JP2011158739A - Large-sized aperture medium telephoto lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a large-sized aperture medium telephoto lens configured, such that an actuator for performing focusing can be housed inside a lens barrel, high performance level is exhibited, even when focusing, and various aberrations are corrected satisfactorily. <P>SOLUTION: The large-sized aperture medium telephoto lens includes, in the order starting from the object side, a first lens group L1 having positive refractive power as a whole, and a second lens group L2 having a positive refractive power as a whole; the first lens group L1 includes a 1a-th lens group L1a, having a positive refractive power and a 1b-th lens group L1b. The 1a-the lens group L1a includes, in the order starting from the object side, at least two positive lenses, and a lens component having negative refractive power and having a lens surface in which the lens face closest to an image is concave in shape as going toward the side of the image. The 1b-th lens group L1b has a lens component, in which the lens face on the object side is concave as going toward the object side. In focusing from an infinity object to a proximity object, the second lens group L2 moves in the direction of an optical axis toward the object side, and satisfies a predetermined conditional expression. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a large-diameter medium telephoto lens that employs a rear focus and is particularly suitable for a digital camera, a silver salt camera, a video camera, and the like.

In a large-diameter medium telephoto lens capable of auto-focusing, it is required to adopt a rear focus or an inner focus that moves a part of the lens system, considering that the lens diameter is large and the weight is heavy.

However, if the lens group near the front having a relatively large lens diameter and heavy is AF-driven as the inner focus group, the drive device and the like increase in size, which may increase the size of the entire lens system.

When the inner focus is adopted near the rear of the entire lens system, the lens group located further on the image side than the inner focus group is generally installed behind the lens barrel, including the lens barrel that holds the lens group. Therefore, it is necessary to reduce the diameter so as to avoid the electrical parts and the like.

Furthermore, when the inner focus is adopted, there is a problem that the driving force transmission mechanism becomes complicated when the fixed lens group is between the body and the movable lens group.

For the above reason, it is desirable to adopt the rear focus as the autofocus method for the large-diameter medium telephoto lens.

The following documents are known as large-diameter medium telephoto lenses that employ a rear focus.

Japanese Unexamined Patent Publication No. Sho 63-316815

Japanese Patent Laid-Open No. 64-0778208

JP 2000-338396 A

Japanese Patent Laid-Open No. 03-200909

In the lenses in Patent Document 1 and Patent Document 2, the rear group of the Gauss type is used for focusing. The Gaussian type is characterized in that aberrations are canceled by forming a symmetrical shape in the rear group of the front group, so that the symmetry of the rear group is lost due to the focusing of the rear group, and aberration fluctuations increase.

In the Gaussian type, particularly when the focus group is moved from infinity to a short distance, the incident ray height of the off-axis tangential ray in the surface with the strong concave surface facing the object side in front of the focus group increases. For this reason, the off-axis light beam has a strong incident angle, and a large amount of under coma flare is generated. Therefore, it is difficult to correct coma flare associated with focusing, and it is difficult to obtain a high-performance large-diameter medium telephoto lens.

In the lens in Patent Document 3, the aperture is fixed between the front group and the rear group during focusing. This is advantageous for reducing the weight of the focus group and simplifying the focusing mechanism. However, the F-number ray height on the aperture surface increases if the space is made as much as the amount of movement of the focus group. When the diameter is increased, the outer diameter of the product is enlarged with an increase in the diameter of the throttle, which is not desirable.

In addition, many tangential coma flares occur when focusing at a short distance. For this reason, when the aperture is increased to about F1.4, it is difficult to correct coma flare, and it is difficult to obtain a high-performance medium aperture telephoto lens.

The lens in Patent Document 4 has a minimum configuration as a rear focus type large-diameter medium telephoto lens. However, it does not correspond to a configuration in which a focusing motor suitable for each lens, which has recently become necessary, is arranged in a lens barrel in order to improve autofocus accuracy.

Furthermore, in a large-diameter medium telephoto lens that requires a high-performance usability, it is desirable to use a ring-type ultrasonic motor or the like in order to obtain added value such as quietness, high response, and full-time manual focus. . In the lens in Patent Document 4, it is very difficult to dispose a ring type ultrasonic motor or the like on the image side in the entire lens system because of interference of various parts such as a diaphragm and electrical parts.

In addition, if a ring type ultrasonic motor or the like is arranged while avoiding interference with various parts such as a diaphragm and electrical parts, an increase in the outer diameter of the product is inevitable.

If an ultrasonic motor or the like is disposed on the object side in the entire lens system, it interferes with the diaphragm due to the movement of the focus group, and if this interference is to be avoided, the outer diameter of the product further increases, which is desirable. Absent.

The present invention provides a large-diameter medium telephoto lens in which the components required for obtaining the above added value can be placed in a lens barrel, which has high performance in focusing and has various aberrations corrected satisfactorily. The purpose is to provide.

In order to solve the above problems, the large-aperture medium telephoto lens of the present invention includes, in order from the object side, a first lens unit L1 having a positive refractive power as a whole and a second lens unit L2 having a positive refractive power as a whole. The first lens unit L1 includes a first a lens unit L1a having a positive refractive power and a first b lens unit L1b. The first a lens unit L1a includes at least two positive lenses in order from the object side. The first b lens unit L1b includes a lens and a lens component having a negative refractive power with the lens surface SFa being a lens surface having the most image-side lens surface concave on the image side. The lens surface SFb is a lens surface that has a concave lens component and has the strongest concave on the object side among the lens surfaces on the object side of the lens components in the first-b lens unit L1b, and the second lens. Group L2 is an object from infinity During focusing from, moves in the optical axis direction toward the object side, and satisfies the following conditional expression.
(1) 0.15 <| RFa / RFb | <0.8
RFa: radius of curvature of lens surface SFa RFb: radius of curvature of lens surface SFb

The large-diameter medium telephoto lens according to the present invention includes, in order from the object side, a first lens unit L1 having a positive refractive power as a whole and a second lens unit L2 having a positive refractive power as a whole. The first lens unit L1 includes a first lens unit L1a having a positive refractive power and a first lens unit L1b. The first lens unit L1a has a positive refractive power using at least one low dispersion medium GL. The second lens unit L2 includes, in order from the object side, a positive lens component, a negative lens component, a stop, and a medium GH having a high refractive index for at least one positive lens. It consists of a positive lens component and satisfies the following conditional expression.
(2) 70.00 <νGL
(3) 1.80000 <nGH
νGL: Abbe number of the low dispersion medium GL (wavelength λ = 587.56 nm)
nGH: Refractive index of medium GH having a high refractive index (wavelength λ = 587.56 nm)

In addition, the large-diameter medium telephoto lens of the present invention satisfies the following conditional expression.
(4) 0.6 <fL2 / f <1.1
fL2: focal length of the second lens unit L2 f: focal length of the entire lens system

In addition, the large-diameter medium telephoto lens according to the present invention includes an actuator for performing focusing between the first lens unit L1a and the second lens unit L2, and an aperture is disposed closer to the image side than the actuator. Features.

In the present invention, by satisfying the above conditions, components required for obtaining added value can be arranged in the lens barrel, and high performance in focusing and various aberrations are corrected well. In addition, a large-diameter medium telephoto lens can be provided.

Lens configuration diagram of Example 1 Longitudinal aberration diagram of the lens of Example 1 in infinity focus state Longitudinal aberration diagram of the lens of Example 1 in a close focus state Lateral aberration diagram of the lens of Example 1 in the infinitely focused state Lateral aberration diagram of the lens of Example 1 in the close-up focus state Lens configuration diagram of Example 2 Longitudinal aberration diagram of the lens of Example 2 in infinity focus state Longitudinal aberration diagram of the lens of Example 2 in a close focus state Lateral aberration diagram of the lens of Example 2 in infinity focus state Lateral aberration diagram of the lens of Example 2 in the close-up focus state Lens configuration diagram of Example 3 Longitudinal aberration diagram of the lens of Example 3 in infinity focus state Longitudinal aberration diagram of the lens of Example 3 in a close focus state Transverse aberration diagram of the lens of Example 3 in the infinitely focused state Lateral aberration diagram of the lens of Example 3 in a close focus state Lens configuration diagram of Example 4 Longitudinal aberration diagram of the lens of Example 4 in an infinitely focused state Longitudinal aberration diagram of the lens of Example 4 in a close focus state Lateral aberration diagram of the lens of Example 4 in the infinitely focused state Lateral aberration diagram of the lens of Example 4 in the close-up focus state Lens configuration diagram of Example 5 Longitudinal aberration diagram of the lens of Example 5 in the infinitely focused state Longitudinal aberration diagram of the lens of Example 5 in a close focus state Lateral aberration diagram of the lens of Example 5 in the infinitely focused state Lateral aberration diagram of the lens of Example 5 in a close focus state Lens configuration diagram of Example 6 Longitudinal aberration diagram of the lens of Example 6 in the infinite focus state Longitudinal aberration diagram in close-up focus state of lens of Example 6 Lateral aberration diagram of the lens of Example 6 in the infinitely focused state Lateral aberration diagram of the lens of Example 6 in a close focus state Lens configuration diagram of Example 7 Longitudinal aberration diagram of the lens of Example 7 in the infinite focus state Longitudinal aberration diagram of the lens of Example 7 in a close focus state Lateral aberration diagram of the lens of Example 7 in the infinitely focused state Transverse aberration diagram of the lens of Example 7 in a close focus state Lens configuration diagram of Example 8 Longitudinal aberration diagram of Example 8 lens in the infinite focus state Longitudinal aberration diagram in close-up focus state of lens of Example 8 Transverse aberration diagram of the lens of Example 8 at infinity in-focus state Lateral aberration diagram of the lens of Example 8 in the close-up focus state

Hereinafter, embodiments according to the large-diameter medium telephoto lens of the present invention will be described.

The large-diameter medium telephoto lens according to the present embodiment includes, in order from the object side, a first lens unit L1 having a positive refractive power as a whole and a second lens unit L2 having a positive refractive power as a whole. The first lens unit L1 includes a first-a lens unit L1a having a positive refractive power and a first-b lens unit L1b. The first-a lens unit L1a, in order from the object side, has at least two positive lenses and the most image. The first lens unit L1b is a lens in which the lens surface on the object side is concave on the object side. Among the lens surfaces on the object side of each lens component in the 1b lens unit L1b, the lens surface having the strongest concave on the object side is defined as a lens surface SFb, and the second lens unit L2 is infinite. When focusing from a distant object to a close object, Configured to move in the optical axis direction toward the side.

In order to mount an actuator for performing focusing in the lens barrel, an interval for arranging the actuator in the lens barrel may be provided between the first lens group L1a and the second lens group L2. desirable.

However, if the first-a lens group L1a is simply spaced apart from the first-a lens group L1a and the first-a lens group L1a is moved away from the image plane to sufficiently secure the F-number light beam, the first-a lens group The lens diameter of L1a increases.

Further, as the lens diameter of the 1a lens unit L1a increases, the light ray height on the surface closest to the image side of the 1a lens unit L1a becomes higher than the aperture diameter and is included in the second lens unit L2. The spherical aberration in the lens group on the object side of the stop increases, and the risk of performance degradation due to manufacturing errors increases significantly.

In the embodiment of the present invention, in particular, the second lens unit L2 is divided into front and rear lens units by a diaphragm, and the structure is more complicated. Therefore, each of the divided groups has a relative eccentricity with respect to the first a lens unit L1a. It is difficult to adjust so as to ensure accuracy.

Therefore, the present invention solves the above problem by providing the first lens group L1b between the first lens group L1a and the second lens group L2.

By providing the 1b lens unit L1b between the 1a lens unit L1a and the second lens unit L2, the light beam that has exited the 1a lens unit L1a is the optimum light beam on the most object side surface of the second lens unit L2. Incident light can be incident at a high position.

As a result, the relationship between the refractive power of the first lens unit L1 and the refractive power of the second lens unit L2 can be maintained in an optimal state, and while suppressing an increase in lens diameter and various aberrations in the entire lens system, It is possible to secure a space for disposing driving components other than the lens in the lens barrel.

The large-diameter medium telephoto lens according to the present embodiment satisfies the following conditional expression.
(1) 0.15 <| RFa / RFb | <0.8
RFa: radius of curvature of lens surface SFa RFb: radius of curvature of lens surface SFb

Conditional expression (1) defines an optimum condition for disposing the first-b lens unit L1b.

When exceeding the upper limit value of the conditional expression (1), the radius of curvature of the lens surface SFb having the strongest concave on the object side among the object side surfaces of the lens components constituting the 1b lens unit L1b is reduced. The light beam incident on the first lens group L1b is strongly bounced off the lens surface SFb in the direction away from the optical axis. As a result, various aberrations including spherical aberration generated in the first lens group L1b are deteriorated. Meridional coma flare increases, making it difficult to improve the performance of the entire lens system.

When falling below the lower limit value of the conditional expression (1), the radius of curvature of the lens surface SFb having the strongest concave on the object side among the lens surfaces on the object side of the lens components constituting the 1b lens unit L1b is large. Thus, the jumping of the light beam on the lens surface SFb is reduced. As a result, the force that bends the light beam incident on the first lens group L1b in the direction away from the optical axis becomes weak, which makes it difficult to increase the optical path length. Further, in order to keep the distance between the first a lens unit L1a and the second lens unit L2, it is necessary to bounce light rays on the image side surface of the first b lens unit L1b instead of the lens surface SFb. The surface on the image side of the lens unit L1b has a strong concave toward the image side, and the radius of curvature becomes small. At this time, the radius of curvature of the image side surface of the first lens unit L1b is close to the radius of curvature of the convex surface closest to the object side of the second lens unit L2. In this case, even when the air space on the axis when the second lens unit L2 is closest to the 1b lens unit L1b at the time of close-up photographing is sufficiently taken, the air interval through which the off-axis rays pass is reduced. Also, if the lens barrels are spaced apart so as not to interfere with each other, the focus movement distance is not sufficient, and the shortest shooting distance is shortened, which is not desirable.

Furthermore, the large-aperture medium telephoto lens according to the present embodiment includes, in order from the object side, a first lens unit L1 having an overall positive refractive power and a second lens unit L2 having an overall positive refractive power. The first lens unit L1 includes a first lens unit L1a having a positive refractive power and a first lens unit L1b. The first lens unit L1a is a positive lens using at least one low dispersion medium GL. The second lens unit L2 includes a lens unit having a refractive power. The second lens unit L2 includes, in order from the object side, a medium GH having a high refractive index in a positive lens component, a negative lens component, a stop, and at least one positive lens. It consists of the positive lens component used, and satisfies the following conditional expression.
(2) 70.00 <νGL
(3) 1.80000 <nGH
νGL: Abbe number of the low dispersion medium GL (wavelength λ = 587.56 nm)
nGH: Refractive index of the high refractive index medium GH (wavelength λ = 587.56 nm)

Conditional expression (2) defines the Abbe number of the medium of the positive lens in the 1a lens unit L1a.

If the lower limit of conditional expression (2) is not reached, the lateral chromatic aberration cannot be corrected well, and the resolution of the peripheral image height can be increased when the aperture diameter is reduced to half or less compared to the open aperture diameter. Can not. In order to ensure the effect of the embodiment, it is preferable to select a medium having anomalous dispersion.

Conditional expression (3) defines the refractive index of the medium of the positive lens in the second lens unit L2.

When the lower limit of conditional expression (3) is not reached, when the radius of curvature is constant, the refracting power becomes weak, so the lens diameter at the rear of the second lens unit L2 increases and the lens barrel outer diameter increases. End up. In particular, when considering mounting on a single-lens reflex camera, interference with the built-in flash housing of the single-lens reflex camera occurs, which is not desirable. Further, when the outer diameter of the lens barrel is suppressed, the space in the lens barrel is narrowed and it is difficult to place components.

Further, if the radius of curvature is decreased by an amount corresponding to a decrease in the refractive index in order to make the refractive power of the second lens unit L2 constant, spherical aberration increases and it becomes difficult to achieve high performance.

On the other hand, when nGH is too large, the Abbe number of the second lens unit L2 becomes small and it becomes difficult to correct the longitudinal chromatic aberration, and the internal transmittance at 400 to 360 nm is lowered. Therefore, it is more desirable to set the upper limit of conditional expression (3) to 1.96000.

Further, the large-diameter medium telephoto lens according to the present embodiment satisfies the following conditional expression.
(4) 0.6 <fL2 / f <1.1
fL2: focal length of the second lens unit L2 f: focal length of the entire lens system

Conditional expression (4) defines conditions under which the focal length of the second lens unit L2 is optimal with respect to the focal length of the entire lens system. This is particularly relevant to securing a focus movement amount, securing a back focus, and correcting aberrations in consideration of the arrangement of components in the lens barrel.

When the upper limit of conditional expression (4) is exceeded, the focal length of the second lens unit L2 as the focus unit is increased, which is advantageous for correcting spherical aberration, and the performance during focusing can be improved. For this reason, it is advantageous for securing the back focus, but in order to shorten the shortest shooting distance, it is necessary to increase the amount of movement of the focus group. At this time, if the distance from the first lens unit L1 is long, the entire length of the entire lens system is extended, and if the lens diameter is suppressed, it is difficult to secure the peripheral light amount.

Further, when the lens diameter is widened to secure the peripheral light quantity, the weight increases due to the increase in the outer diameter of the lens barrel and the increase in the lens thickness, which is not desirable when considering the product size and weight.

When the lower limit of conditional expression (4) is not reached, the focal length of the second lens unit L2 as the focus unit is shortened, which makes it easy to secure the amount of focus movement, which is advantageous for downsizing the lens system. It becomes difficult to secure the back focus. In addition, the variation of spherical aberration during focusing increases, making it difficult to achieve high performance.

Furthermore, the large-diameter medium telephoto lens according to the present embodiment secures a space for mounting an actuator for performing focusing between the first lens unit L1a and the second lens unit L2, and stops the image side closer to the image side than the actuator. Is arranged. By adopting such a configuration, it is possible to suppress an increase in the outer diameter and aperture diameter of the actuator.

The focus actuator for the large-diameter lens needs a certain size to move the relatively heavy focus lens. If the actuator is arranged on the image side with respect to the aperture, the actuator is large, and thus there is a possibility of interfering with electrical parts and the like in the lens barrel.

In order to avoid this interference, it is necessary to provide a gap between the diaphragm in the second lens group and the electrical parts in the lens barrel. For this purpose, the diaphragm must be moved to the object side. In this case, the diaphragm is disposed at a high Fno light beam, which increases the diameter of the diaphragm, which is not desirable.

In order to avoid an increase in the aperture diameter, if an attempt is made to keep the Fno rays low, it is necessary to increase the refractive power of the positive lens component on the object side with respect to the aperture in the second lens unit L2. Then, the spherical aberration of the lens unit on the object side from the stop in the second lens unit L2 increases, the aberration balance deteriorates, and the first lens unit of the lens unit on the object side from the stop in the second lens unit L2. It becomes difficult to ensure the accuracy of relative eccentricity with respect to L1, which is not desirable.

In addition, since the medium telephoto lens in this embodiment has a large aperture ratio, when the actuator is disposed outside the diaphragm, the actuator is disposed further outside the diaphragm having a large diameter. Even when the actuator is not used, a part in the radial direction becomes large and the outer diameter of the product becomes enlarged, which is not desirable.

Furthermore, in the large-aperture medium telephoto lens according to the present embodiment, it is desirable to fix the heavy 1a lens unit L1a to the image plane in order to simplify the focusing mechanism. Further, in order to simplify the focusing mechanism, it is desirable that the first b lens unit L1b having a relatively weak refractive power with respect to the second lens unit L2 is also fixed to the image plane.

Hereinafter, numerical examples of the present invention will be described.

In [Overall specifications], f represents a focal length, Fno represents an F number, and Y represents a maximum image height from the optical axis. In [Lens Specifications], the first column number is the lens surface number from the object side, the second column R is the radius of curvature of the lens surface, the third column D is the lens surface interval, and the fourth column nd is the d line. The refractive index with respect to (wavelength λ = 587.56 nm), the fifth column νd is the Abbe number with respect to the d-line, and the surface with * is an aspherical surface. In addition, “aperture” shown in the second column represents a stop surface, and B.B shown in the third column. F. Represents the back focus. In [Variable interval], the value of the variable interval at each shooting distance is shown.

なお、ｚ は、面の頂点を基準としたときの光軸からの高さｙ の位置での光軸方向の変位であり、κは円錐係数、Ａ４、Ａ６、Ａ８、Ａ１０、Ａ１２は非球面係数であり、ｒは基準球面の曲率半径（ 近軸曲率半径） である。なお、「Ｅ―ⁿ」は「ｘ１０―ⁿ」を示し、例えば、「１．２３４Ｅ―^４ 」は「１．２３４ｘ１０―^４」を示す。 In all the values of the following specifications, “mm” is used as the focal length f, the radius of curvature R, the lens surface interval D, and other length units unless otherwise specified. However, since the same optical performance can be obtained in proportional enlargement and proportional reduction, it is not limited to this. These symbols are the same in the other embodiments below, and the description thereof is omitted.
[Aspherical data] represents an aspherical coefficient and a conical coefficient when the surface number and the shape of the aspherical surface are expressed by the following equations.

Z is the displacement in the optical axis direction at the position of the height y from the optical axis with respect to the vertex of the surface, κ is the conic coefficient, and A4, A6, A8, A10 and A12 are aspherical surfaces. Where r is the radius of curvature of the reference sphere (paraxial radius of curvature). Note that "E- ^n" indicates "X10- ^n", for example, "1.234E- ^4" means "1.234X10- ^4".

L1 First lens unit L2 Second lens unit L1a First lens unit L1a
L1b first lens unit L1b
SFa The most image-side concave lens surface SFa of the first lens unit L1a
SFb Lens surface SFb having the strongest concave on the object side among the lens surfaces on the object side of the lens components in the first-b lens unit L1b
S aperture stop d d line g g line C C line ΔS sagittal image plane ΔM meridional image plane I image plane

Furthermore, in this embodiment, the lens other than the second lens unit L2 or the lens unit may be moved separately in the optical axis direction during focussing. In particular, a part or all of the 1a lens unit L1a and a part or all of the 1b lens unit L1b may be moved separately in the optical axis direction.

In addition, each lens component in the second lens unit L2 may be moved separately in the optical axis direction during focusing. In particular, the lens group having the first positive lens component and the rear lens group having the positive lens component may be moved separately in the optical axis direction.

Furthermore, in the present embodiment, some lens components in the second lens unit L2 may be fixed in the optical axis direction during focusing. In particular, the last lens or lens group of the second lens group may be divided and fixed in the optical axis direction. In this case, the peripheral light amount can be decreased, but the inner focus is achieved, so that the dust resistance can be improved.

Furthermore, when this embodiment is applied to contrast detection type autofocus, a focusing direction by contrast detection can be quickly determined by slightly moving some lenses or lens groups in the optical axis direction. The lens group to be slightly moved is preferably a part of the first lens group L1 or a part or the whole of the second lens group L2. In this case, in particular, the positive lens component at the head of the second lens group is more desirable because it can secure a space for focusing, is light in weight, and has a strong refractive power.

Further, in this embodiment, a part of the lens group is moved in a direction substantially perpendicular to the optical axis, and the image is moved, thereby providing a vibration-proof function for correcting camera shake caused by the photographer. In this case, the lens group that is moved in a direction substantially perpendicular to the optical axis is particularly preferably a part of the first lens group L1 or a part or the whole of the second lens group L2.

Claims (4)

In order from the object side, the lens unit includes a first lens unit L1 having a positive refractive power as a whole and a second lens unit L2 having a positive refractive power as a whole.
The first lens unit L1 includes a first lens unit L1a having a positive refractive power and a first lens unit L1b.
The first-a lens unit L1a includes, in order from the object side, at least two positive lenses, and a lens component having a negative refractive power in which a lens surface whose most image-side lens surface is concave on the image side is a lens surface SFa. Consists of
The 1b lens unit L1b has a lens component in which the lens surface on the object side is concave on the object side, and among the lens surfaces on the object side of the lens components in the 1b lens unit L1b, The lens surface facing the strong concave is the lens surface SFb,
The second lens unit L2 moves in the optical axis direction toward the object side when focusing from an infinitely distant object to a close object, and satisfies the following conditional expression. lens.
(1) 0.15 <| RFa / RFb | <0.8
RFa: radius of curvature of lens surface SFa RFb: radius of curvature of lens surface SFb
In order from the object side, the first lens unit L1 having a positive refractive power as a whole and the second lens unit L2 having a positive refractive power as a whole are configured.
The first lens unit L1 includes the first lens unit L1a having positive refractive power and the first b lens unit L1b.
The first-a lens unit L1a includes a lens unit having a positive refractive power using at least one low-dispersion medium GL,
The second lens unit L2 includes, in order from the object side, a positive lens component, a negative lens component, a stop, and a positive lens component using a high refractive index medium GH for at least one positive lens. The large-aperture medium telephoto lens according to claim 1, wherein the following conditional expression is satisfied.
(2) 70.00 <νGL
(3) 1.80000 <nGH
νGL: Abbe number of the low dispersion medium GL (wavelength λ = 587.56 nm)
nGH: Refractive index of the high refractive index medium GH (wavelength λ = 587.56 nm)
The large-diameter medium telephoto lens according to any one of claims 1 to 2, wherein the second lens unit L2 satisfies the following conditional expression.
(4) 0.6 <fL2 / f <1.1
fL2: focal length of the second lens unit L2 f: focal length of the entire lens system
An actuator for performing focusing is mounted between the first lens group L1a and the second lens group L2, and a stop is disposed on the image side of the actuator. 4. A large-diameter medium telephoto lens according to any one of 3 above.

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