9 is a lateral aberration diagram in a basic state in which image blurring correction is not performed and in a state in which image blurring correction is performed at the telephoto end of the imaging optical system according to the same numerical example. [Figure 10] FIG. 10 is a lens arrangement diagram showing an infinity focused state of the imaging optical system according to the fourth embodiment. [Figure 11] FIG. 11 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 4 of the embodiment in a state focused on an object at infinity. [Figure 12]FIG. 12 is a lateral aberration diagram in a basic state in which image blurring correction is not performed and in a state in which image blurring correction is performed at the telephoto end of the imaging optical system according to the same Numerical Example. [Figure 13] FIG. 13 is a lens arrangement diagram showing an infinity focused state of the imaging optical system according to the fifth embodiment. [Figure 14] FIG. 14 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 5 of the embodiment in a state focused on an object at infinity. [Figure 15] FIG. 15 is a lateral aberration diagram in a basic state in which image blurring correction is not performed and in a state in which image blurring correction is performed, at the telephoto end of the imaging optical system according to this numerical example. [Figure 16] FIG. 16 is a lens arrangement diagram showing an infinity focused state of the imaging optical system according to the sixth embodiment. [Figure 17] FIG. 17 is a longitudinal aberration diagram of the imaging optical system according to Numerical Example 6 of the same embodiment in a state focused on an object at infinity. [Figure 18] FIG. 18 is a lateral aberration diagram in a basic state in which image blurring correction is not performed and in a state in which image blurring correction is performed, at the telephoto end of the imaging optical system according to this numerical example. [Figure 19] FIG. 19 is a schematic diagram of an imaging device including the imaging optical system according to the first embodiment. [Figure 20] FIG. 20 is a schematic configuration diagram of a camera system including the imaging optical system according to the first embodiment. [Figure 21] FIG. 21 is a schematic diagram of a lens barrel including the imaging optical system according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0009] It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0010] (Embodiments 1 to 6) The imaging optical systems according to the first to sixth embodiments will be described individually below with reference to the drawings.

[0011] The imaging optical system of each embodiment includes a first lens group G1, a second lens group G2, a third lens group G3, and subsequent lens groups including a fourth lens group G4, a fifth lens group G5, and a sixth lens group G6.

[0012] 1, 4, 7, 10, 13, and 16 are lens arrangement diagrams showing imaging optical systems in an infinity focused state.

[0013] (a) of Figures 1, 4, 7, 10, 13, and 16 shows the lens arrangement at the wide-angle end (shortest focal length state: focal length fW). (d) of each figure shows the lens arrangement at the intermediate position (intermediate focal length state: focal length fM = √(fW * fT)). (e) of each figure shows the lens arrangement at the telephoto end (longest focal length state: focal length fT). Note that the aspect ratio is the same in (a), (d), and (e) of each figure.

[0014] Also, the broken line arrows shown in (c) of each figure show, from top to bottom, the positions of the lens groups in each state: the wide-angle end (Wide), the mid-position (Mid), and the telephoto end (Tele). Note that the arrows simply connect the wide-angle end and the mid-position, and the mid-position and the telephoto end, and do not show the actual movement of each lens group.

[0015] In each figure, (b) indicates each lens group with a reference symbol G1 to G6 corresponding to the position of each lens group shown in (a).

[0016] An asterisk * next to a surface of a particular lens element shown in (a) of each figure indicates that the surface is aspheric.

[0017] Moreover, the symbols (+) and (-) attached to the reference numerals of each lens group (G1 to G6) shown in (b) of each figure correspond to the power of each lens group. That is, the symbol (+) indicates positive power, and the symbol (-) indicates negative power. Note that the arrows attached to the lens groups shown in the fourth lens group G4 in the first to fifth embodiments and the third lens group G3 in the sixth embodiment conveniently indicate the movement direction of the lens group during focusing from an infinity focused state to a close focused state. The specific lens elements and lens groups that move and their movement directions will be specifically described later for each embodiment.

[0018] In each of (a), (d), and (e) of the figures, the straight line drawn on the right-most side indicates the position of the image surface S (the surface of the image sensor facing the object). Therefore, the left side of the figure corresponds to the object side. Furthermore, between the image surface S and the last lens group facing the image surface S, a parallel plate CG such as a low-pass filter or a cover glass is disposed.

[0019] (Embodiment 1) The imaging optical system according to the first embodiment will be described below with reference to FIG.

[0020] FIG. 1 shows a lens arrangement and operation of an imaging optical system according to the first embodiment.

[0021] As shown in FIG. 1, the imaging optical system of the present embodiment is composed of, in order from the object side to the image side, a first lens group G1 having a positive power, a second lens group G2 having a negative power, an aperture stop A, a third lens group G3 having a positive power, a fourth lens group G4 having a negative power, a fifth lens group G5 having a positive power, and a parallel plate CG. The fourth lens group G4 and the fifth lens group G5 constitute a subsequent lens group. The second lens group G2 is exemplified by the lens group Gm. The third lens group G3 is exemplified by the lens group Gp. The fourth lens group G4 is exemplified by the lens group Gf.

[0022] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having positive power, and a third lens element L3 having positive power. The first lens element L1 and the second lens element L2 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin.

[0023] The second lens group G2 is composed of, in order from the object side to the image side, a fourth lens element L4 having negative power, a fifth lens element L5 having negative power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The fourth lens element L4 is exemplified by the lens element LGmF1. The fifth lens element L5 is exemplified by the lens element LGmF2 or the lens element LGmR3. The sixth lens element L6 is exemplified by the lens element LGmR2. The seventh lens element L7 is exemplified by the lens element LGmR1.

[0024] The third lens group G3 is composed of, in order from the object side to the image side, an eighth lens element L8 having a positive power, a ninth lens element L9 having a positive power, a tenth lens element L10 having a negative power, an eleventh lens element L11 having a positive power, and a twelfth lens element L12 having a positive power. The tenth lens element L10 and the eleventh lens element L11 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin. The eighth lens element L8 is exemplified by the lens element LGpF1. The ninth lens element L9 is exemplified by the lens element LGpF2. The tenth lens element L10 is exemplified by the lens element LGpR3. The eleventh lens element L11 is exemplified by the lens element LGpR2. The twelfth lens element L12 is exemplified by the lens element LGpR1.

[0025] The fourth lens group G4 is composed of a thirteenth lens element L13 having negative power.

[0026] The fifth lens group G5 is composed of a fourteenth lens element L14 having positive power.

[0027] Aperture diaphragm A is disposed between the seventh lens element L7 of the second lens group G2 and the eighth lens element L8 of the third lens group G3.

[0028] The lens elements constituting each lens group in the imaging optical system of this embodiment will be described below.

[0029] First, each lens element in the first lens group G1 will be described.

[0030] The first lens element L1 is a meniscus lens having a convex surface facing the object side, the second lens element L2 is a meniscus lens having a convex surface facing the object side, and the third lens element L3 is a meniscus lens having a convex surface facing the object side.

[0031] Next, each lens element in the second lens group G2 will be described.

[0032] The fourth lens element L4 is a meniscus lens having a convex surface on the object side. The fifth lens element L5 is a meniscus lens having a convex surface on the object side. Both surfaces of the fifth lens element L5 are aspheric. The sixth lens element L6 is a meniscus lens having a concave surface on the object side. The seventh lens element L7 is a biconvex lens.

[0033] Next, each lens element in the third lens group G3 will be described.

[0034] The eighth lens element L8 is a meniscus lens having a convex surface on the object side. Both surfaces of the eighth lens element L8 are aspheric. The ninth lens element L9 is a biconvex lens. The tenth lens element L10 is a meniscus lens having a convex surface on the object side. The eleventh lens element L11 is a biconvex lens. The twelfth lens element L12 is a biconvex lens. Both surfaces of the twelfth lens element L12 are aspheric.

[0035] Next, the lens elements in the fourth lens group G4 will be described.

[0036] The thirteenth lens element L13 is a meniscus lens having a convex surface facing the object side. Both surfaces of the thirteenth lens element L13 are aspheric.

[0037] Furthermore, the lens elements in the fifth lens group G5 will be described.

[0038] The fourteenth lens element L14 is a meniscus lens having a convex surface facing the object side.

[0039] As described above, the imaging optical system of this embodiment is made up of five lens groups.

[0040] Each lens group of the imaging optical system of this embodiment moves as shown by the arrow in FIG. 1(c) during zooming from the wide-angle end (Wide) to the telephoto end (Tele) during imaging.

[0041] Specifically, the first lens group G1 moves toward the object side, and the second lens group G2 moves to draw a convex trajectory toward the image surface S side. The aperture stop A and the third lens group G3 move toward the object side together. Then, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 moves toward the object side. Due to this movement, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. The distance between the third lens group G3 and the fourth lens group G4 increases from the wide-angle end to the middle position, and decreases from the middle position to the telephoto end. The distance between the fourth lens group G4 and the fifth lens group G5 decreases from the wide-angle end to the middle position, and increases from the middle position to the telephoto end. Then, the distance between the fifth lens group G5 and the image surface S increases. In this case, during zooming from the wide-angle end to the telephoto end, the open aperture diameter of the aperture diaphragm A is the same from the wide-angle end to the intermediate position, and is larger at the telephoto end compared to the intermediate position.

[0042] As described above, each lens group moves along the optical axis L as shown by the arrows in Fig. 1(c). Then, each lens group is positioned at the wide-angle end, the intermediate position, and the telephoto end as shown in Fig. 1(a), (d), and (e).

[0043] That is, in the imaging optical system of this embodiment, all the lens groups move relatively along the optical axis L. In other words, the intervals between the lens groups change. This allows zooming from the wide-angle end to the telephoto end.

[0044] During focusing from an infinity focused state to a close focused state, the fourth lens group G4 that constitutes the focusing lens group moves toward the image side along the optical axis L as shown by the arrow in FIG.

[0045] Moreover, the twelfth lens element L12 of the third lens group G3 moves perpendicular to the optical axis L. This optically corrects image blur. Specifically, the movement of the twelfth lens element L12 in the perpendicular direction to the optical axis L corrects image point movement caused by vibration of the entire imaging optical system. As a result, image blur caused by camera shake, vibration, etc. can be optically corrected. Details of image blur correction will be described later with reference to FIG. 21.

[0046] (Embodiment 2) The imaging optical system according to the second embodiment will be described below with reference to FIG.

[0047] FIG. 4 shows a lens arrangement and operation of the imaging optical system according to the second embodiment.

[0048] As shown in Fig. 4, the imaging optical system of this embodiment is composed of, in order from the object side to the image side, a first lens group G1 having positive power, a second lens group G2 having negative power, an aperture stop A, a third lens group G3 having positive power, a fourth lens group G4 having negative power, a fifth lens group G5 having positive power, and a parallel plate CG. The fourth lens group G4 and the fifth lens group G5 constitute a subsequent lens group. The second lens group G2 is exemplified by the lens group Gm. The third lens group G3 is exemplified by the lens group Gp. The fourth lens group G4 is exemplified by the lens group Gf.

[0049] The first lens group G1 is composed of, from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having positive power, and a third lens element L3 having positive power. The first lens element L1 and the second lens element L2 constitute a cemented lens bonded with an adhesive such as an ultraviolet-curable resin.

[0050] The second lens group G2 is composed of, in order from the object side to the image side, a fourth lens element L4 having negative power, a fifth lens element L5 having negative power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The fourth lens element L4 is exemplified by the lens element LGmF1. The fifth lens element L5 is exemplified by the lens element LGmF2 or the lens element LGmR3. The sixth lens element L6 is exemplified by the lens element LGmR2. The seventh lens element L7 is exemplified by the lens element LGmR1.

[0051] The third lens group G3 is composed of, in order from the object side to the image side, an eighth lens element L8 having a positive power, a ninth lens element L9 having a positive power, a tenth lens element L10 having a negative power, an eleventh lens element L11 having a positive power, and a twelfth lens element L12 having a positive power. The tenth lens element L10 and the eleventh lens element L11 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin. The eighth lens element L8 is exemplified by the lens element LGpF1. The ninth lens element L9 is exemplified by the lens element LGpF2. The tenth lens element L10 is exemplified by the lens element LGpR3. The eleventh lens element L11 is exemplified by the lens element LGpR2. The twelfth lens element L12 is exemplified by the lens element LGpR1.

[0052] The fourth lens group G4 is composed of a thirteenth lens element L13 having negative power.

[0053] The fifth lens group G5 is composed of a fourteenth lens element L14 having positive power.

[0054] Aperture diaphragm A is disposed between the seventh lens element L7 of the second lens group G2 and the eighth lens element L8 of the third lens group G3.

[0055] The lens elements constituting each lens group in the imaging optical system of this embodiment will be described below.

[0056] First, each lens element in the first lens group G1 will be described.

[0057] The first lens element L1 is a meniscus lens having a convex surface facing the object side, the second lens element L2 is a meniscus lens having a convex surface facing the object side, and the third lens element L3 is a meniscus lens having a convex surface facing the object side.

[0058] Next, the lens elements in the second lens group G2 will be described.

[0059] The fourth lens element L4 is a meniscus lens having a convex surface on the object side. The fifth lens element L5 is a meniscus lens having a convex surface on the object side. Both surfaces of the fifth lens element L5 are aspheric. The sixth lens element L6 is a meniscus lens having a concave surface on the object side. The seventh lens element L7 is a meniscus lens having a concave surface on the object side.

[0060] Next, each lens element in the third lens group G3 will be described.

[0061] The eighth lens element L8 is a meniscus lens having a convex surface on the object side. Both surfaces of the eighth lens element L8 are aspheric. The ninth lens element L9 is a biconvex lens. The tenth lens element L10 is a meniscus lens having a convex surface on the object side. The eleventh lens element L11 is a biconvex lens. The twelfth lens element L12 is a biconvex lens. Both surfaces of the twelfth lens element L12 are aspheric.

[0062] Next, the lens elements in the fourth lens group G4 will be described.

[0063] The thirteenth lens element L13 is a meniscus lens having a convex surface facing the object side. Both surfaces of the thirteenth lens element L13 are aspheric.

[0064] Furthermore, the lens elements in the fifth lens group G5 will be described.

[0065] The fourteenth lens element L14 is a meniscus lens having a convex surface facing the object side.

[0066] As described above, the imaging optical system of this embodiment is made up of five lens groups.

[0067] Each lens group of the imaging optical system of this embodiment moves as shown by the arrow in FIG. 4(c) during zooming from the wide-angle end to the telephoto end during imaging.

[0068] Specifically, first, the first lens group G1 moves toward the object side, and the second lens group G2 moves to draw a convex locus toward the image surface side. The aperture diaphragm A and the third lens group G3 move toward the object side together. Then, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 moves toward the object side. Due to this movement, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. The distance between the third lens group G3 and the fourth lens group G4 increases from the wide-angle end to the middle position, and decreases from the middle position to the telephoto end. The distance between the fourth lens group G4 and the fifth lens group G5 increases. Then, the distance between the fifth lens group G5 and the image surface S increases. At this time, during zooming from the wide-angle end to the telephoto end, the open aperture diameter of the aperture diaphragm A is the same from the wide-angle end to the middle position, and is larger at the telephoto end than at the middle position.

[0069] As described above, each lens group moves along the optical axis L as shown by the arrows in Fig. 4(c). Then, each lens group is positioned at the wide-angle end, the intermediate position, and the telephoto end as shown in Fig. 4(a), (d), and (e).

[0070] That is, in the imaging optical system of this embodiment, all the lens groups move relatively along the optical axis L. In other words, the intervals between the lens groups change. This allows zooming from the wide-angle end to the telephoto end.

[0071] During focusing from an infinity focused state to a close focused state, the fourth lens group G4 that constitutes the focusing lens group moves toward the image side along the optical axis L as shown by the arrow in FIG. 4(b).

[0072] Moreover, the twelfth lens element L12 of the third lens group G3 moves in a direction perpendicular to the optical axis L. This optically corrects image blur. Specifically, the movement of the twelfth lens element L12 corrects image point movement caused by vibration of the entire imaging optical system, and as a result, image blur caused by camera shake, vibration, etc. can be optically corrected.

[0073] (Embodiment 3) The imaging optical system according to the third embodiment will be described below with reference to FIG.

[0074] FIG. 7 shows a lens arrangement and operation of an imaging optical system according to the third embodiment.

[0075] As shown in Fig. 7, the imaging optical system of this embodiment is composed of, in order from the object side to the image side, a first lens group G1 having a positive power, a second lens group G2 having a negative power, an aperture stop A, a third lens group G3 having a positive power, a fourth lens group G4 having a negative power, a fifth lens group G5 having a positive power, and a parallel plate CG. The fourth lens group G4 and the fifth lens group G5 constitute a subsequent lens group. The second lens group G2 is exemplified by the lens group Gm. The third lens group G3 is exemplified by the lens group Gp. The fourth lens group G4 is exemplified by the lens group Gf.

[0076] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having positive power, and a third lens element L3 having positive power. The first lens element L1 and the second lens element L2 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin.

[0077] The second lens group G2 is composed of, in order from the object side to the image side, a fourth lens element L4 having negative power, a fifth lens element L5 having negative power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The fourth lens element L4 is exemplified by the lens element LGmF1. The fifth lens element L5 is exemplified by the lens element LGmF2 or the lens element LGmR3. The sixth lens element L6 is exemplified by the lens element LGmR2. The seventh lens element L7 is exemplified by the lens element LGmR1.

[0078] The third lens group G3 is composed of, in order from the object side to the image side, an eighth lens element L8 having a positive power, a ninth lens element L9 having a positive power, a tenth lens element L10 having a negative power, an eleventh lens element L11 having a positive power, and a twelfth lens element L12 having a positive power. The tenth lens element L10 and the eleventh lens element L11 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin. The eighth lens element L8 is exemplified by the lens element LGpF1. The ninth lens element L9 is exemplified by the lens element LGpF2. The tenth lens element L10 is exemplified by the lens element LGpR3. The eleventh lens element L11 is exemplified by the lens element LGpR2. The twelfth lens element L12 is exemplified by the lens element LGpR1.

[0079] The fourth lens group G4 is composed of a thirteenth lens element L13 having negative power.

[0080] The fifth lens group G5 is composed of a fourteenth lens element L14 having positive power.

[0081] Aperture diaphragm A is disposed between the seventh lens element L7 of the second lens group G2 and the eighth lens element L8 of the third lens group G3.

[0082] The lens elements constituting each lens group in the imaging optical system of this embodiment will be described below.

[0083] First, each lens element in the first lens group G1 will be described.

[0084] The first lens element L1 is a meniscus lens having a convex surface facing the object side, the second lens element L2 is a meniscus lens having a convex surface facing the object side, and the third lens element L3 is a meniscus lens having a convex surface facing the object side.

[0085] Next, each lens element in the second lens group G2 will be described.

[0086] The fourth lens element L4 is a meniscus lens having a convex surface on the object side. The fifth lens element L5 is a meniscus lens having a convex surface on the object side. Both surfaces of the fifth lens element L5 are aspheric. The sixth lens element L6 is a meniscus lens having a concave surface on the object side. The seventh lens element L7 is a meniscus lens having a concave surface on the object side.

[0087] Next, each lens element in the third lens group G3 will be described.

[0088] The eighth lens element L8 is a meniscus lens having a convex surface on the object side. Both surfaces of the eighth lens element L8 are aspheric. The ninth lens element L9 is a biconvex lens. The tenth lens element L10 is a biconcave lens. The eleventh lens element L11 is a biconvex lens. The twelfth lens element L12 is a biconvex lens. Both surfaces of the twelfth lens element L12 are aspheric.

[0089] Next, the lens elements in the fourth lens group G4 will be described.

[0090] The thirteenth lens element L13 is a meniscus lens having a convex surface facing the object side. Both surfaces of the thirteenth lens element L13 are aspheric.

[0091] Furthermore, the lens elements in the fifth lens group G5 will be described.

[0092] The fourteenth lens element L14 is a meniscus lens having a convex surface facing the object side.

[0093] As described above, the imaging optical system of this embodiment is made up of five lens groups.

[0094] Each lens group of the imaging optical system of this embodiment moves as shown by the arrow in FIG. 7(c) during zooming from the wide-angle end to the telephoto end during imaging.

[0095] Specifically, first, the first lens group G1 moves toward the object side, and the second lens group G2 moves to draw a convex locus toward the image surface side. The aperture stop A and the third lens group G3 move toward the object side as one body. Then, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 moves toward the object side. Due to this movement, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. The distance between the third lens group G3 and the fourth lens group G4 increases from the wide-angle end to the middle position, and decreases from the middle position to the telephoto end. The distance between the fourth lens group G4 and the fifth lens group G5 decreases from the wide-angle end to the middle position, and increases from the middle position to the telephoto end. Then, the distance between the fifth lens group G5 and the image surface S increases. In this case, during zooming from the wide-angle end to the telephoto end, the open aperture diameter of the aperture diaphragm A is the same from the wide-angle end to the intermediate position, and is larger at the telephoto end compared to the intermediate position.

[0096] As described above, each lens group moves along the optical axis L as shown by the arrows in Fig. 7(c). Then, each lens group is positioned at the wide-angle end, the intermediate position, and the telephoto end as shown in Fig. 7(a), (d), and (e).

[0097] That is, in the imaging optical system of this embodiment, all the lens groups move relatively along the optical axis L. In other words, the intervals between the lens groups change. This allows zooming from the wide-angle end to the telephoto end.

[0098] During focusing from an infinity focused state to a close focused state, the fourth lens group G4 that constitutes the focusing lens group moves toward the image side along the optical axis L as shown by the arrow in FIG. 7(b).

[0099] Moreover, the twelfth lens element L12 of the third lens group G3 moves in a direction perpendicular to the optical axis L. This optically corrects image blur.

[0100] (Embodiment 4) The imaging optical system according to the fourth embodiment will be described below with reference to FIG.

[0101] FIG. 10 shows a lens arrangement and operation of an imaging optical system according to the fourth embodiment.

[0102] As shown in Fig. 10, the imaging optical system of this embodiment is composed of, in order from the object side to the image side, a first lens group G1 having positive power, a second lens group G2 having negative power, an aperture stop A, a third lens group G3 having positive power, a fourth lens group G4 having negative power, a fifth lens group G5 having positive power, and a parallel plate CG. The fourth lens group G4 and the fifth lens group G5 constitute a subsequent lens group. The second lens group G2 is exemplified by the lens group Gm. The third lens group G3 is exemplified by the lens group Gp. The fourth lens group G4 is exemplified by the lens group Gf.

[0103] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having positive power, and a third lens element L3 having positive power. The first lens element L1 and the second lens element L2 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin.

[0104] The second lens group G2 is composed of, in order from the object side to the image side, a fourth lens element L4 having negative power, a fifth lens element L5 having negative power, a sixth lens element L6 having negative power, and a seventh lens element L7 having positive power. The fourth lens element L4 is exemplified by the lens element LGmF1. The fifth lens element L5 is exemplified by the lens element LGmF2 or the lens element LGmR3. The sixth lens element L6 is exemplified by the lens element LGmR2. The seventh lens element L7 is exemplified by the lens element LGmR1.

[0105] The third lens group G3 is composed of, in order from the object side to the image side, an eighth lens element L8 having a positive power, a ninth lens element L9 having a positive power, a tenth lens element L10 having a negative power, an eleventh lens element L11 having a positive power, and a twelfth lens element L12 having a positive power. The tenth lens element L10 and the eleventh lens element L11 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin. The eighth lens element L8 is exemplified by the lens element LGpF1. The ninth lens element L9 is exemplified by the lens element LGpF2. The tenth lens element L10 is exemplified by the lens element LGpR3. The eleventh lens element L11 is exemplified by the lens element LGpR2. The twelfth lens element L12 is exemplified by the lens element LGpR1.

[0106] The fourth lens group G4 is composed of a thirteenth lens element L13 having negative power.

[0107] The fifth lens group G5 is composed of a fourteenth lens element L14 having positive power.

[0108] Aperture diaphragm A is disposed between the seventh lens element L7 of the second lens group G2 and the eighth lens element L8 of the third lens group G3.

[0109] The lens elements constituting each lens group in the imaging optical system of this embodiment will be described below.

[0110] First, each lens element in the first lens group G1 will be described.

[0111] The first lens element L1 is a meniscus lens having a convex surface facing the object side, the second lens element L2 is a meniscus lens having a convex surface facing the object side, and the third lens element L3 is a meniscus lens having a convex surface facing the object side.

[0112] Next, each lens element in the second lens group G2 will be described.

[0113] The fourth lens element L4 is a meniscus lens having a convex surface facing the object side. The fifth lens element L5 is a biconcave lens. Both surfaces of the fifth lens element L5 are aspheric. The sixth lens element L6 is a meniscus lens having a concave surface facing the object side. The seventh lens element L7 is a meniscus lens having a concave surface facing the object side.

[0114] Next, each lens element in the third lens group G3 will be described.

[0115] The eighth lens element L8 is a meniscus lens having a convex surface on the object side. Both surfaces of the eighth lens element L8 are aspheric. The ninth lens element L9 is a biconvex lens. The tenth lens element L10 is a biconcave lens. The eleventh lens element L11 is a biconvex lens. The twelfth lens element L12 is a biconvex lens. Both surfaces of the twelfth lens element L12 are aspheric.

[0116] Next, the lens elements in the fourth lens group G4 will be described.

[0117] The thirteenth lens element L13 is a biconcave lens, both of whose surfaces are aspheric.

[0118] Furthermore, the lens elements in the fifth lens group G5 will be described.

[0119] The fourteenth lens element L14 is a meniscus lens having a convex surface facing the object side.

[0120] As described above, the imaging optical system of this embodiment is made up of five lens groups.

[0121] Each lens group of the imaging optical system of this embodiment moves as shown by the arrow in FIG. 10(c) during zooming from the wide-angle end to the telephoto end during imaging.

[0122] Specifically, first, the first lens group G1 moves toward the object side, and the second lens group G2 moves to draw a convex locus toward the image surface side. The aperture diaphragm A and the third lens group G3 move toward the object side together. Then, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 moves toward the object side. Due to this movement, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. The distance between the third lens group G3 and the fourth lens group G4 increases from the wide-angle end to the middle position, and decreases from the middle position to the telephoto end. The distance between the fourth lens group G4 and the fifth lens group G5 increases. Then, the distance between the fifth lens group G5 and the image surface S increases. At this time, during zooming from the wide-angle end to the telephoto end, the open aperture diameter of the aperture diaphragm A is the same from the wide-angle end to the middle position, and is larger at the telephoto end than at the middle position.

[0123] As described above, each lens group moves along the optical axis L as shown by the arrows in Fig. 10(c). Then, each lens group is positioned at the wide-angle end, the intermediate position, and the telephoto end as shown in Fig. 10(a), (d), and (e).

[0124] That is, in the imaging optical system of this embodiment, all the lens groups move relatively along the optical axis L. In other words, the intervals between the lens groups change. This allows zooming from the wide-angle end to the telephoto end.

[0125] During focusing from an infinity focused state to a close focused state, the fourth lens group G4 that constitutes the focusing lens group moves toward the image side along the optical axis L as shown by the arrow in FIG.

[0126] Furthermore, the twelfth lens element L12 of the third lens group G3 moves in a direction perpendicular to the optical axis L. This optically corrects image blur. Specifically, the vertical movement of the twelfth lens element L12 corrects image point movement caused by vibration of the entire imaging optical system. As a result, image blur caused by camera shake, vibration, etc. can be optically corrected.

[0127] (Embodiment 5) The imaging optical system according to the fifth embodiment will be described below with reference to FIG.

[0128] FIG. 13 shows a lens arrangement and operation of an imaging optical system according to the fifth embodiment.

[0129] As shown in Fig. 13, the imaging optical system of this embodiment is composed of, in order from the object side to the image side, a first lens group G1 having positive power, a second lens group G2 having negative power, an aperture stop A, a third lens group G3 having positive power, a fourth lens group G4 having negative power, a fifth lens group G5 having positive power, a sixth lens group G6 having negative power, and a parallel plate CG. The second lens group G2 is exemplified by a lens group Gm. The third lens group G3 is exemplified by a lens group Gp. The fourth lens group G4 is exemplified by a lens group Gf.

[0130] The first lens group G1 is composed of, from the object side to the image side, a first lens element L1 having negative power and a second lens element L2 having positive power. The first lens element L1 and the second lens element L2 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin.

[0131] The second lens group G2 is composed of, in order from the object side to the image side, a third lens element L3 having negative power, a fourth lens element L4 having negative power, a fifth lens element L5 having negative power, and a sixth lens element L6 having positive power. The third lens element L3 is exemplified by the lens element LGmF1. The fourth lens element L4 is exemplified by the lens element LGmF2 or the lens element LGmR3. The fifth lens element L5 is exemplified by the lens element LGmR2. The sixth lens element L6 is exemplified by the lens element LGmR1.

[0132] The third lens group G3 is composed of, in order from the object side to the image side, a seventh lens element L7 having a positive power, an eighth lens element L8 having a positive power, a ninth lens element L9 having a negative power, a tenth lens element L10 having a positive power, and an eleventh lens element L11 having a positive power. The ninth lens element L9 and the tenth lens element L10 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin. The seventh lens element L7 is exemplified by the lens element LGpF1. The eighth lens element L8 is exemplified by the lens element LGpF2. The ninth lens element L9 is exemplified by the lens element LGpR3. The tenth lens element L10 is exemplified by the lens element LGpR2. The eleventh lens element L11 is exemplified by the lens element LGpR1.

[0133] The fourth lens group G4 is composed of a twelfth lens element L12 having negative power.

[0134] The fifth lens group G5 is composed of a thirteenth lens element L13 having positive power.

[0135] The sixth lens group G6 is composed of a fourteenth lens element L14 having negative power.

[0136] An aperture diaphragm A is disposed between the sixth lens element L6 of the second lens group G2 and the seventh lens element L7 of the third lens group G3.

[0137] The lens elements constituting each lens group in the imaging optical system of this embodiment will be described below.

[0138] First, each lens element in the first lens group G1 will be described.

[0139] The first lens element L1 is a meniscus lens having a convex surface facing the object side. The second lens element L2 is a meniscus lens having a convex surface facing the object side.

[0140] Next, each lens element in the second lens group G2 will be described.

[0141] The third lens element L3 is a meniscus lens having a convex surface on the object side. The fourth lens element L4 is a meniscus lens having a convex surface on the object side. Both surfaces of the fourth lens element L4 are aspheric. The fifth lens element L5 is a meniscus lens having a concave surface on the object side. The sixth lens element L6 is a biconvex lens.

[0142] Next, each lens element in the third lens group G3 will be described.

[0143] The seventh lens element L7 is a meniscus lens having a convex surface facing the object side. Both surfaces of the seventh lens element L7 are aspheric. The eighth lens element L8 is a biconvex lens. The ninth lens element L9 is a biconcave lens. The tenth lens element L10 is a biconvex lens. The eleventh lens element L11 is a biconvex lens. Both surfaces of the eleventh lens element L11 are aspheric.

[0144] Next, the lens elements in the fourth lens group G4 will be described.

[0145] The twelfth lens element L12 is a meniscus lens having a convex surface facing the object side. Both surfaces of the twelfth lens element L12 are aspheric.

[0146] Next, the lens elements in the fifth lens group G5 will be described.

[0147] The thirteenth lens element L13 is a meniscus lens having a convex surface facing the object side.

[0148] Furthermore, the lens elements in the sixth lens group G6 will be described.

[0149] The fourteenth lens element L14 is a meniscus lens having a concave surface facing the object side.

[0150] As described above, the imaging optical system of this embodiment is made up of six lens groups.

[0151] Each lens group of the imaging optical system of this embodiment moves as shown by the arrow in FIG. 13(c) during zooming from the wide-angle end to the telephoto end during imaging.

[0152] Specifically, first, the first lens group G1 moves toward the object side, and the second lens group G2 moves to draw a convex trajectory toward the image surface side. The aperture stop A and the third lens group G3 move toward the object side together. Then, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 moves toward the object side. The sixth lens group G6 does not move. Due to this movement, during zooming, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. The distance between the third lens group G3 and the fourth lens group G4 increases from the wide-angle end to the middle position, and decreases at the telephoto end compared to the wide-angle end. The distance between the fourth lens group G4 and the fifth lens group G5 increases. The distance between the fifth lens group G5 and the sixth lens group G6 increases. In this case, during zooming from the wide-angle end to the telephoto end, the open aperture diameter of the aperture diaphragm A is the same from the wide-angle end to the intermediate position, and is larger at the telephoto end compared to the wide-angle end.

[0153] That is, in the imaging optical system of this embodiment, the first lens group G1 to the fifth lens group move along the optical axis L so that the distance between the sixth lens group G6 and the image surface S does not change. In other words, the distance between each lens group changes. This allows zooming from the wide-angle end to the telephoto end.

[0154] When focusing from an infinity focused state to a close focused state, the imaging optical system moves toward the image side along the optical axis L as shown by the arrow in FIG.

[0155] Moreover, the eleventh lens element L11 of the third lens group G3 moves in a direction perpendicular to the optical axis L. This optically corrects image blur. Specifically, the movement of the eleventh lens element L11 corrects image point movement caused by vibration of the entire imaging optical system. As a result, image blur caused by camera shake, vibration, etc. can be optically corrected.

[0156] (Embodiment 6) The imaging optical system according to the sixth embodiment will be described below with reference to FIG.

[0157] FIG. 16 shows a lens arrangement and operation of an imaging optical system according to the fifth embodiment.

[0158] As shown in Fig. 16, the imaging optical system of this embodiment is composed of, in order from the object side to the image side, a first lens group G1 having negative power, an aperture stop A, a second lens group G2 having positive power, a third lens group G3 having negative power, a fourth lens group G4 having positive power, and a parallel plate CG. The first lens group G1 is exemplified by a lens group Gm. The second lens group G2 is exemplified by a lens group Gp. The third lens group G3 is exemplified by a lens group Gf.

[0159] The first lens group G1 is composed of, in order from the object side to the image side, a first lens element L1 having negative power, a second lens element L2 having negative power, a third lens element L3 having negative power, and a fourth lens element L4 having positive power. The first lens element L1 is exemplified by the lens element LGmF1. The second lens element L2 is exemplified by the lens element LGmF2 or the lens element LGmR3. The third lens element L3 is exemplified by the lens element LGmR2. The fourth lens element L4 is exemplified by the lens element LGmR1.

[0160] The second lens group G2 is composed of, in order from the object side to the image side, a fifth lens element L5 having a positive power, a sixth lens element L6 having a positive power, a seventh lens element L7 having a negative power, an eighth lens element L8 having a positive power, and a ninth lens element L9 having a positive power. The seventh lens element L7 and the eighth lens element L8 constitute a cemented lens bonded with an adhesive such as an ultraviolet curable resin. The fifth lens element L5 is exemplified by the lens element LGpF1.

[0161] The third lens group G3 is composed of a tenth lens element L10 having negative power.

[0162] The fourth lens group G4 is composed of an eleventh lens element L11 having positive power.

[0163] An aperture diaphragm A is disposed between the fourth lens element L4 of the first lens group G1 and the fifth lens element L5 of the second lens group G2.

[0164] The lens elements constituting each lens group in the imaging optical system of this embodiment will be described below.

[0165] First, each lens element in the first lens group G1 will be described.

[0166] 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. Both surfaces of the second lens element L2 are aspheric. The third lens element L3 is a meniscus lens having a concave surface on the object side. The fourth lens element L4 is a meniscus lens having a concave surface on the object side.

[0167] Next, each lens element in the second lens group G2 will be described.

[0168] The fifth lens element L5 is a meniscus lens having a convex surface facing the object side. Both surfaces of the fifth lens element L5 are aspheric. The sixth lens element L6 is a biconvex lens. The seventh lens element L7 is a biconcave lens. The eighth lens element L8 is a biconvex lens. The ninth lens element L9 is a biconvex lens. Both surfaces of the ninth lens element L9 are aspheric.

[0169] Next, the lens elements in the third lens group G3 will be described.

[0170] The tenth lens element L10 is a meniscus lens having a convex surface facing the object side.

[0171] Next, the lens elements in the fourth lens group G4 will be described.

[0172] The eleventh lens element L11 is a meniscus lens having a convex surface facing the object side.

[0173] As described above, the imaging optical system of this embodiment is made up of four lens groups.

[0174] The imaging optical system of this embodiment moves as shown by the arrow in FIG. 16(c) when zooming from the wide-angle end to the telephoto end during imaging.

[0175] Specifically, first, the first lens group G1 moves to draw a convex locus toward the image surface S. The aperture diaphragm A and the second lens group G2 move toward the object side together. Then, the third lens group G3 moves toward the object side, and the fourth lens group G4 moves toward the object side. Due to this movement, the distance between the first lens group G1 and the second lens group G2 decreases during zooming. The distance between the second lens group G2 and the third lens group G3 does not change from the wide-angle end to the intermediate position, and increases at the telephoto end compared to the wide-angle end. The distance between the third lens group G3 and the fourth lens group G4 decreases from the wide-angle end to the intermediate position, and increases at the telephoto end compared to the wide-angle end. At this time, during zooming from the wide-angle end to the telephoto end, the open aperture diameter of the aperture diaphragm A is the same from the wide-angle end to the intermediate position, and is larger at the telephoto end compared to the wide-angle end.

[0176] That is, in the imaging optical system of this embodiment, each lens group moves along the optical axis L so as to increase the distance between the fourth lens group G4 and the image surface S. This performs a zooming operation from the wide-angle end to the telephoto end.

[0177] During focusing from an infinity focused state to a close focused state, the third lens group G3 that constitutes the focusing lens group moves toward the image side along the optical axis L as shown by the arrow in FIG.

[0178] Furthermore, the ninth lens element L9 of the second lens group G2 moves in a direction perpendicular to the optical axis L. This optically corrects image blur. Specifically, the vertical movement of the ninth lens element L9 corrects image point movement caused by vibration of the entire imaging optical system. As a result, image blur caused by camera shake, vibration, etc. can be optically corrected.

[0179] (Conditions and effects, etc.) The conditions that can be satisfied by the configurations of the imaging optical systems according to the first to sixth embodiments will be described below.

[0180] That is, a number of possible conditions are defined for the imaging optical system according to each embodiment, and in this case, the imaging optical system having a configuration that satisfies all of the multiple conditions is the most effective.

[0181] However, by satisfying the individual conditions described below, it is possible to obtain an imaging optical system that exhibits the respective effects corresponding to each of the conditions.

[0182] For example, in the imaging optical systems according to the first to sixth embodiments, the spacing between each lens group changes during zooming, and among the lens groups having negative power, the lens group Gm closest to the object side (corresponding to the second lens group G2 in the first to fifth embodiments and the first lens group in the sixth embodiment) is composed of, in order from the object side to the image side, a lens element LGmF1 having negative power, a lens element LGmF2 having an aspherical shape on both sides and having negative power, and two or more lens elements having power.

[0183] With this configuration, even in the case of a wide-angle lens, the thickness deviation ratio of the aspherical lens of the lens element LGmF2 arranged in the lens group Gm can be made small. This allows a spherical lens that is easy to manufacture even if the thickness deviation ratio is large to be arranged as the lens element LGmF1. Therefore, the lens group Gm can be made thin. As a result, the overall length of the imaging optical system can be shortened.

[0184] In this case, as in the first to fifth embodiments, when a lens group (corresponding to the first lens group G1) having positive power is provided on the object side of the lens group Gm (so-called positive lead case), the aperture of the lens group having positive power (the first lens group G1 in the first to fifth embodiments) on the object side of the lens group Gm can be reduced.

[0185] The above configuration is not limited to the positive lead as shown in the first to fifth embodiments (numerical examples 1 to 5), but may be applied to the negative lead as shown in the sixth embodiment (numerical example 6). In this case, the lens group Gm having negative power and located closest to the object side is disposed closest to the object side among the lens groups in the imaging optical system.

[0186] The imaging optical system according to the present disclosure also includes a lens group Gp (corresponding to the third lens group G3 in the first to fifth embodiments and the second lens group G2 in the sixth embodiment) having positive power on the image side of the lens group Gm. The lens group Gp moves in the optical axis direction so that at least the distance between the lens group Gm and the lens group Gp changes when zooming from the wide-angle end to the telephoto end during shooting. This allows the imaging optical system according to the present disclosure to be applied to a zoom lens system.

[0187] It is desirable for an imaging optical system having the above configuration to satisfy, for example, the following condition (1):

[0188] 0.5 < f_LGpF1 / fw < 15 (1) Here, f_LGpF1 is the focal length of the lens element LGpF1, and fw is the focal length at the wide-angle end.

[0189] In other words, the condition (1) defines the relationship between the focal length of the lens element LGpF1 arranged closest to the object in the lens group Gp and the focal length of the entire system at the wide-angle limit.

[0190] If the value is below the lower limit (0.5) of condition (1), the power of the lens element LGpF1 becomes too strong, resulting in insufficient correction of spherical aberration. Conversely, if the value is above the upper limit (15) of condition (1), the focal length of the lens element LGpF1 becomes too long, resulting in excessive correction of spherical aberration.

[0191] In this case, it is more preferable to satisfy either the following condition (1a) or (1b).

[0192] 1.0 < f_LGpF1 / fw (1a) f_LGpF1 / fw < 10 (1b) This further improves the above-mentioned effects.

[0193] It is more preferable if either the following condition (1c) or (1d) is satisfied.

[0194] 1.5 < f_LGpF1 / fw (1c) f_LGpF1 / fw < 7 (1d) This further improves the above-mentioned effects.

[0195] Also, for example, it is desirable that the second lens element LGmR2 from the image side of the lens group Gm has a meniscus shape with a convex surface on the image side. This allows excessive spherical aberration to be corrected. In other words, by using the above shape, negative spherical aberration can be generated at the position where the light ray diverges and heads toward the image surface S side, in contrast to positive spherical aberration. Therefore, the spherical aberration can be corrected by adding them together.

[0196] Also, for example, the lens group Gm is preferably configured to include, from the object side to the image side, a lens element LGmF1 having a negative power and a lens element LGmF2 having a negative power, and, from the image side to the object side, a lens element LGmR1 having a positive power and a lens element LGmR2 having a negative power. In other words, it is preferable that the third lens element LGmR3 of the lens group Gm, from the image side to the object side, has a negative power. Furthermore, when the lens group Gm is configured with five lenses, the degree of freedom in design is significantly increased. Therefore, even in a wide-angle lens, the arrangement of the lens element LGmR1, the lens element LGmR2, and the lens element LGmR3 is not determined. This makes it easy to correct excessive curvature of field at the wide-angle end, which is likely to occur when the lens is made wide-angle. In other words, in the lens group Gm having negative power, the lens element having the strongest negative power generates a curvature of field, which is an aberration in the peripheral part of the screen. Therefore, in order to suppress the occurrence of the field curvature, it is preferable to configure the lens element LGmR3 or the lens element LGmF2 with a lens element having a negative power. Also, by giving the lens element LGmR1 a positive power, the suppression effect is further enhanced.

[0197] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (2).

[0198] 0.5 < THGm_A / THGm_B < 1.5 (2) Here, THGm_A is the air spacing between the first lens element LGmF1 from the object side of the lens group Gm and the second lens element LGmF2 from the object side of the lens group Gm, and THGm_B is the air spacing between the second lens element LGmR2 from the image side of the lens group Gm and the third lens element LGmR3 from the image side of the lens group Gm.

[0199] In other words, condition (2) specifies the relationship between the air spacing between the first lens element LGmF1 and the second lens element LGmF2 from the object side of the lens group Gm, and the air spacing between the second lens element LGmR2 and the third lens element LGmR3 from the image side of the lens group Gm.

[0200] Below the lower limit (0.5) of condition (2), the diameter of the light beam emerging from the lens group Gm becomes too large, causing the aperture diameter to become too large. Conversely, above the upper limit (1.5) of condition (2), the angle of the light beam emerging from the first lens element LGmF1 of the lens group Gm becomes too large, causing the aperture (diameter) of the optical system on the object side to become large.

[0201] In this case, it is more preferable to satisfy either the following condition (2a) or (2b).

[0202] 0.7 < THGm_A / THGm_B ···(2a) THGm_A / THGm_B < 1.3 (2b) This further improves the above-mentioned effects.

[0203] It is more preferable if either the following condition (2c) or (2d) is satisfied.

[0204] 0.8 < THGm_A / THGm_B ···(2c) THGm_A / THGm_B < 1.2 (2d) This further improves the above-mentioned effects.

[0205] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following conditions (3) and (4).

[0206] 1.45 < nd_LGmF2 (3) 35 < vd_LGmF2 (4) Here, nd_LGmF2 is the refractive index of the second lens element LGmF2 from the most object side in the lens group Gm, and vd_LGmF2 is the Abbe number of the second lens element LGmF2 from the most object side in the lens group Gm.

[0207] That is, the conditions (3) and (4) define the refractive index and the Abbe number, respectively, of the second lens element LGmF2 located closest to the object in the lens group Gm.

[0208] When the value falls below the lower limit (1.45) of condition (3), the radius of curvature of the lens element becomes too small, making it difficult to manufacture the lens element. When the value falls below the lower limit (35) of condition (4), it becomes difficult to correct lateral chromatic aberration at the wide-angle end. In other words, lateral chromatic aberration at the wide-angle end occurs in the lens that is closer to the object than the lens element LGmF2, which has a high light ray height. However, the lower the value of condition (4), the greater the chromatic dispersion, making it difficult to correct lateral chromatic aberration.

[0209] In this case, it is more preferable to satisfy either the following condition (3a) or (4a).

[0210] 1.48 < nd_LGmF2 (3a) 38 < vd_LGmF2 (4a) This further improves the above-mentioned effects.

[0211] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (5):

[0212] 0.05 < THGp_A / THGp_B < 0.5 (5) Here, THGp_A is the air gap between the first lens element LGpF1 from the object side of the lens group Gp and the second lens element LGpF2 from the object side of the lens group Gp, and THGp_B is the center-to-center gap between the lenses in the lens group Gp from the most object side to the most image side.

[0213] In other words, condition (5) defines the relationship between the air spacing between the first lens element LGpF1 and the second lens element LGpF2 from the object side of the lens group Gp and the center-to-center spacing of the lens elements from the most object side to the most image side in the lens group Gp.

[0214] If the value is below the lower limit (0.05) of condition (5), the image surface, especially in the meridional direction, will be too under-inclined. Conversely, if the value is above the upper limit (0.5) of condition (5), the image surface will be too over-inclined in the meridional direction.

[0215] In this case, it is more preferable to satisfy either the following condition (5a) or (5b).

[0216] 0.07 < THGp_A / THGp_B ···(5a) THGp_A / THGp_B < 0.3 (5b) This further improves the above-mentioned effects.

[0217] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (6):

[0218] 1.0 < f_Gp / fw < 7 (6) Here, f_Gp is ​​the focal length of the lens group Gp, and fw is the focal length of the entire system at the wide-angle end.

[0219] In other words, condition (6) sets forth the relationship between the focal length of the lens group Gp and the focal length of the entire system at the wide-angle limit.

[0220] When the value is equal to or less than the lower limit (1.0) of condition (6), the focal length of the lens group Gp becomes small, making it difficult to correct aberrations over the entire range. Conversely, when the value is equal to or greater than the upper limit (7) of condition (6), the focal length of the lens group Gp becomes large, making it necessary to move the lens group Gp by an excessive amount in order to ensure a sufficient zoom ratio.

[0221] In this case, it is more preferable to satisfy either the following condition (6a) or (6b).

[0222] 1.3 < f_Gp / fw (6a) f_Gp / fw < 5 (6b) This further improves the above-mentioned effects.

[0223] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following conditions (7) and (8).

[0224] 1.50 < nd_LGf (7) 35 < vd_LGf (8) Here, nd_LGf is the refractive index of the lens elements that make up the lens group Gf, and vd_LGf is the Abbe number of the lens elements that make up the lens group Gf.

[0225] That is, the conditions (7) and (8) define the refractive index and the Abbe number, respectively, of the lens elements that constitute the lens group Gf.

[0226] When the value is less than the lower limit (1.50) of condition (7), fluctuations in curvature of field become large when the lens is close up, and when the value is less than the lower limit (35) of condition (8), it becomes difficult to correct chromatic aberration of magnification when the lens is close up.

[0227] In this case, it is more preferable to satisfy either the following condition (7a) or (8a).

[0228] 1.53 < nd_LGf (7a) 38 < vd_LGf (8a) This further improves the above-mentioned effects.

[0229] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (9):

[0230] 1.5 < |f_Gf| / fw < 5 (9) Here, f_Gf is the focal length of the lens group Gf, and fw is the focal length of the entire system at the wide-angle end.

[0231] In other words, condition (9) sets forth the relationship between the focal length of the lens group Gf and the focal length of the entire system at the wide-angle limit.

[0232] When the condition (9) is equal to or less than the lower limit (1.5), the focal length of the lens group Gf becomes small, making it difficult to correct aberration fluctuations during close focusing. Conversely, when the condition (9) is equal to or greater than the upper limit (5), the focal length of the lens group Gf becomes large, making the amount of movement of the lens group Gf too large.

[0233] It is more preferable if either the following condition (9a) or (9b) is satisfied.

[0234] 2.0 < f_Gf / fw (9a) f_Gf / fw < 4 (9b) This further improves the above-mentioned effects.

[0235] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following conditions (10) and (11).

[0236] 1.75 < nd_LGmF1 (10) 25 < vd_LGmF1 (11) Here, nd_LGmF1 is the refractive index of the lens element LGmF1 closest to the object side in the lens group Gm, and vd_LGmF1 is the Abbe number of the lens element LGmF1 closest to the object side in the lens group Gm.

[0237] That is, the conditions (10) and (11) define the refractive index and the Abbe number, respectively, of the lens element LGmF1 closest to the object side in the lens group Gm.

[0238] When the value is less than the lower limit (1.75) of condition (10), the radius of curvature of the image side surface becomes small. As a result, the inclination angle of the peripheral portion becomes too large, making it difficult to manufacture the lens element. When the value is less than the lower limit (25) of condition (11), it becomes difficult to correct lateral chromatic aberration at the wide-angle end.

[0239] In this case, it is more preferable if either the following condition (10a) or (11a) is satisfied.

[0240] 1.78 < nd_LGmF1 (10a) 31 < vd_LGmF1 (11a) This further improves the above-mentioned effects.

[0241] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (12):

[0242] 0.8 <t_LGmF2(70%) / ct_LGmF2<1.5··(12) Here, t_LGmF2(70%) is the lens element thickness at 70% height from the effective diameter of the object side surface of the second lens element LGmF2 from the object side of the lens group Gm, and ct_LGmF2 is the center thickness of the second lens element LGmF2 from the object side of the lens group Gm.

[0243] In other words, condition (12) specifies the relationship between the lens element thickness at 70% of the height from the effective diameter of the object-side surface of the second lens element LGmF2 from the object side in the lens group Gm and the central thickness of the second lens element LGmF2 from the object side in the lens group Gm.

[0244] If the value is below the lower limit (0.8) of condition (12), the thickness of the lens element becomes too thin, making it difficult to ensure the edge thickness at the height that determines the outer diameter. Conversely, if the value is above the upper limit (1.5) of condition (12), the edge thickness becomes too large, making the lens element closer to the object (for example, lens element LGmF1) larger.

[0245] In this case, it is more preferable to satisfy either the following condition (12a) or (12b).

[0246] 0.9 < t_LGmF2(70%) / ct_LGmF2 (12a) t_LGmF2(70%) / ct_LGmF2 < 1.2 (12b) This further improves the above-mentioned effects.

[0247] It is more preferable if the following condition (12c) or (12d) is satisfied:

[0248] 0.98< t_LGmF2(70%) / ct_LGmF2···(12c) t_LGmF2(70%) / ct_LGmF2 < 1.06··(12d) This further improves the above-mentioned effects.

[0249] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (13):

[0250] 0.1 < ct_LGmF2 / THGm_B < 1.2 ···(13) Here, ct_LGmF2 is the center thickness of the second lens element LGmF2 from the object side of the lens group Gm, and THGm_B is the air spacing between the second lens element LGmR2 from the image side of the lens group Gm and the third lens element LGmR3 from the image side of the lens group Gm.

[0251] In other words, condition (13) defines the relationship between the center distance of the second lens element LGmF2 from the object side in the lens group Gm and the air distance between the second lens element LGmR2 and the third lens element LGmR3 from the image side in the lens group Gm.

[0252] When the condition (13) is equal to or less than the lower limit (0.1), THGm_B becomes large, and LGmF2 is disposed at a position where the on-axis light beam is low. This makes it difficult to correct spherical aberration throughout the entire imaging optical system or the entire zoom range. Conversely, when the condition (13) is equal to or greater than the upper limit (1.2), THGm_B becomes small, and LGmF2 is disposed at a position where the peripheral light beam is low. This makes it difficult to ensure flatness of the image plane at the wide-angle end.

[0253] In this case, it is more preferable to satisfy either the following condition (13a) or (13b).

[0254] 0.15 < ct_LGmF2 / THGm_B ···(13a) ct_LGmF2 / THGm_B < 1.0 (13b) This further improves the above-mentioned effects.

[0255] It is more preferable if either the following condition (13c) or (13d) is satisfied:

[0256] 0.20 < ct_LGmF2 / THGm_B (13c) ct_LGmF2 / THGm_B < 0.5 ···(13d) This further improves the above-mentioned effects.

[0257] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (14):

[0258] 0.1 < (R1_LGmF2+R2_LGmF1) / (R1_LGmF2―R2_LGmF1) < 4.0 ···(14) Here, R2_LGmF1 is the image-side radius of curvature of LGmF1, and R1_LGmF2 is the object-side radius of curvature of LGmF2.

[0259] In other words, condition (14) defines the relationship between the image-side radius of curvature of the first lens element LGmF1 from the object side of the lens group Gm and the object-side radius of curvature of the second lens element LGmF2 from the object side of the lens group Gm.

[0260] If the value is below the lower limit (0.1) of condition (14), it becomes difficult to ensure flatness of the image field throughout the entire imaging optical system or the entire zoom range. Conversely, if the value is above the upper limit (4.0) of condition (14), it becomes difficult to ensure flatness of the image field throughout the entire zoom range.

[0261] In this case, it is more preferable to satisfy either the following condition (14a) or (14b).

[0262] 4 < (R1_LGmF2+R2_LGmF1) / (R1_LGmF2―R2_LGmF1) ···(14a) (R1_LGmF2+R2_LGmF1) / (R1_LGmF2―R2_LGmF1) < 2.0··(14b) This further improves the above-mentioned effects.

[0263] It is more preferable if either the following condition (14c) or (14d) is satisfied:

[0264] 8 < (R1_LGmF2+R2_LGmF1) / (R1_LGmF2―R2_LGmF1) ···(14c) (R1_LGmF2+R2_LGmF1) / (R1_LGmF2―R2_LGmF1) < 1.6 (14d) This further improves the above-mentioned effects.

[0265] Moreover, it is desirable for the imaging optical system according to the present disclosure to satisfy the following condition (15):

[0266] -0.50 < (R1_LGmR2+R2_LGmF1) / (R1_LGmR2―R2_LGmF1) < 1.00··(15) Here, R2_LGmF1 is the image-side radius of curvature of LGmF1, and R1_LGmR2 is the object-side radius of curvature of LGmR2.

[0267] In other words, condition (15) defines the relationship between the image-side radius of curvature of the first lens element LGmF1 from the object side of the lens group Gm and the object-side radius of curvature of the second lens element LGmR2 from the image side of the lens group Gm.

[0268] If the value is below the lower limit (−0.50) of condition (15), it becomes difficult to ensure flatness of the image field throughout the entire imaging optical system or the entire zoom range. Conversely, if the value is above the upper limit (1.00) of condition (15), it becomes difficult to ensure flatness of the image field throughout the entire zoom range.

[0269] In this case, it is more preferable to satisfy either the following condition (15a) or (15b).

[0270] -0.30 < (R1_LGmR2+R2_LGmF1) / (R1_LGmR2―R2_LGmF1) ···(15a) (R1_LGmR2+R2_LGmF1) / (R1_LGmR2―R2_LGmF1) < 0.60··(15b) This further improves the above-mentioned effects.

[0271] It is more preferable if either the following condition (15c) or (15d) is satisfied:

[0272] -0.05 < (R1_LGmR2+R2_LGmF1) / (R1_LGmR2―R2_LGmF1) ···(15c) (R1_LGmR2+R2_LGmF1) / (R1_LGmR2―R2_LGmF1) < 1.60··(15d) This further improves the above-mentioned effects.

[0273] In addition, in the imaging optical system according to the present disclosure, it is desirable to configure the lens group Gf with, for example, one lens element. This allows the lens group Gf to be lightweight. Therefore, high-speed focusing is facilitated when focusing from an infinity focused state to a close focused state. In addition, the thickness of the lens group Gf on the optical axis can be shortened (thinned). Therefore, the imaging optical system can be made compact.

[0274] In addition, in the imaging optical system disclosed herein, it is desirable to configure the aperture stop A and the lens group Gp to move together during zooming, for example, from the wide-angle end to the telephoto end. This reduces the number of cam configurations that drive the lens groups during zooming, and therefore simplifies the configuration of the lens barrel, for example.

[0275] In this case, it is preferable that the open aperture diameter of aperture diaphragm A is larger at the telephoto end than at the wide-angle end, or larger at the telephoto end than at the intermediate position. This makes it possible to reduce the amount of movement of the aperture unit from the wide-angle end to the telephoto end. Here, the aperture unit is a mechanism that moves aperture diaphragm A along the optical axis, and in this embodiment, is a mechanism that moves the lens group that moves together with aperture diaphragm A.

[0276] In addition, the imaging optical system of the present disclosure is preferably configured to hold and drive, for example, the lens group Gf on a shaft 329 attached to a third group frame 313 (corresponding to a frame that holds the second lens group G2 in the case of the imaging optical system of the sixth embodiment) that holds the lens group Gp described below. This makes it possible to reduce the number of cam configurations for driving each lens group during zooming. This allows the configuration of, for example, the lens barrel to be simplified.

[0277] In addition, the imaging optical system according to the present disclosure may be configured such that, for example, the aperture stop A, the lens element LGpR1 for image blur correction arranged in the lens group Gp, and the actuator for driving the lens group Gf, which is the focus lens group, are arranged in a moving frame that moves integrally with the lens group Gp. This allows flexible wiring and a substrate for supplying power to the actuator to be integrally formed. As a result, the configuration of the lens barrel that houses the imaging optical system can be simplified.

[0278] Furthermore, an imaging optical system usually requires a certain clearance to drive the lens group Gf, which is, for example, a focus lens group. Therefore, one-sided blurring is likely to occur due to a relative position error of the lens group Gf with respect to the lens group Gp. Therefore, the imaging optical system according to the present disclosure provides a relative position adjustment mechanism in the lens group Gp (in the third group frame 313 (see FIG. 21)) as described below. This makes it possible to suppress the occurrence of one-sided blurring due to the relative position error. Note that, for example, a relative position adjustment mechanism may be provided in the lens element LGpR1 for image blur correction, which has a one-sided blurring sensitivity relative to the focus lens group. This makes it possible to further suppress the occurrence of one-sided blurring, as described above.

[0279] Moreover, the imaging optical system according to the first to fifth embodiments of the present disclosure includes, in order from the object side to the image side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, and at least one subsequent lens group having a power. The third lens group includes, in order from the object side to the image side, at least a lens element LGpF1 having a positive power and a lens element LGpF2 having a positive power, and, in order from the image side to the object side, a lens element LGpR1 having a positive power, a lens element LGpR2 having a positive power, and a lens element LGpR3 having a negative power. The lens element LGpR3 and the lens element LGpR2 are cemented to each other at one optical surface. The lens element LGpR1 moves so as to have a component perpendicular to the optical axis to optically correct image blur. During zooming from the wide-angle end to the telephoto end during shooting, at least the second lens group and the third lens group are configured to move in the optical axis direction so that the distance between them changes.

[0280] According to this configuration, in a bright lens, even if the lens element LGpR1 located farther from the aperture is moved so as to have a component perpendicular to the optical axis during image blur correction, the occurrence of decentering coma aberration can be reduced, thereby suppressing the deterioration of imaging performance during image blur correction.

[0281] (Schematic configuration of an imaging device to which the first embodiment is applied) A schematic configuration of an imaging device to which the imaging optical system of the first embodiment is applied will be described below with reference to FIG.

[0282] Fig. 19 is a schematic configuration diagram of an imaging device including the imaging optical system according to embodiment 1. Note that, although Fig. 19 illustrates an example in which the imaging optical system of embodiment 1 is applied to an imaging device, the imaging optical systems of embodiments 2 to 6 may be applied to an imaging device, and similar effects can be obtained.

[0283] 19, the imaging device 100 is composed of a housing 104, a lens barrel 302 connected to the housing 104, and the like. The housing 104 has an imaging element 102 therein. The lens barrel 302 has an imaging optical system 101 therein. The imaging device 100 is exemplified by, for example, a digital camera.

[0284] The imaging optical system 101 includes a first lens group G1, a second lens group G2, a third lens group G3, an aperture stop A, a fourth lens group G4, a fifth lens group G5, and the like, and is housed within a lens barrel 302.

[0285] The lens barrel 302 holds the lens groups that constitute the imaging optical system 101 and an aperture stop A.

[0286] The image pickup element 102 is disposed at the position of the image plane S in the imaging optical system of this embodiment.

[0287] The housing 104 also includes an actuator, a lens frame, etc., inside the housing 104. In the actuator and the lens frame, the lens groups and aperture diaphragm A that configure the imaging optical system 101 are arranged so as to be movable during zooming.

[0288] The imaging device 100 is configured as described above. This makes it possible to realize the imaging device 100 that is excellent in correcting various aberrations.

[0289] In the above, the imaging optical system is applied to a digital camera, but the present invention is not limited to this. For example, the imaging optical system may be applied to imaging devices such as a surveillance camera or a smartphone.

[0290] (Schematic configuration of a camera system to which the first embodiment is applied) A schematic configuration of a camera system to which the imaging optical system of the first embodiment is applied will be described below with reference to FIG.

[0291] Fig. 20 is a schematic diagram of a camera system including an imaging optical system according to embodiment 1. Although Fig. 20 illustrates an example in which the imaging optical system of embodiment 1 is applied to a camera system, the imaging optical system of embodiments 2 to 6 may be applied to a camera system, and similar effects can be obtained. Camera system 200 is exemplified by, for example, a lens-interchangeable digital camera system.

[0292] As shown in FIG. 20, a camera system 200 includes a camera body 201, an interchangeable lens device 300 that is detachably connected to the camera body 201, and the like.

[0293] The camera body 201 includes an image sensor 202, a monitor 203, a memory (not shown) for storing image signals, a camera mount unit 204, and a viewfinder 205. The image sensor 202 is formed of, for example, a CMOS image sensor, and receives an optical image formed by the imaging optical system of the interchangeable lens device 300 and converts it into an electrical image signal. The monitor 203 is formed of, for example, an LCD, and displays the image signal converted by the image sensor 202.

[0294] The interchangeable lens device 300 includes an imaging optical system 101 including a first lens group G1, a second lens group G2, an aperture stop A, a third lens group G3, a fourth lens group G4, and a fifth lens group G5.

[0295] The lens barrel 302 holds each lens group of the imaging optical system 101 and an aperture stop A. Furthermore, the lens barrel 302 includes a lens mount portion 304 that is connected to the camera mount portion 204 of the camera body 201.

[0296] The camera mount section 204 of the camera body 201 and the lens mount section 304 of the lens barrel 302 are physically connected by, for example, a bayonet mechanism. A controller (not shown) in the camera body 201 and a controller (not shown) in the interchangeable lens device 300 are electrically connected. In other words, the camera mount section 204 and the lens mount section 304 function as an interface that enables the exchange of signals between them.

[0297] The imaging optical system 101 is made up of each lens group held in a lens barrel 302 of an interchangeable lens device 300, a parallel plate CG in a camera body 201, and the like.

[0298] The imaging optical system 101 includes an actuator and a lens frame controlled by a controller inside. In the actuator and the lens frame, the lens groups constituting the imaging optical system 101, the aperture stop A, and the like are arranged so as to be movable during zooming.

[0299] As described above, camera system 200 is configured, which makes it possible to realize camera system 200 with good correction of various aberrations.

[0300] (Schematic configuration of a lens barrel to which the first embodiment is applied) The schematic configuration of a lens barrel to which the imaging optical system of the first embodiment is applied will be described below with reference to FIG.

[0301] Fig. 21 is a schematic diagram of a lens barrel 302 equipped with an imaging optical system according to embodiment 1. Although Fig. 21 illustrates an example in which the imaging optical system of embodiment 1 is applied to a lens barrel, the imaging optical systems of embodiments 2 to 6 may be applied to a lens barrel, and similar effects can be obtained. When applied to the lens barrel of embodiment 6, the second lens group G2 to the fifth lens group G5 in embodiment 1 correspond to the first lens group G1 to the fourth lens group G4 in the lens barrel of embodiment 6.

[0302] As shown in FIG. 21, the lens barrel 302 includes a first group frame 311, a second group frame 312, a third group frame 313, a fourth group frame 314, a fifth group frame 315, and the like, which hold the respective lens groups of the imaging optical system.

[0303] The first group frame 311 holds the first lens group G1. The second group frame 312 holds the second lens group G2. The third group frame 313 holds the aperture stop A and the third lens group G3. The fourth group frame 314 holds the fourth lens group G4. The fifth group frame 315 holds the fifth lens group G5.

[0304] The second group frame 312, the third group frame 313 and the fifth group frame 315 are engaged with the rectilinear fixed frame 325, the cam barrel 320 and the cam pins 326, and move along the optical axis direction. The first group frame 311 is engaged with a groove (not shown) on the outer circumferential surface of the second group frame 312 via a pin (not shown) of the first group frame 311, and moves along the optical axis direction.

[0305] The third group frame 313 includes an actuator 328, a shaft 329, and the like. The actuator 328 is controlled by a controller (not shown) and drives the fourth group frame 314 in the optical axis direction relative to the third group frame 313. The shaft 329 movably holds the fourth group frame 314. This makes it possible to reduce the number of cam configurations that drive each lens group during zooming. As a result, the configuration of the lens barrel 302 can be simplified.

[0306] The third group frame 313 includes a third group front frame 313a, an OIS base frame 313b, an OIS frame 313c, and an actuator 327. The actuator 327 drives the OIS frame 313c relative to the OIS base frame 313b on a plane perpendicular to the optical axis. The third group front frame 313a holds an aperture stop A and the eighth lens element L8 to the eleventh lens element L11. The OIS frame 313c holds a lens element LGpR1, which is an example of the twelfth lens element L12 of the third lens group G3. The OIS base frame 313b supports the OIS frame 313c via, for example, a ball (not shown) so that the OIS frame 313c can move from a reference position on a plane perpendicular to the optical axis. Note that OIS is an abbreviation for Optical Image Stabilizer, and indicates an optical image blur correction function.

[0307] A controller (not shown) controls the actuator 327 to move the OIS frame 313c that holds the lens element LGpR1, thereby performing image blur correction.

[0308] Furthermore, the OIS base frame 313b is equipped with the above-mentioned relative position adjustment mechanism. The relative position adjustment mechanism moves the OIS base frame 313b in two directions perpendicular to the optical axis (X direction and Y direction) with respect to the third group front frame 313a by the stress of the eccentric pin 323. This adjusts the relative position of the lens element LGpR1 with respect to the reference position. Specifically, when the lens barrel 302 is adjusted for shipment, the relative position of the lens element LGpR1 is adjusted by the eccentric pin 323, and after the adjustment, the lens element is fixed with an adhesive or the like. This makes it possible to suppress the occurrence of one-sided blur.

[0309] (Other embodiments) The technology disclosed in this application has been described above by taking the first to sixth embodiments as examples.

[0310] However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made.

[0311] In the imaging optical systems according to the above-mentioned first to sixth embodiments, the entire zooming range from the wide-angle end to the telephoto end is used, but it is not necessary to use the entire zooming range. For example, a range where optical performance is ensured may be extracted according to a desired zooming range and used as an imaging optical system. That is, it may be used as an imaging optical system with a lower magnification than the imaging optical systems described below in Numerical Example 1 to Numerical Example 6 corresponding to the first to sixth embodiments. Also, a focal length where optical performance is ensured according to a desired zooming position may be extracted and used as a single-focus imaging optical system.

[0312] For example, in the case of use as a single focal length imaging optical system, the lens group Gm, the lens group Gp, and the lens group Gf are as follows.

[0313] When used as a single-focus imaging optical system, the lens group Gm (corresponding to the second lens group G2 in the first to fifth embodiments and the first lens group G1 in the sixth embodiment) located closest to the object among the lens groups having negative power in the imaging optical system according to the first to sixth embodiments is composed of, in order from the object side to the image side, a lens element LGmF1 having negative power, a lens element LGmF2 having an aspheric shape on both sides and negative power, and two or more lens elements having power. The lens element LGmF1 is the lens element having the strongest power among the lens elements located closer to the object than the aperture stop A. In other words, the lens element LGmF1 located closest to the object side of the lens group Gm is the lens element having the strongest negative power among the lens elements located closer to the object than the aperture stop A.

[0314] When used as a single-focus imaging optical system, the lens group Gp described above is a lens group having positive power on the image side of the lens group Gm in the imaging optical system according to the first to sixth embodiments (corresponding to the third lens group G3 in the first to fifth embodiments and the second lens group G2 in the sixth embodiment). The lens group Gp has, in order from the object side to the image side, a lens element LGpF1 having positive power and a lens element LGpF2 having positive power. An aperture diaphragm A is provided on either the object side or the image side of the lens element LGpF1. That is, the lens group Gp has, in order from the object side to the image side, (i) an aperture diaphragm A, a lens element LGpF1 having positive power, and a lens element LGpF2 having positive power, or (ii) a lens element LGpF1 having positive power, an aperture diaphragm A, and a lens element LGpF2 having positive power.

[0315] When used as a fixed focal imaging optical system, the lens group Gf described above is a lens group having negative power on the image side of the lens group Gf in the imaging optical systems according to the first to sixth embodiments (corresponding to the fourth lens group G4 in the first to fifth embodiments and the third lens group G3 in the sixth embodiment). The lens group Gf is a lens group that moves in the optical axis direction during focusing from an infinity focused state to a close focused state. That is, in a fixed focal imaging optical system, the lens group Gp does not move in the optical axis direction during focusing, and the lens group Gf moves in the optical axis direction.

[0316] In addition, in the imaging optical systems according to the first to sixth embodiments, the lens element for image blur correction is moved in a direction perpendicular to the optical axis to perform image blur correction, but the present invention is not limited to this. In other words, as long as the lens element is moved in a manner that has a component perpendicular to the optical axis, image blur can be corrected. Therefore, for example, if the barrel structure can be made complex, the lens element for image blur correction may be rotated to have a center of rotation on the optical axis to perform image blur correction.

[0317] In addition, in the first to sixth embodiments, each lens group constituting the imaging optical system is described as being composed only of a refractive lens element that deflects incident light by refraction (i.e., a type of lens element in which deflection occurs at the interface between media having different refractive indices), but this is not limited thereto. For example, the lens group may be composed of a diffractive lens element that deflects incident light by diffraction, or a refractive-diffractive hybrid lens element that deflects incident light by a combination of a diffractive action and a refracting action. Furthermore, each lens group may be composed of a refractive index distribution lens element that deflects incident light by a refractive index distribution in a medium. In particular, in a refractive-diffractive hybrid lens element, it is more preferable to form a diffractive structure at the interface between media having different refractive indices, since this improves the wavelength dependency of the diffraction efficiency. This makes it possible to realize a camera system with good aberrations.

[0318] (Numerical Example) Below, specific numerical examples implemented in the configurations of the imaging optical systems according to embodiments 1 to 6 will be described with reference to Figures 2, 3, 5, 6, 8, 9, 11, 12, 14, 15, 17, and 18.

[0319] In each numerical example, the unit of length in the table is "mm", and the unit of angle of view is "°". In each numerical example, r is the radius of curvature, d is the surface spacing, nd is the refractive index for the d-line, and νd (also written as vd) is the Abbe number for the d-line. In each numerical example, the surfaces marked with an * are aspheric. The aspheric shape is defined by the following formula. In each numerical example, the aperture diameter is the effective open aperture diameter at each zoom position.

[0320]

number

[0321] Here, Z is the distance from a point on the aspheric surface at a height h from the optical axis to the tangent plane of the vertex of the aspheric surface, h is the height from the optical axis, r is the radius of curvature of the vertex, κ is a conic constant, and An is an n-th order aspheric coefficient.

[0322] 2, 5, 8, 11, 14, and 17 are longitudinal aberration diagrams of the imaging optical systems according to Numerical Examples 1 to 6 in the infinity focused state corresponding to the first to sixth embodiments.

[0323] In each longitudinal aberration diagram, (a) shows the longitudinal aberration at the wide-angle end, (b) shows the longitudinal aberration at the intermediate position, and (c) shows the longitudinal aberration at the telephoto end. From the left, (a) to (c) of each longitudinal aberration diagram show spherical aberration (SA: Spherical Aberration (mm)), astigmatism (AST: Astigmatism (mm)), and distortion (DIS: Distortion (%)).

[0324] In the spherical aberration diagram, the vertical axis represents the F-number (indicated by "F" in the diagram), with the solid line representing the d-line, the short dashed line representing the F-line, and the long dashed line representing the C-line characteristics. In the astigmatism diagram, the vertical axis represents the image height (indicated by "H" in the diagram), with the solid line representing the sagittal plane (indicated by "s" in the diagram), and the dashed line representing the meridional plane (indicated by "m" in the diagram). Furthermore, in the distortion diagram, the vertical axis represents the image height (indicated by "H" in the diagram).

[0325] 3, 6, 9, 12, 15, and 18 are lateral aberration diagrams at the telephoto end of the imaging optical systems according to Numerical Examples 1 to 6 corresponding to the first to sixth embodiments.

[0326] Here, (a) to (c) of each lateral aberration diagram show the characteristics in the basic state where no image blur compensation is performed at the telephoto end, while (d) to (f) of each lateral aberration diagram show the characteristics in the image blur compensation state at the telephoto end where the image blur compensation lens group is moved a specified amount in the direction perpendicular to the optical axis.

[0327] In addition, (a) of each lateral aberration diagram in the basic state shows the characteristics corresponding to the lateral aberration at an image point of 70% of the maximum image height, (b) shows the lateral aberration at an on-axis image point, and (c) shows the lateral aberration at an image point of -70% of the maximum image height. Similarly, (d) of each lateral aberration diagram in the image blur correction state shows the characteristics corresponding to the lateral aberration at an image point of 70% of the maximum image height, (e) shows the lateral aberration at an on-axis image point, and (f) shows the characteristics corresponding to the lateral aberration at an image point of -70% of the maximum image height.

[0328] In each lateral aberration diagram, the horizontal axis represents the distance from the chief ray on the pupil plane, with the solid line representing the d-line, the short dashed line representing the F-line, and the long dashed line representing the C-line characteristics. In each lateral aberration diagram, the meridional plane is taken as the plane that includes the optical axis of the first lens group G1 and the optical axis of the lens element LGpR1.

[0329] Here, for the imaging optical system of each numerical example, the movement amount of the image blur compensation lens group in the direction perpendicular to the optical axis in the image blur compensation state at the telephoto end is shown below.

[0330] Numerical Example 1 0.261mm Numerical Example 2 0.251 mm Numerical Example 3 0.241 mm Numerical Example 4 0.238 mm Numerical Example 5 0.247 mm Numerical Example 6 0.168 mm At the telephoto end where the shooting distance is infinity, the amount of image decentering when the imaging optical system is tilted by 0.4 degrees is equal to the amount of image decentering when the image blur compensation lens group translates by the above values ​​in a direction perpendicular to the optical axis.

[0331] In the above state, it can be seen from the lateral aberration diagrams shown in FIGS. 3, 6, 9, 12, 15 and 18(b) and (e) that the symmetry of the lateral aberration at the axial image point is good.

[0332] In addition, when comparing the lateral aberration at the +70% image point in the basic state shown in (a) of Figures 3, 6, 9, 12, 15, and 18 with the lateral aberration at the -70% image point in the basic state shown in (c), the degree of curvature is small and the slope of the aberration curve is almost the same in both cases. This shows that the decentering coma aberration and decentering astigmatism aberration are small. The above results mean that sufficient imaging performance is obtained even in the image blur correction state.

[0333] Furthermore, when the image blur compensation angle of the imaging optical system is the same, the amount of parallel movement required for image blur compensation decreases as the focal length of the entire imaging optical system becomes shorter. In other words, it can be seen that at any zoom position, sufficient image blur compensation can be performed without degrading imaging characteristics for an image blur compensation angle of about 0.4 degrees.

[0334] (Numerical Example 1) Below, Numerical Example 1 of the imaging optical system corresponding to the first embodiment shown in Fig. 1 is shown. Specifically, as Numerical Example 1, surface data is shown in Table 1, aspheric surface data is shown in Table 2, and various data in the infinity focused state are shown in Tables 3A to 3D. TIFF2025003602000003.tif254143TIFF2025003602000004.tif202151TIFF2025003602000005.tif1641 28TIFF2025003602000006.tif13397TIFF2025003602000007.tif58146TIFF2025003602000008.tif72122

[0335] (Numerical Example 2) Below, Numerical Example 2 of the imaging optical system corresponding to the second embodiment shown in Fig. 4 is shown. Specifically, as Numerical Example 2, surface data is shown in Table 4, aspheric surface data is shown in Table 5, and various data in the infinity focused state are shown in Tables 6A to 6D. TIFF2025003602000009.tif254144TIFF2025003602000010.tif207153TIFF2025003602000011.tif16812 2TIFF2025003602000012.tif136100TIFF2025003602000013.tif61145TIFF2025003602000014.tif69117

[0336] (Numerical Example 3) Below, Numerical Example 3 of the imaging optical system corresponding to the third embodiment shown in Fig. 7 is shown. Specifically, as Numerical Example 3, surface data is shown in Table 7, aspheric surface data is shown in Table 8, and various data in the infinity focused state are shown in Tables 9A to 9D. TIFF2025003602000015.tif254146TIFF2025003602000016.tif203158TIFF2025003602000017.tif1661 33TIFF2025003602000018.tif13093TIFF2025003602000019.tif64142TIFF2025003602000020.tif63117

[0337] (Numerical Example 4) Numerical Example 4 of the imaging optical system corresponding to the fourth embodiment shown in Fig. 10 is shown below. Specifically, as Numerical Example 4, surface data is shown in Table 10, aspheric surface data is shown in Table 11, and various data in the infinity focused state are shown in Tables 12A to 12D. TIFF2025003602000021.tif254143TIFF2025003602000022.tif206154TIFF2025003602000023.tif1711 26TIFF2025003602000024.tif13398TIFF2025003602000025.tif61143TIFF2025003602000026.tif66117

[0338] (Numerical Example 5) Numerical Example 5 of the imaging optical system corresponding to the fifth embodiment shown in Fig. 13 is shown below. Specifically, as Numerical Example 5, surface data is shown in (Table 13), aspheric surface data is shown in (Table 14), and various data in the infinity focused state are shown in (Tables 15A) to (Table 15D). TIFF2025003602000027.tif254137TIFF2025003602000028.tif207154TIFF2025003602000029.tif1671 25TIFF2025003602000030.tif13691TIFF2025003602000031.tif74145TIFF2025003602000032.tif76119

[0339] (Numerical Example 6) Numerical Example 6 of the imaging optical system corresponding to the sixth embodiment shown in Fig. 16 is shown below. Specifically, as Numerical Example 6, surface data is shown in (Table 16), aspheric surface data is shown in (Table 17), and various data in the infinity focused state are shown in (Tables 18A) to (Table 18D). TIFF2025003602000033.tif245153TIFF2025003602000034.tif164156TIFF2025003602000035.tif1561 25TIFF2025003602000036.tif10796TIFF2025003602000037.tif56145TIFF2025003602000038.tif57116

[0340] (Condition's corresponding value) As described above, the imaging optical systems according to the first to sixth embodiments were specifically implemented in Numerical Example 1 to Numerical Example 6.

[0341] Below, values ​​corresponding to the above conditions (1) to (15) in each numerical example are shown in Table 1.

[0342] [Table 1]

[0343] As shown in Table 1, the imaging optical systems implemented in Numerical Example 1 to Numerical Example 6 satisfy the above conditions (1) to (15).

[0344] This makes it possible to realize an imaging optical system that is small, has a high magnification, and has excellent imaging performance over the entire zoom range, as well as an imaging device or camera system that includes the same.

[0345] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, and the like can be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0346] The imaging optical system according to the present disclosure is applicable to digital still cameras, interchangeable lens digital cameras, digital video cameras, cameras in mobile phone devices, cameras in PDAs (Personal Digital Assistances), surveillance cameras in surveillance systems, Web cameras, vehicle-mounted cameras, etc. In particular, the present disclosure is suitable for imaging optical systems that require high image quality, such as digital still camera systems and digital video camera systems. [Explanation of symbols]

[0347] G1 First lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group Gf, Gm, Gp lens group L1 First lens element L2 Second lens element L3 Third lens element L4 Fourth lens element L5 Fifth lens element L6 Sixth lens element L7 Seventh lens element L8 Eighth lens element L9 9th lens element L10 Tenth lens element L11 Eleventh lens element L12 12th lens element L13 13th lens element L14 14th lens element LGmF1, LGmF2, LGmR1, LGmR2, LGmR3 lens elements LGpF1, LGpF2, LGpR1, LGpR2, LGpR3 lens elements A aperture stop CG parallel plate S image plane 100 Imaging device 101 Imaging optical system 102 Image sensor 104 Case 200 Camera System 201 Camera body 202 Image sensor 203 Monitor 204 Camera mount 205 Finder 300 Interchangeable lens device 302 Telescope tube 304 Lens mount 311 1st group frame 312 2nd group frame 313 3rd group frame 313a 3rd group front frame 313b OIS base frame 313c OIS frame 314 4th group frame 315 5th group frame 320 Cam barrel 323 Eccentric pin 325 Straight fixed frame 326 Campin 327,328 Actuator 329 Shaft

Claims

1. During zooming, the spacing between the lens groups changes. Among the lens groups having negative power, the lens group Gm located closest to the object side has the following structure: From the object side to the image side, a lens element LGmF1 having a negative power; a lens element LGmF2 having a double aspheric surface and negative power; and two or more lens elements having power. Imaging optical system.

2. Among the lens groups having negative power, the lens group Gm located closest to the object side is From the object side to the image side, a lens element LGmF1 having a negative power; a lens element LGmF2 having a double aspheric surface and negative power; and two or more lens elements having a power, The lens element LGmF1 is the lens element having the strongest power among the lens elements located closer to the object side than the aperture stop. Imaging optical system.

3. t_LGmF2(70%) is the lens element thickness at a height of 70% from the effective diameter of the object side surface of the second lens element LGmF2 from the object side of the lens group Gm, When ct_LGmF2 is the center thickness of the second lens element LGmF2 from the object side of the lens group Gm, 0.8<t_LGmF2(70%) / ct_LGmF2<1.5...(12) 3. The imaging optical system according to claim 1, which satisfies the above condition (12).

4. The second lens element LGmR2 from the image side of the lens group Gm has a meniscus shape convex toward the image side. The imaging optical system according to claim 1 .

5. The lens group Gm is From the object side to the image side, said lens element LGmF1 having a negative power; said lens element LGmF2 having a negative power; Equipped with At least two lenses, from the image side to the object side, a lens element LGmR1 having a positive power; a lens element LGmR2 having a negative power; The imaging optical system according to claim 1 , comprising:

6. THGm_A is an air gap between the first lens element LGmF1 from the object side of the lens group Gm and the second lens element LGmF2 from the object side of the lens group Gm; When THGm_B is the air distance between the second lens element LGmR2 from the image side of the lens group Gm and the third lens element LGmR3 from the image side of the lens group Gm, 0.5 < THGm_A / THGm_B < 1.5...(2) 3. The imaging optical system according to claim 1, which satisfies the above condition (2).

7. nd_LGmF1 is the refractive index of the lens element LGmF1 closest to the object side of the lens group Gm, When vd_LGmF1 is the Abbe number of the lens element LGmF1 closest to the object side in the lens group Gm, 1.75 < nd_LGmF1 (10) 25 < vd_LGmF1 (11) 3. The imaging optical system according to claim 1, which satisfies the above conditions (10) and (11).

8. nd_LGmF2 is the refractive index of the second lens element LGmF2 from the object side in the lens group Gm, When vd_LGmF2 is the Abbe number of the second lens element LGmF2 from the object side in the lens group Gm, 1.45 < nd_LGmF2 (3) 35 < vd_LGmF2 ... (4) 3. The imaging optical system according to claim 1, which satisfies the above conditions (3) and (4).

9. a lens group Gp having a positive power is provided on the image side of the lens group Gm; The lens group Gp is From the object side to the image side, a lens element LGpF1 having a positive power; a lens element LGpF2 having a positive power; The aperture stop is provided on either the object side or the image side of the lens element LGpF1. The imaging optical system according to claim 1 .

10. The lens group Gp is From the image side to the object side, a lens element LGpR1 having a positive power; a lens element LGpR2 having a positive power; and a lens element LGpR3 having a negative power; The imaging optical system according to claim 9 .

11. a lens group Gp having a positive power is provided on the image side of the lens group Gm; THGp_A is an air gap between the first lens element LGpF1 from the object side of the lens group Gp and the second lens element LGpF2 from the object side of the lens group Gp; When THGp_B is the center-to-center distance between the lens elements closest to the object side and the lens elements closest to the image side in the lens group Gp, 0.05 < THGp_A / THGp_B < 0.5...(5) 2. The imaging optical system according to claim 1, which satisfies the above condition (5).

12. a lens group Gf having a negative power that moves in an optical axis direction during focusing from an infinity focused state to a close focused state, the lens group Gf being disposed on the image side of a lens element that is closest to the image side of the lens group Gp; THGp_A is the air distance between the lens element LGpF1 and the lens element LGpF2, When THGp_B is the center-to-center distance between the lens elements closest to the object side and the lens elements closest to the image side in the lens group Gp, 0.05 < THGp_A / THGp_B < 0.5...(5) 10. The imaging optical system according to claim 9, which satisfies the above condition (5).

13. a lens group Gp having a positive power is provided on the image side of the lens group Gm; During zooming from the wide-angle end to the telephoto end during shooting, at least the lens group Gm and the lens group Gp move in the optical axis direction so that the distance between them changes, f_LGpF1 is the focal length of the lens element LGpF1 closest to the object side in the lens group Gp, When fw is the focal length at the wide-angle end, 0.5 < f_LGpF1 / fw < 15...(1) 2. The imaging optical system according to claim 1, which satisfies the above condition (1).

14. a lens group Gp having a positive power is provided on the image side of the lens group Gm; During zooming from the wide-angle end to the telephoto end during shooting, at least the lens group Gm and the lens group Gp move in the optical axis direction so that the distance between them changes; f_Gp is ​​the focal length of the lens group Gp, When fw is the focal length of the entire system at the wide-angle end, 1.0 < f_Gp / fw < 7...(6) 2. The imaging optical system according to claim 1, which satisfies the above condition (6).

15. a lens group Gp having a positive power is provided on the image side of the lens group Gm; a lens group Gf having a negative power provided on an image side of the lens group Gp; nd_LGf is the refractive index of the lens elements constituting the lens group Gf, When vd_LGf is the Abbe number of the lens element that constitutes the lens group Gf, 1.50 < nd_LGf (7) 35 < vd_LGf (8) 3. The imaging optical system according to claim 1, which satisfies the above conditions (7) and (8).

16. a lens group Gp having a positive power is provided on the image side of the lens group Gm; a lens group Gf having a negative power provided on an image side of the lens group Gp; During zooming from the wide-angle end to the telephoto end during shooting, at least the lens group Gm and the lens group Gp move in the optical axis direction so that the distance between them changes; f_Gf is the focal length of the lens group Gf, When fw is the focal length of the entire system at the wide-angle end, 1.5 < |f_Gf| / fw < 5...(9) 2. The imaging optical system according to claim 1, which satisfies the above condition (9).

17. An interchangeable lens device including the imaging optical system according to claim 1 or 2; a camera body including an image sensor that is detachably connected to the interchangeable lens device via a camera mount and that receives an optical image formed by the imaging optical system and converts the optical image into an electrical image signal; The interchangeable lens device forms the optical image on the image sensor. Camera system.

18. 1. An imaging device that converts an optical image of an object into an electrical image signal and at least one of displays and stores the converted image signal, comprising: an imaging optical system according to claim 1 or 2, which forms an optical image of the object; an image sensor that converts the optical image formed by the image pickup optical system into the electrical image signal; Imaging device.

19. t_LGmF2(70%) is the lens element thickness at a height of 70% from the effective diameter of the object side surface of the second lens element LGmF2 from the object side of the lens group Gm, When ct_LGmF2 is the center thickness of the second lens element LGmF2 from the object side of the lens group Gm, 0.1 < ct_LGmF2 / THGm_B < 1.2 (13) 3. The imaging optical system according to claim 1, which satisfies the relational expression shown in the above condition (13).

20. The radius of curvature on the image side of the lens element LGmF1 closest to the object side of the lens group Gm is R2_LGmF1, When the radius of curvature on the object side of the second lens element LGmF2 from the object side in the lens group Gm is R1_LGmF2, 1 < (R1_LGmF2+R2_LGmF1) / (R1_LGmF2-R2_LGmF1) < 4.0...(14) 3. The imaging optical system according to claim 1, wherein the above condition (14) is satisfied.

21. The radius of curvature of the image side of the lens element LGmF1 is R2_LGmF1, When the radius of curvature of the lens element LGmR2 on the object side is R1_LGmR2, -0.5 < (R1_LGmR2+R2_LGmF1) / (R1_LGmR2-R2_LGmF1) < 1.0...(15) 3. The imaging optical system according to claim 1, wherein the above condition (15) is satisfied.

Images