JP7665199B2 - Imaging Optical System - Google Patents

Description

The present invention relates to an imaging optical system suitable for photographic lenses used in still cameras, video cameras, etc.

Telephoto type imaging optical systems, 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, have been known as imaging optical systems suitable for long focal length photographic lenses (hereafter referred to as telephoto lenses). By adopting a telephoto type power arrangement, it is possible to shorten the overall optical length of telephoto lenses, which tend to be long and heavy.

Telephoto lenses are also often used for photographing sports and animals, and therefore require fast autofocus. If telephoto lenses use 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 autofocus, so an inner focus method is often used.

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. With the contrast detection method, it is common for the focusing unit to perform an action 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.

In addition, in recent years, with the spread of compactly designed mirrorless cameras, there is a demand for small and lightweight telephoto lenses as well. To make a telephoto lens smaller and lighter, it is important to make the moving parts smaller and lighter in addition to making the imaging optical system smaller. This is because the size and positioning of the actuator depend on the size and weight of the moving parts.

Patent No. 6627313

The imaging optical system described in Patent Document 1 achieves high performance while employing inner focusing, but the focusing unit is not sufficiently small and lightweight. In addition, the total optical length relative to the focal length cannot be said to be sufficiently small.

The invention was made in consideration of these circumstances, and aims to provide an imaging optical system that is suitable for small and lightweight telephoto lenses by having a small and lightweight focusing unit and by being small and lightweight itself.

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 space among the air spaces formed on the optical axis by the plurality of lenses is located on the object side of the focusing unit, the first group being made up of all lenses of the plurality of lenses which are arranged on the object side of the focusing unit and having positive power as a whole, a second group being made up of the focusing unit and having negative power as a whole, and a third group being made up of all lenses of the plurality of lenses which are arranged on the image side of 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 which has negative power as a whole and a rear unit which has positive power as a whole, the first group and the rear unit being constantly fixed with respect to the image plane, and satisfying the following conditional expressions:
(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 .

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.

The imaging optical system embodying the present invention is preferably characterized in that the interface between the air and all lenses arranged closer to the object side than the maximum air gap has a convex surface facing the object side within the effective light diameter.

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.

The imaging optical system embodying the present invention is preferably characterized by not having a diffractive optical element.

The imaging optical system embodying the present invention is preferably characterized in that all of the powered surfaces of the multiple lenses are spherical.

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.

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.

The imaging optical system embodying the present invention is preferably characterized by having an aperture stop between the second group and the third group.

In the imaging optical system embodying the present invention, the image blur correction unit preferably has at least one positive lens and at least one negative lens.

The imaging optical system embodying the present invention is small and lightweight, and by having a small and lightweight focusing unit, it is possible to provide an imaging optical system suitable for small and lightweight telephoto lenses.

FIG. 2 is a diagram showing a lens arrangement at infinity according to the first embodiment of the present invention. FIG. 4 is a longitudinal aberration diagram at infinity in Example 1 of the present invention. 5A to 5C are longitudinal aberration diagrams at a shooting distance of 3.2 m in Example 1 of the present invention. FIG. 4 is a lateral aberration diagram at infinity in Example 1 of the present invention. 5A to 5C are diagrams illustrating lateral aberration at a shooting distance of 3.2 m in Example 1 of the present invention. FIG. 11 is a lateral aberration diagram of Example 1 of the present invention at infinity with 0.2° image stabilization. FIG. 11 is a diagram showing a lens arrangement at infinity according to a second embodiment of the present invention. FIG. 11 is a longitudinal aberration diagram at infinity in Example 2 of the present invention. 11A to 11C are longitudinal aberration diagrams at a shooting distance of 3.2 m in Example 2 of the present invention. FIG. 11 is a diagram illustrating lateral aberration at infinity in Example 2 of the present invention. 8A to 8C are diagrams illustrating lateral aberration at a shooting distance of 3.2 m in Example 2 of the present invention. FIG. 11 is a lateral aberration diagram of Example 2 of the present invention at infinity with 0.2° image stabilization. FIG. 11 is a diagram showing a lens arrangement at infinity according to a third embodiment of the present invention. FIG. 11 is a longitudinal aberration diagram at infinity in Example 3 of the present invention. 13A to 13C are longitudinal aberration diagrams at a shooting distance of 3.3 m in Example 3 of the present invention. FIG. 11 is a diagram illustrating lateral aberration at infinity in Example 3 of the present invention. 13A to 13C are lateral aberration diagrams at a shooting distance of 3.3 m in Example 3 of the present invention. FIG. 13 is a lateral aberration diagram of Example 3 of the present invention at infinity with 0.2° image stabilization. FIG. 13 is a diagram showing a lens arrangement at infinity according to a fourth embodiment of the present invention. FIG. 13 is a longitudinal aberration diagram at infinity in Example 4 of the present invention. 13A to 13C are longitudinal aberration diagrams at a shooting distance of 3.1 m in Example 4 of the present invention. FIG. 13 is a diagram illustrating lateral aberration at infinity in Example 4 of the present invention. 13A to 13C are lateral aberration diagrams at a shooting distance of 3.1 m in Example 4 of the present invention. FIG. 13 is a lateral aberration diagram of Example 4 of the present invention at infinity with 0.2° image stabilization. FIG. 13 is a diagram showing a lens arrangement at infinity according to a fifth embodiment of the present invention. FIG. 13 is a longitudinal aberration diagram at infinity in Example 5 of the present invention. 13A to 13C are longitudinal aberration diagrams at a shooting distance of 4.6 m in Example 5 of the present invention. FIG. 13 is a diagram illustrating lateral aberration at infinity in Example 5 of the present invention. 13A to 13C are lateral aberration diagrams at a shooting distance of 4.6 m in Example 5 of the present invention. FIG. 13 is a lateral aberration diagram of Example 5 of the present invention at infinity with 0.2° image stabilization. FIG. 13 is a diagram showing a lens arrangement at infinity according to a sixth embodiment of the present invention. FIG. 13 is a longitudinal aberration diagram at infinity in Example 6 of the present invention. 13A to 13C are longitudinal aberration diagrams at a shooting distance of 2.6 m in Example 6 of the present invention. FIG. 13 is a diagram illustrating lateral aberration at infinity in Example 6 of the present invention. 13A to 13C are lateral aberration diagrams at a shooting distance of 2.6 m in Example 6 of the present invention. FIG. 23 is a lateral aberration diagram of Example 6 of the present invention at infinity with 0.2° image stabilization.

The imaging optical system of the present invention will be described below. 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 a plurality of lenses, has a focusing unit that moves as a unit during focusing, the maximum air gap among the air gaps formed by the plurality of 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 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.

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, the entire system becomes an imaging optical system, so 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.

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

Limiting the upper limit of conditional formula (1) to -6.0 is preferable because it makes the above-mentioned effect more certain.Limiting the lower limit of conditional formula (1) to -14.0 is preferable because it makes the above-mentioned effect more certain.

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.

By having a focusing unit with at least one positive lens and at least one negative lens, it is possible for the focusing unit to correct axial chromatic aberration on its own, making it possible to obtain good performance over a wide range of shooting distances.

The imaging optical system of the present invention is further characterized in that the interface between the air and all lenses arranged closer to the object than the maximum air space faces a convex surface toward the object side within the effective light diameter. In all lenses arranged closer to the object than the maximum air space, the axial marginal ray passes through a high position, making it easy for spherical aberration to occur. However, by making the interface between the lens and the air face convex toward the object side, the shape becomes close to aplanatic, making it possible to reduce the occurrence of spherical aberration.

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.

Condition (2) specifies the ratio of the total optical length and the focal length of the imaging optical system when focused at infinity.

If the total optical length becomes too long, exceeding the upper limit of conditional formula (2), it becomes difficult to make the telephoto lens small and lightweight. 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 minimum 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.

Limiting the upper limit of conditional formula (2) to 0.59 is preferable because it makes the above-mentioned effect more certain.Limiting the lower limit of conditional formula (2) to 0.45 is preferable because it makes the above-mentioned effect more certain.

The imaging optical system of the present invention is further characterized by not using a diffractive optical element. Diffractive optical elements can have chromatic aberration correction effects and aspheric effects on the diffractive surface, but their shape can cause unwanted diffracted light and flare due to light rays outside the angle of view. Because 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.

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

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

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

If the negative power of the second group becomes smaller beyond the upper limit of conditional expression (3), the amount of movement of the second group during focusing becomes large, making it difficult to reduce the size of the imaging optical system. If the negative power of the second group becomes large beyond the lower limit of conditional expression (3), 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.

Limiting the upper limit of conditional formula (3) to -3.0 is preferable because it makes the above-mentioned effect more certain.Limiting the lower limit of conditional formula (3) to -4.6 is preferable because it makes the above-mentioned effect more certain.

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.

Condition (4) specifies the ratio of the power of the third group to the power of the entire system.

When the upper limit of conditional formula (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 becomes large, making it difficult to obtain good performance over a wide shooting distance range. If the negative power of the third group becomes large and the lower limit of conditional formula (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.

Limiting the upper limit of conditional formula (4) to -1.3 is preferable because it makes the above-mentioned effect more certain.Limiting the lower limit of conditional formula (4) to -4.0 is preferable because it makes the above-mentioned effect more certain.

Furthermore, the imaging optical system of the present invention is 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.

Condition (5) specifies 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.

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

Limiting the upper limit of conditional expression (5) to 5.0 is preferable because it makes the above-mentioned effect more certain.

The imaging optical system of the present invention is further characterized by having an aperture stop between the second and third groups.

By placing the aperture diaphragm between the second and third groups, the convergence effect of the first group allows the aperture diaphragm to be made smaller. 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.

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.

By positioning 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 damping coefficient). Increasing the vibration damping 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.

Condition (6) specifies the ratio of the power of the image stabilization unit to the power of the imaging optical system.

When 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 miniaturize the actuator and, ultimately, the telephoto lens. When 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 and astigmatism when driven in a direction perpendicular to the optical axis increase, making it difficult to obtain good performance during image stabilization.

Limiting the upper limit of conditional formula (6) to -8.0 is preferable because it makes the above-mentioned effect more certain.Limiting the lower limit of conditional formula (6) to -12.0 is preferable because it makes the above-mentioned effect more certain.

Further, in the imaging optical system of the present invention, the image blur correction unit has at least one positive lens and at least one negative lens.

By having at least one positive lens and one negative lens, the image blur correction unit can correct chromatic aberration within the image blur correction unit, and good performance can be obtained during image blur correction.

Next, we will explain the lens configuration of an embodiment of the imaging optical system of the present invention. In the following explanation, the lens configuration will be described in order from the object side to the image side.

Figure 1 is a lens configuration diagram of an imaging optical system according to a first embodiment of the present invention.

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 overall. The first group is always fixed with respect to the image surface.

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

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.

The image stabilization unit is composed of a meniscus-shaped positive lens L10 with its convex surface facing the image side and a biconcave negative lens L11, and has a negative power overall. 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.

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 positive power overall. The rear unit is always fixed relative to the image surface.

The object-side subsystem is made up of L1 to L5 and has positive power overall. The image-side subsystem is made up of L6 to L16 and has negative power overall. It also includes the second group as a focusing unit.

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

Figure 7 is a lens configuration diagram of the imaging optical system according to the second embodiment of the present invention.

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 overall. The first group is always fixed with respect to the image surface.

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 power overall. The second lens group also moves along the optical axis from the object side to the image side when focusing from an object at infinity to a close object.

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.

The image stabilization unit is composed of a meniscus-shaped positive lens L10 with its convex surface facing the image side and a biconcave negative lens L11, and has a negative power overall. 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.

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 positive power overall. The rear unit is always fixed relative to the image surface.

The object-side subsystem is made up of L1 to L5 and has positive power overall. The image-side subsystem is made up of L6 to L16 and has negative power overall. It also includes the second group as a focusing unit.

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

Figure 13 is a lens configuration diagram of an imaging optical system according to a third embodiment of the present invention.

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 overall. The first group is always fixed with respect to the image surface.

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

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.

The image stabilization unit is composed of a meniscus-shaped positive lens L10 with its convex surface facing the image side and a biconcave negative lens L11, and has a negative power overall. 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.

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 positive power overall. The rear unit is always fixed relative to the image surface.

The object-side subsystem is made up of L1 to L5 and has positive power overall. The image-side subsystem is made up of L6 to L16 and has negative power overall. It also includes the second group as a focusing unit.

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

Figure 19 is a lens configuration diagram of an imaging optical system according to the fourth embodiment of the present invention.

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 overall. The first group is always fixed with respect to the image surface.

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

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.

The image stabilization unit is composed of a meniscus-shaped positive lens L10 with its convex surface facing the image side and a biconcave negative lens L11, and has a negative power overall. 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.

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 positive power overall. The rear unit is always fixed relative to the image surface.

The object-side subsystem is made up of L1 to L5 and has positive power overall. The image-side subsystem is made up of L6 to L16 and has negative power overall. It also includes the second group as a focusing unit.

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

Figure 25 is a lens configuration diagram of an imaging optical system according to a fifth embodiment of the present invention.

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 overall. The first group is always fixed with respect to the image surface.

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

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.

The image stabilization unit is composed of a meniscus-shaped positive lens L10 with its convex surface facing the image side and a biconcave negative lens L11, and has a negative power overall. 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.

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 positive power as a whole. The rear unit is always fixed relative to the image plane.

The object-side subsystem is made up of L1 to L5 and has positive power overall. The image-side subsystem is made up of L6 to L16 and has negative power overall. It also includes the second group as a focusing unit.

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

Figure 31 is a lens configuration diagram of an imaging optical system according to a sixth embodiment of the present invention.

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 overall. The first group is always fixed with respect to the image surface.

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 power overall. The second lens group also moves along the optical axis from the object side to the image side when focusing from an object at infinity to a close object.

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.

The image stabilization unit is composed of a meniscus-shaped positive lens L10 with its convex surface facing the image side and a biconcave negative lens L11, and has a negative power overall. 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.

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 positive power overall. The rear unit is always fixed relative to the image surface.

The object-side subsystem is made up of L1 to L5 and has positive power overall. The image-side subsystem is made up of L6 to L16 and has negative power overall. It also includes the second group as a focusing unit.

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

Below is given specific numerical data for each embodiment of the imaging optical system of the present invention described above.

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.

BF stands for back focus.

The (Aperture) next to a surface number indicates that an aperture stop is located at that position. The radius of curvature for the plane or aperture stop is marked ∞ (infinity).

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

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

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

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

A list of the corresponding values of the conditional expressions in each of these examples is also provided.

In addition, in the aberration diagrams corresponding to each embodiment, d, g, and C represent the d-line, g-line, and C-line, respectively, and △S and △M represent the sagittal image surface and meridional image surface, respectively.

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 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 Initial surface 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

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 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 Initial surface 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

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 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 Initial surface 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

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 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 Initial surface Focal length
Group 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

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 Initial surface 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

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 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 Initial surface 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

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

G1 First lens unit G2 Second lens unit G3 Third lens unit FG Object-side lens unit RG Image-side lens unit IU Image blur correction unit RU Rear unit S Aperture stop I Image surface

Claims (10)

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 consisting of all 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 . The imaging optical system according to claim 1, characterized in that the focusing unit has at least one positive lens and at least one negative lens. The imaging optical system according to claim 1 or 2, characterized in that the interfaces between all lenses arranged closer to the object side than the maximum air gap and the air face a convex surface toward the object side within the effective light diameter. 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. The imaging optical system according to any one of claims 1 to 4, characterized in that it does not have a diffractive optical element. An imaging optical system according to any one of claims 1 to 5, characterized in that all of the surfaces having power of the plurality of lenses are spherical. 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. 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. The imaging optical system according to claim 1, further comprising an aperture stop between the second lens unit and the third lens unit. 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.

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