Imaging optical system

Abstract

To provide an imaging optical system that is small-sized and light-weight by itself and suitable for a small-sized and lightweight telescope lens by having a compact and lightweight focusing unit.SOLUTION: An imaging optical system includes a focusing unit that is composed of a plurality of lenses and moves integrally at the time of focusing. A maximum air interval of air intervals formed by a plurality of lenses on an optical axis is located closer to an object side than a most object side of the focusing unit, and satisfies prescribed conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an imaging optical system suitable for a photographic lens used in a still camera, a video camera, or the like. [Background technology]

[0002] A telephoto type imaging optical system, in which a lens group with positive power and a lens group with negative power are arranged in that order from the object side to the image side, has been known as an imaging optical system suitable for a long focal length photographic lens (hereinafter referred to as a telephoto lens). By adopting a telephoto type power arrangement, it is possible to shorten the overall optical length of a telephoto lens, which tends to be long and heavy.

[0003] Telephoto lenses are often used for photographing sports, animals, etc., and require fast autofocusing. If a telephoto lens uses a total extension method in which the entire imaging optical system is moved to focus, the weight of the lens that moves during focusing becomes large, making it difficult to achieve fast autofocusing, so an inner focus method is often used.

[0004] Furthermore, in recent years, telephoto lenses have been increasingly used for video shooting. When used for video shooting, autofocus often uses a contrast detection method. In contrast detection methods, it is common for the focusing unit to perform an operation called wobbling in order to detect contrast, so there is a demand for telephoto lenses equipped with focusing units that are lighter than conventional ones.

[0005] In addition, in recent years, with the spread of compact mirrorless cameras, telephoto lenses are also required to be small and lightweight. To make a telephoto lens small and lightweight, it is important to make the moving part small and lightweight in addition to making the imaging optical system small. This is because the size and arrangement of the actuator depend on the size and weight of the moving part. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6627313 Summary of the Invention [Problem to be solved by the invention]

[0007] Although the imaging optical system described in Patent Document 1 achieves high performance while employing inner focusing, the focusing unit is not sufficiently small and lightweight, and the total optical length relative to the focal length is not sufficiently short.

[0008] The invention has been made in consideration of these circumstances, and has an object to provide an imaging optical system that is suitable for use as a small and lightweight telephoto lens by having a small and lightweight focusing unit and by which the imaging optical system itself is small and lightweight. [Means for solving the problem]

[0009] In order to achieve the above object, an image-forming optical system embodying the present invention has a focusing unit which is made up of a plurality of lenses and moves as a unit during focusing, the maximum air gap among the air gaps formed by the plurality of lenses on an optical axis is located on the object side of the focusing unit closest to the object side, the first group being made up of all of the lenses among the plurality of lenses that are arranged closer to the object side than the focusing unit and having positive power as a whole, the second group being made up of the focusing unit and having negative power as a whole, and the third group being made up of all of the lenses among the plurality of lenses that are arranged closer to the image side than the focusing unit and having negative power as a whole, the third group being made up of, in order from the object side to the image side, an image stabilization unit having negative power as a whole and a rear unit having positive power as a whole, the first group and the rear unit being constantly fixed with respect to the image plane, It is characterized in that the following conditional expression is satisfied. (1) -15.0<Φ_rear / Φ<-5.0 (3) -5.0<Φ_G2 / Φ<-1.0 (6) -15.0<Φ_OS / Φ<-5.0 however, Φ_rear is the power of the partial system formed by the lens adjacent to the image side with the largest air gap to the lens located closest to the image side among the multiple lenses when focusing at infinity, Φ is the power of the imaging optical system when focused at infinity 、 Φ_G2 is the power of the second group, Φ_OS is the power of the image stabilization unit It is.

[0010] In addition, the imaging optical system embodying the present invention is preferably characterized in that the focusing unit has at least one positive lens and at least one negative lens.

[0011] Furthermore, the imaging optical system embodying the present invention is preferably characterized in that the interfaces between the air and all lenses located on the object side of the maximum air space have convex surfaces facing the object side within the effective light diameter.

[0012] Moreover, the image-forming optical system embodying the present invention is preferably characterized in that it satisfies the following conditional expression: (2) 0.40 <LT / f<0.60 however, LT is the distance on the optical axis from the surface closest to the object to the image plane when focusing at infinity. f is the focal length of the imaging optical system when focused at infinity.

[0013] Moreover, the imaging optical system embodying the present invention is preferably characterized in that it does not have a diffractive optical element.

[0014] In addition, the imaging optical system embodying the present invention is preferably characterized in that all of the surfaces having power of the plurality of lenses are spherical.

[0016] Moreover, the image-forming optical system embodying the present invention is preferably characterized in that it satisfies the following conditional expression: (4) -5.0<Φ_G3 / Φ<-1.0 where Φ_G3 is the power of the third group.

[0017] Moreover, the image-forming optical system embodying the present invention is preferably characterized in that it satisfies the following conditional expression: (5) |f / R_G1last|<6.0 Here, R_G1last is the radius of curvature of the surface of the first group that is closest to the image side.

[0018] Moreover, the image-forming optical system embodying the present invention is preferably characterized in that it has an aperture stop between the second group and the third group.

[0020] In addition, the imaging optical system embodying the present invention preferably has an imaging Blur The correction unit is characterized by having at least one positive lens and at least one negative lens. Effect of the Invention

[0021] According to an imaging optical system embodying the present invention, the imaging optical system itself is small and lightweight, and by having a small and lightweight focusing unit, it is possible to provide an imaging optical system suitable for a small and lightweight telephoto lens. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a diagram showing the lens arrangement at infinity according to the first embodiment of the present invention. [Diagram 2] FIG. 4 is a longitudinal aberration diagram at infinity in Example 1 of the present invention. [Diagram 3] 1 is a longitudinal aberration diagram at a shooting distance of 3.2 m in Example 1 of the present invention. [Figure 4] FIG. 4 is a diagram showing lateral aberration at infinity in Example 1 of the present invention. [Diagram 5] 4A to 4C are lateral aberration diagrams at a shooting distance of 3.2 m in Example 1 of the present invention. [Figure 6] FIG. 11 is a lateral aberration diagram of Example 1 of the present invention at infinity with 0.2° image stabilization. [Figure 7] FIG. 11 is a diagram showing the lens arrangement at infinity according to the second embodiment of the present invention. [Figure 8] FIG. 11 is a longitudinal aberration diagram at infinity in Example 2 of the present invention. [Figure 9] FIG. 11 is a longitudinal aberration diagram at a shooting distance of 3.2 m in Example 2 of the present invention. [Figure 10] FIG. 11 is a diagram illustrating lateral aberration at infinity in Example 2 of the present invention. [Figure 11]11A to 11C are lateral aberration diagrams at a shooting distance of 3.2 m in Example 2 of the present invention. [Figure 12] FIG. 11 is a lateral aberration diagram of Example 2 of the present invention at infinity with 0.2° image stabilization. [Figure 13] FIG. 11 is a diagram showing the lens arrangement at infinity according to the third embodiment of the present invention. [Figure 14] FIG. 11 is a longitudinal aberration diagram at infinity in Example 3 of the present invention. [Figure 15] 11A to 11C are longitudinal aberration diagrams at a shooting distance of 3.3 m in Example 3 of the present invention. [Figure 16] FIG. 11 is a diagram illustrating lateral aberration at infinity in Example 3 of the present invention. [Figure 17] 11A to 11C are lateral aberration diagrams at a shooting distance of 3.3 m in Example 3 of the present invention. [Figure 18] FIG. 11 is a lateral aberration diagram of Example 3 of the present invention at infinity with 0.2° image stabilization. [Figure 19] FIG. 11 is a diagram showing the lens arrangement at infinity according to the fourth embodiment of the present invention. [Figure 20] FIG. 11 is a longitudinal aberration diagram at infinity in Example 4 of the present invention. [Figure 21] 13A to 13C are longitudinal aberration diagrams at a shooting distance of 3.1 m in Example 4 of the present invention. [Figure 22] FIG. 11 is a diagram illustrating lateral aberration at infinity in Example 4 of the present invention. [Diagram 23] 13A to 13C are lateral aberration diagrams at a shooting distance of 3.1 m in Example 4 of the present invention. [Figure 24] FIG. 13 is a lateral aberration diagram of Example 4 of the present invention at infinity with 0.2° image stabilization. [Diagram 25] FIG. 13 is a diagram showing the lens arrangement at infinity according to the fifth embodiment of the present invention. [Figure 26] FIG. 13 is a longitudinal aberration diagram at infinity in Example 5 of the present invention. [Figure 27] 13A to 13C are longitudinal aberration diagrams at a shooting distance of 4.6 m in Example 5 of the present invention. [Figure 28] FIG. 13 is a diagram illustrating lateral aberration at infinity in Example 5 of the present invention. [Figure 29] 13A to 13C are lateral aberration diagrams at a shooting distance of 4.6 m in Example 5 of the present invention. [Diagram 30] FIG. 13 is a lateral aberration diagram of Example 5 of the present invention at infinity with 0.2° image stabilization. [Diagram 31] FIG. 13 is a diagram showing the lens arrangement at infinity according to the sixth embodiment of the present invention. [Diagram 32] FIG. 13 is a longitudinal aberration diagram at infinity in Example 6 of the present invention. [Diagram 33] 13A to 13C are longitudinal aberration diagrams at a shooting distance of 2.6 m in Example 6 of the present invention. [Diagram 34] FIG. 13 is a diagram illustrating lateral aberration at infinity in Example 6 of the present invention. [Diagram 35] 13A to 13C are lateral aberration diagrams at a shooting distance of 2.6 m in Example 6 of the present invention. [Diagram 36] FIG. 13 is a lateral aberration diagram of Example 6 of the present invention at infinity with 0.2° image stabilization. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The imaging optical system of the present invention will be described. As can be seen from the lens configuration diagrams shown in Figures 1, 7, 13, 19, 25, and 31, the imaging optical system of the present invention is characterized in that it is made up of multiple lenses, has a focusing unit that moves as a unit during focusing, and the maximum air gap among the air gaps formed by the multiple lenses on the optical axis is located closer to the object side than the side closest to the object of the focusing unit, and satisfies the following conditional expression: (1) -15.0<Φ_rear / Φ<-5.0 however, Φ_rear is the power of the partial system formed by the lens adjacent to the image side with the largest air gap to the lens located closest to the image side among the multiple lenses when focusing at infinity, Φ is the power of the imaging optical system when focused at infinity.

[0024] Conditional formula (1) specifies the ratio of the power of the partial system consisting of the lens adjacent to the image side of the maximum air space to the lens arranged most image side among the multiple lenses (hereinafter referred to as the image side partial system) to the power of the imaging optical system. When the image side partial system satisfies conditional formula (1), the image side partial system has a strong negative power as a whole. In this case, since the entire system becomes an imaging optical system, the partial system consisting of all the lenses arranged on the object side of the maximum air space (hereinafter referred to as the object side partial system) has a positive power as a whole. By arranging the object side partial system having a positive power and the image side partial system having a strong negative power separated by the maximum air space, it is possible to configure a telephoto type power arrangement that brings about a strong effect of shortening the total length of the imaging optical system. In addition, the convergence effect of the object side partial system makes it easy to reduce the diameter of the focusing unit arranged in the image side partial system. The smaller the diameter of the focusing unit, the easier it is to make it small and lightweight, and the actuator for moving it is also easy to make it small and lightweight. This makes it easy to make it small and lightweight as a telephoto lens.

[0025] If the negative power of the image-side subsystem becomes smaller beyond the upper limit of conditional formula (1), the power arrangement of the telephoto type will be weakened and the effect of shortening the overall length will be reduced, which is undesirable. It will also be difficult to lower the height of the light beam incident on the image-side subsystem, which is unfavorable for making the diameter of the focusing unit smaller. If the negative power of the image-side subsystem becomes larger beyond the lower limit of conditional formula (1), the symmetry of the power arrangement of the imaging optical system will become too poor, making it difficult to correct distortion, which is undesirable.

[0026] By setting the upper limit of condition (1) to -6.0, the above-mentioned effect can be more reliably achieved, which is preferable, and by setting the lower limit of condition (1) to -14.0, the above-mentioned effect can be more reliably achieved, which is preferable.

[0027] Furthermore, the imaging optical system of the present invention is characterized in that the focusing unit has at least one positive lens and at least one negative lens.

[0028] By having the focusing unit have at least one positive lens and at least one negative lens, it becomes possible for the focusing unit itself to correct axial chromatic aberration, and good performance can be obtained over a wide range of shooting distances.

[0029] Furthermore, the imaging optical system of the present invention is characterized in that the interface between the air and all lenses arranged closer to the object than the maximum air space faces the object side as a convex surface within the effective ray diameter. In all lenses arranged closer to the object than the maximum air space, the axial marginal ray passes through a high position, which tends to cause spherical aberration, but by making the interface between the lens and the air face the convex surface toward the object side, the shape becomes close to aplanatic, making it possible to reduce the occurrence of spherical aberration.

[0030] The imaging optical system of the present invention is further characterized in that it satisfies the following condition: (2) 0.40 <LT / f<0.60 where LT is the distance on the optical axis from the surface closest to the object to the image plane when focusing at infinity, f is the focal length of the imaging optical system when focused at infinity.

[0031] Condition (2) defines the ratio of the total optical length of the image-forming optical system to the focal length when the image-forming optical system is focused at infinity.

[0032] If the total optical length becomes too long, exceeding the upper limit of conditional formula (2), it becomes difficult to achieve a small and lightweight telephoto lens.If the total optical length becomes too short, exceeding the lower limit of conditional formula (2), the amount of movement of the focusing unit cannot be made large, and in order to achieve a practical shortest shooting distance, the magnification of the focusing unit must be increased, which increases the aberrations generated by the focusing unit and makes it difficult to obtain good performance over a wide range of shooting distances.

[0033] By setting the upper limit of condition (2) to 0.59, the above-mentioned effect can be more reliably achieved, which is preferable, and by setting the lower limit of condition (2) to 0.45, the above-mentioned effect can be more reliably achieved, which is preferable.

[0034] Furthermore, the imaging optical system of the present invention is characterized in that it does not use a diffractive optical element. A diffractive optical element can have a chromatic aberration correction effect and an aspheric effect on the diffractive surface, but the shape of the element causes unwanted diffracted light and flare due to light rays outside the angle of view. Since the imaging optical system of the present invention does not use a diffractive optical element, it is easier to suppress the occurrence of flare and ghosting compared to when a diffractive optical element is used.

[0035] Furthermore, the imaging optical system of the present invention is characterized in that all surfaces having power are spherical. Spherical lenses can be processed equally even if rotation occurs around the center of the sphere during processing, so they are easier to manufacture than non-spherical lenses. Since the lenses that make up the imaging optical system of a telephoto lens tend to have large diameters, it is desirable to be able to obtain lenses with good processing accuracy at low processing costs.

[0036] Furthermore, the image-forming optical system of the present invention comprises a first group consisting of all of the multiple lenses that are arranged on the object side of the focusing unit and has positive power as a whole, a second group consisting of the focusing unit and has negative power as a whole, and a third group consisting of all of the multiple lenses that are arranged on the image side of the focusing unit and has negative power as a whole, and is characterized in that it satisfies the following conditional expressions: (3) -5.0<Φ_G2 / Φ<-1.0 where Φ_G2 is the power of the second group.

[0037] Condition (3) defines a preferable range for the ratio of the power of the second lens group to that of the imaging optical system.

[0038] If the upper limit of condition (3) is exceeded and the negative power of the second group becomes smaller, the amount of movement of the second group during focusing becomes large, making it difficult to reduce the size of the image-forming optical system.If the lower limit of condition (3) is exceeded and the negative power of the second group becomes large, aberrations, especially astigmatism, become more likely to occur in the second group, which is the focusing unit, making it difficult to obtain good performance over a wide shooting distance range.

[0039] By setting the upper limit of condition (3) to -3.0, the above-mentioned effect can be more reliably achieved, which is preferable, and by setting the lower limit of condition (3) to -4.6, the above-mentioned effect can be more reliably achieved, which is preferable.

[0040] Further, the imaging optical system of the present invention is characterized in that it satisfies the following conditional expression: (4) -5.0<Φ_G3 / Φ<-1.0 where Φ_G3 is the power of the third group.

[0041] Condition (4) sets forth the ratio of power between the third lens group and the entire system.

[0042] If the upper limit of condition (4) is exceeded and the negative power of the third group becomes small, it is necessary to increase the negative power of the second group in order to maintain the power arrangement of a telephoto type while maintaining the focal length of the entire system. If the negative power of the second group, which is the focusing unit, becomes too large, the variation in astigmatism during focusing increases, making it difficult to obtain good performance over a wide range of shooting distances. If the negative power of the third group becomes large and the lower limit of condition (4) is exceeded, it becomes difficult to ensure sufficient back focus. If the back focus becomes small, the light beam at the peripheral angle of view passes through a position higher from the optical axis when passing through the third group, making it difficult to suppress the occurrence of astigmatism.

[0043] It is preferable to set the upper limit of condition (4) to -1.3, since this makes the above-mentioned effect more certain, and it is preferable to set the lower limit of condition (4) to -4.0, since this makes the above-mentioned effect more certain.

[0044] The imaging optical system of the present invention is further characterized in that it satisfies the following condition: (5) |f / R_G1last|<6.0 Here, R_G1last is the radius of curvature of the surface of the first group that is closest to the image side.

[0045] Condition (5) sets forth the ratio of the focal length of the entire system when focused at infinity to the radius of curvature of the surface of the first lens group closest to the image.

[0046] If the upper limit of condition (5) is exceeded and the curvature of the surface of the first group closest to the image becomes too strong, the coma and astigmatism generated by that surface will become large, making it difficult to obtain good imaging performance.

[0047] By setting the upper limit of condition (5) to 5.0, the above-mentioned effect can be ensured more reliably, which is preferable.

[0048] Further, the imaging optical system of the present invention is characterized in that it has an aperture stop between the second and third groups.

[0049] By placing the aperture diaphragm between the second and third groups, the aperture diaphragm can be made smaller due to the converging effect of the first group. Also, by placing the aperture diaphragm between the second and third groups, the second group, which is the movable group, can be placed in a position where the light beam at the peripheral angle of view is low, making it possible to reduce the diameter of the movable group. This enables high-speed focusing, and furthermore, the actuator of the focusing unit can be made smaller, making it possible to make the telephoto lens smaller and lighter.

[0050] Furthermore, in the imaging optical system of the present invention, the third group comprises, in order from the object side to the image side, an image blur correction unit having negative power as a whole and a rear unit having positive power as a whole, the image blur correction unit is movable in a direction perpendicular to the optical axis so as to reduce image blur caused by shake of the imaging optical system, the first group and the rear unit are always fixed with respect to the image plane, and the following conditional expression is satisfied: (6) -15.0<Φ_OS / Φ<-5.0 Here, Φ_OS is the power of the image stabilization unit.

[0051] By locating a rear unit with positive power, it is possible to increase the negative power of the image stabilization unit while maintaining the negative power of the third group, making it possible to increase the amount of image stabilization relative to the amount of movement of the image stabilization unit (hereinafter referred to as the vibration reduction coefficient). Increasing the vibration reduction coefficient reduces the amount of movement of the image stabilization unit, making it possible to reduce the size of the actuator, which is advantageous for making telephoto lenses smaller and lighter.

[0052] Condition (6) defines the ratio of the power of the image stabilization unit to the power of the imaging optical system.

[0053] If the power of the image stabilization unit decreases beyond the upper limit of conditional formula (6), the vibration reduction coefficient decreases, making it necessary to increase the drive amount of the image stabilization unit, making it difficult to reduce the size of the actuator and, ultimately, the telephoto lens.If the power of the image stabilization unit increases beyond the lower limit of conditional formula (6), the vibration reduction coefficient increases, but the aberrations generated in the image stabilization unit increase, and the fluctuations in coma aberration and astigmatism when driven in a direction perpendicular to the optical axis increase, making it difficult to obtain good performance during image stabilization.

[0054] It is preferable to set the upper limit of condition (6) to -8.0, since this makes the above-mentioned effect more certain, and it is preferable to set the lower limit of condition (6) to -12.0, since this makes the above-mentioned effect more certain.

[0055] Furthermore, the imaging optical system of the present invention Blur The correction unit is characterized by having at least one positive lens and at least one negative lens.

[0056] The image stabilization unit has at least one positive lens and one negative lens. Blur It becomes possible to correct chromatic aberration within the correction unit, and good performance can be obtained during image blur correction.

[0057] Next, the lens configuration of an embodiment of the imaging optical system of the present invention will be described. In the following description, the lens configuration will be described in order from the object side to the image side. EXAMPLES

[0058] FIG. 1 is a lens configuration diagram of an imaging optical system according to a first embodiment of the present invention.

[0059] The first group is composed of a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus negative lens L3 with a convex surface facing the object side, a cemented lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a cemented lens consisting of a meniscus negative lens L6 with a convex surface facing the object side and a biconvex positive lens L7, and has positive power as a whole. The first group is always fixed with respect to the image plane.

[0060] The second lens group is made up of a cemented lens consisting of a meniscus positive lens L8 with its convex surface facing the object side and a meniscus negative lens L9 with its convex surface facing the object side, and has negative power as a whole. The second lens group moves from the object side to the image side on the optical axis when focusing from an object at infinity to a close object.

[0061] The third group is made up of an image stabilization unit and a rear unit, and has negative power overall. The third group is fixed relative to the image plane during focusing.

[0062] The image stabilization unit is composed of a meniscus-shaped positive lens L10 with a convex surface facing the image side and a biconcave negative lens L11, and has a negative power as a whole. The image stabilization unit also moves in a direction perpendicular to the optical axis to reduce image blur caused by shaking of the imaging optical system.

[0063] The rear unit is composed of a biconvex positive lens L12, a meniscus negative lens L13 with its convex surface facing the image side, a biconvex positive lens L14, and a cemented lens consisting of a biconcave negative lens L15 and a biconvex positive lens L16, and has a positive power as a whole. The rear unit is always fixed with respect to the image plane.

[0064] The object-side subsystem is made up of L1 to L5 and has a positive overall power. The image-side subsystem is made up of L6 to L16 and has a negative overall power. The second lens group is included as a focusing unit.

[0065] The aperture stop is located between the second and third groups. EXAMPLES

[0066] FIG. 7 is a lens configuration diagram of an imaging optical system according to a second embodiment of the present invention.

[0067] The first group is composed of a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus negative lens L3 with a convex surface facing the object side, a cemented lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a cemented lens consisting of a meniscus negative lens L6 with a convex surface facing the object side and a biconvex positive lens L7, and has positive power as a whole. The first group is always fixed with respect to the image plane.

[0068] The second lens group is made up of a cemented lens consisting of a biconvex positive lens L8 and a biconcave negative lens L9, and has a negative overall power. The second lens group moves along the optical axis from the object side to the image side when focusing from an object at infinity to a close object.

[0069] The third group is made up of an image stabilization unit and a rear unit, and has negative power overall. The third group is fixed relative to the image plane during focusing.

[0070] The image stabilization unit is composed of a meniscus-shaped positive lens L10 with a convex surface facing the image side and a biconcave negative lens L11, and has a negative power as a whole. The image stabilization unit also moves in a direction perpendicular to the optical axis to reduce image blur caused by shaking of the imaging optical system.

[0071] The rear unit is composed of a biconvex positive lens L12, a meniscus negative lens L13 with its convex surface facing the image side, a biconvex positive lens L14, and a cemented lens consisting of a biconcave negative lens L15 and a biconvex positive lens L16, and has a positive power as a whole. The rear unit is always fixed with respect to the image plane.

[0072] The object-side subsystem is made up of L1 to L5 and has a positive overall power. The image-side subsystem is made up of L6 to L16 and has a negative overall power. The second lens group is included as a focusing unit.

[0073] The aperture stop is located between the second and third groups. EXAMPLES

[0074] FIG. 13 is a lens configuration diagram of an imaging optical system according to a third embodiment of the present invention.

[0075] The first group is composed of a meniscus positive lens L1 with its convex surface facing the object side, a meniscus positive lens L2 with its convex surface facing the object side, a meniscus negative lens L3 with its convex surface facing the object side, a cemented lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a cemented lens consisting of a biconcave negative lens L6 and a biconvex positive lens L7, and has positive power as a whole. The first group is always fixed with respect to the image plane.

[0076] The second lens group is made up of a cemented lens consisting of a meniscus positive lens L8 with its convex surface facing the object side and a meniscus negative lens L9 with its convex surface facing the object side, and has negative power as a whole. The second lens group moves from the object side to the image side on the optical axis when focusing from an object at infinity to a close object.

[0077] The third group is made up of an image stabilization unit and a rear unit, and has negative power overall. The third group is fixed relative to the image plane during focusing.

[0078] The image stabilization unit is composed of a meniscus-shaped positive lens L10 with a convex surface facing the image side and a biconcave negative lens L11, and has a negative power as a whole. The image stabilization unit also moves in a direction perpendicular to the optical axis to reduce image blur caused by shaking of the imaging optical system.

[0079] The rear unit is composed of a biconvex positive lens L12, a meniscus negative lens L13 with its convex surface facing the image side, a biconvex positive lens L14, and a cemented lens consisting of a biconcave negative lens L15 and a biconvex positive lens L16, and has a positive power as a whole. The rear unit is always fixed with respect to the image plane.

[0080] The object-side subsystem is made up of L1 to L5 and has a positive overall power. The image-side subsystem is made up of L6 to L16 and has a negative overall power. The second lens group is included as a focusing unit.

[0081] The aperture stop is located between the second and third groups. EXAMPLES

[0082] FIG. 19 is a lens configuration diagram of an imaging optical system according to a fourth embodiment of the present invention.

[0083] The first group is composed of a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus negative lens L3 with a convex surface facing the object side, a cemented lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a cemented lens consisting of a meniscus negative lens L6 with a convex surface facing the object side and a biconvex positive lens L7, and has positive power as a whole. The first group is always fixed with respect to the image plane.

[0084] The second lens group is made up of a cemented lens consisting of a meniscus positive lens L8 with its convex surface facing the object side and a meniscus negative lens L9 with its convex surface facing the object side, and has negative power as a whole. The second lens group moves from the object side to the image side on the optical axis when focusing from an object at infinity to a close object.

[0085] The third group is made up of an image stabilization unit and a rear unit, and has negative power overall. The third group is fixed relative to the image plane during focusing.

[0086] The image stabilization unit is composed of a meniscus-shaped positive lens L10 with a convex surface facing the image side and a biconcave negative lens L11, and has a negative power as a whole. The image stabilization unit also moves in a direction perpendicular to the optical axis to reduce image blur caused by shaking of the imaging optical system.

[0087] The rear unit is composed of a biconvex positive lens L12, a meniscus negative lens L13 with its convex surface facing the image side, a biconvex positive lens L14, and a cemented lens consisting of a biconcave negative lens L15 and a biconvex positive lens L16, and has a positive power as a whole. The rear unit is always fixed with respect to the image plane.

[0088] The object-side subsystem is made up of L1 to L5 and has a positive overall power. The image-side subsystem is made up of L6 to L16 and has a negative overall power. The second lens group is included as a focusing unit.

[0089] The aperture stop is located between the second and third groups. EXAMPLES

[0090] FIG. 25 is a lens configuration diagram of an imaging optical system according to a fifth embodiment of the present invention.

[0091] The first group is composed of a meniscus positive lens L1 with its convex surface facing the object side, a meniscus positive lens L2 with its convex surface facing the object side, a meniscus negative lens L3 with its convex surface facing the object side, a cemented lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a cemented lens consisting of a biconcave negative lens L6 and a biconvex positive lens L7, and has positive power as a whole. The first group is always fixed with respect to the image plane.

[0092] The second lens group is made up of a cemented lens consisting of a meniscus positive lens L8 with its convex surface facing the object side and a meniscus negative lens L9 with its convex surface facing the object side, and has negative power as a whole. The second lens group moves from the object side to the image side on the optical axis when focusing from an object at infinity to a close object.

[0093] The third group is made up of an image stabilization unit and a rear unit, and has negative power overall. The third group is fixed relative to the image plane during focusing.

[0094] The image stabilization unit is composed of a meniscus-shaped positive lens L10 with a convex surface facing the image side and a biconcave negative lens L11, and has a negative power as a whole. The image stabilization unit also moves in a direction perpendicular to the optical axis to reduce image blur caused by shaking of the imaging optical system.

[0095] The rear unit is composed of a biconvex positive lens L12, a biconcave negative lens L13, a biconvex positive lens L14, and a cemented lens consisting of a biconcave negative lens L15 and a biconvex positive lens L16, and has a positive power as a whole. The rear unit is always fixed with respect to the image plane.

[0096] The object-side subsystem is made up of L1 to L5 and has a positive overall power. The image-side subsystem is made up of L6 to L16 and has a negative overall power. The second lens group is included as a focusing unit.

[0097] The aperture stop is located between the second and third groups. EXAMPLES

[0098] FIG. 31 is a lens configuration diagram of an imaging optical system according to a sixth embodiment of the present invention.

[0099] The first group is composed of a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus negative lens L3 with a convex surface facing the object side, a cemented lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a cemented lens consisting of a meniscus negative lens L6 with a convex surface facing the object side and a biconvex positive lens L7, and has positive power as a whole. The first group is always fixed with respect to the image plane.

[0100] The second lens group is made up of a cemented lens consisting of a biconvex positive lens L8 and a biconcave negative lens L9, and has a negative overall power. The second lens group moves along the optical axis from the object side to the image side when focusing from an object at infinity to a close object.

[0101] The third group is made up of an image stabilization unit and a rear unit, and has negative power overall. The third group is fixed relative to the image plane during focusing.

[0102] The image stabilization unit is composed of a meniscus-shaped positive lens L10 with a convex surface facing the image side and a biconcave negative lens L11, and has a negative power as a whole. The image stabilization unit also moves in a direction perpendicular to the optical axis to reduce image blur caused by shaking of the imaging optical system.

[0103] The rear unit is composed of a biconvex positive lens L12, a meniscus negative lens L13 with its convex surface facing the image side, a biconvex positive lens L14, and a cemented lens consisting of a biconcave negative lens L15 and a biconvex positive lens L16, and has a positive power as a whole. The rear unit is always fixed with respect to the image plane.

[0104] The object-side subsystem is made up of L1 to L5 and has a positive overall power. The image-side subsystem is made up of L6 to L16 and has a negative overall power. The second lens group is included as a focusing unit.

[0105] The aperture stop is located between the second and third groups.

[0106] Specific numerical data for each of the embodiments of the imaging optical system of the present invention described above will be shown below.

[0107] In [Surface Data], the surface number is the lens surface or aperture stop number counted from the object side, r is the radius of curvature of each surface, d is the spacing between each surface, nd is the refractive index for the d line (wavelength 587.56 nm), and vd is the Abbe number for the d line.

[0108] BF stands for back focus.

[0109] The (diaphragm) next to a surface number indicates that an aperture diaphragm is located at that position. The radius of curvature for the plane or aperture diaphragm is marked as ∞ (infinity).

[0110] [Various data] shows values ​​such as focal length for each shooting distance.

[0111] [Variable Distance Data] shows the variable distance and BF values ​​for each shooting distance.

[0112] [Lens Group Data] shows the surface number of each lens group closest to the object and the composite focal length of the entire group.

[0113] In addition, for all of the values ​​of the following specifications, the focal length f, radius of curvature r, lens surface spacing d, and other length units are given in millimeters (mm) unless otherwise specified; however, since the optical system provides equivalent optical performance with proportional magnification and proportional reduction, this is not limited to this.

[0114] Also shown is a list of values ​​corresponding to the conditional expressions in each of these embodiments.

[0115] In addition, in the aberration diagrams corresponding to the respective embodiments, d, g, and C represent the d-line, g-line, and C-line, respectively, and ΔS and ΔM represent the sagittal image surface and the meridional image surface, respectively.

[0116] Numerical Example 1 Unit: mm [Face data] Surface number rd nd vd Object surface ∞ (d0) 1 119.2611 6.6240 1.49700 81.61 2 433.4676 0.1500 3 85.3050 11.0775 1.43700 95.10 4 3375.4296 2.9340 5 84.6193 2.0000 1.69680 55.46 6 58.0189 6.2967 7 59.8186 13.7547 1.43700 95.10 8 -242.6628 1.5000 1.77250 49.62 9 155.1542 56.9376 10 190.8764 1.0000 1.77250 49.62 11 32.6704 6.4954 1.54814 45.82 12 -932.6729 (d12) 13 85.8484 2.6267 1.68893 31.16 14 8483.6313 1.0000 1.77250 49.62 15 46.6606 (d15) 16(Aperture) ∞ 14.2674 17 -130.7700 3.1839 1.85451 25.15 18 -33.5045 0.1500 19 -34.6700 1.0000 1.81600 46.62 20 50.4521 2.7593 21 30.3869 4.6654 1.60342 38.01 22 -46.4305 2.5867 23 -41.4459 1.0000 1.94595 17.98 24 -650.5232 12.7120 25 73.6903 3.3435 1.73037 32.23 26 -73.6903 3.8400 27 -34.3840 1.0000 1.76385 48.49 28 29.4014 5.0955 1.65412 39.68 29 -101.8791 (BF) Image plane ∞ [Various data] Shooting distance INF 3.2m Focal length 485.00 300.92 F-number 5.83 5.96 Full angle of view 2ω 5.06 4.04 Image height Y 21.63 21.63 Lens length 253.13 253.13 [Variable interval data] Shooting distance INF 3.2m d0∞2897.66 d12 5.2654 24.0782 d15 21.9248 3.1121 BF 58.0348 58.0348 [Lens group data] Group starting plane focal length Group 1 1 182.78 Group 2 13 -121.25 Group 3 17 -167.24 FG 1 158.86 RG 10 -50.52 IU 17 -48.02 RU 21 62.33

[0117] Numerical Example 2 Unit: mm [Face data] Surface number rd nd vd Object surface ∞ (d0) 1 132.7896 7.2275 1.49700 81.61 2 490.3147 0.1500 3 86.6652 13.5172 1.43700 95.10 4 4145.0474 1.0751 5 89.8911 2.0000 1.69680 55.46 6 61.9436 8.4767 7 62.9088 14.7435 1.43700 95.10 8 -254.1522 1.5000 1.77250 49.62 9 174.7312 56.4562 10 232.2525 1.0000 1.77250 49.62 11 33.1982 6.5857 1.54814 45.82 12 -999.9996 (d12) 13 94.3610 4.2099 1.68431 26.83 14 -213.3243 1.0000 1.76200 40.10 15 46.8849 (d15) 16(Aperture) ∞ 4.2070 17 -116.3284 2.9024 1.85451 25.15 18 -36.2147 0.1500 19 -37.9787 1.0000 1.81600 46.62 20 57.2563 5.4060 21 38.1020 4.3615 1.60342 38.01 22 -47.0210 3.6162 23 -39.9528 1.0000 1.94595 17.98 24 -222.5717 18.6417 25 107.8590 3.2971 1.73037 32.23 26 -72.6238 3.8444 27 -45.1268 1.0000 1.76385 48.49 28 35.2550 5.1797 1.65412 39.68 29 -93.9194 (BF) Image plane ∞ [Various data] Shooting distance INF 3.2m Focal length 500.00 334.70 F-number 5.82 5.82 Full angle of view 2ω 4.91 3.78 Image height Y 21.63 21.63 Lens total length 270.00 270.00 [Variable interval data] Shooting distance INF 3.2m d0∞2968.94 d12 9.0157 28.6714 d15 22.5963 2.9407 BF 65.8401 65.8401 [Lens group data] Group starting plane focal length Group 1 1 190.20 Group 2 13 -111.11 Group 3 17 -354.21 FG 1 158.33 RG 10 -66.67 IU 17 -51.08 RU 21 67.61

[0118] Numerical Example 3 Unit: mm [Face data] Surface number rd nd vd Object surface ∞ (d0) 1 104.8476 9.4077 1.49700 81.61 2 413.7163 0.3733 3 82.1089 11.2633 1.43700 95.10 4 974.1459 0.1500 5 83.5281 2.0000 1.69680 55.46 6 56.1151 1.3777 7 60.0062 14.9793 1.43700 95.10 8 -315.0736 1.5000 1.77250 49.62 9 159.6367 52.6707 10 -408.4151 1.0000 1.77250 49.62 11 36.3722 7.5571 1.54814 45.82 12 -151.9841 (d12) 13 96.8455 2.5379 1.69895 30.05 14 411.5673 1.0000 1.77250 49.62 15 54.4870 (d15) 16(Aperture) ∞ 26.0417 17 -123.0398 3.5040 1.85451 25.15 18 -32.8891 0.1500 19 -33.8925 1.0000 1.80420 46.50 20 49.6766 2.0000 21 29.4289 5.8082 1.60342 38.01 22 -41.2645 1.8018 23 -39.1421 1.0000 1.94595 17.98 24 -273.7761 10.7608 25 66.9422 6.0897 1.73037 32.23 26 -66.9422 2.2066 27 -33.2576 1.0000 1.76385 48.49 28 26.7870 7.9451 1.65412 39.68 29 -270.2044 (BF) Image plane ∞ [Various data] Shooting distance INF 3.3m Focal length 500.00 303.50 F-number 5.84 6.06 Full angle of view 2ω 4.91 3.99 Image height Y 21.63 21.63 Lens total length 258.28 258.28 [Variable interval data] Shooting distance INF 3.3m d0∞3035.33 d12 2.6622 24.7309 d15 25.6290 3.5603 BF 54.8681 54.8682 [Lens group data] Group starting plane focal length Group 1 1 197.95 Group 2 13 -152.17 Group 3 17 -147.14 FG 1 146.31 RG 10 -41.67 IU 17 -47.65 RU 21 59.54

[0119] Numerical Example 4 Unit: mm [Face data] Surface number rd nd vd Object surface ∞ (d0) 1 118.4940 7.4746 1.49700 81.61 2 497.5543 0.1500 3 87.0510 11.5566 1.43700 95.10 4 3000.0000 2.2086 5 83.8450 2.0000 1.69680 55.46 6 57.4441 3.9993 7 59.4130 14.3551 1.43700 95.10 8 -265.2374 1.5000 1.77250 49.62 9 151.2425 59.6565 10 196.6581 1.0000 1.77250 49.62 11 31.7509 5.8651 1.54814 45.82 12 -677.7707 (d12) 13 81.4010 2.4593 1.68893 31.16 14 606.6246 1.0000 1.77250 49.62 15 46.3432 (d15) 16(Aperture) ∞ 15.7214 17 -107.5844 2.1403 1.85451 25.15 18 -31.2750 0.1500 19 -32.1449 1.0000 1.81600 46.62 20 48.9219 4.9874 21 32.6812 4.8578 1.60342 38.01 22 -48.0733 2.8832 23 -41.8891 1.0000 1.94595 17.98 24 -460.1382 14.6638 25 83.8285 3.9811 1.73037 32.23 26 -83.8285 1.9267 27 -41.1497 1.0000 1.76385 48.49 28 30.7516 6.3773 1.65412 39.68 29 -79.9169 (BF) Image plane ∞ [Various data] Shooting distance INF 3.1m Focal length 485.00 319.16 F-number 5.83 5.96 Full angle of view 2ω 5.08 4.05 Image height Y 21.63 21.63 Lens length 254.81 254.81 [Variable interval data] Shooting distance INF 3.1m d0∞2887.25 d12 2.1558 21.6282 d15 22.6685 3.1961 BF 56.0703 56.0704 [Lens group data] Group starting plane focal length Group 1 1 179.56 Group 2 13 -128.48 Group 3 17 -196.35 FG 1 156.49 RG 10 -60.63 IU 17 -43.95 RU 21 64.49

[0120] Numerical Example 5 Unit: mm [Face data] Surface number rd nd vd Object surface ∞ (d0) 1 122.0032 6.5753 1.49700 81.61 2 362.2572 0.1500 3 81.7246 15.5232 1.43700 95.10 4 1587.5973 3.1606 5 87.5234 2.0000 1.69680 55.46 6 60.0592 4.6518 7 64.0712 19.3517 1.43700 95.10 8 -237.3564 1.5000 1.77250 49.62 9 145.0015 53.0902 10 -207.7836 1.0000 1.77250 49.62 11 39.6508 7.1853 1.56732 42.84 12 -142.2806 (d12) 13 108.2683 2.3840 1.72047 34.71 14 987.3720 1.0000 1.77250 49.62 15 63.3372 (d15) 16(Aperture) ∞ 17.0894 17 -155.5416 3.0994 1.85451 25.15 18 -38.7691 0.1500 19 -39.5427 1.0000 1.80420 46.50 20 65.9488 2.6262 21 31.7510 4.2410 1.63980 34.47 22 -50.8359 1.7967 23 -53.7225 1.0000 1.94595 17.98 24 311.7173 15.5141 25 96.2367 2.2100 1.73037 32.23 26 -96.2367 1.1430 27 -34.2210 1.0000 1.76385 48.49 28 30.9926 6.8694 1.65412 39.68 29 -85.3917 (BF) Image plane ∞ [Various data] Shooting distance INF 4.6m Focal length 700.00 436.52 F-number 7.97 8.63 Full angle of view 2ω 3.52 2.84 Image height Y 21.63 21.63 Lens length 318.72 318.72 [Variable interval data] Shooting distance INF 4.6m d0∞4269.75 d12 7.2639 33.2898 d15 34.4744 8.4485 BF 101.6710 101.6710 [Lens group data] Group starting plane focal length Group 1 1 254.19 Group 2 13 -187.57 Group 3 17 -204.18 FG 1 172.00 RG 10 -51.74 IU 17 -62.41 RU 21 82.07

[0121] Numerical Example 6 Unit: mm [Face data] Surface number rd nd vd Object surface ∞ (d0) 1 138.9435 5.8763 1.49700 81.61 2 796.2817 0.1500 3 77.3072 11.1439 1.43700 95.10 4 5000.0000 0.1500 5 81.7250 2.0000 1.69680 55.46 6 56.0733 7.2002 7 56.4212 13.4955 1.43700 95.10 8 -236.9611 1.5000 1.77250 49.62 9 146.6151 52.7808 10 128.0838 1.0000 1.77250 49.62 11 30.0957 6.2584 1.54814 45.82 12 -500.0078 (d12) 13 80.5300 2.8854 1.68893 31.16 14 -304.9472 1.0000 1.77250 49.62 15 42.5984 (d15) 16(Aperture) ∞ 3.6396 17 -103.1170 2.9553 1.85451 25.15 18 -34.8637 0.1500 19 -36.6463 1.0000 1.81600 46.62 20 52.3987 2.0118 21 36.5369 3.9536 1.60342 38.01 22 -49.7721 2.4288 23 -41.9668 1.0000 1.94595 17.98 24 -334.2943 20.1070 25 85.6564 3.7563 1.73037 32.23 26 -85.6564 10.2444 27 -38.8582 1.0000 1.76385 48.49 28 83.5111 3.7787 1.65412 39.68 29 -86.1326 (BF) Image plane ∞ [Various data] Shooting distance INF 2.6m Focal length 400.00 265.72 F-number 5.06 5.06 Full angle of view 2ω 6.14 4.87 Image height Y 21.63 21.63 Lens length 233.14 233.14 [Variable interval data] Shooting distance INF 2.6m d0∞2365.92 d12 2.1500 17.6287 d15 20.4541 4.9754 BF 49.0742 49.0742 [Lens group data] Group starting plane focal length Group 1 1 149.45 Group 2 13 -105.27 Group 3 17 -181.82 FG 1 146.81 RG 10 -60.61 IU 17 -45.98 RU 21 62.77

[0122] Example corresponding values ex1 ex2 ex3 ex4 ex5 ex6 1) -10.1 -9.8 -10.5 -11.0 -11.2 -8.7 2) 0.52 0.54 0.52 0.53 0.46 0.58 3) -4.0 -4.5 -3.3 -3.8 -3.7 -3.8 4) -2.9 -1.4 -3.4 -2.5 -3.4 -2.2 5) 0.5 0.5 3.3 0.7 4.9 0.8 6) -9.6 -7.5 -12.0 -8.0 -13.5 -6.6 [Explanation of symbols]

[0123] G1 Group 1 G2 2nd group G3 3rd group FG object side subsystem RG image side subsystem IU Image Stabilization Unit RU Rear unit S aperture stop I image plane

Claims

1. It consists of several lenses, A focusing unit that moves as a unit during focusing is provided. a maximum air gap among the air gaps formed by the plurality of lenses on the optical axis is located on the object side of the most object-side surface of the focusing unit; a first lens group including all of the lenses among the plurality of lenses that are disposed closer to the object side than the focusing unit and that has a positive power as a whole; a second lens group including the focusing unit and having a negative power as a whole; a third group including all of the lenses among the plurality of lenses that are disposed closer to the image side than the focusing unit, the third group having negative power as a whole; the third lens unit comprises, in order from the object side to the image side, an image blur correction unit having a negative power as a whole and a rear unit having a positive power as a whole; the first group and the rear unit are always fixed with respect to an image plane, An imaging optical system characterized by satisfying the following conditional expression: (1) -15.0<Φ_rear / Φ<-5.0 (3) -5.0<Φ_G2 / Φ<-1.0 (6) -15.0<Φ_OS / Φ<-5.0 however, Φ_rear is the power of the partial system formed from the lens adjacent to the image side with the largest air gap to the lens arranged closest to the image side among the multiple lenses when focusing at infinity, Φ is the power of the imaging optical system when focused at infinity, Φ_G2 is the power of the second group, Φ_OS is the power of the image stabilization unit.

2. 2. The imaging optical system according to claim 1, wherein the focusing unit has at least one positive lens and at least one negative lens.

3. 3. The imaging optical system according to claim 1, wherein interfaces between all lenses arranged closer to the object side than the maximum air space and the air have convex surfaces facing the object side within an effective light diameter.

4. 4. The imaging optical system according to claim 1, wherein the following condition is satisfied: (2) 0.40<LT / f<0.60 however, LT is the distance on the optical axis from the surface closest to the object to the image plane when focusing at infinity, f is the focal length of the imaging optical system when focused at infinity.

5. 5. The imaging optical system according to claim 1, which does not include a diffractive optical element.

6. 6. The imaging optical system according to claim 1, wherein all of the surfaces having power of the plurality of lenses are spherical.

7. 7. The imaging optical system according to claim 1, wherein the following condition is satisfied: (4) -5.0<Φ_G3 / Φ<-1.0 where Φ_G3 is the power of the third group.

8. 8. The imaging optical system according to claim 1, wherein the following condition is satisfied: (5) |f / R_G1last|<6.0 Here, R_G1last is the radius of curvature of the surface of the first group that is closest to the image side.

9. 9. The imaging optical system according to claim 1, further comprising an aperture stop between the second lens unit and the third lens unit.

10. 10. The imaging optical system according to claim 1, wherein the image blur correction unit has at least one positive lens and at least one negative lens.

Images