JP6189722B2 - Inner focus type lens and imaging device - Google Patents

Description

  The present invention relates to an inner focus lens and an image pickup apparatus that have an image stabilization function suitable for taking a still image or a moving image and can realize high-speed autofocus.

  A single-lens reflex camera (hereinafter, referred to as a “single-lens reflex camera”) generally includes an optical viewfinder, and the reflex mirror disposed between the image pickup lens and the image pickup element causes the image pickup lens to change from the image pickup lens to the image pickup element. The subject light incident on the side is guided to the viewfinder side so that the photographer can visually recognize the same subject image as the subject image formed on the imaging surface. A single-lens reflex camera can enjoy various imaging expressions that cannot be expressed by a compact digital camera by exchanging the imaging lens according to the subject, composition, etc., and manually adjusting the focus and exposure. . However, compared with a compact digital camera, it is necessary to arrange optical elements related to the optical viewfinder, so that the imaging apparatus main body becomes large and heavy, and it is difficult to say that the portability is good.

  On the other hand, the market for mirrorless single-lens cameras in which components related to the optical viewfinder are removed from single-lens reflex cameras has been rapidly expanding in recent years. A mirrorless single-lens camera is smaller and lighter than a single-lens reflex camera, and thus has excellent portability, and can obtain a higher quality image than a compact digital camera. In addition, various imaging expressions can be enjoyed by exchanging lenses as in the case of a single-lens reflex camera. As the market for mirrorless single-lens cameras expands, the demand for interchangeable lenses for mirrorless single-lens cameras is increasing. In particular, there is a high need for medium-telephoto lenses to telephoto lenses having a longer focal length than standard lenses.

  The interchangeable lens of a mirrorless single-lens camera is required to have high image forming performance like the interchangeable lens of a single-lens reflex camera. On the other hand, since the apparatus main body is small and lightweight, the interchangeable lens of the mirrorless single-lens camera is required to be small and lightweight as compared with the interchangeable lens of the single-lens reflex camera. Furthermore, since there are many enthusiasts of general users, the price is required to be easily available. From these points, the interchangeable lens of the mirrorless single-lens camera has more restrictions on the optical design than the single-lens reflex camera.

  As an interchangeable lens of such a mirrorless single-lens camera, for example, an inner focus type lens disclosed in Patent Documents 1 to 3 is known. Each of the inner focus type lenses described in Patent Documents 1 to 3 has a three-group configuration, and the second lens group is a focus group. Since a bright telephoto lens generally has a large entrance pupil diameter, the outer diameter of the lenses constituting the first lens group is large and heavy. For this reason, if the first lens group moves during focusing, the position of the center of gravity of the entire optical system also moves, which may cause blurring in the lens barrel or the imaging apparatus body, leading to blurring of the captured image. Therefore, as in the telephoto lenses described in Patent Documents 1 to 3, the first lens group and the third lens group are fixed groups, and the second lens group is a focus group, so that the center of gravity position during focusing is obtained. Movement can be suppressed, and blurring of the captured image can be suppressed. In addition, by using the first lens group and the third lens group as fixed groups at the time of focusing, there is an advantage that the optical total length does not change at the time of focusing. Thereby, a lens barrel can be made into a sealing structure, and the penetration | invasion into the housing | casing of a foreign material can be suppressed. Further, if the entire length of the lens barrel changes during focusing, depending on the imaging distance and the position of the subject, the tip of the lens may come into contact with the subject or the like, and the subject or the lens may become dirty or damaged. However, such a problem can be prevented by using the first lens group and the third lens group as fixed groups.

Japanese Patent No. 5246226 JP 2012-242690 A JP 2013-161076 A

  By the way, in recent years, there are an increasing number of models capable of capturing a moving image even in an interchangeable lens type imaging apparatus. When moving images are picked up, the image pickup apparatus is moved in accordance with the movement of the subject, so that an image blur is likely to occur when the optical system vibrates due to camera shake or the like. In addition, since it is necessary to focus on the subject instantly in accordance with the movement of the subject, high-speed autofocus is required.

  With respect to this point, the inner focus lens described in Patent Document 1 includes a vibration-proof group in the third lens group, enables image blur correction, and performs excellent aberration correction when image blur occurs. I can do it. However, in the inner focus type lens described in Patent Document 1, since a lens group having a refractive power larger on the object side than the focus group is disposed, aberration generated in the lens group closer to the object side than the focus group is corrected. Requires that the focus group be composed of a plurality of lenses. For this reason, it is difficult to reduce the weight of the focus group, and it is difficult to increase the speed of autofocus. In addition, since the anti-vibration group is composed of a plurality of lenses, the anti-vibration group becomes heavy, and there is a problem in increasing the speed of the anti-vibration operation.

  In the inner focus type lens described in Patent Document 2, the focus group is composed of a single lens, thereby reducing the size and weight of the focus group. In addition, an anti-vibration group is arranged in the first lens group to enable camera shake correction. However, as described above, in the telephoto lens, the outer diameter of the lens constituting the first lens group becomes large. Therefore, when the anti-vibration group is arranged in the first lens group, the lens diameter of the anti-vibration group becomes large, and the anti-shake It is difficult to reduce the weight of the group. For this reason, even in the inner focus lens, it is difficult to increase the speed of the image stabilization operation.

  Also in the inner focus type lens described in Patent Document 3, the focus group is arranged on the image plane side with respect to the stop, and the focus group is configured by a single lens, thereby reducing the size and weight of the focus group. . However, the inner focus lens described in Patent Document 3 does not have a vibration proof group and cannot perform image blur correction.

  Accordingly, an object of the present invention is to reduce the size and weight of the focus group and the vibration proof group, to make the entire optical system compact, and to provide an inner focus lens and an imaging apparatus that can realize good imaging performance. It is to provide.

  As a result of intensive studies, the present inventors have achieved the above object by adopting the following lens configuration.

  The inner focus type lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. And an inner focus type lens that moves the second lens group along the optical axis direction when focusing from an object at infinity to an object at a short distance, and the second lens group includes a negative single lens element. The third lens group has an anti-vibration group composed of negative single lens elements, and the vibration of the optical system is moved by moving the anti-vibration group substantially perpendicular to the optical axis. It is characterized by performing image blur correction that sometimes occurs.

  In the inner focus type lens according to the present invention, it is preferable that the following conditional expression (1) is satisfied.

45.0 ≦ vd2 (1)
However,
vd2: Abbe number with respect to d-line of the single lens elements constituting the second lens group

  In the inner focus type lens according to the present invention, in the optical system, it is preferable that the aperture stop is disposed on the image plane side with respect to the second lens group.

  In the inner focus lens according to the present invention, it is preferable that the following conditional expression (2) is satisfied.

0.30 ≦ f1 / f ≦ 1.20 (2)
However,
f: Focal length of the entire optical system when focusing on infinity f1: Focal length of the first lens group

  In the inner focus type lens according to the present invention, it is preferable that the following conditional expression (3) is satisfied.

0.30 ≦ f3 / f ≦ 3.30 (3)
However,
f: Focal length of the entire optical system when focusing on infinity f3: Focal length of the third lens group

  In the inner focus lens according to the present invention, the third lens group includes, in order from the object side, a front sub-lens group having a positive refractive power, the anti-vibration group, and a rear sub-lens group having a positive refractive power. It is preferable.

  In the inner focus type lens according to the present invention, when the third lens group includes the front sub lens group and the rear sub lens group, it is preferable that the following conditional expression (4) is satisfied.

0.20 ≦ f3a / f ≦ 1.70 (4)
However,
f: Focal length of the entire optical system when focusing on infinity f3a: Focal length of front sub-lens group

  In the inner focus type lens according to the present invention, when the third lens group includes the front sub lens group and the rear sub lens group, it is preferable that the following conditional expression (5) is satisfied.

0.50 ≦ f3c / f ≦ 5.00 (5)
However,
f: Focal length of the entire optical system when focusing on infinity f3c: Focal length of rear sub lens group

  In the inner focus lens according to the present invention, it is preferable that the first lens group includes at least three positive lens elements, and at least one of the positive lens elements satisfies the following conditional expression (6).

60.0 ≦ vd1a (6)
However,
vd1a: Abbe number of any positive lens element in the first lens group with respect to the d-line

  In the inner focus type lens according to the present invention, it is preferable that the lens element arranged closest to the image plane in the third lens group is a negative meniscus lens having a convex surface facing the image plane.

  In the inner focus type lens according to the present invention, it is preferable that the following conditional expressions (7) and (8) are satisfied.

1.6 ≦ nd3b (7)
25.0 ≦ vd3b ≦ 70.0 (8)
However,
nd3b: Refractive index with respect to d-line of a single lens element as a vibration-proof group vd3b: Abbe number with respect to d-line of a single lens element as a vibration-proof group

  In the inner focus type lens according to the present invention, it is preferable that the following conditional expression (9) is satisfied.

−25.0 ≦ vd2−vd1b ≦ 60.0 (9)
However,
vd1b: Abbe number with respect to the d-line of the positive lens element arranged closest to the image plane in the first lens group vd2: Abbe number with respect to the d-line of the single lens element constituting the second lens group

  An image pickup apparatus according to the present invention includes the inner focus lens and an image pickup device that converts an optical image formed by the inner focus lens on the image plane side into an electrical signal.

  By adopting the above configuration, the present invention can reduce the size and weight of the focus group and the anti-vibration group, make the entire optical system compact, and realize good imaging performance. It is possible to provide an inner focus type lens suitable for an interchangeable lens of a small-sized image pickup apparatus whose main body is a single lens camera or the like, and the image pickup apparatus.

It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 1 of this invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens of Example 1 of the present invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens of Example 1 of the present invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the closest focus state of the inner focus lens of Example 1 of the present invention. FIG. 3 is a lateral aberration diagram when the inner focus lens of Example 1 of the present invention is in focus at infinity and during image stabilization. It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 2 of this invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens of Example 2 of the present invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens of Example 2 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism and distortion in the closest focus state of the inner focus type lens of Example 2 of the present invention. It is a lateral aberration figure at the time of infinity focusing of the inner focus type lens of Example 2 of this invention at the time of an anti-vibration. It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 3 of this invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens according to Example 3 of the present invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens of Example 3 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the closest focus state of the inner focus lens of Example 3 of the present invention. It is a lateral aberration figure at the time of infinity focusing of the inner focus type | mold lens of Example 3 of this invention at the time of anti-vibration. It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 4 of this invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens according to Example 4 of the present invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens of Example 4 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the closest focus state of the inner focus lens of Example 4 of the present invention. FIG. 6 is a lateral aberration diagram when the inner focus lens of Example 4 of the present invention is in focus at infinity and during image stabilization. It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 5 of this invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens according to Example 5 of the present invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens according to Example 5 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the closest focus state of the inner focus type lens of Example 5 of the present invention. It is a lateral aberration figure at the time of infinity focusing of the inner focus type lens of Example 5 of this invention at the time of an anti-vibration. It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 6 of this invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens according to Example 6 of the present invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens of Example 6 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism and distortion in the closest focus state of the inner focus type lens of Example 6 of the present invention. It is a lateral aberration figure at the time of infinity focusing of the inner focus type lens of Example 6 of this invention at the time of an anti-vibration. It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 7 of this invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens according to Example 7 of the present invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens of Example 7 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism and distortion in the closest focus state of the inner focus type lens of Example 7 of the present invention. It is a lateral aberration figure at the time of infinity focusing of the inner focus type lens of Example 7 of this invention at the time of an anti-vibration. It is a figure which shows the lens structural example in the infinite point focusing state of the inner focus type | mold lens of Example 8 of this invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens according to Example 8 of the present invention. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at an imaging magnification “1/40 ×” of the inner focus lens of Example 8 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism and distortion in the closest focus state of the inner focus type lens of Example 8 of the present invention. It is a lateral aberration figure at the time of infinity focusing of the inner focus type | mold lens of Example 8 of this invention, and an anti-vibration.

  Hereinafter, embodiments of the inner focus lens and the imaging device according to the present invention will be described.

1. Inner focus type lens 1-1. Configuration of Optical System First, the configuration of the optical system of the inner focus lens according to the present invention will be described. The inner focus type lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. And an inner focus type lens that moves the second lens group along the optical axis direction when focusing from an object at infinity to an object at a short distance, and the second lens group includes a negative single lens element. The third lens group has an anti-vibration group composed of negative single lens elements, and the vibration of the optical system is moved by moving the anti-vibration group substantially perpendicular to the optical axis. It is characterized by performing image blur correction that sometimes occurs.

  In the present invention, since the above lens configuration is adopted, the outer diameter and weight of the lenses constituting the second lens group are smaller than the outer diameters and weights of the lenses constituting the first lens group and the third lens group. Each gets smaller. Therefore, as compared with the case where the first lens group and / or the third lens group is the focus group, it is easy to reduce the diameter and weight of the lens constituting the focus group, and the load on the focus drive system is reduced. Can be reduced. Furthermore, in the present invention, since the second lens group is composed of a negative single lens element, it is possible to further reduce the weight of the second lens group as compared with the case where it is composed of a plurality of lens elements. it can. For this reason, high-speed autofocus can be realized.

  In the present invention, the vibration proof group is arranged in the third lens group, and the vibration proof group is composed of a negative single lens element. In a lens having a long focal length such as a telephoto lens, the outer diameter of the lens constituting the first lens group is larger than that of other lens groups. For this reason, when the anti-vibration group is arranged in the first lens group, the outer diameter of the single lens elements constituting the anti-vibration group becomes large and heavy, making it difficult to perform a quick anti-vibration operation. Become. On the other hand, if the anti-vibration group is disposed in the third lens group, it is easier to reduce the diameter and weight of the lens constituting the anti-vibration group than in the case where the anti-vibration group is disposed in the first lens group. Become. Further, in the present invention, the vibration proof group is composed of a single lens element, so that the weight of the vibration proof group can be further reduced as compared with the case where the vibration proof group is composed of a plurality of lens elements. Furthermore, in this invention, since the refractive power of the said single lens element is made negative, compared with the case where refractive power is positive, a volume becomes small even if it is the same outer diameter. Therefore, by adopting this configuration, it is possible to realize a high speed of the image stabilization operation.

  Further, as described above, the inner focus lens according to the present invention employs a positive and negative three-group configuration in order from the object side. By arranging the refractive power in the optical system in this manner, it is possible to suppress an increase in the optical total length with respect to the focal length, and to make the lens barrel diameter and the lens barrel total length compact. For this reason, when the inner focus type lens according to the present invention is applied to a telephoto lens, the whole can be made compact. In the present invention, the telephoto lens means a lens having a focal length longer than that of the standard lens, and includes lenses referred to as a medium telephoto lens to a super telephoto lens.

  Further, in the present invention, when focusing from infinity to a short distance object, the first lens group disposed closest to the object side and the third lens group disposed closest to the image plane are fixed, and these are arranged inside these. By using the second lens group to be arranged as a focus group, movement of the center of gravity during focusing can be suppressed, and blurring of the captured image can be suppressed. In addition, by using the first lens group and the third lens group as fixed groups at the time of focusing, there is an advantage that the optical total length does not change at the time of focusing. Thereby, a lens barrel can be made into a sealing structure, and the penetration | invasion into the housing | casing of a foreign material can be suppressed. Further, if the entire length of the lens barrel changes during focusing, depending on the imaging distance and the position of the subject, the tip of the lens may come into contact with the subject or the like, and the subject or the lens may become dirty or damaged. However, such a problem can be prevented by using the first lens group and the third lens group as fixed groups.

  Hereinafter, the configuration of the optical system of the inner focus lens according to the present invention will be described in more detail.

(1) First lens group The specific lens configuration of the first lens group is not particularly limited as long as it has positive refractive power. However, when the inner focus lens is applied to a telephoto lens, the first lens group has at least three positive lens elements from the viewpoint of increasing the telephoto ratio and shortening the optical total length with respect to the focal length. It is preferable to have. By disposing at least three positive lens elements, that is, lens elements having a positive refractive power, in the first lens group, the first lens group can be a lens group having a strong positive refractive power. The telephoto ratio can be increased.

  Here, in the present invention, “lens element” refers to an optical element as a minimum unit (hereinafter referred to as “minimum optical element”), and “positive lens element” refers to a minimum optical element that is a positive unit. It means having a refractive power. Accordingly, the “positive lens element” includes, in addition to the “positive single lens”, a positive lens as a constituent optical element of a cemented lens or a compound lens. That is, the “positive lens element” referred to in the present invention refers to a cemented lens, a composite lens having an optical film such as an aspheric film on one side or both sides, before the other lens is joined, or an optical film or the like. A single lens in a state before being attached, which has a positive refractive power. In other words, even if the refractive power of the cemented lens or the compound lens is “negative”, if the refractive power of the “lens element” itself as these constituent optical elements is “positive”, the constituent optics of this cemented lens “Lens element” as an element corresponds to “positive lens element”. Further, when the refractive power as a cemented lens or a compound lens is “positive”, the “positive lens element” does not mean the entire cemented lens or the entire compound lens, but the refractive power of these constituent optical elements is “positive”. "Lens element" is referred to as "positive lens element".

(2) Second Lens Group As described above, the second lens group is a focus group that moves along the optical axis direction during focusing, and includes a negative single lens element. By adopting this configuration, the above-described various effects can be obtained in addition to speeding up autofocus. However, it is preferable to move the second lens group from the object side to the image plane side when focusing from an object at infinity to an object at close range.

  Here, the “single lens element” means a single lens as the lens element itself or a compound lens in which the optical film or the like is provided on one side or both sides of the lens element. The “negative single lens element” means a “single lens element” having a “negative” refractive power. That is, “the second lens group is composed of a negative single lens element” means that the second lens group does not include any other “lens element” other than the “negative single lens element”. For example, the second lens group may be a compound lens whose surface shape or the like is adjusted by attaching an optical film such as an aspheric film on one or both surfaces of the negative lens. This means that the lens is not a cemented lens cemented with another single lens element. This also applies to a vibration proof group described later. In conditional expression (1), which will be described later, the refractive index with respect to the d-line of a single lens element means, in the case of a compound lens, the refractive index with respect to the d-line of the lens element itself before the optical film or the like is attached. Say. Conditional expression (7) and conditional expression (8) shall conform to this.

(3) Third Lens Group As described above, the third lens group is a lens group having a positive refractive power, and includes a vibration-proof group composed of negative single lens elements. As a result, as described above, it is possible to increase the speed of the image stabilization operation.

  As long as the third lens group has a positive refractive power and an anti-vibration group composed of a negative single lens element, the specific lens configuration is not particularly limited. However, from the viewpoint of further reducing the size and weight of the negative single lens element constituting the image stabilizing group and reducing the overall size of the optical system, the third lens group includes positive elements in order from the object side. It is preferable to include a front sub-lens group having a refractive power, the vibration-proof group, and a rear sub-lens group having a positive refractive power. By adopting such a lens configuration, the outer diameter of the negative single lens element constituting the vibration isolation group can be reduced, the vibration isolation group can be further reduced in size and weight, and the vibration isolation operation can be performed. Can be further increased in speed. These points will be further described in conditional expressions (4), (5), (7), and (8) described later.

  In the third lens group, it is preferable to dispose a negative meniscus lens on the most image side. By using a negative meniscus lens as the lens arranged closest to the image plane in the third lens group, an optical system having good imaging performance that can correct field curvature and distortion aberration well. Can do. Also, by directing the convex surface to the image surface side, unlike the case of directing the concave surface to the image surface side, the reflected light on the image sensor surface is reflected on the image surface side of this negative meniscus lens and multiplexed between these surfaces. Repeated reflection can prevent multiple reflected light from re-imaging on the imaging element surface, which is advantageous in suppressing ghosts and the like, and can provide an imaging optical system having good imaging performance. .

(4) Aperture stop In order to realize high-speed autofocusing and image stabilization, the position of the aperture stop in the optical system is not particularly limited as long as it is not in the second lens group. However, in consideration of downsizing of the product size of the inner focus lens according to the present invention and the response speed of the aperture diameter control of the aperture stop, the aperture stop has a larger image plane than the second focus lens group in the optical system. It is preferable to arrange on the side. That is, it is preferable that the aperture stop be disposed between the second lens group and the third lens group or in the third lens group. This is due to the following reason.

  In general, the imaging optical system is configured so that the F value can be adjusted in order to adjust the exposure amount according to the brightness of the subject or to change the depth of field according to the drawing intention. Adjustment of the F value is generally performed by adjusting the aperture diameter of an aperture stop having a variable aperture diameter such as an iris diaphragm. For example, in the case of an iris diaphragm, the aperture diameter is adjusted by adjusting the overlapping degree of the diaphragm blades. In the lens barrel, an aperture drive unit for adjusting the aperture diameter of the aperture stop is provided around the aperture stop. For this reason, if the outer diameter of the aperture stop is large, the outer diameter of the lens barrel also increases, and the product dimensions of the inner focus lens increase. Further, when the outer diameter of the aperture stop is increased, for example, the movable portion that is movable when adjusting the aperture diameter of the aperture blades is increased and becomes heavier, so that the response speed thereof is also decreased.

  In a bright optical system having a long focal length such as a telephoto lens, the outer diameter of the lens constituting the first lens group is larger than that of other lens groups. For this reason, when the aperture stop is disposed in the first lens group, the aperture diameter of the aperture stop is larger than in the case where the aperture stop is disposed in the other lens group. It becomes difficult to obtain responsiveness.

  Further, when the focus group has a negative refractive power, if the aperture stop is disposed in the first lens group, the focus group is disposed on the image plane side of the aperture stop. It is difficult to cut light rays, correction of coma aberration is insufficient, and it becomes difficult to obtain good imaging performance.

  Therefore, when the object distance is infinity, the combined refractive power of the first lens group and the second lens group is positive, and the aperture stop is arranged on the image plane side with respect to the second lens group. A diameter can be made small and each subject mentioned above can be solved.

1-2. Conditional Expression Next, the conditional expression will be described. The inner focus lens according to the present invention preferably employs the configuration of the optical system and satisfies the following conditional expression.

1-2-1. Conditional expression (1)
In the inner focus type lens according to the present invention, it is preferable that the following conditional expression (1) is satisfied.

45.0 ≦ vd2 (1)
However,
vd2: Abbe number with respect to d-line of the single lens elements constituting the second lens group

  Conditional expression (1) defines the Abbe number for the d-line of the negative single lens element constituting the second lens group. By satisfying conditional expression (1), it is possible to reduce chromatic aberration that occurs in the second lens group, which is the focus group, and to reduce variations in chromatic aberration caused by movement of the second lens group during focusing. Therefore, good imaging performance can be obtained from the infinity distance to the closest distance. When the value of conditional expression (1) is below the lower limit value, the chromatic aberration generated in the second lens group becomes large, and it becomes difficult to reduce the variation in chromatic aberration accompanying the movement of the focus group. For this reason, it is difficult to obtain good imaging performance at all object distances.

  From these viewpoints, the value of the conditional expression (1) is preferably within the range of the following formula (1a), and is preferably within the range of the following formula (1b).

55.0 ≦ vd2 (1a)
63.0 ≦ vd2 (1b)

1-2-2. Conditional expression (2)
In the inner focus lens according to the present invention, it is preferable that the following conditional expression (2) is satisfied.

0.30 ≦ f1 / f ≦ 1.20 (2)
However,
f: Focal length of the entire optical system when focusing on infinity f1: Focal length of the first lens group

Conditional expression (2) defines the ratio between the focal length of the first lens group and the focal length of the entire optical system when focusing on infinity. By satisfying the conditional expression (2), the refractive power of the first lens unit becomes appropriate, the spherical aberration that occurs in the first lens unit is suppressed, and an optical system that is small and has good imaging performance. Can be obtained. On the other hand, if the value of conditional expression (2) is below the lower limit, the refractive power of the first lens group becomes strong, so that it becomes difficult to correct spherical aberration, coma aberration, and field curvature, and good imaging It becomes difficult to maintain performance. On the other hand, if the value of conditional expression (2) exceeds the upper limit, the refractive power of the first lens group becomes weak, making it difficult to reduce the telephoto ratio, and the effect of suppressing the total optical length with respect to the focal length is sufficient. Therefore, it is difficult to make the optical system compact.

  From these viewpoints, the value of the conditional expression (2) is preferably within the range of the following expression (2a), and is preferably within the range of the following expression (2b).

0.40 ≦ f1 / f ≦ 1.00 (2a)
0.45 ≦ f1 / f ≦ 0.90 (2b)

2-1-3. Conditional expression (3)
In the inner focus type lens according to the present invention, it is preferable that the following conditional expression (3) is satisfied.

0.30 ≦ f3 / f ≦ 3.30 (3)
However,
f: Focal length of the entire optical system when focusing on infinity f3: Focal length of the third lens group

  Conditional expression (3) defines the ratio between the focal length of the third lens group and the focal length of the entire optical system when focusing on infinity. When the conditional expression (3) is satisfied, the refractive power of the third lens group becomes appropriate, and the optical system can be configured compactly and a bright optical system having good imaging performance can be obtained. . On the other hand, if the value of conditional expression (3) is less than the lower limit, the refractive power of the third lens group becomes strong, so it becomes difficult to correct coma and distortion, and good imaging performance is maintained. It becomes difficult. In this case, since the lens group on the image plane side has a strong positive refractive power, it is difficult to increase the telephoto ratio, and the effect of suppressing the optical total length with respect to the focal length cannot be sufficiently obtained. It becomes difficult to make the optical system compact. If the value of conditional expression (3) exceeds the upper limit value, the refractive power of the third lens group becomes weak. In this case, the F value in the entire optical system tends to increase, and a bright optical system cannot be obtained. On the other hand, in order to realize a bright optical system with good imaging performance in this state, the number of lenses required for aberration correction increases. In particular, it is necessary to increase the number of lenses constituting the first lens group. Therefore, since the number of lenses constituting the optical system increases, it is difficult to reduce the size and weight of the optical system.

  From these viewpoints, the value of the conditional expression (3) is preferably within the range of the following expression (3a), and is preferably within the range of the following expression (3b).

0.40 ≦ f3 / f ≦ 3.00 (3a)
0.55 ≦ f3 / f ≦ 2.80 (3b)

1-2-4. Conditional expression (4)

  In the inner focus type lens according to the present invention, when the third lens group includes the front sub lens group and the rear sub lens group, it is preferable that the following conditional expression (4) is satisfied.

0.20 ≦ f3a / f ≦ 1.70 (4)
However,
f: Focal length of the entire optical system when focusing on infinity f3a: Focal length of front sub-lens group

  Conditional expression (4) is preferably satisfied when the third lens group includes, in order from the object side, a positive front sub-lens group, a negative image stabilization group, and a positive rear sub-lens group. It is. By satisfying the above conditional expression (4), the refractive power of the front sub lens unit disposed closest to the object side in the third lens unit becomes appropriate, and coma and field curvature can be corrected. Thus, an optical system having good vibration isolation performance can be obtained. If the value of conditional expression (4) is less than the lower limit value, the refractive power of the front sub lens group becomes too large, so it becomes difficult to correct coma and field curvature, and the imaging performance during image stabilization deteriorates. Therefore, it is not preferable. If the value of conditional expression (4) exceeds the upper limit value, the refractive power of the front sub-lens group becomes too small to sufficiently converge the light beam incident on the anti-vibration lens group. The effective diameter of the group cannot be reduced, which is not preferable from the viewpoint of reducing the weight of the vibration-proof group and realizing a high speed of the vibration-proof operation.

  From these viewpoints, the value of the conditional expression (4) is preferably within the range of the following expression (4a), and is preferably within the range of the following expression (4b).

0.35 ≦ f3a / f ≦ 1.50 (4a)
0.50 ≦ f3a / f ≦ 1.20 (4b)

1-2-5. Conditional expression (5)
In the inner focus type lens according to the present invention, when the third lens group includes the front sub lens group and the rear sub lens group, it is preferable that the following conditional expression (5) is satisfied.

0.50 ≦ f3c / f ≦ 5.00 (5)
However,
f: Focal length of the entire optical system when focusing on infinity f3c: Focal length of rear sub lens group

  Conditional expression (5) is preferably satisfied when the third lens group includes, in order from the object side, a positive front sub-lens group, a negative image stabilization group, and a positive rear sub-lens group. It is. If the conditional expression (5) is satisfied, the refractive power of the rear sub lens unit disposed closest to the image plane in the third lens unit becomes appropriate, and coma and distortion can be corrected. It is possible to obtain an optical system with good imaging performance during image stabilization. If the value of conditional expression (5) is less than the lower limit, the refractive power of the rear sub lens group becomes too large, so that it becomes difficult to correct coma and distortion, and the imaging performance during image stabilization deteriorates. Therefore, it is not preferable. If the value of conditional expression (5) exceeds the upper limit value, the refractive power of the rear sub lens group becomes too small, and it becomes difficult to realize a bright optical system with a small F value.

  From these viewpoints, the value of the conditional expression (5) is preferably within the range of the following expression (5a), and is preferably within the range of the following expression (5b).

0.60 ≦ f3c ≦ 4.75 (5a)
0.70 ≦ f3c ≦ 4.50 (5b)

1-2-6. Conditional expression (6)
In the inner focus type lens according to the present invention, when the first lens group includes at least three positive lens elements, at least one of the positive lens elements satisfies the following conditional expression (6). preferable.

60.0 ≦ vd1a (6)
However,
vd1a: Abbe number of any positive lens element in the first lens group with respect to the d-line

  Conditional expression (6) indicates that when the first lens group has at least three positive lens elements, at least one of the positive lens elements arranged in the first lens group is positive. It is a preferable conditional expression that the lens element is satisfied. By satisfying the conditional expression (6), it is possible to correct the chromatic aberration in the entire optical system and obtain an optical system having good imaging performance. If the value of conditional expression (6) is less than the lower limit value, chromatic aberration generated in the first lens group becomes large, and the imaging performance deteriorates at any time at infinity or at a finite distance, which is not preferable.

  From these viewpoints, the value of the conditional expression (6) is preferably within the range of the following expression (6a), and is preferably within the range of the following expression (6b).

65 ≦ vd1a (6a)
70 ≦ vd1a (6b)

  Here, in the first lens group, there may be at least one positive lens element that satisfies the conditional expression (6), and there may be a plurality of positive lens elements. The greater the number of positive lens elements that satisfy the conditional expression (6), the better the correction of chromatic aberration. However, among positive lens elements made of existing glass materials, many positive lens elements that satisfy the conditional expression (6) have a low refractive index. For this reason, from the viewpoint of giving a strong positive refractive power to the first lens group, only one positive lens element satisfying the conditional expression (6) is sufficient.

1-2-7. Conditional expression (7) and conditional expression (8)

  In the inner focus type lens according to the present invention, it is preferable that the following conditional expressions (7) and (8) are satisfied.

1.6 ≦ nd3b (7)
25.0 ≦ vd3b ≦ 70.0 (8)
However,
nd3b: Refractive index with respect to d-line of a single lens element as a vibration-proof group vd3b: Abbe number with respect to d-line of a single lens element as a vibration-proof group

  The conditional expression (7) is an expression defining the refractive index with respect to the d-line of the negative single lens element constituting the image stabilizing group provided in the third lens group. By satisfying conditional expression (7), it is possible to obtain an optical system with good imaging performance during image stabilization. Further, by satisfying the conditional expression (7), the amount of movement of the vibration proof group during vibration proof can be reduced, so that the structure of the vibration proof mechanism can be made compact, and the optical system can be downsized. This is also advantageous for achieving the above. On the other hand, if the value of conditional expression (7) is below the lower limit value, the refractive power of the negative single lens element constituting the anti-vibration group becomes small, and it is difficult to maintain good imaging performance during anti-vibration. In addition, since the amount of movement of the vibration proof group during vibration proof becomes large, the vibration proof mechanism becomes large and it becomes difficult to reduce the size of the optical system.

  From these viewpoints, the value of the conditional expression (7) is preferably within the range of the following expression (7a), and is preferably within the range of the following expression (7b).

1.65 ≦ nd3b (7a)
1.70 ≦ nd3b (7b)

  The conditional expression (8) is an expression defining the Abbe number with respect to the d-line of the negative single lens element constituting the image stabilizing group provided in the third lens group. By satisfying conditional expression (8), the variation in chromatic aberration during image stabilization can be reduced, and an optical system having good imaging performance even during image stabilization can be obtained. On the other hand, when the value of conditional expression (8) is below the lower limit value, the Abbe number of the negative single lens element becomes small, the variation in chromatic aberration during image stabilization increases, and good imaging performance is achieved during image stabilization. It becomes difficult to maintain. If the value of conditional expression (8) exceeds the upper limit, the Abbe number of the negative single lens element increases, which is preferable from the viewpoint of correcting chromatic aberration. However, existing glass materials that have an Abbe number that exceeds the upper limit value often have a low refractive index, so if the upper limit value is exceeded, a glass material that has a large Abbe number and a high refractive index is selected. It becomes difficult to do. In addition, when the refractive index of the negative single lens element decreases with increasing Abbe number, it becomes difficult to correct coma aberration and field curvature that occur during image stabilization. It becomes difficult to maintain the imaging performance.

  From these viewpoints, the value of the conditional expression (8) is preferably within the range of the following expression (8a), and is preferably within the range of the following expression (8b).

30.0 ≦ vd3b ≦ 65.0 (8a)
35.0 ≦ vd3b ≦ 60.0 (8b)

1-2-8. Conditional expression (9)

  In the inner focus type lens according to the present invention, it is preferable that the following conditional expression (9) is satisfied.

−25.0 ≦ vd2−vd1b ≦ 60.0 (9)
However,
vd1b: Abbe number with respect to the d-line of the positive lens element arranged closest to the image plane in the first lens group vd2: Abbe number with respect to the d-line of the single lens element constituting the second lens group

  The conditional expression (9) is expressed as follows: the Abbe number with respect to the d-line of the positive lens element disposed closest to the image plane in the first lens group, and the Abbe number with respect to the d-line of the single lens element constituting the second lens group. It is a formula that prescribes the difference. By satisfying conditional expression (9), it is possible to appropriately correct chromatic aberration generated in the first lens group and the second lens group. On the other hand, when the value of conditional expression (9) is lower than the lower limit value or higher than the upper limit value, it is difficult to correct chromatic aberration generated in the first lens group in the second lens group. Thus, it becomes difficult to obtain an optical system having good imaging performance.

  From these viewpoints, the value of the conditional expression (9) is preferably within the range of the following expression (9a), and is preferably within the range of the following expression (9b).

−20 ≦ vd2−vd1b ≦ 50.0 (9a)
−15 ≦ vd2−vd1b ≦ 40.0 (9b)

2. Next, an embodiment of an imaging apparatus according to the present invention will be described. An image pickup apparatus according to the present invention includes the inner focus lens and an image pickup device that converts an optical image formed by the inner focus lens on the image plane side into an electrical signal. Here, there is no particular limitation on the type or the like of the image sensor, and the size of the image sensor is not particularly limited. As described above, the inner focus lens according to the present invention can reduce the size and weight of the focus group and the image stabilization group, reduce the load on the focus drive system, and make the entire optical system compact. Can be made into a telephoto lens that can achieve good imaging performance with a simple configuration and can be made into an interchangeable lens that is excellent in portability. It is suitable for a lens-interchangeable imaging apparatus such as a camera. Furthermore, since the inner focus lens can be configured in a compact manner, it is more preferable that the inner focus lens is a small-lens interchangeable imaging device such as a mirrorless single-lens camera with a small device body. Further, the inner focus type lens according to the present invention can focus at high speed according to the movement of the subject and can also perform the image stabilization operation at high speed. It is particularly suitable for an imaging apparatus capable of capturing moving images. However, the imaging apparatus according to the present invention is not limited to these interchangeable lens cameras, and may be a compact digital camera or the like in which the imaging lens is fixed to the housing in a non-replaceable manner. Of course, the present invention may be applied to various electronic devices such as a mobile phone and a portable electronic device having a communication function.

  Next, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the following examples, the lens configuration described in the following examples is merely an example of the present invention, and the specific lens configuration of the inner focus lens according to the present invention is: Of course, it can be appropriately changed without departing from the gist of the present invention.

  Embodiments of an inner focus lens according to the present invention will be described with reference to the drawings. FIG. 1 is a lens configuration diagram of the optical system of Example 1 in an infinitely focused state.

  As shown in FIG. 1, the photographic lens of Example 1 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refraction. And a third lens group G3 having power. The first lens group G1 includes three positive lens elements, and the second lens group G2 includes a negative single lens element. The third lens group G3 includes, in order from the object side, a front sub lens group having a positive refractive power, a vibration isolation group VC including negative single lens elements, and a rear sub lens group having a positive refractive power. In the third lens group, a negative meniscus lens having a convex surface facing the image surface side is disposed closest to the image surface side. An aperture stop is disposed between the second lens group G2 and the third lens group G3. Further, an optical filter CG is provided on the object side of the image sensor.

  In the inner focus lens, the first lens group G1 and the third lens group 3 are fixed at the time of focusing, and the second lens group G2 at the time of focusing from an object at infinity to a short distance object is As indicated by the arrow F in the figure, the lens moves to the image plane side along the optical axis. The specific lens configuration of each lens group is as shown in FIG.

  Next, in the present Example 1, numerical data and lens data of Numerical Example 1 to which specific numerical values are applied are shown in Tables 1 to 3. In Table 1, “f” is the focal length of the entire optical system, “Fno” is the F value, “2ω” is the angle of view (°), and “FB” is the back focus (mm). “INF” indicates an infinite focus state, “1/40” indicates an imaging magnification, and “MOD” indicates a closest focus state. In Table 2, for each surface number (NS) of each lens, “R” (the radius of curvature of the lens surface), “D” (the lens thickness or the distance between adjacent lens surfaces on the optical axis) ( mm), “nd” (refractive index for d line (wavelength λ = 587.6 nm)), and “vd” (Abbe number for d line). Table 3 is a variable distance table, where “| β |” indicates the imaging magnification, and “d1” and “d2” indicate the surface distances d1 and d2 (mm) at the time of focusing, respectively. . The same applies to Tables 4 to 24 described later. Table 25 shows numerical values of the conditional expressions (1) to (9) in Numerical Example 1.

  2 to 4 show the longitudinal direction of spherical aberration, astigmatism and distortion in the infinitely focused state, the imaging magnification “1/40 ×”, and the closest focus state in the optical system of the first embodiment. Aberration diagrams are shown respectively. Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion aberration (DIS (%)) sequentially from the left side in the drawing. In the spherical aberration diagram, the vertical axis represents the F value (indicated by FNO in the figure), the solid line is the d line (wavelength λ = 587.6 nm), the short broken line is the g line (wavelength λ = 435.8 nm), and the long wave line Is the characteristic of C-line (wavelength λ = 656.3 nm). In the astigmatism diagram, the vertical axis represents the image height (indicated by Y in the figure), the solid line represents the sagittal plane, and the broken line represents the meridional plane. In the distortion diagram, the vertical axis represents the image height (indicated by Y in the figure). The same applies to other longitudinal aberration diagrams.

  FIG. 5 is a transverse aberration diagram of the optical system of Example 1 in the infinite focus state. The three aberration diagrams located on the left side in the drawing correspond to the basic state in which the image stabilization correction is not performed in the infinitely focused state. Also, the three aberration diagrams located on the right side in the drawing correspond to the image stabilization correction state in which the image stabilization group is moved by a predetermined amount in the direction perpendicular to the optical axis. Among the lateral aberration diagrams in the basic state on the left side of the drawing, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows -70% of the maximum image height. Corresponds to the lateral aberration at the image point. In each lateral aberration diagram, the horizontal axis represents the distance from the principal ray on the pupil plane, the solid line is the d line, the short dashed line is the g line, and the long wave line is the C line characteristic. The same applies to other lateral aberration diagrams.

  As can be seen from FIG. 5, the symmetry of the lateral aberration at the axial image point at the time of image stabilization is good. Further, when the lateral aberration at the + 70% image point and the lateral aberration at the −70% image point at the time of image stabilization are compared with the respective lateral aberrations in the basic state, the curvature is small and the inclination of the aberration curve is almost equal. It can be seen that decentration coma and decentration astigmatism are small. This means that sufficient imaging performance is obtained even in the image stabilization correction state. These points are the same for the other embodiments. In the first embodiment, the moving amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.750 mm.

  Next, the optical system of the inner focus lens of Example 2 will be described with reference to the drawings. FIG. 6 is a lens configuration diagram of the optical system of Example 2 in an infinitely focused state. The inner focus type lens of Example 2 has substantially the same configuration as the inner focus type lens of Example 1 although the specific lens configuration of each lens group is different. In the second embodiment, the movement amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.750 mm. FIGS. 7 to 9 show the spherical aberration, astigmatism, and distortion of the inner focus lens of Example 2 in the infinite focus state, the imaging magnification “1/40 ×”, and the closest focus state. Longitudinal aberration diagrams are shown. FIG. 10 shows respective lateral aberration diagrams in the basic state in the infinite focus state and in the image stabilization state.

  Tables 4 to 6 show data of Numerical Example 2 in which specific numerical values are applied. Further, Table 25 shows numerical values of the conditional expressions (1) to (9) in Numerical Example 2.

  Next, the optical system of the inner focus lens of Example 3 will be described with reference to the drawings. FIG. 11 is a lens configuration diagram of the optical system of Example 3 in an infinitely focused state. The inner focus type lens of Example 3 has substantially the same configuration as the inner focus type lens of Example 1, although the specific lens configuration of each lens group is different. In the third embodiment, the movement amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.602 mm. FIGS. 12 to 14 show the spherical aberration, astigmatism, and distortion of the inner focus lens of Example 3 in the infinite focus state, the imaging magnification “1/40 ×”, and the closest focus state. Longitudinal aberration diagrams are shown. FIG. 15 shows lateral aberration diagrams in the basic state in the infinity in-focus state and in the image stabilization state.

  Tables 7 to 9 show data of Numerical Example 3 in which specific numerical values are applied. Further, Table 25 shows numerical values of the conditional expressions (1) to (9) in Numerical Example 3.

  Next, the optical system of the inner focus lens of Example 4 will be described with reference to the drawings. FIG. 16 is a lens configuration diagram of the optical system of Example 4 in an infinitely focused state. The inner focus type lens of Example 4 has substantially the same configuration as the inner focus type lens of Example 1, although the specific lens configuration of each lens group is different. In the fourth embodiment, the moving amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.750 mm. 17 to 19 show the spherical aberration, astigmatism and distortion of the inner focus lens of Example 4 in the infinite focus state, the imaging magnification “1/40 ×”, and the closest focus state. Longitudinal aberration diagrams are shown. FIG. 20 shows lateral aberration diagrams in the basic state in the infinity in-focus state and in the anti-shake correction state.

  Tables 10 to 12 show data of Numerical Example 4 in which specific numerical values are applied. Further, Table 25 shows numerical values of the conditional expressions (1) to (9) in Numerical Example 4.

  Next, an optical system of the inner focus lens of Example 5 will be described with reference to the drawings. FIG. 21 is a lens configuration diagram of the optical system of Example 5 in an infinitely focused state. The inner focus type lens of Example 5 has substantially the same configuration as the inner focus type lens of Example 1 except that the aperture stop is disposed in the front sub lens group of the third lens group. However, the specific lens configuration of each lens group is as shown in FIG. In the fifth embodiment, the moving amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.750 mm. 22 to 24 show the spherical aberration, astigmatism and distortion of the inner focus lens of Example 4 in the infinite focus state, the imaging magnification “1/40 ×”, and the closest focus state. Longitudinal aberration diagrams are shown. Further, FIG. 25 shows respective lateral aberration diagrams in the basic state in the infinitely focused state and in the image stabilization state.

  Tables 13 to 15 show data of Numerical Example 5 in which specific numerical values are applied. Further, Table 25 shows numerical values of conditional expressions (1) to (9) in Numerical Example 5.

  Next, an optical system of the inner focus lens of Example 6 will be described with reference to the drawings. FIG. 26 is a lens configuration diagram of the optical system of Example 6 in an infinitely focused state. The inner focus type lens of Example 6 has substantially the same configuration as the inner focus type lens of Example 1 although the specific lens configuration of each lens group is different. In the sixth embodiment, the movement amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.750 mm. 27 to 29 show the spherical aberration, astigmatism and distortion of the inner focus lens of Example 6 in the infinite focus state, the imaging magnification “1/40 ×”, and the closest focus state. Longitudinal aberration diagrams are shown. Further, FIG. 30 shows respective lateral aberration diagrams in the basic state in the infinitely focused state and in the image stabilization state.

  Tables 16 to 18 show data of Numerical Example 6 to which specific numerical values are applied. Further, Table 25 shows numerical values of the conditional expressions (1) to (9) in Numerical Example 6.

  Next, an optical system of the inner focus lens of Example 7 will be described with reference to the drawings. FIG. 31 is a lens configuration diagram of the optical system of Example 7 in an infinitely focused state. The inner focus type lens of Example 7 has substantially the same configuration as the inner focus type lens of Example 1, although the specific lens configuration of each lens group is different. In the seventh embodiment, the movement amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.750 mm. FIGS. 32 to 34 show the spherical aberration, astigmatism and distortion of the inner focus lens of Example 7 in the infinite focus state, the imaging magnification “1/40 ×”, and the closest focus state. Longitudinal aberration diagrams are shown. Further, FIG. 35 shows respective lateral aberration diagrams in the basic state in the infinitely focused state and in the image stabilization state.

  Tables 19 to 21 show data of Numerical Example 7 to which specific numerical values are applied. Further, Table 25 shows numerical values of the conditional expressions (1) to (9) in Numerical Example 7.

  Next, an optical system of the inner focus lens of Example 8 will be described with reference to the drawings. FIG. 36 is a lens configuration diagram of the optical system of Example 8 in the infinite focus state. The inner focus type lens of Example 8 has substantially the same configuration as the inner focus type lens of Example 1, although the specific lens configuration of each lens group is different. In the eighth embodiment, the movement amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the infinitely focused state is 0.613 mm. FIGS. 37 to 39 show spherical aberration, astigmatism, and distortion in the in-focus state of the inner focus lens of Example 8 in the infinite focus state, the imaging magnification “1/40 ×”, and the closest focus state. Longitudinal aberration diagrams are shown. Also, FIG. 40 shows lateral aberration diagrams in the basic state in the infinity in-focus state and in the image stabilization state.

  Tables 22 to 24 show data in Numerical Example 8 in which specific numerical values are applied. Further, Table 25 shows numerical values of the conditional expressions (1) to (9) in Numerical Example 8.

  The inner focus type lens according to the present invention adopts the above lens configuration and focusing method to reduce the size and weight of the focus group and the vibration isolation group, and to load the focus drive system and the vibration isolation group drive system. In addition to reduction, the entire optical system can be made compact, and good imaging performance can be realized with a simple configuration. For this reason, it is suitable for an interchangeable lens and a small-sized photographing device for a small-sized photographing device with a small casing, and can be focused on the subject at a high speed according to the movement of the subject. Suitable for interchangeable lenses and small imaging devices.

Claims (12)

In order from the object side, a first lens group having a positive refractive power and a second lens group having negative refractive power, a third lens group having positive refractive power, a short distance from infinity An inner focus type lens that moves the second lens group along the optical axis when focusing on an object;
The second lens group is composed of a negative single lens element,
The third lens group has an image stabilization group composed of negative single lens elements, and the image blur that occurs when the optical system vibrates by moving the image stabilization group substantially perpendicular to the optical axis. There line correction,
An inner focus type lens satisfying the following conditional expression (3):
0.30 ≦ f3 / f ≦ 3.30 (3)
However,
f: focal length of the entire optical system in focus at infinity f3: focal length of the third lens group The inner focus type lens according to claim 1, wherein the following conditional expression (1) is satisfied.
45.0 ≦ vd2 (1)
However,
vd2: Abbe number with respect to d-line of the single lens elements constituting the second lens group   3. The inner focus lens according to claim 1, wherein an aperture stop is disposed closer to the image plane than the second lens group in the optical system. The inner focus type lens according to any one of claims 1 to 3, wherein the following conditional expression (2) is satisfied.
0.30 ≦ f1 / f ≦ 1.20 (2)
However,
f: focal length of the entire optical system in focus at infinity f1: focal length of the first lens group The third lens group, one in order from the object side, the front sub-lens group having positive refractive power, of the vibration-proof group, and claims 1 to 4 comprising a rear sub-lens group having positive refractive power The inner focus type lens according to one item. The inner focus type lens according to claim 5, wherein the following conditional expression (4) is satisfied.
0.20 ≦ f3a / f ≦ 1.70 (4)
However,
f: focal length of the entire optical system in focus at infinity f3a: focal length of front sub-lens group The inner focus type lens according to claim 5 or 6, wherein the following conditional expression (5) is satisfied.
0.50 ≦ f3c / f ≦ 5.00 (5)
However,
f: focal length of the entire optical system in the infinitely focused state f3c: focal length of the rear sub lens group Having said first lens group at least three positive lens elements, at least one of the positive lens element, according to any one of claims 1 to 7 satisfies the following conditional expression (6) Inner focus lens.
60.0 ≦ vd1a (6)
However,
vd1a: Abbe number of any positive lens element in the first lens group with respect to the d-line The inner focus type according to any one of claims 1 to 8 , wherein the lens element arranged closest to the image plane side in the third lens group is a negative meniscus lens having a convex surface facing the image plane side. lens. The inner focus type lens according to any one of claims 1 to 9 , wherein the following conditional expression (7) and conditional expression (8) are satisfied.
1.6 ≦ nd3b (7)
25.0 ≦ vd3b ≦ 70.0 (8)
However,
nd3b: Refractive index with respect to d-line of a single lens element as a vibration-proof group vd3b: Abbe number with respect to d-line of a single lens element as a vibration-proof group The inner focus type lens according to any one of claims 1 to 10 , wherein the following conditional expression (9) is satisfied.
−25.0 ≦ vd2−vd1b ≦ 60.0 (9)
However,
vd1b: Abbe number with respect to the d-line of the positive lens element arranged closest to the image plane in the first lens group vd2: Abbe number with respect to the d-line of the single lens element constituting the second lens group The inner focus type lens according to any one of claims 1 to 11 , and an image pickup device that converts an optical image formed by the inner focus type lens into an electrical signal on an image plane side thereof. An imaging apparatus characterized by that.

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