JP2013003354A - Telephoto lens, optical device and manufacturing method of telephoto lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a telephoto lens being compact and having excellent optical performance.SOLUTION: A telephoto lens TL comprises: a first lens group G1 having a positive refractive power; a second lens group G2 having a negative refractive power; and a third lens group G3 having a positive refractive power, and is configured such that, during focusing from an infinite-distance object to a finite-distance object, the second lens group G2 moves along an optical axis. The first lens group G1 comprises: a front group G1a having a positive refractive power; and a rear group G1b. The front group G1a of the first lens group G1 has at least one positive lens and at least one negative lens. When the focal length of the front group G1a of the first lens group G1 is defined as f1F, and the focal length of the rear group G1b is defined as f1R, a conditional expression: 0.00<f1F/|f1R|<0.50 is satisfied.

Description

The present invention relates to a telephoto lens, an optical device, and a telephoto lens manufacturing method suitable for a single-lens reflex camera, an electronic still camera, and the like.

Conventionally, as an optical system (telephoto lens) suitable for a long focal length, a telephoto having a first lens group having a positive refractive power and a second lens group having a negative refractive power in order from the object side. Type optical systems are known (see, for example, Patent Document 1 and Patent Document 2). This type of optical system has the advantage that the overall length can be shortened compared to the focal length. However,
When the focal length is about 800 mm, the total length of the optical system becomes long and the weight becomes heavy. Also,
In recent years, in order to increase the speed of focusing, instead of extending the entire optical system, focusing is performed by moving a part of the focusing lens group. In order to use this focusing module, it is required that the focusing lens group has a small lens diameter.

JP 2009-180827 A Japanese Patent No. 40325502

However, with such a conventional telephoto lens, it has been difficult to achieve miniaturization while maintaining good optical performance.

The present invention has been made in view of such problems, and an object of the present invention is to provide a telephoto lens, an optical device, and a telephoto lens manufacturing method that are compact and have good optical performance.

In order to achieve such an object, the telephoto lens according to the first invention includes a first lens group having a positive refractive power and a second lens having a negative refractive power arranged in order from the object side along the optical axis. A lens group;
A third lens group having a positive refractive power, and when focusing from an object at infinity to an object at finite distance,
A telephoto lens configured such that the second lens group moves along an optical axis, and the first lens group is arranged in order from the object side along the optical axis and has a positive refractive power. And a rear group having the longest air interval in the first lens group with respect to the front group, and the front group of the first lens group includes at least one positive lens and at least one lens And the following conditional expression is satisfied.
0.00 <f1F / | f1R | <0.50
However,
f1F: focal length of the front group of the first lens group,
f1R: focal length of the rear group of the first lens group.

In the above-described telephoto lens, it is preferable that the following conditional expressions are satisfied.
ν1p> 90
ν1n> 48
However,
ν1p: Abbe number of at least one of the positive lenses in the front group of the first lens group,
νn: Abbe number of at least one of the negative lenses in the front group of the first lens group.

The telephoto lens according to the second invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, arranged in order from the object side along the optical axis, and a positive lens. A third lens group having a refractive power, and the second lens group is configured to move along the optical axis when focusing from an object at infinity to a finite distance object, The first lens group is arranged in order from the object side along the optical axis, and has a positive refractive power and a longest air interval in the first lens group with respect to the front group. The front group of the first lens group has at least one positive lens and at least one negative lens, and satisfies the following conditional expressions.
ν1p> 90
ν1n> 48
However,
ν1p: Abbe number of at least one of the positive lenses in the front group of the first lens group,
νn: Abbe number of at least one of the negative lenses in the front group of the first lens group.

In the telephoto lens described above, it is preferable that the following conditional expression is satisfied.
1.60 <N1n <1.80
However,
N1n: a refractive index of at least one of the negative lenses in the front group of the first lens group.

In the telephoto lens described above, the second lens group includes a first negative lens, a positive lens, and a second negative lens arranged in order from the object side along the optical axis. It is preferable.

In the telephoto lens described above, it is preferable that the following conditional expression is satisfied.
24 <ν2a <56
However,
ν2a: Abbe number of the first negative lens in the second lens group.

In the telephoto lens described above, it is preferable that the following conditional expression is satisfied.
1.60 <N2c <1.80
However,
N2c: Refractive index of the second negative lens in the second lens group.

In the telephoto lens described above, it is preferable that the following conditional expression is satisfied.
3.60 <f1 / (− f2) <4.00
However,
f1: the focal length of the first lens group,
f2: focal length of the second lens group.

In the telephoto lens described above, the front group of the first lens group includes a first positive lens, a second positive lens, and a negative lens arranged in order from the object side along the optical axis. It is preferable to be configured.

In the telephoto lens described above, it is preferable that the rear group of the first lens group includes a negative lens and a positive lens.

The optical device according to the present invention is an optical device including a telephoto lens that forms an image of an object on a predetermined surface, and uses the telephoto lens according to the present invention as the telephoto lens.

The telephoto lens manufacturing method according to the first aspect of the invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive lens in order from the object side along the optical axis. And a third lens group having a refractive power of 5 at the time of focusing from an infinite object to a finite distance object, the second lens group moves along the optical axis, The first lens group is arranged in order from the object side along the optical axis, and has a positive refractive power and a longest air interval in the first lens group with respect to the front group. A front group of the first lens group has at least one positive lens and at least one negative lens;
The following conditional expression is satisfied.
0.00 <f1F / | f1R | <0.50
However,
f1F: focal length of the front group of the first lens group,
f1R: focal length of the rear group of the first lens group.

The telephoto lens manufacturing method according to the second invention includes, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive lens. And a third lens group having a refractive power of 5 at the time of focusing from an infinite object to a finite distance object, the second lens group moves along the optical axis, The first lens group is arranged in order from the object side along the optical axis, and has a positive refractive power and a longest air interval in the first lens group with respect to the front group. The front group of the first lens group has at least one positive lens and at least one negative lens, and satisfies the following conditional expressions.
ν1p> 90
ν1n> 48
However,
ν1p: Abbe number of at least one of the positive lenses in the front group of the first lens group,
νn: Abbe number of at least one of the negative lenses in the front group of the first lens group.

  According to the present invention, it is possible to obtain good optical performance while being small.

It is a lens block diagram of the telephoto lens which concerns on 1st Example. It is an aberration diagram in the infinity in-focus state of 1st Example. It is a lens block diagram of the telephoto lens which concerns on 2nd Example. FIG. 12 is a diagram illustrating various aberrations in the infinitely focused state according to the second example. It is a lens block diagram of the telephoto lens which concerns on 3rd Example. It is various aberrational figures in the infinite point focusing state of 3rd Example. It is a lens block diagram of the telephoto lens which concerns on 4th Example. It is an aberration diagram in the infinity in-focus state of 4th Example. It is a lens block diagram of the telephoto lens which concerns on 5th Example. It is an aberration diagram in the infinity in-focus state of 5th Example. It is sectional drawing of a digital single-lens reflex camera. It is a flowchart which shows the manufacturing method of a telephoto lens.

Hereinafter, preferred embodiments of the present application will be described with reference to the drawings. A digital single lens reflex camera CAM provided with a telephoto lens TL according to the present application is shown in FIG. In the digital single-lens reflex camera CAM shown in FIG. 11, light from an object (subject) (not shown) is collected by a telephoto lens (photographing lens) TL and imaged on a focusing screen F via a quick return mirror M. Is done. The light imaged on the focusing screen F is reflected a plurality of times in the pentaprism P and guided to the eyepiece lens E. Thus, the photographer can observe the image of the object (subject) as an erect image through the eyepiece lens E.

When a release button (not shown) is pressed by the photographer, the quick return mirror M is retracted out of the optical path, and the light from the object (subject) collected by the telephoto lens TL forms an image on the image sensor C. To form an image of the subject. As a result, light from the object (subject) is imaged on the image sensor C, picked up by the image sensor C, and recorded in a memory (not shown) as an image of the object (subject). In this way, the photographer can photograph an object (subject) with the digital single-lens reflex camera CAM. Even if the camera does not have the quick return mirror M, the same effect as the camera CAM can be obtained. In addition, FIG.
The digital single-lens reflex camera CAM shown in FIG. 1 may be configured to detachably hold the telephoto lens TL, or may be configured integrally with the telephoto lens TL.

For example, as shown in FIG. 1, the telephoto lens TL includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power, which are arranged in order from the object side along the optical axis. And a third lens group G3 having a positive refractive power so that the second lens group G2 moves along the optical axis when focusing from an object at infinity to an object at a short distance (finite distance). It has become. The first
The lens group G1 is arranged in order from the object side along the optical axis, and has a front group G1a having a positive refractive power, and the longest air gap in the first lens group G1 with respect to the front group G1a. The front group G1a of the first lens group G1 includes the group G1b and includes at least one positive lens and at least one negative lens.

Note that the telephoto lens TL having a long focal length has a long overall length and a center of gravity far from the camera. Therefore, the probability of camera shake increases when handheld shooting is performed. In addition, the image tends to blur when looking through the viewfinder (eyepiece E). In order to solve this problem, it is necessary to introduce an image stabilization mechanism that moves a part of the optical system in a direction perpendicular to the optical axis. If vibration can be prevented with a simple configuration, the first lens group G1 having a positive refractive power and the second lens group G2 having a negative refractive power for focusing are formed to form a substantially afocal lens. It is desirable that a part of the third lens group G3 is an anti-vibration lens group.

In the telephoto lens TL having such a configuration, in order to shorten the overall length while maintaining excellent optical performance, the focal length of the front group G1a of the first lens group G1 is set to f1F, and the rear group G1b of the first lens group G1. It is preferable that the condition represented by the following conditional expression (1) is satisfied when the focal length of f1R is f1R.

  0.00 <f1F / | f1R | <0.50 (1)

Conditional expression (1) is a conditional expression for shortening the total length of the telephoto lens TL. The closer the rear principal point position of the first lens group G1 is to the object side, the shorter the distance between the first lens group G1 and the second lens group G2. Since the first lens group G1 includes a front group G1a having a positive refractive power and a rear group G1b, the longer the focal length of the rear group G1b is, the more the rear principal point position of the first lens group G1 is. It will be located on the object side. Therefore, when the condition is less than the lower limit value of the conditional expression (1), the total length of the telephoto lens TL is shortened, but the distance between the first lens group G1 and the second lens group G2 becomes too short and contacts. . Further, it is not preferable because correction of spherical aberration becomes difficult. On the other hand, when the condition exceeds the upper limit value of the conditional expression (1), the distance between the first lens group G1 and the second lens group G2 becomes long, and the total length of the telephoto lens TL increases. Further, it is not preferable because correction of spherical aberration becomes difficult. Therefore, it is preferable that the above conditional expression (1) is satisfied.

In addition, it is preferable to set the upper limit of conditional expression (1) to 0.45. In order to make the effect of the present embodiment more certain, it is preferable to set the upper limit value of conditional expression (1) to 0.40. Moreover, it is preferable to set the lower limit of conditional expression (1) to 0.005. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.01.

In such a telephoto lens TL, the Abbe number of at least one of the positive lenses in the front group G1a of the first lens group G1 is ν1p, and at least one of the negative lenses in the front group G1a of the first lens group G1. When the Abbe number of the sheet is ν1n, it is preferable that the conditions represented by the following conditional expressions (2) and (3) are satisfied.

ν1p> 90 (2)
ν1n> 48 (3)

Conditional expression (2) is a conditional expression for maintaining good optical performance and shortening the overall length of the telephoto lens TL. When the condition is less than the lower limit value of the conditional expression (2), if the Abbe number is small as described above, it is difficult to correct the longitudinal chromatic aberration in the optical performance. At this time, conditional expression (2
The glass satisfying () is a glass having a low refractive index. Therefore, by using glass with a large Abbe number, when the second lens group G2 and the subsequent lenses have the same configuration, in order to correct chromatic aberration satisfactorily, a power arrangement that satisfies the conditional expression (1) is taken. Therefore, the rear principal point position of the first lens group G1 can be made closer to the object side, which is a preferable condition for shortening the overall length.

In addition, it is preferable to set the lower limit of conditional expression (2) to 91. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 91.2.
In addition, the Abbe number ν1p in conditional expression (2) is more preferably 100 or less.

Conditional expression (3) is a conditional expression for maintaining good optical performance. If the condition is lower than the lower limit value of conditional expression (3), it is not preferable because it is difficult to correct axial chromatic aberration.

In addition, it is preferable to set the lower limit of conditional expression (3) to 49. In order to make the effect of the present embodiment more reliable, it is preferable to set the lower limit value of conditional expression (3) to 50. Further, the Abbe number ν1n in conditional expression (3) is more preferably 65 or less.

In such a telephoto lens TL, when the refractive index of at least one of the negative lenses of the front group G1a of the first lens group G1 is N1n, the condition expressed by the following conditional expression (4) is satisfied. It is preferable to do.

  1.60 <N1n <1.80 (4)

Conditional expression (4) is a conditional expression for reducing the curvature of field. As described above, when a glass having a large Abbe number is used for the positive lens of the front group G1a of the first lens group G1, the refractive index of the glass having a large Abbe number is small. Therefore, the Petzval sum serving as an index of field curvature is reduced. It becomes a plus, and the image surface at a high image height is bent. In order to avoid this, it is preferable that the refractive index of the negative lens of the front group G1a of the first lens group G1 be in the range of the conditional expression (4). Therefore, when the condition exceeds the upper limit value of the conditional expression (4), the Petzval sum becomes large and the image surface is bent, which is not preferable. On the other hand, when the condition is less than the lower limit value of the conditional expression (4), the Petzval sum is small. However, even if this is too small, the best image plane position at the center of the screen and the best image plane position at the periphery are largely separated from each other. End up. When the Petzval sum is large to the positive side, the peripheral image plane is bent toward the subject side, and when the Petzval sum is large to the negative side, the peripheral image plane is bent to the photographer side. Therefore, the flatness of the image surface is impaired, which is not preferable.

In addition, it is preferable to set the upper limit of conditional expression (4) to 1.78. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 1.75. Moreover, it is preferable to set the lower limit of conditional expression (4) to 1.65. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 1.68.

In such a telephoto lens TL, the second lens group G2 includes a first negative lens L2a, a positive lens L2b, and a second negative lens L2c that are arranged in order from the object side along the optical axis. It is preferable to have it. With this configuration, it is possible to satisfactorily correct chromatic aberration and curvature of field.

In such a telephoto lens TL, it is preferable that the condition represented by the following conditional expression (5) is satisfied when the Abbe number of the first negative lens L2a in the second lens group G2 is ν2a.

  24 <ν2a <56 (5)

Conditional expression (5) is a conditional expression regarding chromatic aberration. When the condition is less than the lower limit value of conditional expression (5), the axial chromatic aberration and the lateral chromatic aberration become large when the Abbe number is small as described above, so that the center required for a super telephoto lens having a focal length of about 800 mm is required. It is difficult to obtain the performance. On the other hand, when the condition exceeds the upper limit value of conditional expression (5), chromatic aberration is improved.
The power arrangement of the glass in the second lens group G2 changes, and the focal length of the first negative lens L2a becomes longer. Accordingly, the negative refractive power is weakened, and coma is generated positively, making correction difficult.

In addition, it is preferable to set the upper limit of conditional expression (5) to 53. Moreover, it is preferable to set the lower limit of conditional expression (5) to 30. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (5) to 33.

In such a telephoto lens TL, it is preferable that the condition expressed by the following conditional expression (6) is satisfied when the refractive index of the second negative lens L2c in the second lens group G2 is N2c.

  1.60 <N2c <1.80 (6)

Conditional expression (6) is a conditional expression related to field curvature. As described above, the first lens group G1
When a glass having a large Abbe number is used for the positive lens of the front group G1a, the refractive index of the glass having a large Abbe number is small, so that the Petzval sum is positive. On the other hand, conditional expression (4) should be satisfied so that the Petzval sum is made negative in the first lens group G1, but the effect may be insufficient with a super telephoto lens. Therefore, it is desirable to satisfy the conditional expression (6) in order to obtain a curvature of field suitable for the super telephoto lens. When the condition is lower than the lower limit value of the conditional expression (6), the Petzval sum becomes too negative, the image plane at a position where the image height is high is on the object side, and the image plane is not flat. It is not preferable.
On the other hand, if the condition exceeds the upper limit value of conditional expression (6), the Petzval sum becomes too positive, and the image plane at a position where the image height is high is on the image sensor side, and the image plane is flat. It is not preferable.

In addition, it is preferable to set the lower limit of conditional expression (6) to 1.65. Moreover, it is preferable to set the upper limit of conditional expression (6) to 1.78. In order to make the effect of the present embodiment more certain, it is preferable to set the upper limit of conditional expression (6) to 1.75.

In such a telephoto lens TL, the focal length of the first lens group G1 is f1,
When the focal length of the second lens group G2 is f2, it is preferable to satisfy the condition expressed by the following conditional expression (7).

  3.60 <f1 / (− f2) <4.00 (7)

Conditional expression (7) is a conditional expression related to the ratio of the focal lengths of the first lens group G1 and the second lens group G2. Since the distance between the second lens group G2 and the third lens group G3 is substantially afocal,
The focal length of the entire telephoto lens TL system is f, the focal length of the first lens group G1 is f1, and the second
When the focal length of the lens group G2 is f2, and the focal length of the third lens group G3 is f3, the following expression (a) is established.

  f≈f1 / f2 × f3 (a)

  From this equation (a), the following equation (b) is also established.

  f1 / f2≈f / f3 (b)

When the condition is less than the lower limit value of the conditional expression (7), the focal length of the second lens group G2 becomes long, and when focusing from an infinite object to a short distance (finite distance) object, the focusing lens group ( The movement amount of the second lens group G2) becomes long, and the total length of the telephoto lens TL becomes long. Further, since the amount of movement of the focusing lens group becomes long, it is difficult to keep the effective diameter of the focusing lens group to the level of a conventional telephoto lens in order to obtain a desired angle of view. Further, when the condition is less than the lower limit value of the conditional expression (7), it can be said that the focal length of the third lens group G3 becomes longer from the expression (b). Since the light beam incident on the third lens group G3 is substantially afocal, the focal length and the effective diameter of the third lens group G3 are expressed by f3≈ “F number” × “effective diameter of the third lens group G3”. Is proportional. Therefore, when the focal length of the third lens group G3 is increased, the effective diameter of the third lens group G3 must be increased in order to satisfy a desired F number, and the existing image stabilization mechanism (VR module) is required. ) Becomes difficult to use.

On the other hand, when the condition exceeds the upper limit value of the conditional expression (7), the focal length of the first lens group G1 becomes long, and the total length of the telephoto lens TL becomes long. In addition, since the focal length of the second lens group G2 is shortened, the amount of movement of the second lens group G2, which is the focusing lens group, is shortened when focusing from an object at infinity to an object at a short distance (finite distance). The effective diameter of the second lens group G2 can be reduced. However, since the power of the second lens group G2 also increases, the amount of spherical aberration fluctuation increases when focusing from an object at infinity to an object at a short distance (finite distance), and focusing at a short distance is performed. It becomes difficult to correct spherical aberration in a state.

In addition, it is preferable to set the lower limit of conditional expression (7) to 3.63. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (7) to 3.65. Moreover, it is preferable to set the upper limit of conditional expression (7) to 3.90. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (7) to 3.80.

In such a telephoto lens TL, the front group G1a of the first lens group G1 is arranged in order from the object side along the optical axis, the first positive lens L1a, the second positive lens L1b, and the negative It is preferable to have a lens L1c. With this configuration, spherical aberration and chromatic aberration can be favorably corrected.

Here, a light ray incident in parallel to the optical axis from an object point at infinity on the axis is referred to as a land light ray. Even if the land ray incident on the first lens group G1 of the telephoto lens TL is a ray emitted from a short-distance object point, it enters the first incident surface substantially in parallel with the optical axis. for that reason,
The first lens group G1 needs to be close to the shape of the minimum declination when considered as a set of minute prisms. Since the land light becomes a convergent light beam in the first positive lens L1a that is the first lens component of the first lens group G1, in order to further converge this light beam, the second lens component that is the second lens component of the first lens group G1. The positive lens L1b is a biconvex convex lens having a surface with a higher curvature on the object side so as to have a minimum declination. However, since the spherical aberration and the chromatic aberration become too large only with the positive lens, the negative lens L1c is disposed in the front group G1a of the first lens group G1 to correct the appropriate spherical aberration and chromatic aberration.

In such a telephoto lens TL, it is preferable that the rear group G1b of the first lens group G1 includes a negative lens L1d and a positive lens L1e. With this configuration, spherical aberration and chromatic aberration can be favorably corrected. As described above, according to the present embodiment, it is possible to obtain a telephoto lens TL that is small but has good optical performance, and an optical device (digital single-lens reflex camera CAM) including the telephoto lens TL.

Here, a manufacturing method of the telephoto lens TL having the above-described configuration will be described with reference to FIG. First, in the cylindrical barrel, the first lens group G1 and the second lens group G of the present embodiment.
2 and the third lens group G3 are incorporated (step S1). At this time, the above conditional expression (1
), Conditional expression (2), conditional expression (3), etc.
The lenses 1 to G3 are arranged. When each lens is incorporated into the lens barrel, the lens groups may be incorporated into the lens barrel one by one in the order along the optical axis, and a part or all of the lens groups are integrally held by the holding member and then the lens barrel. You may assemble with a member. After assembling each lens group in the lens barrel, it is confirmed whether an object image is formed in a state where each lens group is incorporated in the lens barrel, that is, whether the centers of the lens groups are aligned (step S2). ). Then, after confirming whether an image is formed, various operations of the telephoto lens TL are confirmed (step S3).

Examples of various operations include a focusing operation in which a lens group that performs focusing from a long-distance object to a short-distance object moves along the optical axis direction, and at least some lenses have a component perpendicular to the optical axis. An image stabilization operation that moves like this can be cited. In the present embodiment, the second lens group G2 moves along the optical axis when focusing from a long distance object (infinite object) to a short distance object (finite distance object). . In addition, the confirmation order of various operations is arbitrary. According to such a manufacturing method, it is possible to obtain a telephoto lens TL that is small but has good optical performance.

(First embodiment)
Embodiments of the present application will be described below with reference to the accompanying drawings. First, a first embodiment of the present application will be described with reference to FIGS. FIG. 1 is a lens configuration diagram of the telephoto lens TL according to the first example in an infinitely focused state. The telephoto lens TL according to the first example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, and an aperture. The first lens group G1 includes a stop S, a third lens group G3 having a positive refractive power, and a filter FL. The first lens group G1 is arranged in order from the object side along the optical axis and has a positive refractive power. The lens group G1a is composed of a group G1a and a rear group G1b having a positive refractive power with the longest air gap in the first lens group G1 with respect to the front group G1a. When focusing from an object at infinity to an object at a short distance (finite distance), the second lens group G2 moves along the optical axis along the image plane I.
Move to the side.

The front group G1a of the first lens group G1 is arranged in order from the object side along the optical axis, and includes a protective glass L11 having a convex surface facing the object side and a biconvex first with a strong convex surface facing the object side. Positive lens L1
a, a biconvex second positive lens L1b, and a biconcave negative lens L1c. The rear group G1b of the first lens group G1 is arranged in order from the object side along the optical axis, and is a negative lens (meniscus lens) L1d having a convex surface toward the object side and a positive lens (meniscus lens) having a convex surface toward the object side ) It is composed of a cemented positive lens formed by joining with L1e. Second lens group G2
Are arranged in order from the object side along the optical axis, a first negative lens L2a having a biconcave shape, a positive lens (meniscus lens) L2b having a concave surface facing the object side, and a second lens having a concave surface facing the object side. Negative lens (meniscus lens) L2c and a cemented negative lens. Third
The lens group G3 is a biconvex first positive lens L3a arranged in order from the object side along the optical axis.
A first negative lens (meniscus lens) L3b having a concave surface facing the object side, a biconvex second positive lens L3c, a biconcave second negative lens L3d, and a biconvex third Positive lens L
3e cemented lens, biconcave third negative lens L3f and biconvex fourth positive lens L
3g and a cemented lens.

Tables 1 to 5 are shown below, and these are values respectively showing values of specifications of the telephoto lenses according to the first to fifth examples. In [Specification Data] in each table, f is the focal length of the entire telephoto lens system, FNO is the F number, ω is the half field angle (maximum incident angle: unit is “°”), and Y is the image height. , TL indicates the total lens length (air equivalent length). In [Specification data]
f1 is the focal length of the first lens group G1, f2 is the focal length of the second lens group G2, f1F is the focal length of the front group G1a of the first lens group G1, and f1R is the rear group of the first lens group G1. The focal length of G1b is shown respectively. In [Lens Data], the surface number is the number of each lens surface counted from the object side, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, and νd is the d-line (wavelength λ = 587). Abbe number with respect to .6 nm), nd is d line (wavelength λ = 587.6 nm)
) Shows the refractive index for each. The curvature radius “0.0000” indicates a plane, and the refractive index nd = 1.0000 of air is omitted from the description.

The [variable interval data] includes the values of the variable intervals D1 and D2 in the infinite focus state (focal length f = 776) and the shortest shooting distance state (shooting magnification β = −0.136), and the back focus (
Air conversion length) Bf is shown. In addition, the focal length f, the radius of curvature r, the surface interval d, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or reduced. However, the same optical performance can be obtained, and the present invention is not limited to this. In addition, the same reference numerals as those of the present embodiment are used in the specification values of the second to fifth embodiments described later.

Table 1 below shows specifications in the first embodiment. In addition, the surface numbers 1-31 in Table 1 respond | correspond to the surfaces 1-31 in FIG.

(Table 1)
[Specification data]
f = 776
FNO = 5.7
2ω = 3.18238
Y = 21.633
TL = 540.57725
f1 = 296.7716
f2 = -80.72333
f1F = 358.5401
f2R = 1395.165
[Lens data]
Surface number r d νd nd
1 1200.3704 5.00 64.20 1.516798
2 1199.7897 1.00
3 176.0124 25.50 91.21 1.456
4 -3999.2353 0.10
5 211.6788 23.00 82.51 1.497823
6 -592.7953 5.10
7 -516.0786 7.90 53.87 1.712995
8 344.4134 61.60
9 134.6337 6.90 53.87 1.712995
10 68.9319 19.00 82.51 1.49782
11 310.3830 (D1)
12 -2853.8608 5.50 40.11 1.762001
13 75.1962 5.50
14 -142.3735 7.00 28.69 1.79504
15 -42.4084 4.60 47.93 1.717
16 -445.8484 (D2)
17 0.0000 6.60 (Aperture stop)
18 255.8969 9.50 70.45 1.48749
19 -63.9713 1.80
20 -63.4444 5.00 27.51 1.755199
21 -231.4913 8.00
22 185.6642 7.00 35.92 1.66446
23 -191.7759 19.24
24 -285.9498 2.40 44.79 1.743997
25 58.3897 8.00 38.01 1.60342
26 -338.4075 2.50
27 -76.0168 2.50 47.93 1.717004
28 281.9472 10.50 42.70 1.56732
29 -61.6152 34.30
30 0.0000 2.00 64.20 1.516798
31 0.0000 (Bf)
[Variable interval data]
Infinite state Shortest shooting distance state
f = 776 β = -0.136
D1 86.2760 101.67
D2 21.6814 6.29
Bf 135.58 135.58
[Conditional expression values]
Conditional expression (1) f1F / | f1R | = 0.570
Conditional expression (2) ν1p = 91.21 (first positive lens L1a)
Conditional expression (3) ν1n = 53.87
Conditional expression (4) N1n = 1.713
Conditional expression (5) ν2a = 40.11
Conditional expression (6) N2c = 1.717
Conditional expression (7) f1 / (− f2) = 3.676

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (7) are satisfied.

FIG. 2 is a diagram illustrating various aberrations of the telephoto lens TL according to Example 1 in the infinitely focused state.
In each aberration diagram, FNO represents an F number, and A represents a half angle of view. In each aberration diagram, d is d-line (λ = 587.6 nm), g is g-line (λ = 435.8 nm), and C is C
The line (λ = 656.3 nm) and F indicate aberrations on the F line (λ = 486.1 nm), respectively. In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. The description of the aberration diagrams is the same in the other examples.

From the respective aberration diagrams, it can be seen that in the first example, various aberrations are corrected well and the imaging performance is excellent. As a result, by mounting the telephoto lens TL of the first embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Second embodiment)
Hereinafter, a second embodiment of the present application will be described with reference to FIGS. FIG. 3 is a lens configuration diagram of the telephoto lens TL according to Example 2 in an infinitely focused state. The telephoto lens TL of the second example has the same configuration as the telephoto lens of the first example, and the first part is included in each part.
The same reference numerals as in the case of the embodiment are attached and detailed description is omitted.

Table 2 below shows specifications in the second embodiment. The surface numbers 1 to 31 in Table 2 correspond to the surfaces 1 to 31 in FIG.

(Table 2)
[Specification data]
f = 776
FNO = 5.7
2ω = 3.18424
Y = 21.633
TL = 525.11596
f1 = 296.7716
f2 = -80.72333
f1F = 311.1842
f2R = 54414.29
[Lens data]
Surface number r d νd nd
1 1200.3704 5.00 64.20 1.516798
2 1199.7897 1.00
3 174.0251 21.40 91.21 1.456
4 -3183.4196 0.10
5 197.0496 21.70 91.20 1.456
6 -606.8420 5.10
7 -536.2416 7.90 53.89 1.713
8 462.7426 61.60
9 132.9337 6.90 53.87 1.712995
10 64.8468 15.40 82.51 1.49782
11 226.8368 (D1)
12 -2453.9875 5.50 39.57 1.8044
13 79.4082 5.50
14 -182.6744 7.00 28.69 1.79504
15 -43.9630 4.60 47.93 1.717
16 -1174.4626 (D2)
17 0.0000 6.60 (Aperture stop)
18 273.6024 6.50 70.45 1.48749
19 -64.0698 1.80
20 -63.3487 2.50 27.51 1.755199
21 -231.8709 13.50
22 181.0270 4.00 35.92 1.66446
23 -187.9554 13.99
24 -290.7250 2.40 44.79 1.743997
25 64.6891 8.00 38.01 1.60342
26 -328.2532 6.50
27 -76.3478 2.50 47.93 1.717004
28 276.6334 8.00 42.70 1.56732
29 -62.4674 34.30
30 0.0000 2.00 64.20 1.516798
31 0.0000 (Bf)
[Variable interval data]
Infinite state Shortest shooting distance state
f = 776 β = -0.136
D1 86.28 97.73
D2 21.68 5.71
Bf 140.38 140.38
[Conditional expression values]
Conditional expression (1) f1F / | f1R | = 0.0057
Conditional expression (2) ν1p = 91.21 (first positive lens L1a)
Conditional expression (2) ν1p = 91.20 (second positive lens L1b)
Conditional expression (3) ν1n = 53.89
Conditional expression (4) N1n = 1.713
Conditional expression (5) ν2a = 39.57
Conditional expression (6) N2c = 1.717
Conditional expression (7) f1 / (− f2) = 3.676

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (7) are satisfied.

FIG. 4 is a diagram illustrating various aberrations of the telephoto lens TL according to Example 2 in the infinite focus state.
From the respective aberration diagrams, it can be seen that in the second example, various aberrations are satisfactorily corrected and the imaging performance is excellent. As a result, by mounting the telephoto lens TL of the second embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Third embodiment)
Hereinafter, the third embodiment of the present application will be described with reference to FIGS. FIG. 5 is a lens configuration diagram of the telephoto lens TL according to the third example in an infinitely focused state. The telephoto lens TL of the third embodiment has the same configuration as that of the telephoto lens of the first embodiment except for a part of the shape of the second lens group G2, and each part has the same configuration as that of the first embodiment. Reference numerals are assigned and detailed description is omitted. The second lens group G2 of the third example includes a biconcave first negative lens L2a arranged in order from the object side along the optical axis, and a positive lens (meniscus lens) with a concave surface facing the object side. ) It is composed of a cemented negative lens formed by cementing L2b and a biconcave second negative lens L2c.

Table 3 below shows specifications in the third embodiment. The surface numbers 1 to 31 in Table 3 correspond to the surfaces 1 to 31 in FIG.

(Table 3)
[Specification data]
f = 776
FNO = 5.7
2ω = 3.18286
Y = 21.633
TL = 523.67402
f1 = 301.4814
f2 = -82.01056
f1F = 311.8013
f2R = -26207.1
[Lens data]
Surface number r d νd nd
1 1200.3704 5.00 64.19 1.516798
2 1199.7897 1.00
3 172.5169 21.40 91.20 1.456
4 -2466.6787 0.10
5 202.4314 21.70 91.20 1.456
6 -574.7534 5.10
7 -506.1788 7.90 53.89 1.713
8 470.0284 55.00
9 141.8310 6.90 53.87 1.712995
10 67.5493 15.40 82.51 1.49782
11 245.8400 (D1)
12 -492.3516 2.10 40.11 1.762
13 106.9941 8.60
14 -3176.8206 6.20 28.69 1.79504
15 -55.4178 2.00 48.45 1.697
16 149.5260 (D2)
17 0.0000 6.60 (Aperture stop)
18 291.9203 6.50 70.44 1.48749
19 -64.7959 1.80
20 -64.1711 2.50 27.51 1.755199
21 -226.9047 8.50
22 172.5060 4.00 35.92 1.66446
23 -200.3533 9.00
24 -317.8547 2.40 44.78 1.743997
25 89.9765 8.00 38.01 1.60342
26 -430.0402 10.00
27 -82.7244 2.50 47.93 1.717004
28 124.0092 8.00 42.70 1.56732
29 -64.7745 34.30
30 0.0000 2.00 64.20 1.516798
31 0.0000 (Bf)
[Variable interval data]
Infinite state Shortest shooting distance state
f = 776 β = -0.136
D1 88.90 104.78
D2 26.08 10.21
Bf 144.19 144.19
[Conditional expression values]
Conditional expression (1) f1F / | f1R | = 0.0119
Conditional expression (2) ν1p = 91.20 (first positive lens L1a)
Conditional expression (2) ν1p = 91.20 (second positive lens L1b)
Conditional expression (3) ν1n = 53.89
Conditional expression (4) N1n = 1.713
Conditional expression (5) ν2a = 40.11
Conditional expression (6) N2c = 1.597
Conditional expression (7) f1 / (− f2) = 3.676

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (7) are satisfied.

FIG. 6 is a diagram illustrating various aberrations of the telephoto lens TL according to the third example in the infinite focus state.
From the respective aberration diagrams, it can be seen that in the third example, various aberrations are satisfactorily corrected and the imaging performance is excellent. As a result, by mounting the telephoto lens TL of the third embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(Fourth embodiment)
Hereinafter, a fourth embodiment of the present application will be described with reference to FIGS. FIG. 7 is a lens configuration diagram of the telephoto lens TL according to the fourth example in an infinitely focused state. The telephoto lens TL according to the fourth example has the same configuration as the telephoto lens of the first example except for a part of the shapes of the second lens group G2 and the third lens group G3. The same reference numerals as those in FIG. The second lens group G2 of the fourth example is arranged in order from the object side along the optical axis, and is a first negative lens (meniscus lens) L2 having a convex surface directed toward the object side.
a and a cemented negative lens formed by cementing a positive lens (meniscus lens) L2b having a concave surface facing the object side and a second negative lens (meniscus lens) L2c having a concave surface facing the object side. The third lens group G3 of the fourth example includes a biconvex first positive lens L3a arranged in order from the object side along the optical axis, and a first negative lens having a concave surface directed toward the object side. (Meniscus lens) L3b, a biconvex second positive lens L3c, and a biconcave second negative lens L
3d and a biconvex third positive lens L3e, a third negative lens (meniscus lens) L3f with a concave surface facing the object side, and a fourth positive lens (meniscus with a concave surface facing the object side) Lens) and a cemented lens with L3g.

Table 4 below shows specifications in the fourth embodiment. The surface numbers 1 to 31 in Table 4 correspond to the surfaces 1 to 31 in FIG.

(Table 4)
[Specification data]
f = 776
FNO = 5.7
2ω = 3.18238
Y = 21.633
TL = 544.63664
f1 = 296.7716
f2 = -80.72333
f1F = 384.1447
f2R = 989.0893
[Lens data]
Surface number r d νd nd
1 1200.3704 5.00 64.20 1.516798
2 1199.7897 1.00
3 177.1578 25.50 91.21 1.456
4 -3261.4194 0.10
5 218.8792 23.00 82.51 1.49782
6 -553.4982 5.10
7 -487.7288 7.90 53.87 1.712995
8 325.3594 61.60
9 136.4375 6.90 53.87 1.712995
10 71.4920 19.00 82.51 1.49782
11 372.8845 (D1)
12 1114.3700 5.50 49.62 1.7725
13 72.0619 5.50
14 -101.3954 7.00 28.69 1.79504
15 -40.7398 4.60 47.93 1.717
16 -225.0953 (D2)
17 0.0000 6.60 (Aperture stop)
18 222.0490 9.50 70.45 1.48749
19 -60.7012 1.80
20 -59.6198 5.00 27.51 1.755199
21 -243.5342 8.00
22 225.3223 7.00 35.92 1.66446
23 -154.4581 20.58
24 -299.2031 2.40 44.79 1.743997
25 51.0851 8.00 38.01 1.60342
26 -471.8480 2.50
27 -75.2888 2.50 47.93 1.717004
28 -504.1282 10.50 42.70 1.56732
29 -61.8695 34.30
30 0.0000 2.00 64.20 1.516798
31 0.0000 (Bf)
[Variable interval data]
Infinite state Shortest shooting distance state
f = 776 β = -0.136
D1 91.30 106.69
D2 20.75 5.36
Bf 134.21 134.21
[Conditional expression values]
Conditional expression (1) f1F / | f1R | = 0.3884
Conditional expression (2) ν1p = 91.21 (first positive lens L1a)
Conditional expression (3) ν1n = 53.87
Conditional expression (4) N1n = 1.713
Conditional expression (5) ν2a = 49.62
Conditional expression (6) N2c = 1.717
Conditional expression (7) f1 / (− f2) = 3.676

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (7) are satisfied.

FIG. 8 is a diagram illustrating various aberrations of the telephoto lens TL according to the fourth example in the infinite focus state.
From the respective aberration diagrams, it can be seen that in the fourth example, various aberrations are corrected satisfactorily and the imaging performance is excellent. As a result, by mounting the telephoto lens TL of the fourth embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

(5th Example)
Hereinafter, a fifth embodiment of the present application will be described with reference to FIGS. 9 to 10 and Table 5. FIG. FIG.
It is a lens block diagram in the infinite point focusing state of the telephoto lens TL which concerns on 5th Example. The telephoto lens TL according to the fifth example has the same configuration as the telephoto lens of the first example.
The same reference numerals as in the case of the embodiment are attached and detailed description is omitted.

Table 5 below shows specifications in the fifth embodiment. In addition, the surface numbers 1-31 in Table 5 respond | correspond to the surfaces 1-31 in FIG.

(Table 5)
[Specification data]
f = 776
FNO = 5.7
2ω = 3.18238
Y = 21.633
TL = 537.17373
f1 = 296.7716
f2 = -80.72333
f1F = 339.1701
f2R = 2154.171
[Lens data]
Surface number r d νd nd
1 1200.3704 5.00 64.20 1.516798
2 1199.7897 1.00
3 176.0965 25.50 91.21 1.456
4 -4429.7754 0.10
5 200.8768 23.00 82.51 1.49782
6 -596.6547 5.10
7 -520.3131 7.90 53.87 1.712995
8 352.3664 61.60
9 137.1824 6.90 53.87 1.712995
10 67.8199 19.00 82.51 1.49782
11 291.4721 (D1)
12 -927.9193 5.50 35.25 1.7495
13 75.8275 5.50
14 -219.8896 7.00 28.69 1.79504
15 -42.9502 4.60 47.93 1.717
16 -6108.0385 (D2)
17 0.0000 6.60 (Aperture stop)
18 345.3926 9.50 70.45 1.48749
19 -64.6466 1.80
20 -64.5049 5.00 27.51 1.755199
21 -209.6868 8.00
22 163.4004 7.00 35.92 1.66446
23 -222.2325 18.94
24 -275.8733 2.40 44.79 1.743997
25 70.4856 8.00 38.01 1.60342
26 -347.9222 2.50
27 -77.4983 2.50 47.93 1.717004
28 154.6170 10.50 42.70 1.56732
29 -61.5432 34.30
30 0.0000 2.00 64.20 1.516798
31 0.0000 (Bf)
[Variable interval data]
Infinite state Shortest shooting distance state
f = 776 β = -0.136
D1 81.88 97.27
D2 21.99 6.60
Bf 136.57 136.57
[Conditional expression values]
Conditional expression (1) f1F / | f1R | = 0.1574
Conditional expression (2) ν1p = 91.21 (first positive lens L1a)
Conditional expression (3) ν1n = 53.87
Conditional expression (4) N1n = 1.713
Conditional expression (5) ν2a = 35.25
Conditional expression (6) N2c = 1.717
Conditional expression (7) f1 / (− f2) = 3.676

Thus, in the present embodiment, it can be seen that all the conditional expressions (1) to (7) are satisfied.

FIG. 10 is a diagram illustrating various aberrations of the telephoto lens TL according to Example 5 in the infinitely focused state. From the respective aberration diagrams, it can be seen that in the fifth example, various aberrations are corrected satisfactorily and the imaging performance is excellent. As a result, by mounting the telephoto lens TL of the fifth embodiment, excellent optical performance can be secured even in the digital single-lens reflex camera CAM.

As described above, according to each embodiment, it is possible to realize a telephoto lens TL and an optical device (digital single-lens reflex camera CAM) that are small but have good optical performance.

In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

In each of the above-described embodiments, the three-group configuration is shown. Further, a configuration in which a lens or a lens group is added to the most object side, or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group refers to a portion having at least one lens separated by an air interval that changes during zooming.

In addition, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. This focusing lens group
It can also be applied to autofocus, and is also suitable for motor drive for autofocus (using an ultrasonic motor or the like). In particular, it is preferable that at least a part of the second lens group is a focusing lens group.

Also, move the lens group or partial lens group so that it has a component in the direction perpendicular to the optical axis,
Alternatively, an anti-vibration lens group that corrects image blur caused by camera shake by rotating (swinging) in the in-plane direction including the optical axis may be used. In particular, it is preferable that at least a part of the third lens group is an anti-vibration lens group.

Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface.
When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and optical performance deterioration due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin with an aspheric shape on the glass surface. Any aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

The aperture stop is preferably disposed in the vicinity of and inside the third lens group. However, the role of the aperture stop may be substituted by a lens frame without providing a member as the aperture stop.

Each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

CAM digital SLR camera (optical device)
TL telephoto lens G1 first lens group G1a front group G1b rear group G2 second lens group G3 third lens group S aperture stop I image surface

Claims (13)

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, arranged in order from the object side along the optical axis; A telephoto lens configured such that the second lens group moves along the optical axis during focusing from an object at infinity to an object at a finite distance;
The first lens group is arranged in order from the object side along the optical axis, and has a positive refractive power and a longest air interval in the first lens group with respect to the front group. A group of
The front group of the first lens group has at least one positive lens and at least one negative lens,
A telephoto lens characterized by satisfying the following conditional expression:
0.00 <f1F / | f1R | <0.50
However,
f1F: focal length of the front group of the first lens group,
f1R: focal length of the rear group of the first lens group. The telephoto lens according to claim 1, wherein the following conditional expressions are satisfied.
ν1p> 90
ν1n> 48
However,
ν1p: Abbe number of at least one of the positive lenses in the front group of the first lens group,
νn: Abbe number of at least one of the negative lenses in the front group of the first lens group. 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, arranged in order from the object side along the optical axis; A telephoto lens configured such that the second lens group moves along the optical axis during focusing from an object at infinity to an object at a finite distance;
The first lens group is arranged in order from the object side along the optical axis, and has a positive refractive power and a longest air interval in the first lens group with respect to the front group. A group of
The front group of the first lens group has at least one positive lens and at least one negative lens,
A telephoto lens that satisfies the following conditional expressions:
ν1p> 90
ν1n> 48
However,
ν1p: Abbe number of at least one of the positive lenses in the front group of the first lens group,
νn: Abbe number of at least one of the negative lenses in the front group of the first lens group. The telephoto lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
1.60 <N1n <1.80
However,
N1n: a refractive index of at least one of the negative lenses in the front group of the first lens group. The second lens group includes a first negative lens, a positive lens, and a second negative lens arranged in order from the object side along the optical axis. The telephoto lens according to any one of 1 to 4. The telephoto lens according to claim 5, wherein the following conditional expression is satisfied.
24 <ν2a <56
However,
ν2a: Abbe number of the first negative lens in the second lens group. The telephoto lens according to claim 5, wherein the following conditional expression is satisfied.
1.60 <N2c <1.80
However,
N2c: Refractive index of the second negative lens in the second lens group. The telephoto lens according to any one of claims 1 to 7, wherein the following conditional expression is satisfied.
3.60 <f1 / (− f2) <4.00
However,
f1: the focal length of the first lens group,
f2: focal length of the second lens group. The front group of the first lens group is a first positive lens arranged in order from the object side along the optical axis;
The telephoto lens according to claim 1, comprising a second positive lens and a negative lens. The telephoto lens according to any one of claims 1 to 9, wherein the rear group of the first lens group includes a negative lens and a positive lens. An optical device including a telephoto lens that forms an image of an object on a predetermined surface,
The optical device according to claim 1, wherein the telephoto lens is the telephoto lens according to claim 1. A telephoto lens in which 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 are arranged in this order from the object side along the optical axis. A manufacturing method of
When focusing from an object at infinity to an object at a finite distance, the second lens group moves along the optical axis;
The first lens group is arranged in order from the object side along the optical axis, and has a positive refractive power and a longest air interval in the first lens group with respect to the front group. A group of
The front group of the first lens group has at least one positive lens and at least one negative lens,
A telephoto lens manufacturing method characterized by satisfying the following conditional expression:
0.00 <f1F / | f1R | <0.50
However,
f1F: focal length of the front group of the first lens group,
f1R: focal length of the rear group of the first lens group. A telephoto lens in which 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 are arranged in this order from the object side along the optical axis. A manufacturing method of
When focusing from an object at infinity to an object at a finite distance, the second lens group moves along the optical axis;
The first lens group is arranged in order from the object side along the optical axis, and has a positive refractive power and a longest air interval in the first lens group with respect to the front group. A group of
The front group of the first lens group has at least one positive lens and at least one negative lens,
A telephoto lens manufacturing method characterized by satisfying each of the following conditional expressions:
ν1p> 90
ν1n> 48
However,
ν1p: Abbe number of at least one of the positive lenses in the front group of the first lens group,
νn: Abbe number of at least one of the negative lenses in the front group of the first lens group.

Images