JPH10232351A - Variable power optical system capable of image shift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a variable power optical system which is compact and suitable to realize high variable power and where image shift can be performed by moving either of two partial lens groups of a 3rd lens group in a perpendicular direction as a shift lens group so that the image shift may be performed and setting a distance between the surface of the shift lens group nearest to an image side and an aperture diaphragm and the focal distance of the shift lens group to specified relation. SOLUTION: This system is equipped with 1st to 4th lens groups G1 to G4 respectively having positive, negative, positive and negative refractive power in order from an object side. The 3rd lens group G3 has at least two partial lens groups and at least either of two partial lens groups is moved in nearly perpendicular direction to an optical axis as the shift lens group Gs so as to perform the image shift. The aperture diaphragm S is provided between the 2nd lens group G2 and the 3rd lens group G3. When it is assumed that the distance along the optical axis between the surface of the shift lens group Gs nearest to the image side and the aperture diaphragm S is D, and the focal distance of the shift lens group Gs is (fs), a condition D/fs<0.2 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-magnification optical system capable of image shifting, and more particularly to a variable-magnification optical system capable of shifting an image by moving some lens groups in a direction substantially perpendicular to the optical axis. It relates to a magnification optical system.

[0002]

2. Description of the Related Art In recent years, a zoom lens is generally used in a photographing optical system used for a still camera, a video camera, and the like. In particular, cameras equipped with a so-called high zoom ratio zoom lens having a zoom ratio exceeding 3 times are becoming mainstream.
In this type of camera, a standard zoom lens (a zoom lens having a focal length range including an angle of view with a focal length of about 50 mm in a 35 mm format) is generally used. Note that a so-called multi-unit zoom lens, which is configured so that three or more lens units move at the time of zooming, is mainly used as the high-magnification zoom lens. In addition, in an integrated camera in which a photographing optical system and a camera body are integrally formed, portability is regarded as important, so that a reduction in size and weight is required. Therefore, various proposals regarding zoom lenses suitable for miniaturization and weight reduction have been made. In these zoom lenses, the focal length has been increased with an increase in the zoom ratio.

By the way, conventionally, when the shutter speed is low, there is a case where an image is blurred during exposure due to camera shake due to hand shake or the like, and photographing fails.
In general, when a part of lens groups (hereinafter, referred to as a “shift lens group”) of a lens group constituting a lens system is moved in a direction perpendicular to the optical axis, an image is shifted in a direction perpendicular to the optical axis. It is known. In this case, an optical system capable of obtaining good imaging performance even when the shift lens group is moved in a direction perpendicular to the optical axis is called an image shiftable optical system.

[0004] In order to solve the problem of photographing failure caused by the above-mentioned camera shake or the like, an optical system capable of image shift and a shake of the optical system (camera shake when applied to a camera) are detected. 2. Description of the Related Art A so-called anti-vibration optical device is known in which a shake detection system that outputs shake information and a drive system that moves a shift lens group are combined. In the image stabilizing optical device, the shake detection system detects the shake of the optical system due to hand shake, etc., and shifts the image by the drive system so as to cancel the fluctuation of the image position caused by the detected shake of the optical system. The image shift is performed by moving the lens group. In this way, the image stabilizing optical apparatus can correct a change in the image position, that is, an image blur caused by the blur of the optical system, due to the intentionally generated image shift.

[0005]

However, with a small and lightweight camera, it is difficult to hold the camera without blurring. For this reason, when the release button is pressed, camera shake is likely to occur, and as a result, image blur is often recorded. In particular, with a photographing lens that has a long focal length in order to increase the zoom ratio, remarkable image blurring is likely to occur even with a slight blur of the camera, and photographing is likely to fail. In this case, by applying an image stabilizing optical device incorporating an optical system capable of shifting an image to a camera, it is also possible to correct a change in an image position caused by camera shake due to camera shake or the like. However, in the image stabilizing optical device, since an optical system capable of image shift is excessively restrained in correcting aberration, it is difficult to realize high zoom ratio while suppressing performance deterioration occurring at the time of image shift.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a variable-magnification optical system which is compact and capable of image shifting suitable for high magnification.

[0007]

According to a first aspect of the present invention, there is provided a first lens group G1 having a positive refractive power and a negative lens having a negative refractive power. The zoom lens includes a second lens group G2, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a negative refractive power. When the lens position changes from the wide-angle end state to the telephoto end state, The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the third lens group G3 decreases. At least the first lens group G1 and the fourth lens group G4 move toward the object side so that the distance from the fourth lens group G4 decreases, and the third lens group G3 has at least two partial lens groups. , The at least two
An image shift is performed by moving one of the two partial lens groups as a shift lens group Gs in a direction substantially perpendicular to the optical axis, and the shift between the second lens group G2 and the third lens group G3 is performed. An aperture stop is provided therebetween, and a distance along the optical axis between the most image-side surface of the shift lens group Gs and the aperture stop is D, and a focal length of the shift lens group Gs is fs. Then, there is provided a variable power optical system capable of image shift, characterized by satisfying the following condition: D / fs <0.2.

According to a preferred aspect of the first invention, the third lens group G3 includes, in order from the object side, a first positive partial lens group G31 having a positive refractive power and a second positive lens group G31 having a positive refractive power.
The first positive partial lens group G31 constitutes the shift lens group Gs, the focal length of the third lens group G3 is f3, and the focal length of the shift lens group Gs is When fs is satisfied, the condition of 0.35 <f3 / fs <0.7 is satisfied.

According to the second aspect of the present invention, in order from the object side, the first lens group G1 having at least a positive refractive power, the second lens group G2 having a negative refractive power, and the positive refractive power A lens group GA having a power is disposed, and a final lens group GE having a negative refractive power is disposed on the most image side, and when the lens position state changes from the wide-angle end state to the telephoto end state,
The first lens group G1 and the second lens group G2 are moved toward the object side by changing the distance between the first lens group G1 and the second lens group G2 so as to enhance the convergence action of the first lens group G1 and the second lens group G2. The lens group GE moves to the object side,
The second lens group G2 includes, in order from the object side, a negative partial lens group G2a having a negative refractive power and a positive partial lens group G2b having a positive refractive power. Having a lens group, performing image shift by moving a partial lens group disposed adjacent to the aperture stop of the plurality of partial lens groups as a shift lens group Gs in a direction substantially perpendicular to the optical axis, The negative partial lens group G
The focal length of 2a is f2a, the focal length of the positive partial lens group G2b is f2b, and the combined focal length of the first lens group G1 and the second lens group G2 in the telephoto end state is fvt.
And the focal length of the entire optical system in the telephoto end state is ft.
│f2a│ / f2b <0.4, and 0.2 <│fvt│ / ft <0.4. I do.

[0010]

As described above, according to the first aspect of the present invention, the first lens group G1 having a positive refractive power and the second lens group G1 having a negative refractive power are arranged in order from the object side. G2
And a third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power. And
When the lens position changes from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. Then, at least the first lens group G1 and the fourth lens group G4 move toward the object side so that the distance between the third lens group G3 and the fourth lens group G4 decreases. Also, the third
The lens group G3 has at least two partial lens groups,
Image shifting is performed by moving one of the at least two partial lens groups as a shift lens group Gs in a direction substantially perpendicular to the optical axis. further,
An aperture stop is provided between the second lens group G2 and the third lens group G3. In the present invention, by configuring the variable power optical system as described above, it is possible to achieve a high variable power while favorably suppressing deterioration of various aberrations generated when an image is shifted.

First, a general description will be given of a zoom lens suitable for a lens-integrated camera in which a taking lens system is incorporated in a camera body such as a lens shutter camera.
In an optical system used in these lens-integrated cameras, since there is no restriction on the back focus, a telephoto-type refractive power arrangement suitable for miniaturization is used, and a negative lens group is arranged on the most image side of the optical system.

The aperture stop is located closer to the object side than the negative lens group. From the wide-angle end state (the state with the shortest focal length) to the telephoto end state (the state with the longest focal length)
When the lens position changes, the distance between the aperture stop and the negative lens group is reduced, and the negative lens group is moved to the object side. By reducing the distance between the aperture stop of [I] and the negative lens group, the off-axis light beam passing through the negative lens group moves away from the optical axis in the wide-angle end state and approaches the optical axis in the telephoto end state. Further, by moving the negative lens unit of [II] to the object side, the negative lens unit is multiplied (the lateral magnification in the telephoto end state is larger than in the wide-angle end state). The above two points [I] and [II]
Accordingly, it is possible to achieve a certain high zoom ratio while satisfactorily correcting the fluctuation of the off-axis aberration caused by the change of the lens position state.

However, if the back focus is too short in the wide-angle end state, the shadow of dust adhering to the surface of the negative lens unit near the image plane is superimposed on the subject image and recorded on the film. Therefore, it is necessary to set the back focus in the wide-angle end state to an appropriate value, and as a result, the lateral magnification of the negative lens group is substantially constant in the wide-angle end state. As described above, the multi-group zoom lens has a plurality of movable lens groups. By arranging the positive lens group closest to the object side and shortening the overall length of the lens in the wide-angle end state, the lens diameter of the positive lens group is reduced. The size is reduced. Conversely, in the telephoto end state, by moving the positive lens group toward the object side so that the distance between the positive lens group and the lens group arranged on the image side increases, the luminous flux is strongly converged by the positive lens group. The overall length of the lens is reduced to some extent.

As a specific type of multi-unit zoom lens suitable for miniaturization and high zoom ratio, for example, (A) positive / negative 3
A group type and a (B) positive / negative / positive / negative four-group type are known. In the case of the (A) positive / negative three-group type, the lateral magnification of the third lens group in the telephoto end state is very large, and when the zoom ratio is high, the lateral magnification of the third lens group in the telephoto end state is sharply increased. growing. When the third lens group moves in the optical axis direction by a very small amount, the image plane position becomes equal to 2 × the lateral magnification of the third lens group.
Move in relation to the square. For this reason, in the case of the (A) positive / negative three-group type, if the zoom ratio becomes high, there is a disadvantage that the performance is rapidly lowered due to the lens stopping accuracy.

On the other hand, in the case of the positive / negative positive / negative four-group type (B), the number of movable lens groups is larger than that of the positive / negative / negative three-group type (A). Since the change in the lateral magnification is reduced, the performance degradation due to the lens stopping accuracy can be suppressed as compared with the three-group positive / negative type shown in FIG. Based on the above considerations, in the present invention, it is possible to achieve a high zoom ratio by employing a positive, negative, positive and negative four-group type.

However, as described above, if the focal length in the telephoto end state becomes longer as the magnification becomes higher, image blurring is likely to occur due to camera shake due to camera shake or the like. Therefore, conditions for achieving a variable-magnification optical system capable of image shift necessary for configuring an image stabilizing optical system capable of reducing the occurrence of image blur will be described below. First, a description will be given of the aberration correction function required for the shift lens group. Normally, the shift lens group is required to be in an aberration correction state such that good imaging performance can be obtained even during image shifting. Specifically, it is required that the spherical aberration and the sine condition (sine condition) are properly corrected and that an appropriate Petzval sum is used.

The good correction of the spherical aberration and the sine condition is a condition for suppressing the eccentric coma generated at the center of the screen when the shift lens group is moved in a direction substantially perpendicular to the optical axis. It is. The appropriate Petzval sum is a condition for suppressing the curvature of field that occurs at the periphery of the screen when the image is shifted by moving the shift lens group. In the present invention, in order to satisfy the condition (1), it is preferable that the shift lens group includes at least two lenses. Especially,
By forming a shift lens group with at least one positive lens and at least one negative lens, axial aberration can be corrected well.

In general, in a zoom lens, in order to obtain a predetermined optical performance, fluctuations in axial aberration generated at the time of zooming are corrected well, and fluctuations of off-axis aberrations generated at the time of zooming are reduced. Needs to be corrected.
Therefore, it is desirable to perform aberration correction on each lens group so as to be in an aberration correction state suitable for satisfying the conditions (1) and (2). Specifically, in order to satisfy the condition (1), it is necessary to satisfactorily correct the spherical aberration generated by each lens group alone. In order to satisfy the condition (1), it is necessary to suppress the coma aberration generated in each lens unit and to set the Petzval sum of each lens unit to an appropriate value. In particular, in order to increase the zoom ratio, it is desirable that the on-axis aberration generated for each lens group be corrected better and the off-axis aberration be set to a more appropriate aberration correction state.

When a shift lens group is constituted by one lens group in a zoom lens, the Petzval sum suitable for satisfying the condition and the Petzval sum suitable for satisfying the condition do not always match. Therefore, when a shift lens group is constituted by one lens group, excessive restriction is imposed on the optical design. In the present invention, one lens group is constituted by a plurality of partial lens groups in order to obtain good imaging performance even at the time of image shift while achieving a high zoom ratio. One partial lens group constitutes a shift lens group. As a result, it is possible to favorably suppress the fluctuation of the off-axis aberration caused by the change in the lens position state, while favorably suppressing the fluctuation of the field curvature when the shift lens group is moved.

Next, the positional relationship between the shift lens group and the aperture stop will be described. In an optical system, an off-axis light beam passes near the optical axis in a lens group near the aperture stop, while passes through a position away from the optical axis in a lens group far from the aperture stop. For this reason, the lens group near the aperture stop has a smaller lens diameter (that is, the so-called effective diameter is smaller than the lens group distant from the aperture stop). When the lens diameter of the shift lens group is large, the size of a driving system that drives the shift lens group in a direction substantially perpendicular to the optical axis is increased. As a result, the size of the camera body increases, and the power consumption also increases. Therefore, it is desirable that the shift lens group is arranged near the aperture stop.

When the shift lens group is located away from the aperture stop, an off-axis light beam passing through the shift lens group moves away from the optical axis. As a result, when the shift lens group is moved to shift the image, eccentric coma is likely to occur in the peripheral portion of the screen. In particular, when an off-axis light beam incident on the shift lens group forms a large angle with respect to the optical axis, decentered coma aberration is likely to occur at the periphery of the screen. Therefore, from the viewpoint of aberration correction, it is preferable that the shift lens group is disposed near the aperture stop. Also, in a zoom optical system with a high zoom ratio,
In order to satisfactorily correct the variation of off-axis aberration that occurs during zooming, the height of the off-axis luminous flux passing through each lens group changes when the lens position changes from the wide-angle end state to the telephoto end state. Is preferred.

In the present invention, an aperture stop is arranged between the second lens group G2 and the third lens group G3. In this case, in the wide-angle end state, the off-axis light beam passing through the fourth lens group G4 separates from the optical axis according to a change in the angle of view. Move away from optical axis. In this way, high zoom ratio can be realized while maintaining high optical performance. In order to secure a sufficient back focus in the wide-angle end state, the second lens group G2 has a strong negative refractive power. For this reason, the angle formed by the principal ray exiting from the second lens group G2 with respect to the optical axis is small, and the height at which the principal ray enters the third lens group G3 is close to the optical axis. As a result, it is possible to easily correct the eccentric coma generated at the peripheral portion of the screen when the shift lens group forming a part of the third lens group G3 is moved in a direction substantially perpendicular to the optical axis.

Based on the above considerations, in the present invention, the second
An aperture stop is arranged between the lens group G2 and the third lens group G3, and when the lens position changes, the aperture stop is moved integrally with the third lens group G3, and a plurality of lenses constituting the third lens group G3 are formed. By moving one of the sub-lens groups in a direction substantially perpendicular to the optical axis, the performance degradation that occurs at the time of image shift is suppressed well. As described above, according to the configuration of the present invention, a compact and variable power optical system having a high variable power ratio, in which the performance deterioration occurring at the time of image shift is suppressed well.

Hereinafter, the conditional expressions of the present invention will be described. In the first aspect of the present invention, the following conditional expression (1) is satisfied. D / fs <0.2 (1) where, D: distance along the optical axis between the most image-side surface of the shift lens group Gs and the aperture stop fs: focal length of the shift lens group Gs

Conditional expression (1) is a conditional expression that defines the positional relationship between the aperture stop and the shift lens group Gs. When the value exceeds the upper limit of the conditional expression (1), the off-axis light flux passing through the shift lens group Gs is separated from the optical axis, so that when the shift lens group Gs is moved in a direction substantially perpendicular to the optical axis, the periphery of the screen is reduced. The eccentric coma generated in the portion increases, and the contrast of the recorded image decreases. In the present invention, to properly correct various aberrations generated by the shift lens group Gs alone, it is necessary to secure a certain thickness of the lens of the shift lens group Gs. In order to ensure a predetermined optical performance, it is desirable to set the lower limit of conditional expression (1) to 0.05. In order to further suppress the deterioration of the optical performance that occurs at the time of image shift, It is desirable to set the upper limit of conditional expression (1) to 0.15.

In the first invention, the third lens group G3 includes, in order from the object side, a positive refractive power in order to further suppress the performance degradation that occurs at the time of image shift while realizing a high zoom ratio. The first positive partial lens group G31 having a positive refractive power and the second positive partial lens group G32 having a positive refractive power. The first positive partial lens group G31 close to the aperture stop forms the shift lens group Gs. It is preferable to satisfy the conditional expression (2). 0.35 <f3 / fs <0.7 (2) where, f3 is the focal length of the third lens group G3.

The third lens group G3 is a lens group having a strong positive refractive power for converging the light flux once diverged by the second lens group G2. In general, when the refractive power of the shift lens group Gs increases, the number of lenses increases in order to favorably correct the axial aberration generated by the shift lens group Gs alone. As a result, the driving system of the shift lens group Gs becomes difficult. It becomes large. Therefore, in the present invention, the third lens group G3 is composed of at least two positive partial lens groups, and the shift lens group Gs is composed of the positive partial lens group arranged closest to the object side, so that the overall size of the camera is reduced. Has been realized. In particular, by setting the focal length of the shift lens group Gs so as to satisfy the conditional expression (2), the number of lenses constituting the third lens group G3 and the shift lens group Gs
Can be optimized with the number of lenses that compose the above.

Here, a description will be given of the amount of image shift generated when a shift lens group including a part of lens groups in the optical system is moved in a direction perpendicular to the optical axis. Assuming that the lateral magnification of the shift lens group is βa and the lateral magnification of the entire lens group disposed on the image side of the shift lens group is βb, the image shift amount δh with respect to the shift amount Δ of the shift lens group is expressed by the following equation ( a). δh = (1−βa) βb · Δ (a) where k = | (1−βa) βb |
This is called the blur coefficient.

If the blurring coefficient k is small, the amount of movement of the shift lens group necessary to shift the image by a predetermined amount becomes large, and the driving mechanism of the shift lens group becomes complicated. Conversely, when the blur coefficient k is large, if the movement amount of the shift lens group slightly fluctuates due to a control error, the image shift amount largely fluctuates, and contrast for a high spatial frequency is lacking. Therefore, it is desirable to set the blur coefficient k to an appropriate value.

In the case of a variable power optical system, the lateral magnification βa of the shift lens group and the lateral magnification βb of the lens group arranged closer to the image side than the shift lens group are constant from the wide-angle end state to the telephoto end state. Not exclusively. As in the present invention, when the fourth lens group G4 arranged on the image side of the shift lens group Gs is movable at the time of zooming, the blur coefficient k changes with the change of the lens position state. By the way, the fluctuation amount δa of the image position that occurs when the optical system is tilted by ω (and by extension, the camera) is expressed by the following equation (b), where f is the focal length of the optical system. δa = f · tanω (b)

Therefore, by moving the shift lens group Gs to provide the image shift amount δh so as to satisfy the following expression (c), the image variation amount δa due to the blur (tilt) of the optical system can be reduced. Can be corrected. δa + δh = 0 (c) In the wide-angle end state, the shift amount Δw of the shift lens group required to correct the image fluctuation amount δaw caused by the inclination ω of the optical system.
The shift amount Δt of the shift lens group required to correct the image fluctuation amount δat caused by the inclination ω of the optical system in the telephoto end state is expressed by the following equations (d) and (e), respectively.

Δw = −δaw / kw (d) Δt = −δat / kt (e) where kw is a blur coefficient in a wide-angle end state, and k
t is a blur coefficient in the telephoto end state. Therefore,
The ratio between the required movement amount Δt in the telephoto end state and the required movement amount Δw in the wide-angle end state is represented by the following equation (f).

Δt / Δw = (δat / kt) / (δaw / kw) = (ft / fw) / (kt / kw) (f) where ft is the focal length of the entire optical system in the telephoto end state. And fw is the focal length of the entire optical system in the wide-angle end state.

Therefore, in the first invention, it is preferable to satisfy the following conditional expression (3). 0.4 <{(1−β3t) βst} / {(1−β3w) βsw} / Z <0.9 (3) where β3w: lateral magnification of the shift lens group Gs in the wide-angle end state βsw: shift lens Lateral magnification β3t in the wide-angle end state of the lens group arranged closer to the image side than group Gs β3t: Lateral magnification in the telephoto end state of shift lens group Gst βst: Telephoto magnification of the lens group arranged closer to the image side than shift lens group Gs Lateral magnification Z in end state: magnification ratio of variable magnification optical system

The conditional expression (3) is a conditional expression that defines the reciprocal of the expression (f). The required optical performance on the image plane is constant regardless of the focal length of the taking lens. For example, when the amount of movement of the shift lens group required to correct image blur when the camera is tilted by a predetermined blur angle is significantly different between the wide-angle end state and the telephoto end state, while maintaining the predetermined optical performance, Control of the shift lens group cannot be performed easily. When the amount of movement of the shift lens group necessary to correct the image blur when the camera is tilted by a predetermined shake angle is constant without depending on the lens position state, that is, the value of equation (f) is always constant When the aberration correction
Since the degree of freedom for selecting the zoom trajectory and the degree of freedom for selecting the lateral magnification of each lens group are lost, it is difficult to increase the zoom ratio.

In the first aspect of the invention, by setting the upper limit value and the lower limit value of the above (f) in a range satisfying the conditional expression (3), it is possible to realize a high zoom ratio and to achieve a small control error with a small control error. Control can be performed. In order to control the lens position more easily, it is desirable to set the upper limit of conditional expression (3) to 0.6 and the lower limit to 0.5.
In the present invention, a detection system for detecting camera shake (optical system), an operation system for calculating the drive amount of the shift lens group based on the output from the detection system, and a shift lens based on the operation result of the operation system By combining with a drive system for driving a group, it is possible to make the variable power optical system of the present invention function as a vibration proof optical system.

According to the second aspect of the present invention, in order from the object side, the first lens group G1 having at least a positive refractive power, the second lens group G2 having a negative refractive power, and the positive refractive power A lens group GA having a power is disposed, and a final lens group GE having a negative refractive power is disposed closest to the image side. Then, when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group G1 and the second lens group G2 are moved so that the convergence action of the first lens group G1 and the second lens group G2 is strengthened. The distance is changed to move to the object side, and the final lens group GE moves to the object side. The second lens group G2 includes, in order from the object side, a negative partial lens group G2a having a negative refractive power and a positive partial lens group G2b having a positive refractive power. Further, the lens group GA has a plurality of partial lens groups, and among the plurality of partial lens groups, a partial lens group disposed adjacent to the aperture stop is referred to as a shift lens group Gs in a direction substantially perpendicular to the optical axis. The image is shifted by moving.

In the second aspect of the present invention, the following conditional expressions (4) and (5) are satisfied. 0.1 <| f2a | / f2b <0.4 0.2 <| fvt | / ft <0.4 where f2a: focal length of the negative partial lens group G2a f2b: focal length of the positive partial lens group G2b fvt : Composite focal length of first lens group G1 and second lens group G2 in telephoto end state ft: focal length of entire optical system in telephoto end state

As described above, if the blur coefficient k changes greatly from the wide-angle end state to the telephoto end state, it becomes difficult to control the shift lens group. By the way, the blur coefficient k is
It depends on the lateral magnification of the shift lens group and the lateral magnification of the lens group arranged on the image side of the shift lens group. Therefore, as the zooming action of the lens unit arranged on the image side of the shift lens unit increases, the change of the blur coefficient k increases. In the present invention, the shift lens group Gs
Any lens position from the wide-angle end to the telephoto end by increasing the zooming effect of the lens group arranged on the object side and suppressing the change in the blur coefficient k due to the change in the lens position. , The shift lens group Gs can be easily controlled.

Further, in order to satisfy a predetermined optical performance and efficiently suppress the deterioration of the optical performance which occurs at the time of image shift, while efficiently achieving high zoom ratio with a small number of lens components,
Also in the second invention, similarly to the first invention, the aperture stop is arranged near the shift lens group Gs, and the shift lens group Gs
Is composed of a plurality of partial lens groups. In order to reduce the overall length of the lens, a final lens group GE having a negative refractive power is disposed closest to the image side of the optical system. When the lens position changes from the wide-angle end state to the telephoto end state, the final lens group GE changes. The group GE is moved to the object side to increase the magnification.

Further, in the second aspect, conditional expression (4) is set in order to obtain a sufficient back focus in the wide-angle end state and to shorten the total lens length in the telephoto end state. Conditional expression (4) defines an appropriate range for the ratio between the focal length of the negative partial lens group G2a and the focal length of the positive partial lens group G2b in the second lens group G2. When the value exceeds the upper limit of the conditional expression (4), the off-axis light beam passing through the negative partial lens unit G2a of the second lens unit G2 in the wide-angle end state is separated from the optical axis, and a large coma aberration occurs in the peripheral portion of the screen. Therefore, it becomes impossible to obtain a predetermined optical performance with a small number of lenses. Conversely, if the lower limit of conditional expression (4) is not reached, the overall length of the lens will increase in the telephoto end state as described above.

However, in order to reduce the total length of the lens in the telephoto end state and to set the blur coefficient k in the telephoto end state to an appropriate value, the first lens group G in the telephoto end state is required.
The composite focal length of the first lens unit and the second lens group G2 is conditional expression (5).
It is necessary to satisfy When the blur coefficient k increases, the control error of the image position due to the control error of the drive system for driving the shift lens group Gs increases, and the image blurs even when the image is not shifted. Conversely, if the blur coefficient k is small, the required driving amount of the shift lens group Gs required to shift the image by a predetermined amount becomes extremely large.

As described above, in the present invention, the positional relationship between the aperture stop and the shift lens group is important for aberration correction. Further, in order to increase the zoom ratio in the present invention, it is desirable to dispose the aperture stop near the center of the optical system, and it is desirable to configure the optical system with three or more movable lens groups. Furthermore, in the present invention, it is desirable to move the second lens group G2 as a focusing group in the optical axis direction to focus on a short-distance object. If the focusing group is configured by a lens group arranged on the image side of the shift lens group Gs, the blurring coefficient k changes depending on the subject position (object position) even in the same lens position state. On the other hand, if the focusing group is formed by a lens group disposed closer to the object side than the shift lens group Gs, for example, as in the second lens group G2, the blur coefficient k will be constant regardless of the subject position.

The variable power optical system capable of image shift according to the present invention is not limited to a lens shutter type camera. For example, a telephoto zoom lens for a single-lens reflex camera disclosed in Japanese Patent Application Laid-Open No. Sho 60-55314. It is easily possible to apply. In each of the following embodiments, an aspherical surface is introduced. However, if an aspherical surface is introduced into a lens arranged near an aperture stop, a large aperture can be achieved. In addition, when an aspherical surface is introduced into a lens disposed at a position distant from the aperture stop, off-axis aberrations such as field curvature and distortion can be better corrected, and a wide angle and high performance can be achieved. be able to. In the variable power optical system according to the present invention, sufficiently high optical performance can be obtained even in a use state where image shifting is not performed, and it is possible to function sufficiently as a normal variable power optical system.

[0044]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a refractive power distribution of a variable power optical system according to each embodiment of the present invention and a state of movement of each lens group during zooming from a wide-angle end state (W) to a telephoto end state (T). It is. As shown in FIG. 1, the variable power optical system according to each example of the present invention includes, 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. And a third lens group G3 having a positive refractive power
And a fourth lens group G4 having a negative refractive power. When 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 second lens group G2 and the third lens group G3
All the lens groups move toward the object side so that the air gap between the third lens group G3 and the fourth lens group G4 decreases.

In each embodiment, the aspherical surface has a height y in a direction perpendicular to the optical axis, a displacement (sag amount) in the optical axis direction at the height y of S (y), and a reference radius of curvature of R. , The conic coefficient is κ, and the n-th order aspherical coefficient is Cn, and is expressed by the following equation (g).

[Number 2] ^{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 · Y ¹⁰ + ··· (g) In each embodiment, the aspherical surface is marked with an asterisk on the right side of the surface number.

[First Embodiment] FIG. 2 is a diagram showing a configuration of a variable power optical system according to a first embodiment of the present invention. In the variable power optical system shown in FIG. 2, the first lens group G1 includes, in order from the object side, a cemented positive lens L1 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side. Also,
The second lens group G2 includes, in order from the object side, a biconcave lens L2.
1, and a cemented positive lens L2 of a biconvex lens and a biconcave lens
Consists of two. Further, the third lens group G3 is
It comprises a cemented positive lens L31 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and a biconvex lens L32. The fourth lens group G4 includes, in order from the object side, a positive meniscus lens L41 having a concave surface facing the object side, and a biconcave lens L42.

Therefore, considering the variable power optical system of the first embodiment in accordance with the second invention, the third lens group G3 constitutes the lens group GA, and the fourth lens group G4 constitutes the final lens group GE. ing. Further, the biconcave lens L21 in the second lens group G2 serves as the negative partial lens group G2a, and the second lens group G2
The middle cemented positive lens L22 constitutes the positive partial lens group G2b.

The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and moves together with the third lens group G3 when zooming from the wide-angle end state to the telephoto end state. I do. 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, of the two lens components constituting the third lens group G3, the cemented positive lens L31 is moved as a shift lens group Gs in a direction substantially perpendicular to the optical axis to shift the image, and the image position caused by camera shake or the like is shifted. The fluctuation has been corrected. Furthermore, the second
Focusing is performed by moving the lens group G2 along the optical axis.

Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1), f is the focal length,
FNO represents the F number, ω represents the half angle of view, Bf represents the back focus, and D0 represents the distance along the optical axis between the object and the surface closest to the object. Furthermore, the surface number indicates the order of the lens surface from the object side along the direction in which the light rays travel,
The refractive index and Abbe number are each d-line (λ = 587.6).
nm).

[0050]

Table 1 f = 36.0 to 75.00 to 170.00 FNO = 3.78 to 6.29 to 11.00 ω = 31.10 to 15.54 to 7.11 ° Surface number Curvature radius Surface spacing Refractive index Abbe number 1 54.1928 4.250 1.48749 70.45 2 -52.3691 1.375 1.84666 23.83 3 -92.1386 (d3 = variable) 4 -25.5701 1.000 1.80420 46.51 5 26.6803 1.000 6 * 21.2449 3.500 1.71736 29.50 7 -13.5167 1.000 1.83500 42.97 8 72.4913d ) 9 ∞ 1.250 (Aperture stop S) 10 34.0724 3.125 1.48749 70.45 11 -13.2038 1.000 1.84666 23.83 12 -23.7313 1.125 13 53.3181 2.625 1.51450 63.05 14 * -25.4556 (d14 = variable) 15 * -248.6454 2.712 1.68893 31.16 16 -43.5428 7.353 17 -15.2053 1.250 1.77250 49.61 18 549.3023 (Bf ) ( aspheric data) R κ C ₄ 6 faces ^{21.2449 1.1736 + 1.72430 × 10 -6 C} 6 C 8 C 10 + 1.91380 × 10 -7 -3.91910 × 10 -9 + 4.47150 × 10 ^-11 R κ C ₄ 14 surface ^{-25.4556 1.5838 + 3.34760 × 10 -5 C} 6 C 8 C 10 + 5.06200 × 10 -8 -2.72670 × 10 -10 + 1.01290 × 10 -12 kappa C ₄ 15 faces ^{-248.6454 -1.2808 + 1.49020 × 10 -5 C} 6 C 8 C 10 -3.03490 × 10 -8 + 2.80520 × 10 -10 + 2.09070 × 10 -13 ( variable spacing in zooming) f 35.9994 74.9983 170.0006 d3 2.8161 15.7797 28.8035 d8 4.2483 2.6490 1.2500 d14 20.8296 10.9664 2.8750 Bf 7.8751 31.1383 78.2651 (Focusing movement amount δG2 of the second lens group G2 when the photographing magnification is -1/30) Focal length f 35.9994 74.9983 170.0006 D0 1027.5967 2147.3279 4876.992 Moving amount 0.8752 0.7208 0.7057 However, the sign of the amount of movement assumes that movement toward the object side is positive (relationship between amount of movement Δs of cemented positive lens L31 and amount of image shift δs) Focal length f 35.9994 74.9983 170.0006 Image shift amount δs 0.3600 0.7500 1.7000 Lens movement amount Δs 0.3425 0.4306 0.5605 (values corresponding to conditional expressions) fs = 43.9348 f3 = 20.5014 βsw = −0.1794 β3w = 6.8571 βst = −0.3525 β3t = 9.6059 f2a = 16.0983 f2b = 66.2384 fvt = −50.2071 Z = 4.7223 (1) D / fs = 0.122 (2) f3 / fs = 0.467 (3) (1−β3t) βst / ( 1−β3w) βsw / Z = 0.611 (4) | f2a | /f2b=0.243 (5) | fvt | /ft=0.295

FIGS. 3 to 8 show the d-line (λ = 587.6n).
FIG. 7 is a diagram illustrating various aberrations of the first example with respect to m). FIG. 3 is a diagram illustrating various aberrations in the infinity in-focus condition in the wide-angle end state, FIG. 4 is a diagram illustrating various aberrations in the infinity in-focus condition in the intermediate focal length state, and FIG. FIG. 4 is a diagram illustrating various aberrations in a focused state. FIG. 6 is a diagram illustrating various aberrations at a photographing magnification of −1 / 30 × in the wide-angle end state, FIG. 7 is a diagram illustrating various aberrations at a photographing magnification of −1 / 30 × in the intermediate focal length state, and FIG. Magnification -1/3 at telephoto end
FIG. 7 is a diagram illustrating various aberrations at a magnification of 0.

9 to 14 are coma aberration diagrams when the image is shifted by 0.01 rad (radian) with respect to the optical axis in the first embodiment. FIG. 9 is a coma aberration diagram in the infinity in-focus state in the wide-angle end state.
0 is a coma aberration diagram in an infinity in-focus condition in an intermediate focal length state, and FIG. 11 is a coma aberration diagram in an infinity in-focus condition in a telephoto end state. FIG. 12 is a coma aberration diagram at a photographing magnification of −1 / 30 × in the wide-angle end state, and FIG. 13 is a photographing magnification of −1/30 in the intermediate focal length state.
FIG. 14 is a coma aberration diagram at a magnification of −1/30 in the telephoto end state. Each of the aberration diagrams in FIGS. 9 to 14 shows that Y = 15.0,0, -15.0 when the cemented positive lens L31 is moved in the positive direction of the image height Y.
Shows the coma aberration at.

In each aberration diagram, FNO represents the F number,
NA indicates the numerical aperture, Y indicates the image height, A indicates the half angle of view for each image height, and H indicates the object height for each image height. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, in the aberration diagram showing the spherical aberration, a broken line indicates a sine condition (sine condition). As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected even at the time of image shift in each shooting distance state and each focal length state.

[Second Embodiment] FIG. 15 is a diagram showing a configuration of a variable power optical system according to a second embodiment of the present invention. FIG.
In the variable magnification optical system, the first lens group G1 includes, in order from the object side, a cemented positive lens L1 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side. The second lens group G2 includes, in order from the object side, a biconcave lens L21, and a cemented positive lens L22 of a biconvex lens and a biconcave lens. Further, the third lens group G3
Comprises a cemented positive lens L31 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and a biconvex lens L32. The fourth lens group G4 includes, in order from the object side, a biconvex lens L41 and a biconcave lens L42.

Therefore, considering the variable power optical system of the second embodiment in correspondence with the second invention, the third lens group G3 constitutes the lens group GA, and the fourth lens group G4 constitutes the final lens group GE. ing. Further, the biconcave lens L21 in the second lens group G2 serves as the negative partial lens group G2a, and the second lens group G2
The middle cemented positive lens L22 constitutes the positive partial lens group G2b.

The aperture stop S is arranged between the second lens group G2 and the third lens group G3, and moves together with the third lens group G3 when zooming from the wide-angle end state to the telephoto end state. I do. FIG. 15 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, of the two lens components constituting the third lens group G3, the cemented positive lens L31 is moved as a shift lens group Gs in a direction substantially perpendicular to the optical axis to shift the image, and the image position caused by camera shake or the like is shifted. The fluctuation has been corrected. Furthermore, the second
Focusing is performed by moving the lens group G2 along the optical axis.

Table 2 below summarizes data values of the second embodiment of the present invention. In Table (2), f is the focal length,
FNO represents the F number, ω represents the half angle of view, Bf represents the back focus, and D0 represents the distance along the optical axis between the object and the surface closest to the object. Furthermore, the surface number indicates the order of the lens surface from the object side along the direction in which the light rays travel,
The refractive index and Abbe number are each d-line (λ = 587.6).
nm).

[0058]

Table 2 f = 38.93 to 75.60 to 183.96 FNO = 3.85 to 6.14 to 11.00 ω = 28.78 to 15.43 to 6.58 ° Surface number Curvature radius Surface spacing Refractive index Abbe number 1 51.8167 4.284 1.48749 70.45 2 -53.7693 1.386 1.84666 23.83 3 -97.0444 (d3 = variable) 4 -26.4310 1.008 1.77250 49.61 5 33.0387 0.756 6 * 22.2667 3.528 1.68893 31.16 7 -13.3299 1.008 1.80420 46.51 8 53.2684d ) 9 ∞ 1.260 (Aperture stop S) 10 33.7458 3.150 1.48749 70.45 11 -14.0844 1.008 1.84666 23.83 12 -25.9907 1.134 13 51.2297 2.646 1.51450 63.05 14 * -25.9086 (d14 = variable) 15 * 325.0348 3.098 1.68893 31.16 16 -60.6443 6.915 17- 14.3830 1.260 1.77250 49.61 18 3325.7186 (Bf ) ( aspheric data) R κ C ₄ 6 faces ^{22.2667 1.4465 + 1.32815 × 10 -6 C} 6 C 8 C 10 + 2.29845 × 10 -7 -4.26665 × 10 -9 + 3.87369 × 10 ^-11 R κC ₄ 14 side -25.9086 1.3985 + 2.83877 × 10 ^-5 C ₆ C ₈ C ₁₀ + 2.11412 × 10 ^-7 -3.76902 × 10 ^-9 + 2.80604 × 10 ^-11 R κ C ₄ 15 side 325.0348 11.0000 + 1.95413 × 10 ^-5 C ₆ C ₈ C ₁₀ + 4.87122 × 10 ^-8 -3.67858 × 10 ^-10 + 3.55599 × 10 ^-12 (variable interval in zooming) f 38.9344 75.6011 183.9649 d3 3.0033 14.6630 29.5856 d8 4.0122 2.8704 1.2600 d14 21.7699 12.0689 2.8980 Bf 7.9388 29.1277 78.7294 (Focusing moving amount δG2 of the second lens group G2 at a magnification of −1/30) Focal length f 38.9344 75.6011 183.9649 D0 1108.6260 2157.6195 5220.4865 Moving amount δG2 0.96 0.9719 where the sign of the movement amount is positive for movement toward the object side (relationship between movement amount Δs of cemented positive lens L31 and image shift amount δs) Focal length f 38.9344 75.6011 183.9649 Image shift amount δs 0.3893 0.7560 1.8397 Movement amount Δs 0.3825 0.4667 0.6338 (value corresponding to the conditional expression) fs = 46.5407 f3 = 20.4699 βsw = −0.2130 β3w = 5.7660βst = −0.3194 β3t = 10.0910 f2a = 18.8689 f2b = 122.0734 fvt = -57.08654 Z = 4.7250 (1) D / fs = 0.116 (2) f3 / fs = 0.440 (3) (1-β3t) βst / ( 1−β3w) βsw / Z = 0.605 (4) | f2a | /f2b=0.155 (5) | fvt | /ft=0.310

FIGS. 16 to 21 show the d-line (λ = 587.
FIG. 9 is a diagram illustrating various aberrations of the second example with respect to 6 nm). FIG.
FIG. 17 is a diagram illustrating various aberrations at the infinity in-focus condition in the wide-angle end state, FIG. 17 is a diagram illustrating various aberrations at the infinity in-focus condition in the intermediate focal length state, and FIG. It is a some aberration figure in a state. FIG. 19 is a diagram of various aberrations at a photographing magnification of −1 / 30 × in the wide-angle end state, and FIG. 20 is a photographing magnification of −1/30 in the intermediate focal length state.
FIG. 21 is a diagram illustrating various aberrations at 30 ×, and FIG. 21 is a diagram illustrating various aberrations at a photographing magnification of −1 / 30 × in the telephoto end state.

FIGS. 22 to 27 are coma aberration diagrams when the image is shifted by 0.01 rad (radian) with respect to the optical axis in the second embodiment. FIG. 22 is a coma aberration diagram at the infinity in-focus condition in the wide-angle end state.
FIG. 23 is a coma aberration diagram in an infinity in-focus condition in an intermediate focal length state, and FIG. 24 is a coma aberration diagram in an infinity in-focus condition in a telephoto end state. FIG. 25 is a coma aberration diagram at a photographing magnification of −1/30 in the wide-angle end state, and FIG. 26 is a photographing magnification of −1 in the intermediate focal length state.
FIG. 27 is a coma aberration diagram at a photographing magnification of −1 / 30 × in the telephoto end state. FIG.
Each of the aberration diagrams in FIGS. 2 to 27 shows that Y = 15.0,0, -1 when the cemented positive lens L31 is moved in the positive direction of the image height Y.
The figure shows the coma aberration at 5.0.

In each aberration diagram, FNO represents the F number,
NA indicates the numerical aperture, Y indicates the image height, A indicates the half angle of view for each image height, and H indicates the object height for each image height. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, in the aberration diagram showing the spherical aberration, a broken line indicates a sine condition (sine condition). As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected even at the time of image shift in each shooting distance state and each focal length state.

[Third Embodiment] FIG. 28 is a view showing the arrangement of a variable power optical system according to a third embodiment of the present invention. FIG.
In the variable magnification optical system, the first lens group G1 includes, in order from the object side, a cemented positive lens L1 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side. The second lens group G2 includes, in order from the object side, a biconcave lens L21, and a cemented positive lens L22 of a biconvex lens and a biconcave lens. Further, the third lens group G3
Comprises a cemented positive lens L31 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and a biconvex lens L32. The fourth lens group G4 includes, in order from the object side, a biconvex lens L41 and a biconcave lens L42.

Therefore, considering the variable power optical system of the third embodiment in accordance with the second invention, the third lens group G3 constitutes the lens group GA, and the fourth lens group G4 constitutes the last lens group GE. ing. Further, the biconcave lens L21 in the second lens group G2 serves as the negative partial lens group G2a, and the second lens group G2
The middle cemented positive lens L22 constitutes the positive partial lens group G2b.

The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and moves together with the third lens group G3 when zooming from the wide-angle end state to the telephoto end state. I do. FIG. 28 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, of the two lens components constituting the third lens group G3, the cemented positive lens L31 is moved as a shift lens group Gs in a direction substantially perpendicular to the optical axis to shift the image, and the image position caused by camera shake or the like is shifted. The fluctuation has been corrected. Furthermore, the second
Focusing is performed by moving the lens group G2 along the optical axis.

Table 3 below summarizes data values of the third embodiment of the present invention. In Table (3), f is the focal length,
FNO represents the F number, ω represents the half angle of view, Bf represents the back focus, and D0 represents the distance along the optical axis between the object and the surface closest to the object. Furthermore, the surface number indicates the order of the lens surface from the object side along the direction in which the light rays travel,
The refractive index and Abbe number are each d-line (λ = 587.6).
nm).

[0066]

Table 3 f = 38.80 to 75.34 to 183.30 FNO = 3.99 to 6.21 to 10.98 ω = 29.26 to 15.48 to 6.61 ° Surface number Curvature radius Surface spacing Refractive index Abbe number 1 47.5258 3.516 1.48749 70.45 2 -56.0972 1.381 1.84666 23.83 3 -106.0453 (d3 = variable) 4 -28.0826 1.004 1.77250 49.61 5 24.9169 0.753 6 * 22.0995 3.956 1.68893 31.16 7 -12.1624 1.004 1.80420 46.51 8 94.4937 ) 9 ∞ 1.256 (Aperture stop S) 10 33.8221 3.140 1.49782 82.52 11 -13.6984 1.005 1.80518 25.46 12 -26.3091 1.130 13 75.0518 2.637 1.51450 63.05 14 * -26.4349 (d14 = variable) 15 * 3619.3393 2.763 1.72825 28.31 16 -61.4390 7.660 17- 15.3827 1.256 1.73400 51.04 18 425.5221 (Bf ) ( aspheric data) R κ C ₄ 6 faces _{^{22.0995 1.9417 -1.90305 × 10 -6 C 6}} C 8 C 10 + 3.49236 × 10 -7 -9.33533 × 10 -9 + 9.75434 × 10 ^-11 R ^κ C ₄ 14 surface ^{-26.4349 1.3464 + 2.25498 × 10 -5 C} 6 C 8 C 10 + 3.22854 × 10 -7 -8.27256 × 10 -9 + 7.94160 × 10 -11 kappa C ₄ 15 faces ^{3619.3393 11.0000 + 1.43908 × 10 -5 C} 6 C 8 C 10 + 9.51657 × 10 -9 + 3.86881 × 10 -11 + 8.05797 × 10 -13 ( variable spacing in zooming) f 38.8002 75.3363 183.3010 d3 3.0768 14.6630 29.5856 d8 4.0122 2.8704 1.2600 d14 21.7699 12.0689 2.8980 Bf 7.9388 29.1277 78.7294 (Focusing moving amount δG2 of the second lens group G2 at a photographing magnification of −1/30) Focal length f 38.8002 75.3363 183.3010 D0 1103.8760 2144.7139 5149.0072 Moving amount δG2 1.0081 0.9040 1.2037 However, the sign of the amount of movement is positive for movement toward the object side (relationship between amount of movement Δs of cemented positive lens L31 and image shift amount δs) Focal length f 38.8002 75.3363 183.3010 Image shift amount δs 0.3880 0.7535 1.8336 Movement amount Δs 0.3568 0.4445 0.6138 (Values corresponding to conditional expressions) fs = 46.9493 f3 = 21.4158 βsw = −0.0927 β3w = + 12.9804 βst = 0.0041 β3t = −737.193 2a = -16.9507 f2b = + 68.4681 fvt = -60.135 135 Z = 4.7242 (1) D / fs = 0.123 (2) f3 / fs = 0.456 (3) (1-β3t) βst / (1−β3w) βsw / Z = 0.482 (4) | f2a | /f2b=0.248 (5) | fvt | /ft=0.328

FIGS. 29 to 34 show the d-line (λ = 587.
FIG. 9 is a diagram illustrating various aberrations of the third example with respect to (6 nm). FIG.
FIG. 30 is a diagram illustrating various aberrations at the wide-angle end state in an infinity in-focus state, FIG. 30 is a diagram illustrating various aberrations at an intermediate focal length state in an infinity in-focus state, and FIG. It is a some aberration figure in a state. FIG. 32 is a diagram of various aberrations at a photographing magnification of −1 / 30 × in the wide-angle end state, and FIG. 33 is a photographing magnification of −1/30 in the intermediate focal length state.
FIG. 34 is a diagram of various aberrations at 30 ×, and FIG. 34 is a diagram of various aberrations at a photographing magnification of −1 / 30 × in the telephoto end state.

FIGS. 35 to 40 are coma aberration diagrams when the image is shifted by 0.01 rad (radian) with respect to the optical axis in the third embodiment. FIG. 35 is a coma aberration diagram in the infinity in-focus state in the wide-angle end state.
FIG. 36 is a coma aberration diagram in an infinity in-focus condition in an intermediate focal length state, and FIG. 37 is a coma aberration diagram in an infinity in-focus condition in a telephoto end state. FIG. 38 is a coma aberration diagram at a photographing magnification of −1 / 30 × in the wide-angle end state, and FIG. 39 is a photographing magnification of −1 in the intermediate focal length state.
FIG. 40 is a coma aberration diagram at a photographing magnification of −1/30 in the telephoto end state. FIG.
5 to FIG. 40 show that Y = 15.0,0, −1 when the cemented positive lens L31 is moved in the positive direction of the image height Y.
The figure shows the coma aberration at 5.0.

In each aberration diagram, FNO represents an F number,
NA indicates the numerical aperture, Y indicates the image height, A indicates the half angle of view for each image height, and H indicates the object height for each image height. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, in the aberration diagram showing the spherical aberration, a broken line indicates a sine condition (sine condition). As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected even at the time of image shift in each shooting distance state and each focal length state.

[Fourth Embodiment] FIG. 41 is a view showing the arrangement of a variable power optical system according to a fourth embodiment of the present invention. FIG.
In the variable magnification optical system, the first lens group G1 includes, in order from the object side, a cemented positive lens L1 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side. The second lens group G2 includes, in order from the object side, a biconcave lens L21, and a cemented positive lens L22 of a biconvex lens and a biconcave lens. Further, the third lens group G3
Comprises a cemented positive lens L31 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and a biconvex lens L32. The fourth lens group G4 includes, in order from the object side, a biconvex lens L41 and a biconcave lens L42.

Therefore, considering the variable power optical system of the fourth embodiment in correspondence with the second invention, the third lens group G3 constitutes the lens group GA, and the fourth lens group G4 constitutes the last lens group GE. ing. Further, the biconcave lens L21 in the second lens group G2 serves as the negative partial lens group G2a, and the second lens group G2
The middle cemented positive lens L22 constitutes the positive partial lens group G2b.

The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and moves together with the third lens group G3 when zooming from the wide-angle end state to the telephoto end state. I do. FIG. 41 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, of the two lens components constituting the third lens group G3, the cemented positive lens L31 is moved as a shift lens group Gs in a direction substantially perpendicular to the optical axis to shift the image, and the image position caused by camera shake or the like is shifted. The fluctuation has been corrected. Furthermore, the second
Focusing is performed by moving the lens group G2 along the optical axis.

Table 4 below summarizes the data values of the fourth embodiment of the present invention. In Table (4), f is the focal length,
FNO represents the F number, ω represents the half angle of view, Bf represents the back focus, and D0 represents the distance along the optical axis between the object and the surface closest to the object. Furthermore, the surface number indicates the order of the lens surface from the object side along the direction in which the light rays travel,
The refractive index and Abbe number are each d-line (λ = 587.6).
nm).

[0074]

F = 38.81 to 75.35 to 183.35 FNO = 3.96 to 6.19 to 11.00 ω = 29.28 to 15.48 to 6.61 ° Surface number Curvature radius Surface spacing Refractive index Abbe number 1 47.8034 3.516 1.48749 70.45 2 -54.9592 1.381 1.84666 23.83 3 -103.2755 (variable d3) 4 -27.1841 1.005 1.77250 49.61 5 25.8384 0.754 6 * 23.0512 3.830 1.68893 31.16 7 -12.4666 1.005 1.80420 46.51 8 102.5292d ) 9 ∞ 1.256 (Aperture stop S) 10 33.6151 3.140 1.48749 70.45 11 -13.8736 1.005 1.84666 23.83 12 -25.1751 1.130 13 76.4471 2.637 1.51450 63.05 14 * -26.0362 (d14 = variable) 15 * 230.4906 3.077 1.68893 31.16 16 -64.5403 7.284 17- 15.7104 1.256 1.77250 49.61 18 344.0289 (Bf ) ( aspheric data) R κ C ₄ 6 faces ^{23.0512 1.8286 + 1.21080 × 10 -6 C} 6 C 8 C 10 + 3.38130 × 10 -7 -8.34260 × 10 -9 + 8.44440 × 10 ^-11 R ^κ C ₄ 14 surface ^{-26.0362 1.3174 + 2.31200 × 10 -5 C} 6 C 8 C 10 + 2.94030 × 10 -7 -7.48990 × 10 -9 + 7.13870 × 10 -11 kappa C ₄ 15 faces ^{230.4906 4.2292 + 1.55880 × 10 -5 C} 6 C 8 C 10 + 1.19210 × 10 -8 + 1.69680 × 10 -11 + 9.96150 × 10 -13 ( variable spacing in zooming) f 38.8051 75.3501 183.3537 d3 3.0734 14.7292 29.5415 d8 4.8400 3.1203 1.2558 d14 23.4140 13.4834 2.9108 Bf 7.9206 28.6020 78.4385 (Focusing moving amount δG2 of the second lens group G2 at a magnification of −1/30) Focal length f 38.8051 75.3501 183.3537 D0 1103.8874 2144.7388 5149.0620 Moving amount δG 1.0081 1.2037 However, the sign of the amount of movement assumes that movement toward the object side is positive (relationship between amount of movement Δs of cemented positive lens L31 and amount of image shift δs) Focal length f 38.8051 75.3501 183.3537 Image shift amount δs 0.3880 0.7532 1.8331 Movement amount Δs 0.3492 0.4362 0.6008 (Value corresponding to conditional expression) fs = 45.0429 f3 = 21.5586 βsw = −0.1236 β3w = 9.8010 βst = −0.0759 β3t = 40.3589 f2a = 17.0079 f2b = + 71.1832 fvt = −59.8488 Z = 4.7250 (1) D / fs = 0.123 (2) f3 / fs = 0.479 (3) (1−β3t) βst / ( 1−β3w) βsw / Z = 0.581 (4) | f2a | /f2b=0.239 (5) | fvt | /ft=0.326

FIGS. 42 to 47 show d-line (λ = 587.
FIG. 10 is a diagram illustrating various aberrations of the fourth example with respect to (6 nm). FIG.
FIG. 43 is a diagram showing various aberrations at the infinity in-focus condition in the wide-angle end state, FIG. 43 is a diagram showing various aberrations at the infinity in-focus condition in the intermediate focal length state, and FIG. It is a some aberration figure in a state. FIG. 45 is a diagram showing various aberrations at a photographing magnification of −1 / 30 × in the wide-angle end state, and FIG. 46 is a photographing magnification of −1/30 in the intermediate focal length state.
FIG. 47 is a diagram of various aberrations at 30 ×, and FIG. 47 is a diagram of various aberrations at a photographing magnification of −1 / 30 × in the telephoto end state.

FIGS. 48 to 53 are coma aberration diagrams when the image is shifted by 0.01 rad (radian) with respect to the optical axis in the fourth embodiment. FIG. 48 is a coma aberration diagram at the infinity in-focus condition in the wide-angle end state.
FIG. 49 is a coma aberration diagram in an infinity in-focus condition in an intermediate focal length state, and FIG. 50 is a coma aberration diagram in an infinity in-focus condition in a telephoto end state. FIG. 51 is a coma aberration diagram at a photographing magnification of −1 / 30 × in the wide-angle end state, and FIG. 52 is a photographing magnification −1 in the intermediate focal length state.
FIG. 53 is a coma aberration diagram at a photographing magnification of −1 / 30 × in the telephoto end state. FIG.
8 to 53 show that Y = 15.0,0, -1 when the cemented positive lens L31 is moved in the positive direction of the image height Y.
The figure shows the coma aberration at 5.0.

In each aberration diagram, FNO represents an F number,
NA indicates the numerical aperture, Y indicates the image height, A indicates the half angle of view for each image height, and H indicates the object height for each image height. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, in the aberration diagram showing the spherical aberration, a broken line indicates a sine condition (sine condition). As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected even at the time of image shift in each shooting distance state and each focal length state.

[0078]

As described above, according to the present invention, it is possible to realize a variable-magnification optical system that is compact, has high performance, and is suitable for high magnification with a magnification ratio of about 5 times. it can. It goes without saying that the introduction of a plurality of aspherical surfaces into the lens unit of the variable power optical system can further increase the aperture, increase the power, and reduce the size.

[Brief description of the drawings]

FIG. 1 is a diagram showing a refractive power distribution of a variable power optical system according to each embodiment of the present invention and a state of movement of each lens group during zooming from a wide-angle end state (W) to a telephoto end state (T). It is.

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 illustrating various aberrations of the first example in a focused state at infinity in a wide-angle end state.

FIG. 4 is a diagram illustrating various aberrations of the first embodiment in an infinity in-focus state in an intermediate focal length state.

FIG. 5 is a diagram illustrating various aberrations of the first example at a telephoto end in an infinity in-focus condition;

FIG. 6 is a photographing magnification-1 in the wide-angle end state according to the first embodiment.
It is a graph of various aberrations at / 30 time.

FIG. 7 is a diagram illustrating various aberrations at an imaging magnification of −1/30 in the intermediate focal length state according to the first example.

FIG. 8 is a photographing magnification −1 in the telephoto end state of the first embodiment.
It is a graph of various aberrations at / 30 time.

FIG. 9 is a coma aberration diagram at the time of image shifting in an infinity in-focus state in a wide-angle end state according to the first example.

FIG. 10 is a coma aberration diagram when an image is shifted in an infinity in-focus state in an intermediate focal length state according to the first embodiment.

FIG. 11 is a coma aberration diagram at the time of image shift in an infinity in-focus condition in the telephoto end state of the first embodiment.

FIG. 12 shows a photographing magnification of the first embodiment in the wide-angle end state.
It is a coma aberration figure at the time of image shift at 1/30 time.

FIG. 13 is a coma aberration diagram at the time of image shift at a photographing magnification of −1/30 in the intermediate focal length state according to the first example.

FIG. 14 shows a photographing magnification in the telephoto end state of the first embodiment.
It is a coma aberration figure at the time of image shift at 1/30 time.

FIG. 15 is a diagram showing a configuration of a variable power optical system according to Example 2 of the present invention.

FIG. 16 is a diagram illustrating various aberrations of the second example in an infinity in-focus condition in a wide-angle end state.

FIG. 17 is a diagram illustrating various aberrations of the second example in an intermediate focal length state in an infinity in-focus state;

FIG. 18 is a diagram illustrating various aberrations of the second embodiment at a telephoto end in an infinity in-focus condition;

FIG. 19 shows a photographing magnification in the wide-angle end state according to the second embodiment.
It is a some-aberration figure at 1/30 time.

FIG. 20 is a diagram illustrating various aberrations at an imaging magnification of −1/30 in the intermediate focal length state of the second example.

FIG. 21 shows a photographing magnification in the telephoto end state according to the second embodiment.
It is a some-aberration figure at 1/30 time.

FIG. 22 is a coma aberration diagram at the time of image shift in an infinity in-focus condition in the wide-angle end state according to the second embodiment.

FIG. 23 is a coma aberration diagram at the time of image shifting in an infinity in-focus state in an intermediate focal length state according to the second embodiment.

FIG. 24 is a coma aberration diagram at the time of image shift in an infinity in-focus condition in the telephoto end state according to the second embodiment.

FIG. 25 shows a photographing magnification in the wide-angle end state according to the second embodiment.
It is a coma aberration figure at the time of image shift at 1/30 time.

FIG. 26 is a coma aberration diagram when an image is shifted at an imaging magnification of −1/30 in the intermediate focal length state according to the second embodiment.

FIG. 27 shows a photographing magnification in the telephoto end state of the second embodiment.
It is a coma aberration figure at the time of image shift at 1/30 time.

FIG. 28 is a diagram showing a configuration of a variable power optical system according to Example 3 of the present invention.

FIG. 29 is a diagram illustrating various aberrations of the third example in an infinity in-focus condition in a wide-angle end state;

FIG. 30 is a diagram illustrating various aberrations of the third example in an intermediate focal length state in an infinity in-focus state;

FIG. 31 is a diagram illustrating various aberrations of the third example at a telephoto end in an infinity in-focus condition;

FIG. 32 shows a photographing magnification of the third embodiment in the wide-angle end state.
It is a some-aberration figure at 1/30 time.

FIG. 33 is a diagram illustrating various aberrations at an imaging magnification of −1 / 30 × in the intermediate focal length state of the third example.

FIG. 34 shows a photographing magnification in the telephoto end state of the third embodiment.
It is a some-aberration figure at 1/30 time.

FIG. 35 is a coma aberration diagram at the time of image shift in an infinity in-focus condition in the wide-angle end state according to the third example.

FIG. 36 is a coma aberration diagram at the time of image shifting in an infinity in-focus state in the intermediate focal length state of the third example.

FIG. 37 is a coma aberration diagram at the time of image shift in an infinity in-focus condition in the telephoto end state of the third embodiment.

FIG. 38 shows a photographing magnification in the wide-angle end state according to the third embodiment.
It is a coma aberration figure at the time of image shift at 1/30 time.

FIG. 39 is a coma aberration diagram at the time of image shift at an imaging magnification of −1/30 in the intermediate focal length state according to the third example.

FIG. 40—Photographing magnification in the telephoto end state of the third embodiment—
It is a coma aberration figure at the time of image shift at 1/30 time.

FIG. 41 is a diagram showing a configuration of a variable power optical system according to Example 4 of the present invention.

FIG. 42 is a diagram illustrating various aberrations of the fourth example in a focused state at infinity in a wide-angle end state.

FIG. 43 is a diagram illustrating various aberrations of the fourth example in the intermediate focal length state in the infinity in-focus state;

FIG. 44 is a diagram illustrating various aberrations of the fourth example in the infinity in-focus state in the telephoto end state.

FIG. 45 shows a photographing magnification of the fourth embodiment in the wide-angle end state.
It is a some-aberration figure at 1/30 time.

FIG. 46 is a diagram illustrating various aberrations at an imaging magnification of −1 / 30 × in the intermediate focal length state of the fourth example.

FIG. 47 shows a photographing magnification in the telephoto end state of the fourth embodiment.
It is a some-aberration figure at 1/30 time.

FIG. 48 is a coma aberration diagram at the time of image shift in an infinity in-focus condition in the wide-angle end state according to the fourth example.

FIG. 49 is a coma aberration diagram at the time of image shift in an infinity in-focus state in the intermediate focal length state of the fourth example.

FIG. 50 is a coma aberration diagram at the time of image shift in an infinity in-focus condition in the telephoto end state of the fourth embodiment.

FIG. 51—Photographing magnification in the wide-angle end state of the fourth embodiment—
It is a coma aberration figure at the time of image shift at 1/30 time.

FIG. 52 is a coma aberration diagram at the time of image shift at a photographing magnification of −1/30 in the intermediate focal length state of the fourth example.

FIG. 53 is a photographing magnification in the telephoto end state of the fourth embodiment.
It is a coma aberration figure at the time of image shift at 1/30 time.

[Description of Signs] G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group Li Each lens component S Aperture stop

Claims (5)

[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, and a fourth lens group G4 having a negative refractive power. When the lens position state changes from the wide-angle end state to the telephoto end state, the first The lens group G1 and the second lens group G2
, The distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the fourth lens group G4 decreases. The first lens group G1 and the fourth lens group G
4 moves to the object side, the third lens group G3 has at least two partial lens groups, and one of the at least two partial lens groups is substantially shifted along the optical axis as a shift lens group Gs. An image shift is performed by moving the shift lens group Gs in the vertical direction, and an aperture stop is provided between the second lens group G2 and the third lens group G3. The image shift satisfies the condition of D / fs <0.2, where D is a distance along the optical axis from the aperture stop, and fs is a focal length of the shift lens group Gs. Possible zoom optics. 2. The third lens group G3 includes, in order from the object side, a first positive partial lens group G31 having a positive refractive power and a second positive partial lens group G32 having a positive refractive power. When the first positive partial lens group G31 constitutes the shift lens group Gs, the focal length of the third lens group G3 is f3, and the focal length of the shift lens group Gs is fs, 0.35 < 2. The variable power optical system according to claim 1, wherein a condition of f3 / fs <0.7 is satisfied. 3. The shift lens, wherein a lateral magnification of the shift lens group Gs in the wide-angle end state is β3w, and a lateral magnification of the lens group disposed closer to the image side than the shift lens group Gs in the wide-angle end state is βsw. The lateral magnification in the telephoto end state of the group Gs is β3t, the lateral magnification in the telephoto end state of the lens group arranged closer to the image side than the shift lens group Gs is βst, and the magnification ratio of the zoom optical system is Z 0.4 <{(1−β3t) βst} / {(1−β3w) βsw}
3. A variable power optical system according to claim 1, wherein the following condition is satisfied: /Z<0.9. 4. The apparatus according to claim 1, wherein the second lens group G2 is moved along an optical axis to correct a change in an image plane position caused by a change in an object position. The variable-power optical system capable of image shift according to the above item. 5. A first lens group G1 having at least a positive refractive power and a second lens group G1 having a negative refractive power in order from the object side.
A lens group G2 and a lens group GA having a positive refractive power are arranged, and the last lens group GE having a negative refractive power is located closest to the image side.
The first lens group G1 and the second lens group G2 are used when the lens position changes from the wide-angle end state to the telephoto end state.
The first lens group G so as to enhance the convergence effect of
1 and the second lens group G2 move toward the object side by changing the distance between them, and the last lens group GE moves toward the object side. The second lens group G2 is negatively refracted in order from the object side. A negative partial lens group G2a having a positive power, and a positive partial lens group G2b having a positive refractive power. The lens group GA has a plurality of partial lens groups. The image is shifted by moving a partial lens group disposed adjacent to the stop as a shift lens group Gs in a direction substantially perpendicular to the optical axis. The focal length of the negative partial lens group G2a is f2a, and the positive The focal length of the lens group G2b is f2b, the combined focal length of the first lens group G1 and the second lens group G2 in the telephoto end state is fvt, and the focal length of the entire optical system in the telephoto end state is ft. When 0.1 <| f2a | / f2b <0.4 0.2 <| fvt | / ft <image shiftable variable magnification optical system, characterized by satisfying 0.4 conditions.