JP3476909B2 - telescope lens - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephoto lens, and more particularly to a large aperture telephoto lens capable of photographing from infinity to about -1/2 times.

[0002]

2. Description of the Related Art In recent years, general-purpose mid-telephoto lenses have been developed to support a wide range of shooting from infinity to short-distance objects.
A modified Gaussian type with a large number of components is used. Furthermore, in order to suppress aberration fluctuations during focusing, we have also adopted a floating mechanism.

The feature is that the whole system is basically moved in focusing, and the image plane correcting lens group located on the image plane side has a low magnification. However, when it comes to a telephoto lens system with a narrow angle of view, considering the shortening of the total length, it is composed of a telephoto type having positive and negative refracting power from the object side. The reality is that there are many methods.

However, there are situations where the close-up photographing function is limited due to reasons such as performance, and even the proposal of a telephoto lens capable of obtaining a high magnification has not yet been completed. .

Up to now, a telephoto lens for close-up photography with an aperture ratio of about 1: 4 has been proposed, and close-up photography magnification is emphasized rather than the aperture ratio, and high-order spherical aberration caused by the large aperture ratio. Actually, the problem of increasing the error sensitivity due to the occurrence of is left.

On the other hand, as a focusing method, US Pat. No. 4,534,626 and US Pat. No. 4,609,263 by the present applicant disclose a method of moving a plurality of lens groups. These telephoto lens systems were proposals of a basic focusing method, and proposals showing the possibility of expanding the function to a finite distance. In other words, it is a proposal of a focusing method showing the practicality of the aberration variation correction effect by the movement of a plurality of lens groups.

[0007]

The present invention is different from the above-mentioned conventional proposals, and its object is to arrange a movable lens group in a lens system subordinate to the main lens system to obtain a zooming effect and an aberration. It is to provide a large-aperture telephoto lens capable of shooting from infinity to about −1/2 times by reducing the burden of aberration correction by having a correcting action.

A more specific object of the present invention is to provide an optical system having an aperture ratio of about 1: 2.8 and an angle of view of about 14.5 ° or less, and a photographing magnification of about -1/2 times from an object at infinity. It is to provide a telephoto lens that can obtain almost stable optical performance over the entire range.

[0009]

[Means for Solving the Problems]

The telephoto lens of the present invention which achieves the above object is, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power. And a second rear lens group having a negative refractive power and a second rear lens group having a negative refractive power, the second lens group from an infinite object to a finite object. In focusing, the first lens group and the third lens group are fixed with respect to the image plane, and the second rear lens group is moved to the image side, which satisfies the following conditions. 0.5 <f _2INF / f _2MOD ≦ 0.9943 ...
(5) ′ where f _{2INF is} the focal length of the second lens group at infinity shooting, and f _{2MOD is} the focal length of the second lens group at the shortest shooting distance.

Another telephoto lens of the present invention comprises, in order from the object side, a first lens group having a positive refracting power, a second lens group having a negative refracting power, a third lens group having a positive refracting power, and a negative refracting power. A fourth lens unit having a power, the second lens unit further having a second front lens unit having a negative refractive power and a second rear lens unit having a negative refractive power, and an object at a finite distance from an object at infinity. When focusing on, the first lens group and the third lens group are fixed with respect to the image plane, the second rear lens group is moved to the image side, and the fourth lens group is at least two lens groups. And satisfies the following conditions. 0.1 <f _4INF / f _4MOD ≦ 0.89589 ...
(6) ′ where f _{4INF is} the focal length of the fourth lens group at the time of infinity shooting, and f _{4MOD is} the focal length of the fourth lens group at the shortest shooting distance.

Still another telephoto lens of the present invention is, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative lens group. A fourth lens group having a refractive power, the fourth lens group further having a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and having a finite distance from an object at infinity. When focusing on an object, the first lens group and the third lens group are fixed with respect to the image plane, the fourth front lens group is moved to the object side, and the second lens group is at least two. It is composed of a lens group and satisfies the following conditions. 0.5 <f _2INF / f _2MOD ≦ 0.9943 ...
(5) ′ where f _{2INF is} the focal length of the second lens group at infinity shooting, and f _{2MOD is} the focal length of the second lens group at the shortest shooting distance. Still another telephoto lens of the present invention comprises, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and
The third lens unit has a positive refracting power and the fourth lens unit has a negative refracting power, and the fourth lens unit further has a fourth lens unit having a positive refracting power.
A front lens group and a fourth rear lens group having negative refractive power,
During focusing from an object at infinity to an object at a finite distance, the first lens group and the third lens group are fixed with respect to the image plane, and the fourth front lens group is moved to the object side,
It satisfies the following conditions. 0.1 <f _4INF / f _4MOD ≦ 0.89589 ...
(6) ′ where f _{4INF is} the focal length of the fourth lens group at the time of infinity shooting, and f _{4MOD is} the focal length of the fourth lens group at the shortest shooting distance.

[0012]

The reason why the above structure is adopted and the function of the present invention will be described below. The present invention has been obtained by solving the problems centering on the focusing method for suppressing the aberration variation, as a technical achievement means of the telephoto lens which is sufficient in terms of the imaging performance of a near object including infinity. .

There are two types of conventional telephoto lenses for short distance photography. One is a lens system for exclusive use of a finite distance, in which aberration is corrected only in a specific range of magnification. The other is a lens which has an object point at infinity intended by the present invention as a starting point and is subjected to aberration correction within a range of about -1/2 or about 1: 1 to obtain stable imaging performance. It is a system.

The latter has the drawback that, when it is attempted to realize it with a single focusing lens group, the amount of focusing movement increases as the magnification increases, and at the same time, fluctuations in aberration increase. Therefore, in order to solve the problem, it is required to correct the aberration variation and achieve a high photographing magnification by a method of moving a lens unit other than the basic focusing lens unit.

In the present invention, as a means for solving this problem, the major feature is that the whole optical system is divided into a convergent main optical system and a sub optical system having a magnifying power, and the focusing unit is composed of two partial systems. Is.

That is, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens group having a positive refractive power.
The lens group and the fourth lens group having a negative refractive power constitute an all-optical system, and when focusing from an object at infinity to an object at finite distance with reference to the position of each lens group with respect to an object at infinity, With the first lens group and the third lens group fixed to the image plane, at least some of the lens components of the second lens group and the fourth lens group are separated from each other by an axial distance from the third lens group. This is a telephoto lens that is moved by reducing its size and satisfies the following conditional expression. 0.4 <−f ₁ / f ₂ <2.5 (1) 0.3 <D ₁₂₃ /f<1.5 (2) β ₄ > 1 (3) However, f ₁ : focal length of the first lens group, f ₂ : focal length of the second lens group, D ₁₂₃ : first lens surface apex of the first lens group to the final lens surface apex of the third lens group at infinity object On the optical axis, f: focal length of the entire system at infinity object, β ₄ : paraxial lateral magnification of the fourth lens group at infinity object,

In this optical system, the first lens unit having positive refracting power, the second lens unit movable and having negative refracting power, and the third lens unit having positive refracting power in the fixed unit.
A main imaging optical system is composed of three lens groups. However, when the shooting range is extended to a shooting distance having a high magnification with this configuration, aberration fluctuations such as spherical aberration and chromatic aberration also increase as the focusing movement amount increases.

Therefore, the fourth lens group serving as the sub-lens system is an optical system necessary for compensating for aberration fluctuations occurring during focusing and for compensating for zooming, and for obtaining the focal length of the entire lens system at an object at infinity. Are configured.

In order to correct the field curvature and the like which are governed by the first lens group, which is the main part of the entire lens system, and the second lens group, which is the focusing lens group, each refracting power arrangement is important. Conditional expression (1) defines this relationship. When the upper limit of 2.5 in this conditional expression is exceeded and the refractive power of the first lens group is considered to be constant and the refractive power of the second lens group is increased, the Petzval sum balance is lost and field curvature Of the spherical aberration and coma aberration, and it becomes difficult to achieve good performance. If the refractive power of the second lens group is considered to be constant and the refractive power of the first lens group is increased, the Petzval sum becomes too small, excessive correction of spherical aberration, increase of off-axis chromatic aberration, etc. Invite. In addition, fluctuations of various aberrations during focusing become large, which is not desirable.

When the lower limit of 0.4 to condition (1) is not reached, the Petzval sum tends to increase, and axial chromatic aberration and off-axis chromatic aberration tend to increase. In addition, spherical aberration and astigmatism at short distance fluctuate with little correction, and it becomes difficult to obtain good performance.

As already described, the fourth lens group is a sub-lens system which can be considered as a dedicated variable magnification attachment lens, in contrast to the main optical system composed of the first lens group to the third lens group. is there. In the above configuration, the conditional expression (2) defines the refractive power of the main lens system for an appropriate overall length. That is, the expression (2) defines the condition regarding the total length of the main lens system. When the upper limit of 1.5 to this conditional expression is exceeded, the overall length of the main lens system is extended due to the lens structure. Therefore, if changes in axial chromatic aberration and the like can be corrected, it is extremely advantageous for aberration correction. However,
The Petzval sum is also increasing, and the total length is increasing, which results in an increase in size and is not desirable. On the other hand, when the lower limit of 0.3 is exceeded, on the contrary, it is advantageous for downsizing.
The situation is not suitable for large aperture ratios. That is, even if the first lens group and the second lens group have large refracting powers and a large movable space can be secured during focusing of the fourth lens group,
The chromatic aberration balance of the entire system is lost, the manufacturing error sensitivity becomes high, and the problem of assembly becomes large, which is not desirable. Also, it becomes difficult to correct aberration fluctuations during focusing, the correction in the rear lens group is not sufficient, the number of lens components increases in the main lens system itself, and conversely, the movement space during focusing is limited, This is not desirable because it results in an increase in the shortest shooting distance.

The condition (3) limits the paraxial lateral magnification of the fourth lens unit at the time of an object at infinity, and further defines the range in which the refractive power is negative. Basically, as in conditional expression (3), it is desirable to have a positive magnification. In other words, it means that the fourth lens group has a magnifying power. The relationship of the refractive powers can be expressed as follows if the main lens system is shown. f ₁₂₃ <f where f ₁₂₃ is the combined focal length from the first lens group to the third lens group, and f is the focal length of the entire system when an object is at infinity.

That is, outside the conditional expression (3), the advantage in terms of aberration correction appears, but the total length of the main lens system becomes large,
Moreover, the refractive power of the fourth lens group tends to be small,
This is not desirable because it causes a drawback that the lens system becomes large.

Further, in the optical system of the present invention, when focusing on the first lens group and the second lens group at infinity, the synthetic optical system (G ₁₂ ) has an axial paraxial line passing through the second lens group. It is more preferable that the exit inclination angle of the light beam be within the range of the expression (4).

−0.05 <u ₂ ′ <0.05 (4) where u ₂ ′ is the axial paraxial exit tilt angle (radian) from the final lens surface of the second lens unit at infinity. , U ₂ '= u ₂ + h
₂ φ ₂ , the subscript indicates the group number, the subscript 2 indicates the second lens group, u is the paraxial tilt angle, h is the paraxial configuration height, and φ is the refracting power. Design method "(Kyoritsu Shuppan Co., Ltd.).

Within this conditional expression, it is possible to more easily suppress fluctuations due to focusing of the spherical aberration, which is characteristic of a telephoto lens that employs a focusing method by moving the rear lens unit.

However, in constructing the entire optical system, the first
The combined system of the lens group and the second lens group may form a convergent system. Further, it is desirable that the second lens group is composed of two lens groups, and each lens group satisfies the following movement relationship during focusing. 0.5 <f _2INF / f _2MOD <1.5 (5) where f _{2INF is} the focal length of the second lens group at infinity shooting, and f _{2MOD is} the shortest shooting distance of the second lens group. The focal length is.

If the upper limit of 1.5 to condition (5) is exceeded, it becomes difficult to correct astigmatism, field curvature, etc., and if the lower limit of 0.5 is exceeded, the maximum magnification is obtained. In the vicinity, interference such as contact between the second lens group and the third lens group is likely to occur, which is not desirable.

Further, the fourth lens group is composed of at least two lens groups, and when focusing, each lens group satisfies the following movement relationship, so that when the second lens group does not necessarily perform the related movement, This is a floating method that provides a degree of freedom in image forming performance.

0.1 <f _4INF / f _4MOD <1.8 (6) where f _{4INF is} the focal length of the fourth lens group at infinity shooting, and f _{4MOD is} the shortest shooting of the fourth lens group. The focal length at a distance is

When the upper limit of 1.8 is exceeded in this conditional expression,
In the vicinity of the maximum magnification, the distance between the focusing lenses in the fourth lens group becomes large and a large moving space is required, which is not desirable. Further, when the lower limit of 0.1 is exceeded, the possibility that the lenses in the fourth lens group interfere with each other increases, which is not desirable.

With the above structure, the paraxial structure is composed of a composite system of a main lens system and a sub-lens system having a magnifying power. It can also be configured independently as a so-called modular design with two subsystems.

As for the aberration correction surface, the first lens group is made up of a plurality of positive lens groups and a specific negative lens of about one sheet, and an air lens is always arranged to provide a surface where various aberrations occur. It is necessary to make corrections at the same time. Also,
In order to reduce the total lens length, the number of positive lens components of the first lens group is increased and a light beam having a strong convergence is made incident on the second lens group.

Further, it is convenient to arrange the second lens group so as to be almost adjacent to the first lens group in order to secure a moving space for the focusing lens group when the proximity magnification is increased. In addition, as shown in the equation (5), the second
It is extremely effective to correct the field curvature by dividing the lens group into about two lens elements and changing the distance between them to correct the aberration variation during focusing.

On the other hand, the fourth lens group is also composed of two or more lens groups, and the same effect can be obtained in aberration correction by changing the mutual movement or space. This is a feature of the present invention. In addition, the second lens group in the main lens system and the fourth lens group in the sub lens system are used for focusing at the same time to effectively act both in terms of zooming and aberration correction, and from infinity to the shortest shooting distance. It is possible to achieve stable optical performance.

Next, it is considered to allocate a thick lens after the paraxial structure is almost decided, but it is desirable to adopt the following structure. The first lens group is composed of at least two positive lens groups and one negative lens. To reduce the telephoto ratio of the optical system, about three positive lenses and one positive lens are used.
It is desirable to compose of a negative lens. This allows
By reducing the amount of residual monochromatic aberrations and chromatic aberrations at an object at infinity and reducing the amount of residual aberrations of each lens unit during focusing, it is possible to increase the stability of the performance of the entire system.

The second lens group has a function of correcting the aberration generated in the first lens group and, at the same time, part of the function of varying the magnification as a focusing lens group. Therefore, chromatic aberration in the lens group is corrected by using a doublet of a positive lens and a negative lens, in particular, a cemented lens, so that fluctuation of aberration during focusing is suppressed as much as possible.

The third lens group, which has an image forming action, is characterized in that it is a fixed lens group during focusing on an object at finite distance. In fact, the present applicant has proposed a movable third lens group, and has a feature that is significantly different from this. Its configuration is at least 1
It is a doublet configuration consisting of a positive lens and a negative lens,
In particular, when a cemented lens is used, it is very effective in obtaining stable image forming performance.

The fourth lens group is the first lens system as the first lens system.
It is an optical system that is considered as an attachment lens from the lens group to the third lens group, and its configuration is based on the specifications of the optical system including the variable conditions such as the variable range and the air gap, and the minimum configuration of the positive lens and the negative lens. I can think.

[0040]

EXAMPLES Examples 1 to 7 of the telephoto lens of the present invention will be described below.
Will be described. Numerical data of each example will be described later, but FIGS. 1A and 1B are cross-sectional views of Example 1 at an object point at infinity and at a finite object point at a lateral magnification of -1/2, respectively. In this embodiment, the first lens group G1 includes the biconvex lens 2
It is composed of a single lens, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The converging light flux from the first lens group G1 enters the third lens group G3 with its paraxial on-axis rays becoming somewhat divergent by the second lens group G2 having negative refractive power. The second lens group G2 is composed of a doublet of a biconvex lens and a biconcave lens, and one biconcave lens, and moves toward the image side when focusing from an infinite object to a finite object. The third lens group G3 is a fixed group as shown in the figure, which is a major feature. The configuration is a doublet of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. Of course, a single positive lens can be used, but it is not easy to obtain higher imaging performance.

The fourth lens group G4 is composed of a movable front group G ₄₁ and a fixed rear group G ₄₂ in this embodiment. Moreover, the front group G ₄₁ moves toward the object side during focusing from an infinite object to a finite object. In this embodiment, the front group G ₄₁ is composed of a doublet of a biconvex lens and a biconcave lens, and the rear group G ₄₂ is composed of a biconcave lens. FIGS. 8 and 9 show aberration diagrams of this example at the infinite point and at the finite object point with a lateral magnification of −1/2. The aberration diagram shows spherical aberration, astigmatism, chromatic aberration of magnification, and distortion. same as below.

Example 2 at infinity and lateral magnification -1 /
2 (a) and 2 (a) are cross-sectional views of the object at the finite object point, respectively.
It shows in (b). In this embodiment, the first lens group G1 includes two biconvex lenses, a biconcave lens, and a positive meniscus lens having a convex surface directed toward the object side. The convergent light flux from the first lens group G1 is converted by the second lens group G2 having negative refractive power into
The paraxial ray becomes somewhat divergent, and the third lens group G
It is incident on 3. The second lens group G2 is a movable front group G.
₂₁ and movable rear group G ₂₂ . Both groups move to the image side during focusing from an object at infinity to an object at finite distance, but the distance between both groups decreases. The front group G ₂₁ is composed of a doublet of a biconvex lens and a biconcave lens, and the rear group G ₂₂ is composed of one biconcave lens. The third lens group G3 is a fixed group as shown in the drawing, and its configuration is a doublet of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 is composed of a movable front group G ₄₁ and a fixed rear group G ₄₂ , and the front group G ₄₁ moves toward the object side during focusing from an infinite object to a finite object.
In this embodiment, the front group G ₄₁ is composed of a doublet of a biconvex lens and a biconcave lens, and the rear group G ₄₂ is composed of a biconcave lens. This embodiment is characterized in that the amount of movement of the second lens group G2 during focusing is different, and is effective in suppressing aberration fluctuations. FIGS. 10 and 11 are aberration diagrams of this example at the infinite point and at the finite object point with a lateral magnification of −1/2.

Example 3 at infinity object point and lateral magnification -1 /
2 (a) and 2 (b) are sectional views of the object at finite object point 2 respectively.
It shows in (b). In this embodiment, the first lens group G1 includes two biconvex lenses, a biconcave lens, and a positive meniscus lens having a convex surface directed toward the object side. The second lens unit G2, constitutes in front of the movable group G ₂₁ and the rear group movable G _22. Both groups,
At the time of focusing from infinity to an object at finite distance, it moves to the image side, but the distance between both groups decreases. The front group G ₂₁ includes a doublet including a biconvex lens and a biconcave lens.
₂₂ is composed of one biconcave lens. The third lens group G3 is a fixed group, and its configuration is a doublet of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 is composed of a movable front group G ₄₁ and a rear group G ₄₂ , and the front group G ₄₁ moves toward the object side during focusing from an infinite object to a finite object. The rear group G ₄₂ moves toward the image side during focusing from an object at infinity to an object at finite distance. In this embodiment, the front group G ₄₁ is composed of a biconvex lens and a doublet of a negative meniscus lens having a convex surface facing the image side, and the rear group G ₄₂ is composed of a biconcave lens. 12 and 13 show aberration diagrams of this example at the point of infinity and at the point of finite object at a lateral magnification of -1/2, respectively.

Example 4 at infinity object point and lateral magnification -1 /
2A and 2B are sectional views of the object at finite object point 2 in FIG.
It shows in (b). In this embodiment, the first lens group G1 includes two biconvex lenses, a biconcave lens, and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 is composed of a doublet of a biconvex lens and a biconcave lens, and one biconcave lens, and moves toward the image side when focusing from an infinite object to a finite object. The third lens group G3 is a fixed group, and its configuration is a doublet of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 is composed of a movable front group G ₄₁ and a fixed rear group G ₄₂ , and the front group G ₄₁ moves toward the object side during focusing from an infinite object to a finite object. The front group G _41, the rear group G ₄₂ both constitute a single lens, the front group G ₄₁ positive meniscus lens having a convex surface directed toward the object side, the rear group G ₄₂ is constituted by a biconcave lens. Aberration diagrams of this example at the time of an object point at infinity and at a lateral object point of −1/2 at a finite object point are shown in FIGS. 14 and 15, respectively.

Example 5 at infinity and lateral magnification -1 /
2 (a) and 2 (b) are sectional views of the object at finite object point 2 respectively.
It shows in (b). In this embodiment, the first lens group G1 is composed of two biconvex lenses, a biconcave lens and a biconvex lens.
The second lens group G2 is composed of a doublet of a biconvex lens and a biconcave lens, and one biconcave lens, and moves toward the image side when focusing from an infinite object to a finite object. The third lens group G3 is a fixed group, and its configuration is a doublet of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 includes a movable front group G ₄₁ and a rear group G ₄₂ , and the front group G ₄₁ and the rear group G _{42 are included.}
Both move toward the object side when focusing from an object at infinity to an object at finite distance, but move separately so that the distance between the two expands. In this embodiment, both the front group G ₄₁ and the rear group G ₄₂ are composed of a single lens. The front group G ₄₁ has a positive meniscus lens having a convex surface facing the object side, and the rear group G ₄₂ has a convex surface facing the image side. It consists of a negative meniscus lens. 16 and 17 are aberration diagrams of this example at the point of infinity and at the object point of finite distance with a lateral magnification of -1/2, respectively.

Example 6 at infinity object point and lateral magnification -1 /
2A and 2B are cross-sectional views of the object at the finite object point in FIG.
It shows in (b). In this embodiment, the first lens group G1 includes two biconvex lenses, a biconcave lens, and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 is composed of a doublet of a biconvex lens and a biconcave lens, and one biconcave lens, and moves toward the image side when focusing from an infinite object to a finite object. The third lens group G3 is a fixed group, and its configuration is a doublet of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 is composed of a movable front group G ₄₁ and a fixed rear group G ₄₂ , and the front group G ₄₁ moves toward the object side during focusing from an infinite object to a finite object. In this embodiment, both the front lens group G ₄₁ and the rear lens group G ₄₂ are composed of a single lens,
The front group G ₄₁ is a positive meniscus lens having a convex surface directed toward the object side,
The rear group G ₄₂ is composed of a biconcave lens. FIGS. 18 and 19 are aberration diagrams of this example at an object point at infinity and at a finite object point at a lateral magnification of −1/2.

Example 7 at infinity and lateral magnification -1 /
2 (a) and 2 (b) are sectional views of the object at the finite object point, respectively.
It shows in (b). In this embodiment, the first lens group G1 includes a biconvex lens, a positive meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The second lens unit G2, and constituted by a movable front group G ₂₁ and the movable after the group G _22, first at the time of focusing 2
This is the case where the floating amount of the lens group G2 is limited. Both groups move to the image side during focusing from an object at infinity to an object at finite distance, but the distance between both groups decreases. The front group G ₂₁ is composed of a doublet including a biconvex lens and a biconcave lens, and the rear group G ₂₂ is composed of one negative meniscus lens having a convex surface facing the object side. The third lens group G3 is a fixed group, and is a doublet of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. Further, the fourth lens group G4 is
It consists of a movable front group G ₄₁ and a fixed rear group G ₄₂ .
₄₁ moves to the object side when focusing from an infinite object to a finite object. Both the front group G ₄₁ and the rear group G ₄₂ are composed of a single lens. The front group G ₄₁ is composed of a positive meniscus lens having a convex surface facing the object side, and the rear group G ₄₂ is composed of a biconcave lens. 20 and 21 are aberration diagrams of this example at the point of infinity and at the point of finite object at a lateral magnification of -1/2, respectively.

Numerical data of Examples 1 to 7 will be shown below. Symbols are other than the above, f is the focal length of the entire system, F _NO is the F number, 2ω is the angle of view, r ₁ , r ₂ ... The radii of curvature of the lens surfaces, d ₁ , d ₂ ... _Are the intervals between the lens surfaces, n _d1 , n _d2
Is the d-line refractive index of each lens, and ν _d1 , ν _d2 are the Abbe numbers of each lens. In addition, ∞ in the focusing group interval data is when the object point is focused at infinity, and β = −1 / 2 is the lateral magnification −1.
/ 2 represents the object at infinity at a finite object point.

Example 1 f = 177.8, F _NO = 2.96, 2ω = 13.874 ° r ₁ = 262.0751 d ₁ = 5.8220 n _d1 = 1.61800 ν _d1 = 63.38 r ₂ = -318.8412 d ₂ = 0.2500 r ₃ = 94.6117 d ₃ = 11.2455 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = -139.8985 d ₄ = 1.6577 r ₅ = -129.5848 d ₅ = 3.2500 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 190.5678 d ₆ = 0.1500 r ₇ = 86.6422 d ₇ = 6.5412 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = 1048.1473 d ₈ = (variable) r ₉ = 260.7504 d ₉ = 4.1077 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = -144.8628 d ₁₀ = 1.9000 n _d6 = 1.51823 ν _d6 = 58.96 r ₁₁ = 45.3400 d ₁₁ = 9.8507 r ₁₂ = -1272.3963 d ₁₂ = 1.9900 n _d7 = 1.51823 ν _d7 = 58.96 r ₁₃ = 79.5719 d ₁₃ = (variable) r ₁₄ = ∞ (aperture) d ₁₄ = 1.0000 r ₁₅ = 61.5072 d ₁₅ = 1.7000 n _d8 = 1.84666 ν _d8 = 23.88 r ₁₆ = 52.2195 d ₁₆ = 5.9253 n _d9 = 1.48749 ν _d9 = 70.20 r ₁₇ = -115.6318 d ₁₇ = (variable) r ₁₈ = 67.4090 d ₁₈ = 4.5675 n _d10 = 1.67790 ν _d10 = 55.33 r ₁₉ = -153.3366 d ₁₉ = 0.9899 r ₂₀ = -126.0203 d ₂₀ = 1.7000 n _d11 = 1.61293 ν _d11 = 37.00 r ₂₁ = 179.9403 d ₂₁ = (variable) r ₂₂ = -95.7491 d ₂₂ = 1.5000 n _d12 = 1.72916 ν _d12 = 54.68 r ₂₃ = 154.2466

Example 2 f = 180.14, F _NO = 2.88, 2ω = 13.7 ° r ₁ = 221.0100 d ₁ = 5.8777 n _d1 = 1.61800 ν _d1 = 63.38 r ₂ = -361.7757 d ₂ = 0.1500 r ₃ = 91.1785 d ₃ = 11.1367 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = -140.8237 d ₄ = 1.6770 r ₅ = -130.5435 d ₅ = 3.3500 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 182.5607 d ₆ = 0.1500 r ₇ = 79.4358 d ₇ = 6.7133 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = 881.4254 d ₈ = (variable) r ₉ = 290.3131 d ₉ = 4.0458 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = -136.4317 d ₁₀ = 1.9331 n _d6 = 1.53996 ν _d6 = 59.57 r ₁₁ = 42.1457 d ₁₁ = (variable) r ₁₂ = -432.3833 d ₁₂ = 2.0000 n _d7 = 1.51821 ν _d7 = 65.04 r ₁₃ = 84.2143 d ₁₃ = (variable) r ₁₄ = ∞ (aperture) d ₁₄ = 1.0000 r ₁₅ = 61.8964 d ₁₅ = 1.7500 n _d8 = 1.80518 ν _d8 = 25.43 r ₁₆ = 49.8593 d ₁₆ = 6.7401 n _d9 = 1.48749 ν _d9 = 70.20 r ₁₇ = -100.5404 d ₁₇ = (variable) r ₁₈ = 71.1579 d ₁₈ = 4.0565 n _d10 = 1.69680 ν _d10 = 55.52 r ₁₉ = -439.3857 d _{19 = 1.8630 r 20 = -213.8762 d 20} = 1.8500 n d11 = 1.63980 ν d11 = 34.48 r 21 = 228.3005 d 21 = ( _{Variable) r 22 = -107.1144 d 22 =} 1.9000 n d12 = 1.61800 ν d12 = 63.38 r 23 = 146.7397

Example 3 f = 197.5, F _NO = 2.86, 2ω = 12.5 ° r ₁ = 268.3172 d ₁ = 7.3637 n _d1 = 1.60300 ν _d1 = 65.48 r ₂ = -304.7913 d ₂ = 0.1500 r ₃ = 102.9617 d ₃ = 13.1396 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = -156.4655 d ₄ = 1.3500 r ₅ = -147.2821 d ₅ = 3.3500 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 206.4306 d ₆ = 0.1500 r ₇ = 79.7258 d ₇ = 8.1126 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = 579.9983 d ₈ = (variable) r ₉ = 331.9196 d ₉ = 4.3051 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = -156.3746 d ₁₀ = 1.8000 n _d6 = 1.53996 ν _d6 = 59.57 r ₁₁ = 51.6743 d ₁₁ = (variable) r ₁₂ = -782.8614 d ₁₂ = 2.0000 n _d7 = 1.51821 ν _d7 = 65.04 r ₁₃ = 66.5063 d ₁₃ = (variable) r ₁₄ = ∞ (aperture) d ₁₄ = 2.0000 r ₁₅ = 66.3476 d ₁₅ = 1.7500 n _d8 = 1.80518 ν _d8 = 25.43 r ₁₆ = 56.4544 d ₁₆ = 6.8962 n _d9 = 1.49700 ν _d9 = 81.61 r ₁₇ = -126.0868 d ₁₇ = (variable) r ₁₈ = 87.9049 d ₁₈ = 4.1723 n _d10 = 1.69680 ν _d10 = 55.53 r ₁₉ = -510.5517 d ₁₉ = 2.7842 r ₂₀ = -116.2583 d ₂₀ = 1.8500 n _d11 = 1.63980 ν _d11 = 34.48 r ₂₁ = -446.0581 d ₂₁ = (variable) r ₂₂ = -155.4716 d ₂₂ = 1.8000 n _d12 = 1.61800 ν _d12 = 63.39 r ₂₃ = 119.3063

Example 4 f = 181, F _NO = 2.83, 2ω = 13.63 ° r ₁ = 218.3602 d ₁ = 6.3853 n _d1 = 1.61800 ν _d1 = 63.38 r ₂ = -280.4587 d ₂ = 0.2500 r ₃ = 94.8563 d ₃ = 10.8511 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = -148.7559 d ₄ = 1.2011 r ₅ = -140.9565 d ₅ = 3.2500 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 160.0205 d ₆ = 0.1500 r ₇ = 83.8409 d ₇ = 6.6031 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = 959.0535 d ₈ = (variable) r ₉ = 135.9481 d ₉ = 4.6720 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = -154.9684 d ₁₀ = 1.9000 nd _d6 = 1.51823 ν _d6 = 58.96 r ₁₁ = 53.5362 d ₁₁ = 5.6086 r ₁₂ = -165.9578 d ₁₂ = 1.9900 n _d7 = 1.56013 ν _d7 = 46.99 r ₁₃ = 52.4970 d ₁₃ = (variable) r ₁₄ = ∞ (aperture) d ₁₄ = 1.4999 r ₁₅ = 63.8234 d ₁₅ = 2.2500 n _d8 = 1.84666 ν _d8 = 23.88 r ₁₆ = 51.8726 d ₁₆ = 7.3413 n _d9 = 1.48749 ν _d9 = 70.20 r ₁₇ = -89.4499 d ₁₇ = (variable) r ₁₈ = 54.6471 d ₁₈ = 3.9114 n _d10 = 1.49700 ν _d10 = 81.61 r ₁₉ = 272.2085 d ₁₉ = (Variable) r ₂₀ = -85.3564 d ₂₀ = 1.8500 n _d11 = 1.61025 ν _d11 = 56.51 r ₂₁ = 127.3330

Example 5 f = 180, F _NO = 2.826, 2ω = 13.706 ° r ₁ = 162.8431 d ₁ = 6.4199 n _d1 = 1.61800 ν _d1 = 63.38 r ₂ = -490.0011 d ₂ = 0.2500 r ₃ = 93.2788 d ₃ = 10.8927 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = -152.6832 d ₄ = 1.1262 r ₅ = -148.2091 d ₅ = 3.2500 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 165.2975 d ₆ = 0.1500 r ₇ = 82.6075 d ₇ = 7.4655 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = -948.0851 d ₈ = (variable) r ₉ = 251.3899 d ₉ = 4.2951 n _d5 = 1.78470 ν _d5 = 26.30 r ₁₀ = -135.8557 d ₁₀ = 1.8990 n _d6 = 1.51823 ν _d6 = 58.96 r ₁₁ = 62.6100 d ₁₁ = 5.7466 r ₁₂ = -125.0567 d ₁₂ = 1.9900 n _d7 = 1.51633 ν _d7 = 64.15 r ₁₃ = 52.1813 d ₁₃ = (variable) r ₁₄ = ∞ (aperture) d ₁₄ = 1.4944 r ₁₅ = 55.4671 d ₁₅ = 2.2500 n _d8 = 1.84666 ν _d8 = 23.88 r ₁₆ = 44.2764 d ₁₆ = 7.9380 n _d9 = 1.49700 ν _d9 = 81.61 r ₁₇ = -108.3520 d ₁₇ = (variable) r ₁₈ = 103.5378 d ₁₈ = 2.6921 n _d10 = 1.74950 ν _d10 = 35.27 r ₁₉ = 457.6827 d ₁₉ = (Variable) r ₂₀ = -56.4930 d ₂₀ = 1.8500 n _d11 = 1.69680 ν _d11 = 55.52 r ₂₁ = -598.2399

Example 6 f = 180.32, F _NO = 2.825, 2ω = 13.682 ° r ₁ = 227.9638 d ₁ = 6.3082 n _d1 = 1.61800 ν _d1 = 63.38 r ₂ = -277.1411 d ₂ = 0.2500 r ₃ = 97.2565 d ₃ = 11.2426 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = -128.4099 d ₄ = 1.1587 r ₅ = -123.2120 d ₅ = 3.2500 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 176.5792 d ₆ = 0.1500 r ₇ = 82.8875 d ₇ = 6.7990 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = 1342.6623 d ₈ = (variable) r ₉ = 123.7908 d ₉ = 5.2425 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = -170.3875 d ₁₀ = 5.2272 n _d6 = 1.51823 ν _d6 = 58.96 r ₁₁ = 55.1048 d ₁₁ = 5.6360 r ₁₂ = -194.6008 d ₁₂ = 1.9900 n _d7 = 1.59551 ν _d7 = 39.21 r ₁₃ = 53.2801 d ₁₃ = (variable) r ₁₄ = ∞ (aperture) d ₁₄ = 1.4919 r ₁₅ = 82.7386 d ₁₅ = 2.2500 n _d8 = 1.84666 ν _d8 = 23.88 r ₁₆ = 67.3676 d ₁₆ = 6.4729 n _d9 = 1.48749 ν _d9 = 70.20 r ₁₇ = -82.6450 d ₁₇ = (variable) r ₁₈ = 57.9483 d ₁₈ = 3.8662 n _d10 = 1.49700 ν _d10 = 81.61 r ₁₉ = 348.3846 d ₁₉ = (Variable) r ₂₀ = -119.4562 d ₂₀ = 1.8500 n _d11 = 1.56873 ν _d11 = 63.16 r ₂₁ = 90.6863

Example 7 f = 180, F _NO = 2.83, 2ω = 13.7 ° r ₁ = 155.3384 d ₁ = 8.7962 n _d1 = 1.49700 ν _d1 = 81.61 r ₂ = -225.5733 d ₂ = 0.2500 r ₃ = 82.5638 d ₃ = 12.0196 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = 555.7519 d ₄ = 4.2718 r ₅ = -258.3860 d ₅ = 3.4532 n _d3 = 1.71736 ν _d3 = 29.51 r ₆ = 153.9451 d ₆ = 0.1500 r ₇ = 77.0710 d ₇ = 7.1568 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = 349.1017 d ₈ = (variable) r ₉ = 171.5875 d ₉ = 3.0476 n _d5 = 1.84666 ν _d5 = 23.78 r ₁₀ = -523.9859 d ₁₀ = 4.6903 n _d6 = 1.61700 ν _d6 = 62.79 r ₁₁ = 50.7174 d ₁₁ = (variable) r ₁₂ = 513.8327 d ₁₂ = 3.1235 n _d7 = 1.69680 ν _d7 = 55.52 r ₁₃ = 64.1814 d ₁₃ = (variable) r ₁₄ = ∞ (aperture) d ₁₄ = 1.5000 r ₁₅ = 94.2568 d ₁₅ = 5.6444 n _d8 = 1.71736 ν _d8 = 29.51 r ₁₆ = 61.1205 d ₁₆ = 6.4554 n _d9 = 1.60311 ν _d9 = 60.70 r ₁₇ = -95.1589 d ₁₇ = (variable) r ₁₈ = 49.2884 d ₁₈ = 3.9983 n _d10 = 1.60311 ν _d10 = 60.70 r ₁₉ = 97.3910 d ₁₉ = (possible (Mod) r ₂₀ = -344.2371 d ₂₀ = 2.3031 n _d11 = 1.74400 ν _d11 = 44.73 r ₂₁ = 81.6888

The values of conditional expressions (1) to (6) in each of the above embodiments are shown below. .

The above telephoto lens of the present invention can be constructed as follows. [1] In order from the object side, the whole optical system is composed of a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power. Focusing from an object at infinity to an object at finite distance,
Among the second lens group and the fourth lens group with the first lens group and the third lens group fixed with respect to the image plane with reference to the position of each lens group with respect to an object at infinity,
A telephoto lens satisfying the following conditional expression, which is obtained by moving at least a part of lens components so as to reduce an axial distance from the third lens group. 0.4 <−f ₁ / f ₂ <2.5 (1) 0.3 <D ₁₂₃ /f<1.5 (2) β ₄ > 1 (3) However, f ₁ : focal length of the first lens group, f ₂ : focal length of the second lens group, D ₁₂₃ : first lens surface apex of the first lens group to the final lens surface apex of the third lens group at infinity object On the optical axis, f: focal length of the entire system at infinity object, β ₄ : paraxial lateral magnification of the fourth lens group at infinity object,

[2] In order from the object side, the first positive refractive power first
The second lens group includes a lens group, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power, and the second lens group has a second lens group having a negative refractive power. When focusing from an object at infinity to an object at a finite distance, the first lens unit has a front lens unit and a second rear lens unit having a negative refractive power, and
Fixing the lens group and the third lens group with respect to the image plane,
A telephoto lens that moves the second rear lens group to the image side.

[3] In order from the object side, the first positive refractive power
The lens unit includes a second lens unit having a negative refracting power, a third lens unit having a positive refracting power, and a fourth lens unit having a negative refracting power, and the fourth lens unit has a fourth lens unit having a further positive refracting power. It has a front lens group and a fourth rear lens group having a negative refractive power, and when focusing from an object at infinity to an object at a finite distance, the first lens
Fixing the lens group and the third lens group with respect to the image plane,
A telephoto lens that moves the fourth front lens unit toward the object side.

[4] Upon focusing, the second lens group moves integrally toward the image side [1].
Alternatively, the telephoto lens according to [2].

[5] Upon focusing, the fourth lens group moves integrally toward the image side [1].
The telephoto lens according to any one of [3] to [3].

[6] The telephoto lens according to the above [2], wherein the second front lens unit moves toward the image side while changing the relative distance between the second front lens unit and the second rear lens unit during the focusing.

[7] The telephoto lens according to the above [6], wherein the change in the relative distance moves so as to reduce the distance during focusing from an object at infinity to an object at a finite distance.

[8] At the time of focusing, the fourth rear lens group moves toward the object side while changing the relative distance between the fourth rear lens group and the fourth front lens group.
Telephoto lens described.

[0065]

[9] The fourth lens group further has a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and the fourth front lens group is an object when focusing. The telephoto lens according to the above [2], which moves to the side.

[10] The fourth lens group further has a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and the fourth rear lens group upon focusing. The telephoto lens according to the above [2], which moves the lens toward the object side.

[11] The fourth lens group further has a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and the fourth front lens group is provided during focusing. The telephoto lens according to the above item [2], wherein the group and the fourth rear lens group move toward the object side while changing the relative distance.

[12] The telephoto lens according to the above [8] or [11], wherein the change in the relative distance moves so as to reduce the distance during focusing from an object at infinity to an object at a finite distance.

[13] The above [2] satisfying the following condition
The telephoto lens according to any one of [12] to [12]. 0.4 <−f ₁ / f ₂ <2.5 (1) 0.3 <D ₁₂₃ /f<1.5 (2) β ₄ > 1 (3) However, f ₁ : focal length of the first lens group, f ₂ : focal length of the second lens group, D ₁₂₃ : first lens surface apex of the first lens group to the final lens surface apex of the third lens group at infinity object On the optical axis, f: focal length of the entire system at infinity object, β ₄ : paraxial lateral magnification of the fourth lens group at infinity object,

[14] The above [2] which satisfies the following conditions:
The telephoto lens according to any one of [13] to [13]. −0.05 <u ₂ ′ <0.05 (4) where u ₂ ′ is the axial paraxial exit tilt angle (radian) from the final lens surface of the second lens unit at the time of an object at infinity, u ₂ '= u ₂
+ H ₂ φ ₂ , the subscript 2 indicates the second lens group, and u
Is the paraxial tilt angle, h is the paraxial configuration height, and φ is the refractive power.

[15] The above [2] which satisfies the following condition
The telephoto lens according to any one of [14] to [14]. 0.5 <f _2INF / f _2MOD <1.5 (5) where f _{2INF is} the focal length of the second lens group at infinity shooting, and f _{2MOD is} the shortest shooting distance of the second lens group. The focal length is.

[16] The above [2] which satisfies the following condition
The telephoto lens according to any one of [15] to [15]. 0.1 <f _4INF / f _4MOD <1.8 (6) where f _{4INF is} the focal length of the fourth lens group at infinity shooting, and f _{4MOD is} the shortest shooting distance of the fourth lens group. The focal length is.

[0073]

As is apparent from the above description, according to the telephoto lens of the present invention, the first lens group to the third lens group constitute the main lens system, and the fourth lens group includes the sub lens system. The focusing lens group is provided for each of them, and the zoom lens and the aberration correcting function are provided at the same time so that the shortest shooting distance from infinity and the maximum magnification are −
It has become possible to obtain stable optical performance from 1/2 to around 1: 1.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a telephoto lens according to a first exemplary embodiment of the present invention at an object point at infinity and at a finite object point at a lateral magnification of −1/2.

2 is a sectional view similar to FIG. 1 of Example 2. FIG.

3 is a sectional view similar to FIG. 1 of Example 3. FIG.

FIG. 4 is a sectional view similar to FIG. 1 of Example 4.

5 is a sectional view similar to FIG. 1 of Example 5. FIG.

FIG. 6 is a sectional view similar to FIG. 1 of Example 6;

FIG. 7 is a sectional view similar to FIG. 1 of Example 7.

FIG. 8 is an aberration diagram for Example 1 at an object point at infinity.

FIG. 9 is an aberration diagram of Example 1 at a finite object point with a lateral magnification of −1/2.

FIG. 10 is an aberration diagram for Example 2 at an object point at infinity.

FIG. 11 is an aberration diagram of Example 2 at a finite object point with a lateral magnification of −1/2.

FIG. 12 is an aberration diagram for Example 3 at an object point at infinity.

FIG. 13 is an aberration diagram of Example 3 at a finite object point with a lateral magnification of −1/2.

FIG. 14 is an aberration diagram for Example 4 at an object point at infinity.

FIG. 15 is an aberration diagram for Example 4 at a finite object point with a lateral magnification of −1/2.

FIG. 16 is an aberration diagram of Example 5 upon an object point at infinity.

FIG. 17 is an aberration diagram of Example 5 at a finite object point with a lateral magnification of −1/2.

FIG. 18 is an aberration diagram for Example 6 at an object point at infinity.

FIG. 19 is an aberration diagram for Example 6 at a finite object point with a lateral magnification of −1/2.

FIG. 20 is an aberration diagram for Example 7 at an object point at infinity.

FIG. 21 is an aberration diagram for Example 7 at a finite object point with a lateral magnification of −1/2.

[Explanation of symbols]

G1 ... the first lens group G2 ... the second lens group G3 ... third lens group G4 ... fourth lens group G ₂₁ ... group G ₄₁ ... fourth lens after the previous group G ₂₂ ... second lens group in the second lens group Front group G ₄₂ ... Rear group of 4th lens group

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-75107 (JP, A) JP-A-58-82217 (JP, A) JP-A-61-51117 (JP, A) JP-A-53- 134425 (JP, A) JP 54-70827 (JP, A) JP 61-69016 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 13/02 G02B 9 / 00

Claims (16)

(57) [Claims] 1. A first lens having positive refracting power in order from the object side.
A second lens unit having a negative refracting power, a third lens unit having a positive refracting power, and a fourth lens unit having a negative refracting power,
The lens group further has a second front lens group having a negative refractive power and a second rear lens group having a negative refractive power, and when focusing from an object at infinity to an object at a finite distance, the first lens group and the first lens group A telephoto lens in which the third lens group is fixed to the image plane, the second rear lens group is moved to the image side, and the following conditions are satisfied. 0.5 <f2INF / f2MOD ≦ 0.9994 ...
(5) ' However, f2INF: focus of the second lens group at infinity shooting
Point distance, f2MOD: focal length of the second lens group at the shortest shooting distance
Away . 2. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power in order from the object side. Become the second
The lens group further has a second front lens group having a negative refractive power and a second rear lens group having a negative refractive power, and when focusing from an object at infinity to an object at a finite distance, the first lens group and the first lens group A telephoto lens having three lens groups fixed to the image plane, the second rear lens group being moved to the image side, and the fourth lens group including at least two lens groups, which satisfies the following conditions. 0.1 <f4INF / f4MOD ≦ 0.89589 ...
(6) ' However, f4INF: focus of the fourth lens group at the time of infinity shooting
Point distance, f4MOD: Focal length of the fourth lens group at the shortest shooting distance
Away . 3. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power in order from the object side. The fourth lens group further has a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and when focusing from an object at infinity to an object at a finite distance, The lens unit and the third lens unit are fixed to the image plane,
A telephoto lens in which the front lens group is moved to the object side and the second lens group is composed of at least two lens groups, and which satisfies the following conditions. 0.5 <f2INF / f2MOD ≦ 0.9994 ...
(5) ' However, f2INF: focus of the second lens group at infinity shooting
Point distance, f2MOD: focal length of the second lens group at the shortest shooting distance
Away . 4. A first lens group having a positive refractive power in order from the object side.
And a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power, the fourth lens group further including a fourth front portion having a positive refractive power. A lens unit and a fourth rear lens unit having a negative refractive power, the first lens unit and the third lens unit are fixed with respect to the image plane during focusing from an object at infinity to an object at a finite distance; The fourth
A telephoto lens that moves the front lens group to the object side and satisfies the following conditions. 0.1 <f4INF / f4MOD ≦ 0.89589 ...
(6) ' However, f4INF: focus of the fourth lens group at the time of infinity shooting
Point distance, f4MOD: Focal length of the fourth lens group at the shortest shooting distance
Away . Upon wherein said focusing telephoto lens according to claim 2, wherein said second lens group moves toward the image side together. 6. The telephoto lens according to claim 3 , wherein the fourth lens group moves integrally toward the image side during the focusing. Upon wherein said focusing claim 1 or 2 telephoto lens according the second front lens group is moved to the respective image side while changing the relative distance between the second rear lens group. 8. The telephoto lens according to claim 7, wherein the change of the relative distance moves so as to reduce the distance when focusing from an object at infinity to an object at finite distance. Upon wherein said focusing, the fourth rear lens group claim 3 or 4 telephoto lens according to respectively move toward the object side while changing the relative distance between the fourth front lens group. 10. The fourth lens group further includes a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and the fourth front lens group upon focusing. The telephoto lens according to claim 1 , wherein the telephoto lens moves toward the object side. 11. The fourth lens group further includes a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and the fourth rear lens group is provided at the time of focusing. The telephoto lens according to claim 1 , wherein the telephoto lens is moved to the object side. 12. The fourth lens group further includes a fourth front lens group having a positive refractive power and a fourth rear lens group having a negative refractive power, and the fourth front lens group upon focusing. and the claim 1 or telephoto lens 2 according to the fourth rear lens group moves respectively to the object side while changing the relative spacing. 13. The change of the relative distance is infinite upon focusing from a far object to a finite distance object, claim 9 or 12 telephoto lens described moves in <br/> so that to expand the interval. 14. The method according to any one of claims 1 to 13 which satisfies the following conditions.
The telephoto lens according to any one of 1. 0.4 <−f ₁ / f ₂ <2.5 (1) 0.3 <D ₁₂₃ /f<1.5 (2) β ₄ > 1 (3) However, f ₁ : focal length of the first lens group, f ₂ : focal length of the second lens group, D ₁₂₃ : first lens surface vertex of the first lens group at the time of an object at infinity to the final lens surface of the third lens group Optical axis distance to apex, f: Focal length of whole system at infinity object,
β ₄ : paraxial lateral magnification of the fourth lens group when an object at infinity is obtained. 15. The method according to any one of claims 1 to 14 which satisfies the following conditions.
The telephoto lens according to any one of 1. −0.05 <u ₂ ′ <0.05
(4) where u ₂ ′ is the axial paraxial exit tilt angle (radian) from the final lens surface of the second lens unit when an object at infinity is u ₂ ′ =
u ₂ + h ₂ φ ₂ , the subscript 2 indicates the second lens group, u is the paraxial tilt angle, h is the paraxial configuration height, and φ is the refractive power. 16. The following condition is satisfied according to claim 1 or 3 telephoto lens according. 0.1 <f _4INF / f _4MOD <1.8 ...
(6) where f _{4INF is} the focal length of the fourth lens group when shooting at infinity, and f _{4MOD is} the focal length of the fourth lens group when shooting at the shortest shooting distance.