JPH09230238A - Variable power optical system capable of focusing in short distance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a variable power optical system having a wide angle of view, suitable for miniaturization and attaining high variable power, and having small aberration fluctuations at the time of focusing in a short distance by satisfying a specified conditional expression. SOLUTION: In the case of varying power from a wide angle end state to a telephotographing end state, at least a 1st lens group G1 and a 5th lens group G5 are moved to an object side so that a distance between the 1st lens group G1 and a 2nd lens group G2 is increased, a distance between the lend group G2 and a 3rd lens group G3 is decreased, and a distance between a 4th lens group G4 and the 5th lens group G5 is decreased; and at least the lens group G4 is moved so that an axial distance between the lens groups G2 and G4 is decreased; then at least the lens group G4 is moved along an optical axis so as to bring a short-distance object into focus. Then, the following conditional expressions are satisfied: 0.7<f3/f4<1.1, 0.3<|f2|/(fw.ft)<1/2> <0.5. Provided that f2 to f4 express the focal distances of the lens groups G2 to G4 and fw and ft express the focal distance of an entire optical system at the wide angle end state and the telephotographing end state in the expressions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable power optical system capable of focusing at a short distance, and more particularly to a small variable power optical system capable of focusing at a high distance and capable of focusing at a short distance.

[0002]

2. Description of the Related Art In recent years, as a lens shutter type camera, a camera equipped with a zoom lens is becoming popular. In particular, a camera equipped with a so-called high-zoom zoom lens having a zoom ratio of more than 3 is becoming mainstream. In these high-magnification zoom lenses, so-called multi-group zoom lenses having three or more lens groups that are movable during zooming are mainly used. Various proposals have been made centering on a zoom lens having an angle of view of about 60 ° in the wide-angle end state.

Further, in the lens shutter type camera,
Miniaturization is required, and various proposals have been made regarding zoom lenses suitable for miniaturization. In a zoom lens, a mainstream is to move a part of the lens group of the lens system in the optical axis direction to focus on a short-distance object. Focusing methods of this type include (1) front focus (FF) method, (2) inner focus (IF) method,
(3) Rear focus (RF) method.

[0004]

However, in the conventional high variable power zoom lens, as the variable power ratio becomes higher,
The focal length in the telephoto end state becomes long. As a result, the total length of the lens becomes large and the aperture diameter becomes large, so that the camera becomes large and the portability deteriorates.

Conversely, if an attempt is made to achieve a high zoom ratio by shortening the focal length in the wide-angle end state without increasing the focal length in the telephoto end state, then in the wide-angle end state, the light quantity in the peripheral portion of the screen is obtained by the cos 4 law. The shortage becomes noticeable. Therefore, vignetting must be reduced so that the lack of light is not noticeable. However, since the angle of view is increased by shortening the focal length in the wide-angle end state, the off-axis light flux passing through the lens group away from the diaphragm is separated from the optical axis, which causes an increase in the lens diameter. there were.

In general, the smaller the lens diameter of the focusing lens group that is driven when focusing on a short distance, the more compact the drive mechanism can be. Further, the smaller the weight of the focusing lens group, the smaller the driving force, and therefore the driving mechanism can be simplified. Therefore, it is desirable to configure the focusing lens group with a lightweight lens group having a small lens diameter. In a multi-group zoom lens, since the aperture stop is arranged near the center of the lens system, the lens diameter of the lens such as the front lens and the rear lens that are arranged apart from the aperture stop is large. Therefore, when the FF method or the RF method is used, it is not possible to reduce the size of the driving mechanism of the focusing lens group.

The present invention has been made in view of the above-mentioned problems, and has a wide angle of view, is suitable for downsizing and high zooming, and has a small variation in aberration when focusing at a short distance. The purpose is to provide an optical system.

[0008]

In order to solve the above problems, in the present invention, a first lens group G1 having a positive refractive power and a second lens group having a negative refractive power are arranged in order from the object side. G2 and the third lens group G3 having a positive refractive power
And a fourth lens group G4 having a positive refracting power and a fifth lens group G5 having a negative refracting power, and at the time of zooming from the wide-angle end state to the telephoto end state, the first lens group G1 The air gap between the second lens group G2 and the second lens group G2 increases,
At least the first lens group G1 and the first lens group G1 so that the air gap between the lens group G2 and the third lens group G3 decreases and the air gap between the fourth lens group G4 and the fifth lens group G5 decreases. At least the fourth lens group G4 moves so that the fifth lens group G5 moves toward the object side and the axial distance between the second lens group G2 and the fourth lens group G4 decreases, and the fourth lens group G4 moves. The lens unit G4 is moved along the optical axis to focus on a short-distance object, the focal length of the second lens unit G2 is f2, the focal length of the third lens unit G3 is f3, and When the focal length of the four lens group G4 is f4, the focal length of the entire optical system in the wide-angle end state is fw, and the focal length of the entire optical system in the telephoto end state is ft, 0.7 <f3 / f4 <1 .1 0.3 <| f2 | / (f · Ft) ^1/2 <provides a near-focus possible variable magnification optical system characterized by satisfying 0.5 conditions.

According to a preferred embodiment of the present invention, the lateral magnification of the fourth lens group G4 in the telephoto end state is β4t,
The lateral magnification of the fourth lens group G4 in the wide-angle end state is β
When 4w and the zoom ratio is Z, the condition of 0.18 <(β4t / β4w) / Z <0.38 is satisfied. Further, it is preferable that at least one lens surface of the plurality of lens surfaces forming the fourth lens group G4 is formed in an aspherical shape.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, a general description will be given of a zoom lens suitable for miniaturization and capable of high zooming. A zoom lens used for a lens shutter type camera and a telephoto zoom lens for a single-lens reflex camera require a lens system having a high zoom ratio and a small size. As a zoom lens suitable for this requirement, a multi-group zoom lens including three or more movable lens groups, such as a positive / negative type and a positive / negative / negative type, is often used.

In order to reduce the total length of the lens, a positive lens group is arranged on the most object side of the lens system to strengthen the converging action,
It is desirable to adopt a telephoto type in which the negative lens unit is arranged closest to the image side to enhance the diverging action. In particular, unlike a single-lens reflex camera, a lens shutter type camera has no restriction on the back focus of the taking lens system. Therefore, in many lens systems, the negative lens group is arranged closest to the image side of the taking lens system in order to reduce the lens diameter and the total lens length. Then, in the wide-angle end state, the back focus is shortened, and the off-axis light flux passing through the negative lens group is separated from the optical axis along with the change in the angle of view, so that the on-axis aberration and the off-axis aberration can be independent. Correcting. Also, by increasing the back focus at the time of zooming from the wide-angle end state to the telephoto end state, the height of the off-axis light flux passing through the negative lens group is changed by zooming, and fluctuations in off-axis aberrations due to zooming are changed. It is suppressed so that good imaging performance can be obtained.

In many lens systems, the positive lens group is arranged closest to the object side of the taking lens system in order to reduce the lens diameter and the total lens length. In the wide-angle end state, the height of the off-axis light flux passing through the positive lens group is shortened by shortening the distance between the positive lens group and the lens group disposed adjacent to the image side and shortening the total lens length. Is closer to the optical axis to reduce the lens diameter. On the other hand, in the telephoto end state, the distance between the positive lens group and the lens group adjacent to the image side thereof is widened and the positive lens group is moved to the object side, so that the refractive power arrangement is set to the telephoto type and the entire lens length is increased. Is being shortened. The diaphragm is arranged near the center of the lens system between the positive lens group and the negative lens group.

Japanese Patent Application Laid-Open No. 7-2797 filed by the present applicant
In the zoom lens of positive / negative / positive / negative type disclosed in Japanese Patent Laid-Open No. 9-90, the lens chamber holding the second lens group and the lens chamber holding the fourth lens group are integrated to form a second lens group and a fourth lens group.
The lens group and the lens group are driven integrally during zooming. Further, the third lens group is a focusing lens group, and the third lens group is driven in the optical axis direction relative to the second lens group by the same drive system both during zooming and during focusing. By configuring the zoom lens in this way, the second lens group is attached to the object side and the fourth lens group is attached to the image side of the unit including the drive system for driving the third lens group in the optical axis direction, and A lens barrel structure can be adopted in which the third lens group is moved relative to the unit. In this way, even though the lens barrel structure is the same as that of the positive / negative three-group type, high zoom ratio and high performance are realized.
However, because the degree of freedom in selecting the zoom orbit is reduced, the refractive power of each lens group tends to increase when attempting to achieve a higher zoom ratio, and performance deterioration due to mutual eccentricity between lens groups tends to increase. It was Therefore, in the present invention, the refractive power of each lens group is weakened by independently driving the second lens group G2 and the fourth lens group G4 during zooming.

Generally, the focusing lens group is driven by a focusing drive system independently of the other lens groups. Although the lens position accuracy of the focusing drive system in the optical axis direction does not change during zooming, the depth of field becomes smaller in the telephoto end state than in the wide-angle end state because the focal length of the entire optical system changes. Therefore, in the case of the FF method in which the amount of extension is constant between the wide-angle end state and the telephoto end state, particularly when trying to achieve a high zoom ratio, in the wide-angle end state, fairly coarse lens position accuracy is sufficient, whereas in the telephoto end state. In that case, since very high lens position accuracy is required, control of the focusing lens group is not efficient.

On the other hand, in the IF system and the RF system, the lateral magnification of the focusing lens group changes due to zooming. Therefore, by setting the change in lateral magnification of the focusing lens group when zooming from the wide-angle end state to the telephoto end state to an appropriate size (range), the required position accuracy of the focusing lens group becomes the entire zoom range. It is possible to set the same level throughout. When the RF method is used, since the lateral magnification of the fifth lens group arranged closest to the image side is always larger than 1 during zooming and used for multiplication, focusing movement in the telephoto end state is greater than in the wide-angle end state. The amount becomes extremely small, and it becomes difficult to control the focusing lens group.

Therefore, in the present invention, the IF system is adopted, which can reduce the size of the driving mechanism of the focusing lens group. Thus, even when the variable power optical system according to the present invention is incorporated in the camera body, the camera body can be downsized. Also, by setting the change in lateral magnification due to zooming of the focusing lens group to an appropriate value, the change in the required lens position accuracy of the focusing lens group due to zooming can be reduced, and the control of the focusing lens group can be made more efficient. I am trying.

In the present invention, from the wide-angle end state to the telephoto end state, the lateral magnification β of the focusing lens group does not include the lens position state where | β | = 1, and the lateral magnification β of the focusing lens group is It is desirable to change so as not to have an extreme value with respect to the focal length. In general, the moving amount Δ of the focusing lens group is expressed by the following equation, where δ is the moving amount of the subject image by the lens group arranged on the object side of the focusing lens group and β is the lateral magnification of the focusing lens group. Given in (a).

Δ = {β ² / (β ² −1)} · δ (a) In the equation (a), k = β ² / (β ² −1)
The value of k depends on the value of β ² and the following equations (b) and (c)
Will be represented by. 1 ≦ k (β ² > 1) (b) 0> k (β ² <1) (c)

Therefore, in order to reduce the magnitude of the focusing movement amount Δ, it is necessary to bring 1 / β close to 0 when | β |> 1. When | β | <1, it is necessary to bring β close to 0. Therefore, when zooming from the wide-angle end state to the telephoto end state, 1 / |
β | becomes extremely large (| β |> 1) or |
When β | is extremely small (| β | <1), the focusing movement amount required for focusing on the same subject is extremely small in the telephoto end state as compared with the wide-angle end state.
Also, 1 / | β | becomes extremely small (| β |> 1)
Or, | β | becomes extremely large (| β | <1)
In this case, the amount of movement required to focus on the same subject becomes extremely large in the telephoto end state as compared with the wide-angle end state.
In either case, the required positional accuracy of the focusing lens group required for lens position control is greatly different between the wide-angle end state and the telephoto end state, so the position control of the focusing group cannot be performed efficiently. .

Next, the function of each lens unit constituting the variable power optical system according to the present invention will be described. In the variable power optical system according to the present invention, the negative lens unit is arranged closest to the image side in the variable power optical system of the present invention, as in the zoom lens of the multi-group structure according to the conventional technique. Then, in the shortest focal length state (wide-angle end state), by shortening the back focus, the height of the off-axis light flux passing through the negative lens group is changed depending on the angle of view, and the on-axis aberration and the off-axis aberration are respectively changed. The correction is done independently. However, if the back focus is extremely shortened, the off-axis light flux passing through the negative lens group will be too far from the optical axis, so that the lens diameter cannot be reduced. Also,
Dust easily attaches to the lens surface closest to the image side, but if the back focus becomes too short, the dust attached to the lens surface will be reflected in the photograph. Therefore, it is important to set the back focus to an appropriate value in the wide-angle end state.

On the contrary, in the longest focal length state (telephoto end state), the back focus is increased. That is, by moving the negative lens group toward the object side when the focal length of the optical system changes from the shortest focal length state to the longest focal length state, the negative lens group is passed in the longest focal length state rather than the shortest focal length state. By making the height of the off-axis light flux closer to the optical axis, the fluctuation of the off-axis aberration that occurs when the focal length of the optical system changes is suppressed as much as possible.

In the present invention, in order to achieve a variable power optical system that is small in size and has a high zoom ratio, but has little aberration variation during focusing at a short distance, in order from the object side,
The first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, the third lens group G3 having a positive refractive power, the fourth lens group G4 having a positive refractive power, and the fifth lens group having a negative refractive power. The lens group G5 is arranged and each lens group is made to function so as to satisfy the following five conditions.

The lateral magnification of the fourth lens group G4, which is the focusing lens group, is set to an appropriate value over the variable power range from the wide-angle end state to the telephoto end state. The aperture stop is arranged near the fourth lens group G4. The negative lens group (fifth lens group G5) is arranged closest to the image side so that the lateral magnification of the negative lens group becomes positively large when the focal length of the optical system changes from the wide-angle end state to the telephoto end state. The negative lens group is moved to the object side. When the focal length of the optical system changes from the wide-angle end state to the telephoto end state, the combined refractive power of the third lens group G3 and the fourth lens group G4 is positively weakened. When the focal length of the optical system changes from the wide-angle end state to the telephoto end state, at least the first lens group G1 is moved to the object side so that the air gap between the first lens group G1 and the second lens group G2 increases. Let

As described above, in order to efficiently control the lens position of the focusing lens unit, the lateral magnification of the fourth lens unit G4, which is the focusing lens unit, must be appropriately set over the entire zoom range. It is essential and the condition of is necessary. Next, when the aperture stop is arranged at a position distant from the fourth lens group G4, the height of the off-axis light flux passing through the fourth lens group G4 greatly changes according to the change of the subject position, and the off-axis aberration changes. Will become bigger. Therefore, according to the condition of, the aperture stop is changed to the fourth lens group G4.
By arranging in the vicinity of, it is possible to suppress variation in aberration when focusing on a short distance.

Conventionally, in a lens system such as a taking lens system of a lens shutter type camera, which has no restriction on back focus, it is arranged on the most image side when the focal length changes from the wide-angle end state to the telephoto end state. The negative lens group is used for multiplication by moving the negative lens group toward the object side so as to narrow the distance from the principal point position of the entire lens group disposed closer to the object side than the negative lens group. Thus, as described above, not only the fluctuation of the off-axis aberration due to zooming is suppressed well, but also the zooming effect is effectively performed. Similarly, in the present invention, the negative lens group (fifth lens group G5) is closest to the image side.
Are placed, and the conditions of are required.

The telephoto ratio is known as one measure for shortening the total lens length. The telephoto ratio is a value obtained by dividing the total lens length by the focal length. In order to reduce the telephoto ratio and shorten the overall lens length, the refractive power of the positive lens group arranged on the object side, the refractive power of the negative lens group arranged on the image side,
It is important to properly set the principal point distance between these two lens groups. In the present invention, the converging action of the positive partial system including the third lens group G3 and the fourth lens group G4 arranged on the image side of the second lens group G2 is weakened in the telephoto end state rather than in the wide-angle end state. That is, in the telephoto end state, the combined refractive power of the third lens group G3 and the fourth lens group G4 is positively weakened, and the combined refractive power from the second lens group G2 to the negative lens group arranged closest to the image side is reduced. By making it negative, the refractive power arrangement is set to the telephoto type, and the telephoto ratio is set to 1 or less.

In the wide-angle end state, the first lens group G1
And the second lens group G2, a negative partial system, a positive partial system including a plurality of positive lens groups, and a negative lens group arranged closest to the image side constitute a refractive power arrangement. Therefore, if the positive subsystem does not have a strong positive refractive power, a predetermined focal length cannot be obtained, and the refractive power of the positive subsystem is positively strengthened in the wide-angle end state rather than in the telephoto end state. . From the above, the condition of is required.

In the present invention, the wide-angle end state has a negative and positive symmetrical refractive power arrangement, and the telephoto end state has a positive and negative telescopic refractive power arrangement. In the wide-angle end state, the total lens length is shortened to bring the off-axis light flux passing through the first lens group G1 closer to the optical axis to reduce the lens diameter. Further, in the telephoto end state, since the converging action of the first lens group G1 is effectively used for shortening the total lens length, the first lens group G1 is changed upon zooming from the wide-angle end state to the telephoto end state.
It is desirable that the first lens group G1 moves toward the object side so that the distance between the first lens group G1 and the second lens group G2 increases, and the condition of is necessary.

Each conditional expression of the present invention will be described below. In the present invention, the following conditional expressions (1) and (2)
To be satisfied. 0.7 <f3 / f4 <1.1 (1) 0.3 <| f2 | / (fw · ft) ^1/2 <0.5 (2)

Here, f2: focal length of the second lens group G2 f3: focal length of the third lens group G3 f4: focal length of the fourth lens group G4 fw: focal length of the entire optical system in the wide-angle end state ft: Focal length of the entire optical system at the telephoto end

Conditional expression (1) defines an appropriate range for the ratio between the focal length of the third lens group G3 and the focal length of the fourth lens group G4. If the upper limit of conditional expression (1) is exceeded, the converging action of the third lens group G3 weakens, and the overall lens length in the telephoto end state increases.
On the contrary, when the lower limit value of the conditional expression (1) is exceeded, the converging action of the third lens group G3 becomes strong, and the lateral magnification of the fourth lens group G4 approaches 1. As a result, the focusing movement amount of the fourth lens group G4 becomes large.

Conditional expression (2) defines an appropriate range for the focal length of the second lens group G2. Conditional expression (2)
If the upper limit of the second lens group G2 is exceeded, the diverging action of the second lens group G2 is weakened, so that a sufficient back focus cannot be obtained in the wide-angle end state, and the lens diameter of the fifth lens group G5 becomes large. When the value goes below the lower limit of conditional expression (2), the diverging action of the second lens group G2 becomes stronger, and the off-axis light flux passing through the second lens group G2 approaches the optical axis. As a result, it becomes difficult to independently correct the on-axis aberration and the off-axis aberration.

Further, in the present invention, it is desirable that the following conditional expression (3) is satisfied in order to improve the efficiency of the position control of the focusing lens unit. 0.18 <(β4t / β4w) / Z <0.38 (3) where β4t: lateral magnification of the fourth lens group G4 in the telephoto end state β4w: lateral magnification of the fourth lens group G4 in the wide-angle end state Z : Zoom ratio

Conditional expression (3) is a conditional expression that regulates the amount of change in lateral magnification of the fourth lens group G4 due to zooming. When the upper limit of conditional expression (3) is exceeded, the focusing movement amount becomes extremely large in the telephoto end state as compared with the wide-angle end state. Conversely, if the lower limit of conditional expression (3) is exceeded,
The focusing movement amount in the wide-angle end state becomes extremely large. As a result, in any case, it becomes impossible to efficiently control the lens position of the focusing lens group. In order to more efficiently control the lens position of the focusing lens unit, it is desirable to set the upper limit of conditional expression (3) to 0.3.

Further, in the present invention, at least one lens surface of the fourth lens group G4, which is a focusing lens group, is formed into an aspherical surface in order to satisfactorily correct the fluctuations of various aberrations that occur during short-distance focusing. It is desirable to form.

The second lens group G2 includes a negative subgroup,
It is desirable to have a positive subgroup arranged on the image side. With this configuration, the image-side principal point position of the second lens group can be moved to the object side, and a sufficient back focus can be obtained in the wide-angle end state. At this time, it is desirable that the positive subgroup includes at least one positive lens and at least one negative lens. Here, although the off-axis light flux passing through the second lens group G2 has a large change in the incident angle to the second lens group G2 in each state from the wide-angle end state to the telephoto end state (from the optical axis). There is no significant change in the incident height. Therefore, it is desirable to satisfactorily correct the aberration generated by the second lens group G2 alone. In the configuration of the present invention, since the off-axis light flux passing through the second lens group G2 passes through a portion having a height close to the optical axis, in order to correct the positive spherical aberration generated by the second lens group alone, It is desirable that the positive subgroup includes at least one positive lens and at least one negative lens. Needless to say, high performance can be achieved by configuring the second lens group G2 with a larger number of lenses.

In the present invention, as described above, the fifth lens group G5 has a large ratio of zooming. Therefore, in order to improve the performance, it is necessary for the fifth lens group G5 to independently perform better aberration correction. Further, in order to suppress the occurrence of spherical aberration, it is desirable that the fifth lens group G5 be composed of at least one positive lens and at least one negative lens. Further, in order to reduce the lens diameter closest to the image plane, it is desirable to dispose a positive lens closest to the object in the fifth lens group G5 and a negative lens closest to the image plane in the fifth lens group G5. In addition, the fifth lens group G5
High performance can be achieved by introducing an aspherical surface into. Further, by constructing the positive lens in the fifth lens group G5 with an aspherical lens made of a plastic material, not only high performance but also weight saving and cost reduction can be achieved at the same time.

According to another aspect, according to the present invention, in order to prevent a photographing failure due to an image blur caused by a hand shake or the like which tends to occur in a high-magnification zoom lens, a blur detection for detecting blur of an optical system is performed. The system and the driving means can be combined into a lens system. An image caused by the blur of the optical system detected by the blur detection system is shifted by decentering one or all of the lens groups constituting the optical system as a shift lens group. By correcting the blur (change in image position), the variable power optical system of the present invention can be used as a so-called anti-vibration optical system.

Needless to say, the variable power optical system according to the present invention is not limited to a zoom lens but can be applied to a varifocal zoom lens in which the focal length state does not continuously exist.

[0040]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the basic configuration of a variable power optical system according to each example of the present invention and the manner of movement of each lens group during zooming from the wide-angle end state (W) to the telephoto end state (T). It is a figure. As shown in FIG. 1, in each embodiment, the variable power optical system according to the present invention has, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power.
A third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power. During zooming from the wide-angle end state to the telephoto end state, the air gap between the first lens group G1 and the second lens group G2 increases, and the air gap between the second lens group G2 and the third lens group G3 increases. Decreased, the third lens group G3 and the fourth lens group G
The respective lens groups are moved toward the object side such that the air distance between the lens groups 4 and 4 increases and the air distance between the fourth lens group G4 and the fifth lens group G5 decreases. It should be noted that the axial distance between the second lens group G2 and the fourth lens group G4 decreases during zooming from the wide-angle end state to the telephoto end state. Further, the fourth lens group G4 is moved along the optical axis to focus on a short-distance object.

In each embodiment, the aspherical surface has a height y in the direction perpendicular to the optical axis, a displacement amount (sag amount) in the optical axis direction at the height y of S (y), and a reference radius of curvature (apex). When the radius of curvature) is R, the conic coefficient is κ, and the aspherical coefficient of the nth order is Cn, it is expressed by the following mathematical expression (d).

## EQU1 ## S (y) = (y ² / R) / {1+ (1-κ · y ² / R ² ) ^1/2 } + C ₄ · y ⁴ + C ₆ · y ⁶ + C ₈ · y ⁸ + C ₁₀ in · y ¹⁰ + ··· (d) each of the embodiments, the aspheric are asterisked right of the surface number.

[First Embodiment] FIG. 2 is a view showing the arrangement of a variable power optical system according to the first embodiment of the present invention. The variable power optical system of FIG. 2 includes, in order from the object side, a first lens group G1 including a cemented positive lens L1 including a biconvex lens and a negative meniscus lens having a concave surface facing the object side, a biconcave lens L21, and a biconvex lens. A second lens group G2 including a positive lens L22 cemented with a biconcave lens, a third lens group G3 including a biconvex lens L3, a positive meniscus lens having a concave surface facing the object side, and a negative meniscus lens having a concave surface facing the object side. A fourth lens including a cemented negative lens L41 and a biconvex lens L42.
The lens group G4 includes a positive meniscus lens L51 having a concave surface facing the object side, a biconcave lens L52, and a fifth lens group G5 including a negative meniscus lens L53 having a concave surface facing the object side.

The third lens group G3 and the fourth lens group G
An aperture stop S is disposed between the lens unit 4 and the lens unit 4 and moves integrally with the third lens group G3 during zooming from the wide-angle end state to the telephoto end state. FIG. 2 shows the positional relationship between the lens groups in the wide-angle end state, and moves on the optical axis along a zoom trajectory indicated by an arrow in FIG. 1 during zooming to the telephoto end state. Further, when focusing on an object at infinity to a near object, the fourth lens group G4, which is a focusing lens group, moves toward the object side.

Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1), f is the focal length,
FNO is the F number, ω is the half angle of view, Bf is the back focus, and D0 is the object point distance (the distance from the object to the lens surface closest to the object along the optical axis).
Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light beam, and the refractive index and the Abbe number respectively indicate values with respect to the d line (λ = 587.6 nm).

[0045]

[Table 1] f = 30.90 ~ 60.59 ~ 109.06 ~ 147.83 FNO = 4.28 ~ 6.63 ~ 9.27 ~ 11.00 ω = 36.25 ~ 19.09 ~ 10.93 ~ 8.15 ° Surface number Curvature radius Surface spacing Refractive index Abbe number 1 41.5078 5.4529 1.48749 70.45 2 -55.2266 1.3329 1.84666 23.83 3 -113.7644 (d3 = variable) 4 -74.5157 0.9694 1.80420 46.51 5 14.7591 3.4674 6 19.1638 4.2412 1.71736 29.50 7 -21.9421 0.9694 1.83500 42.97 8 96.1461 (d8 = variable) 9 139.1311 1.8176 1.62280 56.93 10 11-25.756 (1.2 11 11 -25.756) (d11 = variable) (Aperture stop S) 12 -13.4641 2.4235 1.48749 70.45 13 -11.1444 0.9694 1.84666 23.83 14 -25.4463 0.1212 15 * 50.7008 3.0294 1.51680 64.20 16 * -12.5596 (d16 = variable) 17 -79.9123 3.1162 1.80518 25.46 18 -23.2642 0.1212 19 -53.8623 1.2118 1.77250 49.61 20 186.7832 5.2044 21 -14.3495 1.4541 1.83500 42.97 22 -63.8978 (Bf) ( aspheric data) κ C ₄ 15 faces _{^{0.3958 4.73140 × 10 -6 C 6 C}} 8 C 10 -3.61077 × 10 -7 - ^{5.45939 × 10 -9 2.94834 × 10 -10} κ C 4 16 faces _{^{0.7183 5.14723 × 10 -5 C 6 C}} 8 C 10 1.96845 ^{10 -7 -1.73463 × 10 -8 3.96586 ×} 10 -10 ( variable spacing in zooming) f 30.8998 60.5880 109.0585 147.8331 d3 1.3329 11.7434 22.1481 27.2882 d8 7.2489 3.9698 2.0599 1.8177 d11 3.4992 4.1256 4.9212 5.2106 d16 18.1965 10.4219 4.7835 1.8177 Bf 7.5734 27.0734 51.7002 69.7402 (focusing movement amount Δ of the fourth lens group G4 at a photographing magnification of −1 / 30 ×) Focal length f 30.8998 60.5880 109.0585 147.8331 Object point distance D0 915.7731 1794.0639 3228.4984 4376.5357 Movement amount Δ 0.6959 0.5563 0.4987 0.4617 (however, focusing movement amount) The sign of Δ is positive for the movement toward the object side. (Condition corresponding value) f3 = 35.0437 f4 = 40.8743 f2 = -27.0333 fw = 30.8998 ft = 147.8331 β4w = 0.34853 β4t = 0.39146 Z = 4.7843 (1) f3 / f4 = 0.857 (2) | f2 | / (fw.ft) ^1/2 = 0.400 (3) (β4t / β4w) /Z=0.235

3 to 10 show the d line (λ =
587.6 nm). FIG. 3 is a diagram of various aberrations in the infinity focused state in the wide-angle end state (shortest focal length state), and FIG. 4 is a diagram of various aberrations in the infinity focused state in the first intermediate focal length state. 5 is a diagram of various aberrations in the second intermediate focal length state in the infinity focused state, and FIG. 6 is a diagram of various aberrations in the telephoto end state (the longest focal length state) in the infinity focused state. Further, FIG. 7 is a diagram showing various aberrations in a short-distance focused state (shooting magnification -1/30) in the wide-angle end state, and FIG. 8 is a short-distance focused state (shooting magnification − in the first intermediate focal length state). FIG. 9 is a diagram of various aberrations in 1/30), FIG. 9 is a diagram of various aberrations in a short distance in-focus state (shooting magnification −1/30) in the second intermediate focal length state, and FIG. 10 is in a telephoto end state. Short-distance focus state (shooting magnification -1 /
It is a various-aberration figure in 30).

In each aberration diagram, FNO is the F number,
NA is the numerical aperture, Y is the image height, A is the angle of view for each image height, and H is the object height for each image height.
Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. Further, in the aberration diagram showing spherical aberration, the broken line shows the sine condition. As is clear from each aberration diagram, in the present embodiment, it is understood that various aberrations are satisfactorily corrected in each focal length state from the infinity in-focus state to the short distance in-focus state.

[Second Embodiment] FIG. 11 is a view showing the arrangement of a variable power optical system according to the second embodiment of the present invention. FIG.
Is a cemented positive lens L in which, in order from the object side, a biconvex lens and a negative meniscus lens having a concave surface facing the object side are cemented in order from the object side.
The first lens group G1 including 1; the biconcave lens L21; the second lens group G2 including the cemented positive lens L22 including the biconvex lens and the biconcave lens; the third lens group G3 including the biconvex lens L3; A fifth lens group G4 including a negative meniscus lens L41 having a concave surface and a biconvex lens L42, a positive meniscus lens L51 having a concave surface facing the object side, and a negative meniscus lens L52 having a concave surface facing the object side. The lens group G5.

The third lens group G3 and the fourth lens group G
An aperture stop S is disposed between the lens unit 4 and the lens unit 4 and moves integrally with the third lens group G3 during zooming from the wide-angle end state to the telephoto end state. FIG. 11 shows the positional relationship between the lens groups in the wide-angle end state.
Move on the optical axis along the zoom trajectory indicated by the arrow. Further, when focusing on an object at infinity to a near object, the fourth lens group G4, which is a focusing lens group, moves toward the object side.

The following table (2) lists the values of specifications of the second embodiment of the present invention. In Table (2), f is the focal length,
FNO is the F number, ω is the half angle of view, Bf is the back focus, and D0 is the object point distance (the distance from the object to the lens surface closest to the object along the optical axis).
Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light beam, and the refractive index and the Abbe number respectively indicate values with respect to the d line (λ = 587.6 nm).

[0051]

[Table 2] f = 30.90 ~ 60.19 ~ 147.85 FNO = 4.19 ~ 6.45 ~ 11.01 ω = 35.79 ~ 19.26 ~ 8.20 ° Surface number Curvature radius Surface spacing Refractive index Abbe number 1 36.2429 4.8479 1.48749 70.45 2 -79.1332 1.3332 1.84666 23.83 3 -243.6949 (d3 = variable) 4 -132.2711 0.9696 1.83500 42.97 5 13.4559 3.3935 6 17.5087 3.3995 1.72825 28.31 7 -34.5361 0.9696 1.83500 42.97 8 69.4881 (d8 = variable) 9 56.3355 1.8180 1.51680 64.20 10 -28.1202 1.2120 11 ∞ (d11 = variable) (aperture) Aperture S) 12 -10.9870 3.0294 1.84666 23.83 13 -22.1579 0.1212 14 * 94.8478 2.4235 1.56384 60.82 15 * -11.4089 (d15 = variable) 16 * -50.9443 2.9087 1.58518 30.24 17 -24.1224 4.4843 18 -13.4409 1.4544 1.77250 49.61 19 -140.6555 (Bf ) (Aspherical data) κ C ₄ 14 surface 1.0000 2.69882 × 10 ^-5 C ₆ C ₈ C ₁₀ 1.27874 × 10 ^-7 -1.26432 × 10 ^-9 9.49046 × 10 ^-12 κ C ₄ 15 surface 0.7210 5.68412 × 10 ^-5 C ₆ C ₈ C ₁₀ 1.75906 × 10 ^-7 -1.37054 × 10 ^-8 4.23423 × 10 ^-10 κ C ₄ 16 surface 0.2719 3.98989 × 10 ^-6 C ₆ C ₈ C ₁₀ -3.53545 × 10 ^-8 -1 .85839 × 10 ^-8 5.72 505 × 10 ^-10 (variable distance in zooming) f 30.9000 60.1919 147.8463 d3 1.3332 11.8150 27.0110 d8 7.0874 3.7088 1.8180 d11 3.4750 4.1339 4.1339 d15 18.2855 10.5162 1.8180 Bf 8.3145 27.9098 73.9420 (shooting magnification-1 / 30x) Focusing movement amount of the fourth lens group G4 at that time Δ) Focal length f 30.9000 60.1919 147.8463 Object point distance D0 917.7488 1784.9810 4382.6958 Movement amount Δ 0.6730 0.5486 0.4219 (However, the sign of the movement amount Δ for focusing is the movement toward the object side. (Condition corresponding value) f3 = 36.5634 f4 = 39.4759 f2 = 27.3447 fw = 30.9000 ft = 147.8463 β4w = 0.3148 β4t = 0.3857 Z = 4.7847 (1) f3 / f4 = 0.926 (2) | f2 | / ( fw · ft) ^1/2 = 0.405 (3) (β4t / β4w) / Z = 0.256

12 to 17 show d line (λ
= 587.6 nm). FIG. 12 is a diagram of various aberrations in the infinity focused state in the wide-angle end state, FIG. 13 is a diagram of various aberrations in the infinity focused state in the intermediate focal length state, and FIG. 14 is infinity in the telephoto end state. FIG. 7 is a diagram of various types of aberration in a far focus state. FIG. 15 is a diagram of various aberrations in the close-range focus state (shooting magnification −1/30) in the wide-angle end state, and FIG. 16 is the short-range focus state in the intermediate focal length state (shooting magnification −1/30). FIG. 17 is a diagram of various aberrations in 30), and FIG. 17 is a diagram of various aberrations in a short distance in-focus state (shooting magnification −1/30) in the telephoto end state.

In each aberration diagram, FNO represents the F number,
NA is the numerical aperture, Y is the image height, A is the angle of view for each image height, and H is the object height for each image height.
Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. Further, in the aberration diagram showing spherical aberration, the broken line shows the sine condition. As is clear from each aberration diagram, in the present embodiment, it is understood that various aberrations are satisfactorily corrected in each focal length state from the infinity in-focus state to the short distance in-focus state.

[Third Embodiment] FIG. 18 is a diagram showing the structure of a variable power optical system according to the third embodiment of the present invention. FIG.
Is a cemented positive lens L in which, in order from the object side, a biconvex lens and a negative meniscus lens having a concave surface facing the object side are cemented in order from the object side.
A first lens group G1 composed of 1 and a second lens composed of a biconcave lens L21, a biconvex lens L22, and a biconcave lens L23.
From a lens group G2, a third lens group G3 including a biconvex lens L3, a cemented negative lens L41 of a positive meniscus lens having a concave surface facing the object side and a negative meniscus lens having a concave surface facing the object side, and a biconvex lens L42. And a positive meniscus lens L having a concave surface facing the object side.
51, a biconcave lens L52, and a fifth lens group G5 including a negative meniscus lens L53 having a concave surface facing the object side.

The third lens group G3 and the fourth lens group G
An aperture stop S is disposed between the lens unit 4 and the lens unit 4 and moves integrally with the third lens group G3 during zooming from the wide-angle end state to the telephoto end state. FIG. 18 shows the positional relationship of each lens group in the wide-angle end state.
Move on the optical axis along the zoom trajectory indicated by the arrow. Further, when focusing on an object at infinity to a near object, the fourth lens group G4, which is a focusing lens group, moves toward the object side.

Table (3) below lists values of specifications of the third embodiment of the present invention. In Table (3), f is the focal length,
FNO is the F number, ω is the half angle of view, Bf is the back focus, and D0 is the object point distance (the distance from the object to the lens surface closest to the object along the optical axis).
Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light beam, and the refractive index and the Abbe number respectively indicate values with respect to the d line (λ = 587.6 nm).

[0057]

[Table 3] f = 30.91 〜 60.56 〜 108.75 〜147.79 FNO ＝ 4.29 〜 6.80 〜 10.11 〜 11.08 ω ＝ 35.47 〜 19.08 〜 11.02 〜 8.15 ° Surface number Curvature radius Surface spacing Refractive index Abbe number 1 39.7793 5.4529 1.48749 70.45 2 -57.2345 1.3329 1.84666 23.83 3 -125.1163 (d3 = variable) 4 -195.9410 0.9694 1.80420 46.51 5 13.2476 4.2412 6 18.8668 3.8776 1.71736 29.50 7 -49.1158 1.2118 8 -37.2068 0.9694 1.83500 42.97 9 88.7773 (d9 = variable) 10 329.7999 1.8176 1.62041 1.2118 12 ∞ (d12 = variable) (aperture stop S) 13 -16.4460 3.0294 1.48749 70.45 14 -16.2558 0.9694 1.84666 23.83 15 -36.9396 0.1212 16 * 41.2706 2.4235 1.51680 64.20 17 * -15.1786 (d17 = variable) 18 -41.3062 3.0221 1.80518 25.46 19 -23.3882 1.2214 20 -101.1149 1.2118 1.80420 46.51 21 717.9226 5.4529 22 -15.5913 1.4541 1.83500 42.97 23 -100.8166 (Bf) (aspherical data) κ C ₄ 16 surface 1.0000 -1.41981 × 10 ^-5 C ₆ C ₈ C ₁₀ 3.35268 × 10 ^-7 -1.70549 × 10 ^-8 1.57922 × 10 ^-10 κ C ₄ 17 surface 1.0000 4.25633 × 10 ^-5 C ₆ C ₈ C ₁₀ 1.417 30 × 10 ^-7 -2.165 60 × 10 ^-9 -5.10 870 × 10 ^-11 (Variable spacing during zooming) f 30.9085 60.5596 108.7492 147.7930 d3 0.6059 10.3280 18.3581 25.6688 d9 7.9183 4.9246 3.0855 1.8177 d12 3.5538 3.3180 3.2536 5.2106 d17 17.9040 9.9580 4.6131 1.8177 Bf 7.4454 27.8259 56.2960 68.4730 (focusing movement amount Δ of the fourth lens group G4 at a photographing magnification of −1 / 30 ×) focal length f 30.9085 60.5596 108.7492 147.7930 object point distance D0 916.1613 1794.7822 3228.0551 4380.6388 movement amount Δ 0.7004 0.5475 0.4343 0.4646 (However, the sign of the amount of focusing movement Δ is the movement to the object side is positive) (Conditional value) f3 = 36.1161 f4 = 42.5607 f2 = -25.6056 fw = 30.9085 ft = 147.7929 β4w = 0.32704 β4t = 0.34761 Z = 4.7816 (1) f3 / f4 = 0.849 (2) | f2 | / (fw · ft) ^1/2 = 0.379 (3) (β4t / β4w) / Z = 0.222

19 to 26 show the d line (λ
= 587.6 nm). FIG. 19 is a diagram of various aberrations in the infinity focused state in the wide-angle end state, FIG. 20 is a diagram of various aberrations in the infinity focused state in the first intermediate focal length state, and FIG. 21 is a second intermediate focus state. FIG. 23 is a diagram of various types of aberration in a state of infinity in a state of distance, and FIG.
[Fig. 3] is an aberration diagram at infinity in the telephoto end. FIG. 23 is a diagram of various aberrations in a short-distance focus state (shooting magnification −1/30) in the wide-angle end state, and FIG. 24 is a short-distance focus state (shooting magnification −1 in the first intermediate focal length state).
FIG. 25 is a diagram of various types of aberrations at 1/30), and FIG. 25 shows a close-range in-focus state (shooting magnification −1/3) in the second intermediate focal length state.
FIG. 26 is a diagram of various aberrations in 0), and FIG. 26 is a diagram of various aberrations in a short-distance focus state (shooting magnification −1/30) in the telephoto end state.

In each aberration diagram, FNO is the F number,
NA is the numerical aperture, Y is the image height, A is the angle of view for each image height, and H is the object height for each image height.
Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. Further, in the aberration diagram showing spherical aberration, the broken line shows the sine condition. As is clear from each aberration diagram, in the present embodiment, it is understood that various aberrations are satisfactorily corrected in each focal length state from the infinity in-focus state to the short distance in-focus state.

[0060]

As described above, according to the present invention, 70 °
It is possible to realize a compact variable power optical system having an angle of view that exceeds, a high zoom ratio, and a small aberration fluctuation during focusing at a short distance.

[Brief description of drawings]

FIG. 1 shows a basic configuration of a variable power optical system according to each example of the present invention and a state of movement of each lens unit during zooming from a wide-angle end state (W) to a telephoto end state (T). It is a figure.

FIG. 2 is a diagram illustrating a configuration of a variable power optical system according to a first example of the present invention.

FIG. 3 is a diagram of various types of aberration in a wide-angle end state of the first example at an infinity in-focus state.

FIG. 4 is a diagram of various types of aberration in the first intermediate focal length state and the infinity in-focus state according to the first example;

FIG. 5 is a diagram of various types of aberration in the second intermediate focal length state of Example 1 in the infinity in-focus state.

FIG. 6 is a diagram of various types of aberration in the infinity in-focus state in the telephoto end state of the first example.

FIG. 7 is a photographing magnification −1/3 in the wide-angle end state of the first embodiment.
It is a various-aberration figure at 0 time.

FIG. 8 is a diagram of various types of aberration at a photographing magnification of −1/30 in the first intermediate focal length state of the first example.

FIG. 9 is a diagram of various types of aberration at a photographing magnification of −1/30 in the second intermediate focal length state of the first example.

FIG. 10 is a photographing magnification −1 / in the telephoto end state of the first embodiment.
It is a various-aberration figure in 30 times.

FIG. 11 is a diagram showing a configuration of a variable power optical system according to Example 2 of the present invention.

FIG. 12 is a diagram of various types of aberration in the second example at the wide-angle end and in the in-focus state at infinity.

FIG. 13 is a diagram illustrating various aberrations of the second example in an intermediate focal length state and focused on infinity.

FIG. 14 is a diagram illustrating various aberrations of the second example in a state at infinity in a telephoto end state.

FIG. 15 is a photographing magnification −1 / in the wide-angle end state of the second embodiment.
It is a various-aberration figure in 30 times.

FIG. 16 is a diagram of various types of aberration at a photographing magnification of −1/30 in the intermediate focal length state of the second example.

FIG. 17 is a photographing magnification −1 / in the telephoto end state of the second embodiment.
It is a various-aberration figure in 30 times.

FIG. 18 is a diagram showing the configuration of a variable power optical system according to the third example of the present invention.

FIG. 19 is a diagram of various types of aberration in a state of focusing at infinity in the wide-angle end state of Example 3;

FIG. 20 is a diagram of various types of aberration in the first intermediate focal length state and the infinity in-focus state according to the third example;

FIG. 21 is a diagram of various types of aberration in the second intermediate focal length state and the infinity in-focus state according to the third example;

FIG. 22 is a diagram of various types of aberration in the telephoto end state of the third example in the in-focus state at infinity.

FIG. 23 is a photographing magnification −1 / in the wide-angle end state of the third embodiment.
It is a various-aberration figure in 30 times.

FIG. 24 is a diagram of various types of aberration at a photographing magnification of −1/30 in the first intermediate focal length state of the third example.

FIG. 25 is a diagram of various types of aberration at a photographing magnification of −1/30 in the second intermediate focal length state of the third example.

FIG. 26 is a photographing magnification −1 / in the telephoto end state of the third embodiment.
It is a various-aberration figure in 30 times.

[Explanation of symbols]

 G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group G5 fifth lens group S aperture stop

Claims (3)

[Claims] 1. A first lens group G1 having a positive refractive power and a second lens group G having a negative refractive power in order from the object side.
2, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power, the wide-angle end state to the telephoto end. When changing the magnification to the state, the first
The air gap between the lens group G1 and the second lens group G2 increases, the air gap between the second lens group G2 and the third lens group G3 decreases, and the fourth lens group G4 and the fifth lens group G3 decrease.
At least the first lens group G1 and the fifth lens group G5 are moved toward the object side so that the air gap between the lens group G5 and the second lens group G2 and the fourth lens group G4 is reduced. At least the fourth lens group G4 moves so that the upper distance decreases, and the fourth lens group G4 moves along the optical axis to focus on a short-distance object, and the second lens group G2. F2 as the focal length of
The focal length of the lens group G3 is f3, the focal length of the fourth lens group G4 is f4, the focal length of the entire optical system in the wide-angle end state is fw, and the focal length of the entire optical system in the telephoto end state is ft. Then, it is possible to focus at a short distance characterized by satisfying the condition of 0.7 <f3 / f4 <1.1 0.3 <| f2 | / (fw · ft) ^1/2 <0.5. Variable magnification optical system. 2. The fourth lens group G in the telephoto end state.
When the lateral magnification of 4 is β4t, the lateral magnification of the fourth lens group G4 in the wide-angle end state is β4w, and the zoom ratio is Z, 0.18 <(β4t / β4w) / Z <0.38 The variable power optical system capable of focusing at a short distance according to claim 1, wherein the condition is satisfied. 3. The short-distance combination according to claim 1, wherein at least one lens surface of the plurality of lens surfaces forming the fourth lens group G4 is formed in an aspherical shape. Focusable variable magnification optical system.