JP2019066676A - Inner-focus imaging optical system and image capturing device - Google Patents

Abstract

To provide an inner-focus imaging optical system which is compact and light-weight and offers good aberration correction and high-performance image-forming capability, and to provide an image capturing device having the same.SOLUTION: An inner-focus imaging optical system is provided, comprising a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a rear lens group GR having positive refractive power in order from the object side to the image side, where the system is configured such that the second lens group G2 moves along an optical axis for focusing and that the constituent lenses satisfy predetermined conditional expressions. An image capturing device having such system is also provided herein.SELECTED DRAWING: Figure 1

Description

  The present invention is an inner focus type imaging optical system which is small in size and light in weight and whose aberration is well corrected, and which is suitable as an imaging optical system such as a digital still camera, a film camera or a video camera, and The present invention relates to an imaging device provided.

In recent years, with increasing pixel pitch and performance of solid-state imaging devices such as CMOS image sensors, along with that, solid-state imaging devices such as small-sized, light-weight and high-performance digital still cameras such as microfour SARS systems have been developed. The imaging device system used is rapidly spreading.
Further, along with that, the image forming optical system has also been improved in performance, and in particular, as a telephoto optical system, there is a demand for a compact, lightweight and telephoto type image forming optical system with well corrected aberrations, particularly a so-called super telephoto lens. It is rising.

As a large aperture ratio inner focusing type super telephoto lens with excellent optical performance and small focusing lens group diameter, a first lens group G1 having positive refracting power and a second refracting power in order from the object side An internally focusing telephoto lens including a lens group G2 and a third lens group G3 having positive refracting power, and moving the second lens group G2 along the optical axis to perform focusing, the first lens group G1 In order from the object side, a focusing lens group diameter which comprises a front group G11 having positive refractive power and a rear group G12 having positive refractive power similar to that of the front group G11 and satisfies a predetermined conditional expression is A small and large aperture ratio inner focusing type imaging optical system has been proposed (see, for example, Patent Document 1).
In Examples 1 to 3 of Patent Document 1, the effective diameter of the second lens group G2 which is the focus lens group is about 1⁄5 of the effective diameter of the first lens group G1, and is extremely miniaturized. .

  On the other hand, in the inner focusing type image forming optical system with the large aperture ratio of Patent Document 1, the number of lenses in the front group G11 is large and the aperture is large, so that the degree of reduction in size and weight of the entire optical system is low. There's a problem.

As another telephoto lens optical system realizing a reduction in diameter, a first lens group of positive refracting power, a second lens group of negative refracting power, and a rear lens group of positive refracting power are sequentially arranged from the object side to the image side A telephoto lens system having a first sub lens unit and a second sub lens unit is disclosed in the order from the object side to the image side of the second lens group (see, for example, Patent Document 2).
In the telephoto lens system disclosed in Patent Document 2, the second sub-lens unit is disposed with a large air gap from the first sub-lens unit, thereby reducing the aperture of the second sub-lens unit to achieve optical The system has been reduced in size and weight.

  On the other hand, in the telephoto lens optical system of Patent Document 2, the aperture of the focus lens unit is not sufficiently miniaturized, and the movement amount of the focus lens unit is large, so that sufficient downsizing of the actuator is not achieved. . The vibration reduction lens unit also has a three-lens configuration, and the aperture is not sufficiently miniaturized, so sufficient downsizing of the actuator and the mechanical unit has not been achieved.

The first lens group G1 of positive refracting power and negative refraction in order from the object side to the image side as a telephoto lens optical system which realizes the reduction in size and weight reduction, and in particular, the focus group and the vibration reduction group are miniaturized. Inner-focusing type imaging optical system that is composed of a second lens group G2 of power and a third lens group G3 of negative refractive power, and focusing is performed by moving the second lens group G2 along the optical axis In the first lens group G1, the first lens group G1a having positive refractive power and the first b lens group G1b having positive refractive power at the widest lens interval in the first lens group G1, and the first lens group G1a G1a discloses an inner focusing type telephoto lens optical system including at least one positive lens and at least one negative lens, and the first lens subunit G1b includes one positive lens and one negative lens. (See, for example, Patent Document 3).
In the telephoto lens optical system disclosed in Patent Document 3, aberrations are corrected well while achieving downsizing by appropriately sharing the first lens group G1 with a plurality of partial groups with a positive refractive power. There is.

  On the other hand, in the inner focusing type imaging optical system of Patent Document 3, the lens disposed on the image side in the lens group G1a is not sufficiently small in diameter, and sufficient weight reduction of the optical system is achieved. Not. In addition, the second lens group G2 which is the focus lens group is not sufficiently reduced in diameter, and sufficient downsizing of the actuator and the mechanical unit is not achieved.

Unexamined-Japanese-Patent No. 11-326754 JP, 2016-148707, A Unexamined-Japanese-Patent No. 2017-32809

(Object of the Invention)
The present invention is made in view of the above-described problems of the inner focus type imaging optical system and the imaging apparatus according to the prior art, and is an inner focus type imaging optical system that is compact and lightweight, with well corrected aberrations and capable of high-performance imaging. It is an object of the present invention to provide a system and an imaging device provided with the system.

A first invention according to an aspect of the present invention is
A first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear lens group GR having a positive refractive power, in order from the object side to the image side, the second lens group G2 An inner focusing type imaging optical system which moves along the optical axis to perform focusing;
The first lens group G1 is composed of a first f lens group G1 f and a first c lens group G1 c, which are sequentially disposed from the object side with an air gap therebetween.
The first f lens group G1 f is composed of a first a lens group G1 a and a first b lens group G1 b, which are sequentially disposed from the object side with an air gap therebetween.
An inner focus type image forming optical system characterized by satisfying the following conditional expression.
H1c / H1a ≦ 0.75 (1a)
H1b / H1a ≦ 0.95 (1b)
0.7 ≦ F1 f / F1 c ≦ 2.2 (1c)
2.5 ≦ β2 × βR ≦ 4.5 (1d)
However,
H1a: height from the optical axis of the intersection point of the surface of the first lens group G1a closest to the object side and the marginal ray at the time of opening the aperture upon focusing on an infinite distance object
H1b: The height from the optical axis of the intersection point of the surface on the most object side of the first lens subunit G1b and the marginal ray at the time of aperture opening at focusing on an infinite distance object
H1c: height from the optical axis of the intersection point of the surface on the most object side of the first c lens group G1c and the marginal ray at the time of aperture opening at focusing on an infinite distance object
F1 f: focal length of the first f lens group G1 f
F1c: focal length β2 of the first c lens group G1c: lateral magnification βR at infinity focusing of the second lens group G2: lateral magnification at infinity focusing of the rear lens group GR.

A second invention according to one aspect of the present invention is
The inner side of the inner focusing type imaging optical system according to the first aspect of the present invention is provided with an imaging device for converting an optical image formed by the inner focusing type imaging optical system into an electrical signal. It is an imaging device provided with a focusing type imaging optical system.

  According to the invention of one aspect of the present invention, it is possible to form an inner focus type imaging optical system which is compact and lightweight, and whose aberration is well corrected. Further, a high-performance imaging apparatus can be configured to form a good image formation on the imaging element by the inner focus type imaging optical system.

It is a lens block diagram at the time of infinity focusing of the 1st Example of the inner-focusing type imaging optical system of this invention. FIG. 7 is a longitudinal aberration diagram at the time of focusing at infinity of the first embodiment of the inner focusing type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate | middle object of 1st Example of the inner-focusing type imaging optical system of this invention. It is a lens block diagram at the time of infinity focusing of 2nd Example of the inner-focusing type imaging optical system of this invention. It is a longitudinal aberration figure at the time of focusing to infinity of the 2nd example of an inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate | middle object of 2nd Example of the inner-focusing type imaging optical system of this invention. It is a lens block diagram at the time of infinity focusing of 3rd Example of the inner-focusing type imaging optical system of this invention. It is a longitudinal aberration figure at the time of focusing to infinity of the 3rd example of an inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate | middle object of 3rd Example of the inner-focusing type imaging optical system of this invention. It is a lens block diagram at the time of infinity focusing of 4th Example of the inner-focusing type imaging optical system of this invention. It is a longitudinal aberration figure at the time of focusing to infinity of the 4th example of an inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate | middle object of 4th Example of the inner-focusing type imaging optical system of this invention. It is a lens block diagram at the time of infinity focusing of 5th Example of the inner-focusing type imaging optical system of this invention. It is a longitudinal aberration figure at the time of focusing to infinity of the 5th example of an inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate | middle object of 5th Example of the inner-focusing imaging optical system of this invention. It is a lens block diagram at the time of infinity focusing of the 6th example of the inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to infinity of a 6th example of an inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate | middle object of 6th Example of the inner-focusing type imaging optical system of this invention. It is a lens block diagram at the time of infinity focusing of 7th Example of the inner-focusing type imaging optical system of this invention. It is a longitudinal aberration figure at the time of focusing to infinity of the 7th example of an inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate | middle object of 7th Example of the inner-focusing type imaging optical system of this invention. It is a lens block diagram at the time of infinity focusing of the 8th example of the inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of the focusing to infinity of the 8th example of the inner focus type imaging optical system of the present invention. It is a longitudinal aberration figure at the time of focusing to the intermediate object of the 8th example of the inner focus type imaging optical system of the present invention. It is a lens block diagram of the 1st combination of the lens unit in a 1st lens group. It is a lens block diagram of the 2nd combination of the lens unit in a 1st lens group. It is a lens block diagram of the 3rd combination of the lens unit in a 1st lens group.

Hereinafter, embodiments of the present invention will be described.
(Embodiment)
An inner focus type imaging optical system according to an embodiment of the present invention is
A first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear lens group GR having a positive refractive power, in order from the object side to the image side, the second lens group G2 An inner focusing type imaging optical system which moves along the optical axis to perform focusing;
The first lens group G1 is composed of a first f lens group G1 f and a first c lens group G1 c, which are sequentially disposed from the object side with an air gap therebetween.
The first f lens group G1 f is composed of a first a lens group G1 a and a first b lens group G1 b arranged in order from the object side with an air gap therebetween.
An inner focus type image forming optical system characterized by satisfying the following conditional expression.
H1c / H1a ≦ 0.75 (1a)
H1b / H1a ≦ 0.95 (1b)
0.7 ≦ F1 f / F1 c ≦ 2.2 (1c)
2.5 ≦ β2 × βR ≦ 4.5 (1d)
However,
H1a: height from the optical axis of the intersection point of the surface of the first lens group G1a closest to the object side and the marginal ray at the time of aperture opening when focusing on an infinite distance object
H1b: The height from the optical axis of the intersection point of the surface on the most object side of the first lens subunit G1b and the marginal ray at the time of aperture opening at focusing on an infinite distance object
H1c: height from the optical axis of the intersection point of the surface on the most object side of the first c lens group G1c and the marginal ray at the time of aperture opening at focusing on an infinite distance object
F1 f: focal length of the first f lens group G1 f
F1c: focal length β2 of the first c lens group G1c: lateral magnification βR at infinity focusing of the second lens group G2: lateral magnification at infinity focusing of the rear lens group GR.

  The inner focusing type imaging optical system according to one embodiment of the present invention includes, in order from the object side to the image side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a positive lens group. The inner focusing type imaging optical system includes a rear lens group GR having a refractive power, and the second lens group G2 moves along an optical axis to perform focusing.

The first lens group G1 has a positive refractive power as a whole, and in order from the object side, the first f lens group G1 f and the first c lens so as to satisfy the conditional expression (1a) and the conditional expression (1b). It is comprised by group G1c. The first f lens group G1 f is composed of, in order from the object side, a first a lens group G1 a and a first b lens group G1 b. As long as it has this configuration, the specific lens configuration that constitutes each lens group is not particularly limited.
Further, the light beam incident on the inner focusing type imaging optical system of the present invention is lowered in height of the light beam by being incident on the lens group G1a, and is disposed at a position satisfying the conditional expression (1b). By entering the 1b lens group G1b, the height of the light beam is further lowered, and the 1c lens group G1c disposed at a position satisfying the conditional expression (1a) enters.
With this configuration, the first lens group G1b and the first lens group G1c can be downsized, and the weight of the first lens group G1 that contributes the most to the lens mass in the telephoto optical system can be reduced. Furthermore, by reducing the diameter of the first c lens group G1c, the second lens group G2 disposed on the image side of the first c lens group G1c can be reduced in diameter, and is moved along the optical axis to It is possible to prevent the driving device for focusing from becoming large and heavy, and it is possible to miniaturize the actuator and the mechanical unit for driving the second lens group G2.

  As long as the lens group G1a includes the lens disposed closest to the object side in the first lens group G1, its specific lens configuration is not particularly limited. For example, it is preferable that the lens sub-unit G1a have a positive refractive power in order to obtain the effect of reducing the height of the light beam.

  The first b lens group is disposed on the image side of the first a lens group G1a in the first lens group G1, and the lens disposed closest to the object side of the first b lens group G1b satisfies the conditional expression (1b). As long as it is arranged, the specific lens configuration is not particularly limited. For example, it is preferable that the 1b-th lens unit G1b have a positive refractive power in order to obtain an effect of reducing the height of a light beam. In addition, in order to correct the aberration generated in the first a lens group G1a, it is preferable to include a negative lens. Furthermore, it is preferable to dispose a lens of an anomalous dispersion glass material in the 1b-th lens group G1b because the 1b-th lens group G1b can be smaller in aperture than the 1a-th lens group G1a. Since the anomalous dispersion glass material has a smaller specific gravity than other glass materials, chromatic aberration can be effectively corrected while reducing the diameter and reducing the weight by disposing it in the first lens subunit G1b.

  The first f lens group G1 f is a lens group including the first a lens group G1 a and the 1 b lens group G1 b. In order to reduce the weight of the 1b-th lens group G1b by reducing the aperture, it is preferable to have the largest air gap in the 1f-th lens group G1f between the 1a-th lens group G1a and the 1b-th lens group G1b. Here, the largest air gap means that the air gap has a certain refractive power and does not include a lens that contributes to aberration correction or miniaturization, and does not have a filter or a refractive power in the air gap, or Included is the placement of lenses with small refractive power.

  The first c lens group G1c is disposed on the image side of the first f lens group G1f in the first lens group G1, and the lens disposed closest to the object side of the first c lens group G1c satisfies the conditional expression (1a). The specific lens configuration is not particularly limited as long as it is disposed. For example, it is preferable that the first c lens group G1c has a positive refractive power in order to lower the height of light incident on the second lens group G2 and to reduce the diameter of the second lens group G2. Also, in order to correct the aberration, a negative lens may be included.

  As long as the second lens group G2 has a negative refractive power as a whole, its specific lens configuration is not particularly limited. For example, it is preferable that the second lens group G2 move to the image side along the optical axis to perform focusing. Further, in order to suppress aberration variation at the time of focusing, it is preferable that the second lens group G2 includes at least one positive lens.

  As long as the rear lens group GR has a positive refractive power as a whole, the specific lens configuration is not particularly limited. For example, a lens group that is movable with the second lens group G2 at the time of focusing, or a converter lens group for changing the magnification of the entire optical system may be included.

  The conditional expression (1a) is an expression for defining the first lens subunit G1f and the first lens subunit G1c which are disposed at an air gap and which constitute the first lens group G1. The conditional expression (1b) is an expression for defining a first a lens group G1a and a first b lens group G1b which are disposed at an air interval and which constitute the first f lens group G1f.

By satisfying the conditional expressions (1a) and (1b), the heights of the light rays incident to the 1b lens group G1b lens and the 1c lens group G1c disposed on the image side of the 1a lens group G1a are appropriately reduced. This makes it possible to reduce the spherical aberration and coma aberration of the first lens group G1 while achieving weight reduction by reducing the diameter of the first lens group G1b and the second lens group G2 that constitute the first lens group G1. It is possible to make corrections to
If the upper limit of conditional expression (1a) is exceeded, the height of light incident on the 1c lens group G1c disposed on the image side of the 1a lens group G1a can not be sufficiently lowered. It is difficult to reduce the diameter of the second lens group G2 disposed on the side, which is not preferable.
In addition, if the upper limit of conditional expression (1b) is exceeded, the height of the light beam incident on the 1b lens group G1b disposed on the image side of the 1a lens group G1a can not be sufficiently lowered, so the 1b lens group G1b Leading to a large diameter, making weight reduction difficult and not preferable.
The air gap separating the 1a lens group G1a from the 1bb lens group G1b is more preferably the largest air gap in the 1f lens group G1f.

The upper limit of conditional expression (1a) is more preferably 0.65, more preferably 0.55, and still more preferably 0.45.
The upper limit of conditional expression (1b) is more preferably 0.93, more preferably 0.91, and even more preferably 0.89.

In each lens unit constituting the first lens unit G1, excessively lowering the height of the light beam makes it difficult to correct the aberration generated in each lens unit, and in turn each lens for aberration correction The increase in the number of lenses constituting the group leads to a weight increase. Lowering the beam height too much will also provide a large air gap to reduce the height of the light beam incident on the group located on the image side while suppressing aberration correction. It is not preferable because it causes an increase. Here, the total optical length indicates the distance from the first surface of the imaging optical system to the image plane.
Therefore, for the conditional expression (1a), if the lower limit value is determined, it is preferably 0.15, more preferably 0.20, and even more preferably 0.25. In addition, with regard to the conditional expression (1b), when the lower limit value is determined, it is preferably 0.50, more preferably 0.60, and still more preferably 0.70.

The inner focus type imaging optical system of the present invention is characterized by satisfying the following conditional expression.
0.7 ≦ F1 f / F1 c ≦ 2.2 (1c)
F1 f: focal length of the first f lens group G1 f
F1c: Focal length of the 1c lens group G1c

The conditional expression (1c) is an expression for defining the ratio of the focal length of the first f lens group G1 f and the first c lens group G1 c.
By satisfying the conditional expression (1c), it is possible to satisfactorily correct the spherical aberration and the coma aberration in the first lens subunit G1f while reducing the optical length of the first lens subunit G1. Here, the optical length of the lens group indicates the distance from the most object side surface to the most image side surface of the lens group.
If the upper limit of conditional expression (1c) is exceeded, the focal length of the first f lens group G1 f becomes longer than the focal length of the first c lens group G1 c, so the first c lens group is satisfied so as to satisfy conditional expression (1a). When G1c is disposed, the air gap between the first f lens group G1 f and the first c lens group G1 c becomes large. As a result, the optical length of the first lens group G1 becomes large, which makes it difficult to miniaturize, which is not preferable. If the lower limit of conditional expression (1c) is divided, the focal length of the first f lens group G1f becomes short, which makes it difficult to satisfactorily correct chromatic aberration, spherical aberration and coma aberration in the first f lens group G1f. .

The lower limit of conditional expression (1c) is more preferably 0.80, more preferably 0.90, and still more preferably 0.95.
The upper limit of conditional expression (1c) is more preferably 2.10, more preferably 2.00, and more preferably 1.95.

The inner focus type imaging optical system of the present invention is characterized by satisfying the following conditional expression.
2.5 ≦ β2 × βR ≦ 4.5 (1d)
However,
β2: Lateral magnification of the second lens group G2: Lateral magnification of the rear lens group GR The conditional expression (1d) is an equation for defining the product of the lateral magnification of the second lens group G2 and the rear lens group GR.
By satisfying the conditional expression (1d), the first lens group G1 properly corrects the aberration of the combined lateral magnification of the second lens group G2 and the rear lens group GR disposed on the image side of the first lens group G1. It is possible to correct the spherical aberration and the coma aberration in the first lens group G1 well while reducing the overall optical length. Here, the total optical length is the distance from the most object side surface of the imaging optical system, that is, the first surface to the image plane position.
If the upper limit of conditional expression (1d) is exceeded, the combined lateral magnification of the second lens group G2 and the rear lens group GR becomes too large, so it is necessary to shorten the focal length of the first lens group. Therefore, it is difficult to satisfactorily correct spherical aberration and coma aberration in the first lens group G1, which is not preferable. Further, if the lower limit of the conditional expression (1d) is divided, the combined lateral magnification of the second lens group G2 and the rear lens group GR becomes too small, so it is necessary to increase the focal length of the first lens group. As a result, the overall optical length becomes large, making it difficult to miniaturize, which is not preferable.

The lower limit of conditional expression (1d) is more preferably 2.60, more preferably 2.65, and still more preferably 2.70.
The upper limit of conditional expression (1d) is more preferably 4.30, more preferably 4.10, and still more preferably 4.00.

  Here, the fact that the first lens group G1 has three or more air gaps in the technical scope of the present invention will be described. When there are two air gaps in the first lens group G1, the 1a lens group G1a, the 1b lens group G1b, the 1c lens group G1c, and the 1f lens group G1f constituting the first lens group G1 are It can be uniquely identified.

  However, when there are three air gaps in the first lens group G1, the first lens group G1a, the first lens group G1b, the first lens group G1c, and the first lens group G1f are also different according to the definition. It is possible to form a combination of For example, as shown in FIGS. 25A, 25B, and 25C, the first lens unit G1 includes, from the object side, the first lens unit LU1, the second lens unit LU2, the third lens unit LU3, and the fourth lens unit LU4. It is assumed that there is an air gap between each lens unit.

In the first combination of the first lens group G1, as shown in FIG. 25A, the 1a-th lens group G1a is the first lens unit LU1. The first b lens group G1 b is a second lens unit LU2. The first lens unit G1c is a third lens unit LU3 and a fourth lens unit LU4.
As a second combination of the first lens group G1, as shown in FIG. 25B, the first lens group G1a is a first lens unit LU1 and a second lens unit LU2. The first b lens group G1 b is a third lens unit LU3. The first lens unit G1c is a fourth lens unit LU4.
In the third combination of the first lens group G1, as shown in FIG. 25C, the 1a-th lens group G1a is the first lens unit LU1. The first b lens group G1 b is a second lens unit LU2 and a third lens unit LU3. The first lens unit G1c is a fourth lens unit LU4.

  If at least one of the three combinations described above satisfies the conditional expression (1a) to the conditional expression (1d), an inner-focusing imaging optical system that is compact and lightweight and whose aberration is corrected well The imaging optical system is within the scope of the present invention.

  Even in the case where the first lens group G1 has four or more air gaps, it is apparent that the concept of the case where the first lens group G1 has three air gaps is applicable.

It is preferable that the inner focus type imaging optical system of the present invention satisfies the following conditional expression.
0.5 ≦ F1a / F1c ≦ 4.0 (2)
However,
F1a: Focal length of the lens group G1a

The conditional expression (2) is an expression for defining the ratio of the focal length of the 1a-th lens group G1a and the 1st-c lens group G1c.
By satisfying the conditional expression (2), it is possible to satisfactorily correct the spherical aberration and the coma aberration in the lens subunit G1a while reducing the overall optical length.

  If the upper limit of conditional expression (2) is exceeded, the focal length of the 1a lens group G1a will be long, so the overall optical length will be large, and miniaturization will be difficult, which is not preferable. Further, if the lower limit of conditional expression (2) is divided, the focal length of the 1a-th lens group G1a becomes short, so it is difficult to suppress the occurrence of spherical aberration and coma aberration in the 1a-th lens group G1a and the 1c lens group G1c. It is not preferable.

The lower limit of conditional expression (2) is more preferably 0.60, more preferably 0.90, and still more preferably 1.20.
Further, the upper limit of the conditional expression (2) is more preferably 3.50, more preferably 3.00, and still more preferably 2.70.

It is preferable that the inner focus type imaging optical system of the present invention satisfies the following conditional expression.
0.4 ≦ F1 / F1c ≦ 1.5 (3)
However,
F1: focal length of the first lens group G1

The conditional expression (3) is an expression for defining the ratio of the focal length of the first lens group G1 and the focal length of the first c lens group G1c.
By satisfying the conditional expression (3), it is possible to satisfactorily correct the chromatic aberration, the spherical aberration and the coma aberration in the first lens group G1 while reducing the overall optical length.

If the upper limit of conditional expression (3) is exceeded, the focal length of the 1c lens group G1c becomes short, which makes it difficult to suppress the occurrence of spherical aberration and coma aberration in the 1c lens group G1c, which is not preferable.
Further, dividing the lower limit of the conditional expression (3) makes the focal length of the first f lens group G1 f short, which makes it difficult to suppress the occurrence of chromatic aberration, spherical aberration and coma aberration in the first f lens group G1 f, which is not preferable. .

The lower limit of conditional expression (3) is more preferably 0.50, more preferably 0.60, and still more preferably 0.65.
Further, the upper limit of the conditional expression (3) is more preferably 1.40, more preferably 1.30, and still more preferably 1.20.

It is preferable that the inner focus type imaging optical system of the present invention satisfies the following conditional expression.
H1c / H1b ≦ 0.80 (4)
The conditional expression (4) is the height from the optical axis of the point of intersection of the surface on the most object side of the 1c lens group G1c and the marginal ray at the time of focusing on an infinite distance object, the 1b lens It is an equation for defining the ratio of the height from the optical axis of the intersection point of the most object side surface of the group G1b and the marginal ray at the time of focusing on an infinite distance object.

  By satisfying the conditional expression (4), the diameter of the second lens group G2 can be reduced, and the size and weight of an actuator for driving the second lens group G2 can be reduced.

  If the upper limit of conditional expression (4) is exceeded, it is difficult to reduce the diameter of the first c lens group G1c, which leads to the increase in the diameter of the second lens group G2, and the size of the actuator for driving the second lens group G2 is reduced. And it is not preferable because weight reduction becomes difficult.

  The upper limit of conditional expression (4) is more preferably 0.70, more preferably 0.60, and still more preferably 0.55.

  In the inner focusing type imaging optical system of the present invention, it is preferable that at least a part of the rear lens group GR move so as to include a component in the direction perpendicular to the optical axis. With this configuration, it is possible to correct image blur caused by camera shake or the like, that is, to perform camera shake correction, and it is also possible to correct decentration aberration at the time of image stabilization.

Further, in the inner focusing type imaging optical system of the present invention, the rear lens group GR includes, in order from the object side to the image side, the 3a lens group G3a having positive refractive power and the 3b lens group G3b having negative refractive power. It is preferable to provide a third c lens group G3c having positive refractive power, and move at least a part of the third b lens group G3b so as to include a component in a direction perpendicular to the optical axis.
With this configuration, it is possible to correct image blur caused by camera shake or the like, that is, to perform camera shake correction, and it is also possible to satisfactorily correct decentration aberration at the time of camera shake correction. In addition, since it is possible to reduce the diameter of the third b lens group G3b, it is possible to reduce the size of the actuator and the mechanical unit for driving.

Further, it is preferable that the 3b-th lens unit G3b be configured to include an object-side cemented lens and an image-side cemented lens in order from the object side to the image side.
Further, it is preferable to move the image side cemented lens so as to include a component in a direction perpendicular to the optical axis.
The object side cemented lens is composed of, in order from the object side to the image side, a negative lens and a positive lens, and the image side cemented lens is a positive lens and a negative lens in order from the object side to the image side And are more preferable.

    In the inner focus type image forming optical system of the present invention, it is preferable that the first lens subunit G1b has at least two negative lenses and at least two positive lenses. With this configuration, it is possible to satisfactorily correct the aberration of the first lens subunit G1b while reducing the overall optical length. In the following embodiments, the first lens subunit G1b will be described by way of an example including two negative lenses and three positive lenses. However, as described above, the negative lens included in the first lens subunit G1b is The number of lenses may be three or more, and the number of positive lenses may be two or four or more.

In order to correct aberrations more favorably, it is more preferable that the first lens subunit G1b has at least two negative lenses and at least three positive lenses.
More preferably, the 1b-th lens unit G1b includes, in order from the object side to the image side, a negative lens, a positive lens, a positive lens, and a negative lens.
Furthermore, it is more preferable that the 1b-th lens unit G1b be composed of, in order from the object side to the image side, a negative lens, a positive lens, a positive lens, a negative lens, and a positive lens.

It is preferable that the inner focus type imaging optical system of the present invention satisfies the following conditional expression.
−0.30 ≦ F2 / F ≦ −0.05 (7)
However,
F2: focal length of the second lens group G2
F: Focal length of inner focus type imaging optical system

The conditional expression (7) is an expression for defining the ratio of the focal lengths of the second lens group G2 and the inner focusing type imaging optical system.
By satisfying the conditional expression (7), it is possible to reduce the amount of movement of the second lens group G2 at the time of focusing, and to miniaturize the actuator and mechanism unit for driving the second lens group G2. Is possible.

If the upper limit of conditional expression (7) is exceeded, the amount of movement of the second lens group G2 during focusing from infinity to a close object becomes too small, and the movement of the second lens group G2 can be accurately controlled. Unfavorably difficult.
Further, when the lower limit of conditional expression (7) is divided, the amount of movement of the second lens group G2 at the time of focusing from infinity to a close object becomes too large, and an actuator for driving the second lens group G2 and It is difficult to miniaturize the mechanical unit, which is not preferable.

The lower limit of conditional expression (7) is more preferably −0.25, more preferably −0.20, and still more preferably −0.15.
The upper limit of conditional expression (7) is more preferably -0.06, more preferably -0.065, and still more preferably -0.07.

It is preferable that the inner focus type imaging optical system of the present invention satisfies the following conditional expression.
0.25 ≦ FR / F ≦ 1.00 (8)
However,
FR: focal length of rear lens group GR
F: Focal length of inner focus type imaging optical system

The conditional expression (8) is an expression for defining the ratio of the focal lengths of the rear lens group GR and the inner focusing type imaging optical system.
By satisfying conditional expression (8), it is possible to sufficiently shorten the focal length of the first lens group G1, and it is possible to satisfactorily correct the aberration generated in the rear lens group GR.

If the upper limit of conditional expression (8) is exceeded, the focal length of the rear lens group GR becomes too long, and the focal lengths of the first lens group G1 and the second lens group G2 become too short. It is difficult to correct the aberration generated in G1 and the second lens group G2, which is not preferable.
If the lower limit of conditional expression (8) is broken, the focal length of the rear lens group GR becomes too short, which makes it difficult to correct aberrations generated in the rear lens group GR, which is not preferable.

The lower limit of conditional expression (8) is more preferably 0.27, more preferably 0.28, and still more preferably 0.29.
Further, the upper limit of conditional expression (8) is more preferably 0.80, more preferably 0.60, and still more preferably 0.50.

The inner focusing type imaging optical system of the present invention preferably has a stop on the image side of the second lens unit G2.
With this configuration, it is possible to miniaturize the mechanical unit for driving the stop, and to reduce the diameter of the entire rear lens group GR.

  The diaphragm may be disposed in the rear lens group because the mechanical unit for driving the diaphragm can be miniaturized as long as the diaphragm is disposed on the image side of the second lens group G2. It may be disposed on the image side of the rear lens group.

It is preferable that the inner focusing type super telephoto lens of the present invention satisfies the following conditional expression.
70 ≦ G G1 p max ≦ 110 (10)
However,
G G 1 p max: Abbe number which is the largest among the Abbe numbers for the d-line of the material of the positive lens in the 1 b lens group G 1 b

The conditional expression (10) defines the Abbe number of the material of the positive lens in the 1b-th lens unit G1b.
Since the 1b-th lens group G1b has a small aperture, it is preferable to dispose a lens of an anomalous dispersion glass material in the 1b-th lens group G1b. Since the anomalous dispersion glass material has a smaller specific gravity than other glass materials, chromatic aberration can be effectively corrected while reducing the aperture diameter by arranging it in the first lens subunit G1b.
By satisfying conditional expression (10), the anomalous dispersion glass material having a relatively large specific gravity is disposed in the first b lens group G1 b which can make the aperture smaller than the first a lens group G1 a, so weight reduction can be achieved. It is possible to correct the chromatic aberration well.

If the upper limit of conditional expression (10) is exceeded, chromatic aberration will be corrected excessively.
Further, dividing the lower limit of the conditional expression (9) is not preferable because it becomes difficult to correct the chromatic aberration.

The lower limit of conditional expression (10) is more preferably 75, more preferably 80, and still more preferably 90.
The upper limit of conditional expression (10) is more preferably 105, and more preferably 100.

It is preferable that the inner focus type imaging optical system of the present invention satisfies the following conditional expression.
1.75 ≦ NdGRnmax ≦ 2.15 (11)
However,
NdGRnmax: Of the refractive index to the d-line of the material of the negative lens in the rear lens group GR,
Index of refraction that is maximum

The conditional expression (11) defines the refractive index of the material of the negative lens in the rear lens group GR.
By satisfying the conditional expression (11), a negative lens having a high refractive index is disposed in the rear lens group GR, and therefore it is possible to correct field curvature properly.

If the upper limit of the conditional expression (11) is exceeded, selection of materials becomes difficult, which is not preferable.
Further, dividing the lower limit of the conditional expression (10) is not preferable because correction of curvature of field becomes difficult.

The lower limit of conditional expression (11) is more preferably 1.79, more preferably 1.84, and still more preferably 1.89.
Further, the upper limit of conditional expression (11) is more preferably 2.07, more preferably 2.02, and more preferably 1.97.

  The inner-focusing type imaging optical system of the present invention includes an imaging element that converts an optical image formed by the optical system into an electrical signal. Here, the imaging device or the like is not particularly limited, and for example, a solid-state imaging device such as a CCD sensor or a CMOS sensor can also be used.

(Example)
Hereinafter, embodiments of the inner focusing type imaging optical system of the present invention will be described based on the attached drawings.
In Table 1, Table 4, Table 7, Table 10, Table 13, Table 16, Table 19, Table 22 showing optical data of each example, r is a radius of curvature, d is a lens thickness or a lens interval, and Nd is a d-line The refractive index at ν, d d indicates the Abbe number of the d-line standard.
In Tables 2, 5, 8, 11, 11, 14, 20 and 23 showing the specification table (infinity) of each example, f is the focal length of the entire system, and Fno is the F number. , Ω is a half angle of view [deg], Y is an image height, and TL is an optical total length.
In Table 3, Table 6, Table 9, Table 12, Table 15, Table 18, Table 21 and Table 24, which show the variable interval table of each example, the focal length is in the row indicated by f and β and in the column of infinity. In the middle distance focusing column describing the focusing distance, the lateral magnification β of the entire system is shown.

  2, 5, 8, 11, 14, 17, FIG. 20, FIG. 23, and an intermediate distance in focus (in the respective embodiments) showing longitudinal aberration at the time of infinity object focusing in each embodiment. The intermediate focusing distance is shown in the variable distance table of each example), FIG. 3, FIG. 6, FIG. 9, FIG. 12, FIG. It shows spherical aberration [mm], astigmatism [mm], distortion [%], and lateral chromatic aberration [mm].

In the spherical aberration diagram, the vertical axis represents F number (in the figure, indicated by Fno), solid line represents d line (in the figure, indicated by d), short broken line represents C line (in the figure, indicated by C), long broken line Represents the characteristics of the g-line (indicated by g in the figure).
In the astigmatism diagram, the vertical axis represents a half angle of view (denoted by ω in the figure), the solid line represents the characteristic of the sagittal plane (denoted by ΔS in the figure), and the broken line represents the characteristic of the meridional plane (denoted by ΔM in the figure) Represent each.
In the distortion aberration diagram, the vertical axis represents the angle of view (denoted by ω in the figure).
In the magnification chromatic aberration diagram, the vertical axis represents the angle of view (denoted by ω in the figure), the short dashed line represents the chromatic aberration of magnification of C line at the d line standard (denoted by C in the figure), and the long dashed line represents g at the d line standard The characteristics of the lateral chromatic aberration of the line (indicated by g in the figure) are shown.

(First embodiment)
The first embodiment of the inner-focusing type imaging optical system according to the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a diaphragm S, and a rear lens group in order from the object side. It has GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. Optical data of the first example is shown in Table 1.

The specification table of the first embodiment is shown in Table 2.

The variable interval table of the first embodiment is shown in Table 3.

Second Embodiment
The second embodiment of the inner-focusing type imaging optical system according to the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a diaphragm S, and a rear lens group in order from the object side. It has GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. Optical data of the second embodiment is shown in Table 4.

Table 5 shows a specification table of the second embodiment.

The variable interval table of the second embodiment is shown in Table 6.

Third Embodiment
The third embodiment of the inner-focusing type imaging optical system according to the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a diaphragm S, and a rear lens group in order from the object side. It has GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. Optical data of the third example is shown in Table 7.

Table 8 shows a specification table of the third embodiment.

The variable interval table of the third embodiment is shown in Table 9.

Fourth Embodiment
The fourth embodiment of the inner-focusing type imaging optical system according to the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a diaphragm S, and a rear lens group in order from the object side. It has GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. Optical data of the fourth embodiment is shown in Table 10.

Table 11 shows a specification table of the fourth embodiment.

The variable interval table of the fourth embodiment is shown in Table 12.

Fifth Embodiment
The fifth embodiment of the inner-focusing type imaging optical system according to the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a diaphragm S, and a rear lens group in order from the object side. It has GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. Optical data of the fifth example is shown in Table 13.

Table 14 shows a specification table of the fifth example.

The variable interval table of the fifth embodiment is shown in Table 15.

Sixth Embodiment
The sixth embodiment of the inner focusing type imaging optical system of the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, and a rear lens group in order from the object side. It has GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. Optical data of the sixth example are shown in Table 16.

Table 17 shows a specification table of the sixth embodiment.

The variable interval table of the sixth embodiment is shown in Table 18.

Seventh Embodiment
The seventh embodiment of the inner focusing type imaging optical system of the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, and a rear lens group in order from the object side. It has GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. Optical data of the seventh example are shown in Table 19.

Table 20 shows a specification table of the seventh example.

The variable interval table of the seventh embodiment is shown in Table 21.

Eighth embodiment
The optical data of the seventh embodiment of the inner focusing type imaging optical system of the present invention comprises a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a diaphragm S in order from the object side. , And a rear lens group GR. By moving the second lens group G2 to the image side along the optical axis, focusing from an infinite distance to a near distance object is performed. The first lens group G1 has a first lens group G1f of positive refractive power, a first lens group G1c of positive refractive power, and a maximum air gap of the first lens group G1c via the maximum air gap in the first lens group G1. The second lens group G1a has positive refractive power, and the first lens group G1b has positive refractive power. Assuming that the rear lens group GR is a positive 3a lens group, a negative 3b lens group, and a positive 3c lens group in this order from the object side, the cemented lens disposed on the image side of the 3b lens group is a vibration reduction lens Shake correction is performed by moving in the direction perpendicular to the optical axis. An eighth example is shown in Table 22.

The specification table of the eighth embodiment is shown in Table 23.

The variable interval table of the eighth embodiment is shown in Table 24.

Data relating to the conditional expressions of the examples of the inner focus type imaging optical system of the present invention are shown in Table 25.

G1 1st lens group
G2 Second lens group
GR rear lens group
G1a 1a lens group
G1b 1b lens group
G1c 1c lens group
G1 f 1 f lens group
G3a 3rd lens group
G3b 3rd lens group
G3c 3rd lens group
S aperture
CG cover glass
F focus lens group
VC camera shake correction lens group

Claims (12)

A first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a rear lens group GR having a positive refractive power, in order from the object side to the image side, the second lens group G2 An inner focusing type imaging optical system which moves along the optical axis to perform focusing;
The first lens group G1 is composed of a first f lens group G1 f and a first c lens group G1 c, which are sequentially disposed from the object side with an air gap therebetween.
The first f lens group G1 f is composed of a first a lens group G1 a and a first b lens group G1 b, which are sequentially disposed from the object side with an air gap therebetween.
An inner focus type image forming optical system characterized by satisfying the following conditional expression.
H1c / H1a ≦ 0.75 (1a)
H1b / H1a ≦ 0.95 (1b)
0.7 ≦ F1 f / F1 c ≦ 2.2 (1c)
2.5 ≦ β2 × βR ≦ 4.5 (1d)
However,
H1a: height from the optical axis of the intersection point of the surface of the first lens group G1a closest to the object side and the marginal ray at the time of aperture opening when focusing on an infinite distance object
H1b: The height from the optical axis of the intersection point of the surface on the most object side of the first lens subunit G1b and the marginal ray at the time of aperture opening at focusing on an infinite distance object
H1c: height from the optical axis of the intersection point of the surface on the most object side of the first c lens group G1c and the marginal ray at the time of aperture opening at focusing on an infinite distance object
F1 f: focal length of the first f lens group G1 f
F1c: focal length β2 of the first c lens group G1c: lateral magnification βR at infinity focusing of the second lens group G2: lateral magnification at infinity focusing of the rear lens group GR The inner focus type image forming optical system according to claim 1, which satisfies the following conditional expression.
0.5 ≦ F1a / F1c ≦ 4.0 (2)
However,
F1a: focal length of the first lens group G1a The inner focus type imaging optical system according to claim 1 or 2, which satisfies the following conditional expression.
0.4 ≦ F1 / F1c ≦ 1.5 (3)
However,
F1: focal length of the first lens group G1 The inner focus type imaging optical system according to any one of claims 1 to 3, which satisfies the following conditional expression.
H1c / H1b ≦ 0.80 (4)   The inner focus type imaging optical system according to any one of claims 1 to 4, characterized in that at least a part of the rear lens group GR moves so as to include a component in a direction perpendicular to the optical axis. system.   The inner focus type imaging according to any one of claims 1 to 5, wherein the first b lens group G1b has at least two negative lenses and at least two positive lenses. Optical system. The inner focus type imaging optical system according to any one of claims 1 to 6, which satisfies the following conditional expression.
−0.30 ≦ F2 / F ≦ −0.05 (7)
However,
F2: focal length of the second lens group G2
F: Focal length of the inner focusing type imaging optical system The inner focus type imaging optical system according to any one of claims 1 to 7, which satisfies the following conditional expression.
0.25 ≦ FR / F ≦ 1.00 (8)
However,
FR: focal length of the rear lens group GR
F: Focal length of the inner focusing type imaging optical system   The inner focus type image forming optical system according to any one of claims 1 to 8, further comprising a stop on the image side of the second lens group G2. The inner focus type image forming optical system according to any one of claims 1 to 9, wherein the first b lens group has at least one positive lens satisfying the following conditional expression.
70 ≦ G G1 p max ≦ 110 (10)
However,
G G 1 p max: Abbe number which is the largest among the Abbe numbers for the d-line of the material of the positive lens in the first b lens group G 1 b The inner focus type image forming optical system according to any one of claims 1 to 10, wherein the rear lens group GR has at least one negative lens satisfying the following conditional expression.
1.75 ≦ NdGRnmax ≦ 2.15 (11)
However,
NdGRnmax: Of the refractive index to the d-line of the material of the negative lens in the rear lens group GR,
Index of refraction that is maximum   The image side of the inner focus type image forming optical system is provided with an image pickup element for converting an optical image formed by the inner focus type image forming optical system into an electrical signal. An imaging device provided with the inner focus type imaging optical system according to any one of Items 11.

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