JP2010015003A - Variable magnification optical system, optical instrument equipped with the variable magnification optical system, and method for variable magnification of variable magnification optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable magnification optical system with good optical performance, an optical instrument equipped with the variable magnification optical system, and a method for variable magnification of a variable magnification optical system. <P>SOLUTION: The variable magnification optical system ZL mounted in an electronic still camera 1 or the like is constituted of a front lens group FG and a rear lens group RG in order from an object side along an optical axis. The rear lens group RG includes a first lens group RG1 having positive refractive power, a second lens group RG2 having negative refractive power and a third lens group RG3 having positive refractive power. The second lens group RG2 has two more lenses and is movable so that at least a part of the second lens group RG2 may have a component in a direction almost perpendicular to the optical axis and the surface on the most object side of the third lens group RG3 is configured to be concave toward the object side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a variable magnification optical system, an optical apparatus including the variable magnification optical system, and a variable magnification method for the variable magnification optical system.

Conventionally, a variable power optical system suitable for a photographic camera, an electronic still camera, a video camera, and the like has been proposed (see, for example, Patent Document 1).
JP 2006-85155 A

  However, the conventional variable magnification optical system has a problem that it cannot achieve good optical performance.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a variable magnification optical system that is small and has a high zoom ratio and that can achieve good optical performance.

In order to solve the above problems, a variable magnification optical system according to the present invention has a front lens group and a rear lens group in order from the object side along the optical axis, and the rear lens group has a positive refractive power. A first lens group having a negative refractive power, a third lens group having a positive refractive power, and a second lens group having two or more lenses. At least a part of the third lens unit is movable so as to have a component in a direction substantially perpendicular to the optical axis, and the most object side surface of the third lens group is configured with a concave surface facing the object side. When the radius of curvature of the object side surface of the 3A lens located closest to the object side of the third lens group is r3AR1, and the radius of curvature of the image side surface of the 3A lens is r3AR2, the following equation -2 20 <(r3AR1−r3AR2) / (r3AR1 + r3AR2) <0.55
It is configured to satisfy the following conditions.

  Further, in such a variable magnification optical system, the front lens group includes, in order from the object side, a lens group with a positive refractive power and a lens group with a negative refractive power, from the wide-angle end state to the telephoto end state. In zooming, it is preferable that the distance between the lens unit having a positive refractive power and the lens unit having a negative refractive power is increased.

Also, in such a variable magnification optical system, when the radius of curvature of the object side surface of the 3A lens is r3AR1, and the focal length in the wide angle end state of the entire variable magnification optical system is fw, 50 <(− r3AR1) / fw <5.00
It is preferable to satisfy the following conditions.

Further, in such a variable magnification optical system, the distance between the first lens group and the second lens group in the wide-angle end state is d12w, and the second lens group and the second lens group are in the wide-angle end state upon zooming from the wide-angle end state to the telephoto end state. The distance between the three lens groups is d23w, the distance between the first lens group and the second lens group in the telephoto end state is d12t, the distance between the second lens group and the third lens group is d23t, and in the wide-angle end state. When the combined focal length of the first lens group, the second lens group, and the third lens group is fw123, 0.03 <(d12t−d12w) / fw123 <0.32
0.03 <(d23w−d23t) / fw123 <0.32
It is preferable to satisfy the following conditions.

Further, in such a variable magnification optical system, when the magnification is changed from the wide-angle end state to the telephoto end state, the amount of movement of the first lens group with respect to the image plane is Δx1, and the first lens group and the second lens in the wide-angle end state are set. When the combined focal length of the first lens group and the third lens group is fw123, the following expression 0.35 <| Δx1 | / fw123 <1.50
It is preferable to satisfy the following conditions.

Also, in such a variable magnification optical system, the focal length of the second lens group is f2, and the combined focal length of the first lens group, the second lens group, and the third lens group in the wide-angle end state is fw123. The following formula 0.50 <(− f2) / fw123 <1.60
It is preferable to satisfy the following conditions.

  Further, in such a variable magnification optical system, the first lens unit and the third lens unit move in the object direction and the amount of movement with respect to the image plane is equal when zooming from the wide-angle end state to the telephoto end state. Is preferred.

  Such a variable magnification optical system preferably has an aperture stop closer to the object side than the second lens group.

  An optical apparatus according to the present invention includes any of the above-described variable magnification optical systems.

The zooming method of the zooming optical system according to the present invention includes a front lens group and a rear lens group in order from the object side along the optical axis, and the rear lens group has a positive refractive power. A first lens group, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, the second lens group having two or more lenses, and at least A part of the third lens unit is movable so as to have a component in a direction substantially perpendicular to the optical axis, and the most object side surface of the third lens unit is configured with a concave surface facing the object side. When the radius of curvature of the object side surface of the 3A lens located on the object side is r3AR1, and the radius of curvature of the image side surface of the 3A lens is r3AR2, the following equation-2.20 <(r3AR1-r3AR2) /(R3AR1+r3AR2)<0.55
This is performed using a variable magnification optical system that satisfies the above conditions.

  When the variable power optical system according to the present invention, the optical apparatus equipped with the variable power optical system, and the variable power method of the variable power optical system are configured as described above, a small and high variable power optical system is obtained. And good optical performance can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the present specification, the wide-angle end state and the telephoto end state refer to an infinitely focused state unless otherwise specified. As shown in FIG. 1, the variable magnification optical system ZL includes a front lens group FG and a rear lens group RG in order from the object side along the optical axis. The rear lens group RG has a positive refractive power. A first lens group RG1 having a negative refractive power, a second lens group RG2 having a negative refractive power, and a third lens group RG3 having a positive 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 RG1 and the second lens group RG2 in the telephoto end state is d12t, and the first lens group RG1 in the wide-angle end state is set. The distance between the second lens group RG2 and the second lens group RG2 is d12w, the distance between the second lens group RG2 and the third lens group RG3 in the telephoto end state is d23t, and the second lens group RG2 and the third lens group RG3 in the wide-angle end state. Is the distance between the front lens group FG and the first lens group RG1, the distance between the first lens group RG1 and the second lens group RG2 increases from d12w to d12t, and the second lens The interval between the group RG2 and the third lens group RG3 is configured to decrease from d23w to d23t.

  With such a configuration, at the time of zooming from the wide-angle end state to the telephoto end state, the principal point position of the rear lens group RG can be moved from the image plane side to the object side, and the variable obtained by the rear lens group RG can be obtained. It is possible to make the entire system a highly variable optical system by increasing the double amount. Furthermore, it is possible to satisfactorily correct variations in field curvature and spherical aberration during zooming.

  In addition, the zoom optical system ZL moves at least a part of the second lens group RG2 having two or more lenses so as to have a component in a direction substantially perpendicular to the optical axis when camera shake occurs. It is desirable that the image position is corrected when the camera shake occurs. As described above, since the image plane fluctuation can be corrected at the time of occurrence of camera shake, the variable magnification optical system ZL can be used as an image stabilization optical system. Further, the second lens group RG2 is composed of a relatively small optical element, and it is possible to achieve both the size and weight reduction of the lens barrel and the image forming performance when image plane correction is performed when camera shake occurs. Further, since the second lens group RG2 has two or more lenses, the aberration generated in the second lens group RG2 can be reduced by adjusting the curvature radius of each lens surface. The configuration of the second lens group RG2 only needs to have two or more lenses, and all the lenses may be bonded together to form one cemented lens. Note that at least a part of the second lens group RG2 may be moved so as to have at least a component in a direction substantially perpendicular to the optical axis. Therefore, at least a part of the second lens group RG2 moves in a direction substantially perpendicular to the optical axis, moves in an oblique direction with respect to the optical axis, or draws an arc with respect to the direction perpendicular to the optical axis. You may move on.

  Further, in the zoom optical system ZL, the first lens group RG1 and the third lens group RG3 move in the object direction when the lens position changes from the wide-angle end state to the telephoto end state, and the image plane It is desirable that the amount of movement with respect to be equal. As described above, during zooming from the wide-angle end state to the telephoto end state, the first lens group RG1 and the third lens group RG3 are moved in the object direction, thereby reducing the overall length at the wide-angle end and various aberrations. Good correction can be achieved at the same time. Further, by making the movement amounts of the first lens group RG1 and the third lens group RG3 equal, the first lens group RG1 and the third lens group RG3 can be integrated. By adopting such a structure, the change in mutual decentration between the first lens group RG1 and the third lens group RG3 can be kept small during zooming from the wide-angle end state to the telephoto end state. Performance degradation can be alleviated.

  The variable magnification optical system ZL has a radius of curvature of the object side surface of the third A lens (for example, the negative meniscus lens RL31 in FIG. 1), which is the lens located closest to the object side of the third lens group RG3, as r3AR1. When the radius of curvature of the image side surface of the 3A lens is r3AR2, it is desirable to satisfy the following conditional expression (1).

-2.20 <(r3AR1-r3AR2) / (r3AR1 + r3AR2) <0.55 (1)

  Conditional expression (1) defines the relationship between the radius of curvature of the object-side surface of the 3A lens and the radius of curvature of the image-side surface. If the upper limit of conditional expression (1) is exceeded, the positive refractive power of the 3A lens tends to increase, making it difficult to correct spherical aberration and coma at the telephoto end. Further, when image plane correction is performed when camera shake occurs, the decentration coma aberration becomes excessive at the telephoto end, which makes it difficult to correct. In addition, the effect of this invention can be made more reliable by making the upper limit of conditional expression (1) into 0.35, 0.29, 0.22. On the other hand, if the lower limit of conditional expression (1) is not reached, the negative refractive power of the 3A lens tends to increase, and the height of off-axis peripheral rays increases on the image plane side from the 3A lens. This is not preferable because the cylinder is enlarged. In addition, when image plane correction at the time of occurrence of camera shake is performed, the decentered image plane taole at the wide angle end becomes excessive and correction becomes difficult, which is not preferable. In addition, the effect of this invention can be made more reliable by making the minimum of conditional expression (1) into -1.20, -0.50, -0.30.

  Further, it is desirable that the variable magnification optical system ZL satisfies the following conditional expression (2) when the focal length in the wide-angle end state is fw.

0.50 <(-r3AR1) / fw <5.00 (2)

  Conditional expression (2) defines the relationship between the radius of curvature of the object-side surface of the 3A lens and the focal length in the wide-angle end state of the variable magnification optical system ZL. If the upper limit value of conditional expression (2) is exceeded, the refraction angle of off-axis peripheral rays in the 3A lens increases at the wide-angle end. As a result, higher-order coma aberration and curvature of field occur and correction becomes difficult, which is not preferable. Further, when image plane correction is performed when camera shake occurs, the sagittal curvature of field due to decentering becomes excessive at the wide-angle end, making correction difficult, which is not preferable. In addition, the effect of this invention can be made more reliable by making the upper limit of conditional expression (2) into 3.20, 2.50, 1.20. On the other hand, if the lower limit of conditional expression (2) is not reached, the radius of curvature of the object-side surface of the 3A lens becomes small, and the spherical aberration and coma aberration at the telephoto end become excessive, which is not preferable. Further, when image position correction at the time of occurrence of camera shake is performed, the decentered coma aberration becomes excessive at the telephoto end, which is not preferable because correction becomes difficult. Furthermore, when the radius of curvature of the object side surface of the 3A lens becomes too small, there arises a problem that the most image side lens of the second lens group RG2 and the 3A lens interfere with each other in the peripheral portion of the lens outer diameter. In order to avoid this, if the distance between the second lens group RG2 and the third lens group RG3 is increased, it becomes difficult to correct curvature of field and coma at the wide-angle end. In addition, this is not preferable because it leads to an increase in size at the wide-angle end. In addition, the effect of this invention can be made more reliable by making the minimum of conditional expression (2) into 0.60, 0.80, 1.00.

  By satisfying both of the conditional expressions (1) and (2), the zooming optical system ZL can satisfactorily correct aberration fluctuations when performing image plane correction when camera shake occurs. Further, as described above, the 3A lens is effective for correcting aberrations when image position correction is performed when camera shake occurs. However, the sensitivity tends to increase. For this reason, when such a lens is arranged as a single lens group, it is not easy to adjust the sensitivity at the time of manufacture, and a deviation occurs between the lens groups due to mechanical clearance when moving the lens group during zooming. The optical characteristics may be deteriorated. However, the highly sensitive 3A lens like the variable magnification optical system ZL is fixedly arranged in the third lens group RG3, so that sensitivity adjustment at the time of manufacture is easy and manufacturing errors are reduced. The sensitivity between the second lens group GR2 and the third lens group GR3 can be reduced, and the deterioration of optical performance against mechanical play due to clearance can be alleviated, and good optical performance can be achieved in the entire zoom range. Obtainable.

  In this variable magnification optical system ZL, the third A lens may be composed of either a positive lens or a negative lens, but is desirably composed of a negative lens. By adopting such a configuration, various aberrations of the positive refractive power component generated in the first lens group RG1 and the third lens group RG3 when the image plane correction at the time of occurrence of camera shake is performed can be applied to the third A lens. Can be canceled by various aberrations of the negative refractive power component, and high aberration correction capability can be exhibited as a whole.

  Further, in this variable magnification optical system ZL, when the combined focal length of the first lens group RG1, the second lens group RG2, and the third lens group RG3 in the wide-angle end state is fw123, the following conditional expression It is desirable to satisfy (3) and (4).

0.03 <(d12t-d12w) / fw123 <0.32 (3)
0.03 <(d23w−d23t) / fw123 <0.32 (4)

  Conditional expression (3) defines the amount of change in the distance between the first lens group RG1 and the second lens group RG2 when the zooming optical system ZL zooms from the wide-angle end state to the telephoto end state. is there. Conditional expression (4) defines the amount of change in the distance between the second lens group RG2 and the third lens group RG3 when the zooming optical system ZL zooms from the wide-angle end state to the telephoto end state. Is. By satisfying the conditional expressions (3) and (4), the zooming optical system ZL can satisfactorily change the aberration when the image plane is corrected when the camera shake occurs while ensuring a large zooming ratio. It can be corrected.

  If the upper limit value of conditional expression (3) is exceeded, the distance between the first lens group RG1 and the second lens group RG2 at the telephoto end becomes large, and it becomes difficult to correct spherical aberration and coma at the telephoto end. Further, when image plane correction is performed when camera shake occurs, the decentration coma aberration becomes excessive at the telephoto end, which makes it difficult to correct. In addition, the effect of this invention can be made more reliable by making the upper limit of conditional expression (3) into 0.29, 0.26, 0.23. On the other hand, if the lower limit value of conditional expression (3) is not reached, the variation in spherical aberration becomes large and the correction becomes difficult at the time of zooming from the wide-angle end state to the telephoto end state. In addition, the effect of this invention can be made more reliable by making the minimum of conditional expression (3) into 0.10, 0.14, 0.18.

  If the upper limit value of conditional expression (4) is exceeded, the distance between the second lens group RG2 and the third lens group RG3 at the wide angle end becomes large, and the ray height of the off-axis peripheral rays at the wide angle end at the third lens group RG3 becomes large. growing. This makes it difficult to correct curvature of field and coma at the wide-angle end, which is not preferable. Further, when image plane correction is performed when camera shake occurs, off-axis peripheral rays at the wide-angle end greatly vary in the third lens group RG3, making it difficult to correct the eccentric image plane taole. In addition, the effect of this invention can be made more reliable by making the upper limit of conditional expression (4) 0.29, 0.26, 0.23. On the other hand, if the lower limit value of conditional expression (4) is not reached, it is not preferable because fluctuations in field curvature become large and correction becomes difficult when zooming from the wide-angle end state to the telephoto end state. In addition, the effect of this invention can be made more reliable by making the minimum of conditional expression (4) into 0.10, 0.14, 0.18.

  Further, in this variable magnification optical system ZL, the amount of movement of the first lens group RG1 relative to the image plane when the lens position changes from the wide-angle end state to the telephoto end state is Δx1, and the first lens group RG1 in the wide-angle end state. When the combined focal length of the second lens group RG2 and the third lens group RG3 is fw123, it is desirable that the following conditional expression (5) is satisfied.

0.35 <| Δx1 | / fw123 <1.50 (5)

  Conditional expression (5) defines the amount of movement of the first lens group RG1 relative to the image plane when the zooming optical system ZL zooms from the wide-angle end state to the telephoto end state. The zooming optical system ZL satisfies the conditional expression (5), so that the zooming ratio exceeds 5 times while maintaining good imaging performance when the image plane is corrected when camera shake occurs. It is possible to realize a highly variable magnification optical system.

  If the upper limit value of conditional expression (5) is exceeded, the lateral magnification (absolute value) of the first lens group RG1 and the third lens group RG3 at the telephoto end of the variable magnification optical system ZL increases, and spherical aberration and It becomes difficult to correct coma. Further, when image plane correction is performed when camera shake occurs, the decentration coma aberration becomes excessive at the telephoto end, making correction difficult, which is not preferable. There is also a problem that the amount of extension of the first lens group RG1 becomes large and the mechanical configuration becomes difficult. In order to compensate for this, it is necessary to increase the optical total length at the wide-angle end, but this is not preferable because the total length of the lens barrel increases. In addition, the effect of this invention can be made more reliable by making the upper limit of conditional expression (5) into 1.25, 1.10, 0.95. On the other hand, if the lower limit of conditional expression (5) is not reached, the amount of zooming earned by the rear lens group RG will be small, making it difficult to obtain a predetermined zooming ratio. In order to compensate for this, if the refractive powers of the first lens group RG1, the second lens group RG2, and the third lens group RG3 are increased, it becomes difficult to correct spherical aberration and coma at the telephoto end. Further, the imaging performance is deteriorated due to a manufacturing error such as decentration between lens groups, that is, the decentration coma aberration and the decentered image plane taole increase. In addition, the effect of this invention can be made more reliable by making the minimum of conditional expression (5) into 0.50, 0.62, 0.75.

  Further, the variable magnification optical system ZL sets the focal length of the second lens group RG2 to f2, and the combined focal length of the first lens group RG1, the second lens group RG2, and the third lens group RG3 in the wide-angle end state to fw123. It is desirable that the following conditional expression (6) is satisfied.

0.50 <(− f2) / fw123 <1.60 (6)

  Conditional expression (6) defines the focal length of the second lens group RG2 of the variable magnification optical system ZL. By satisfying this conditional expression (6), the present variable magnification optical system ZL alleviates optical performance degradation due to manufacturing errors while maintaining good imaging performance when image plane correction is performed when camera shake occurs. can do. If the upper limit value of conditional expression (6) is exceeded, the refractive power of the second lens group RG2 becomes small, and the image stabilization correction coefficient (image position movement amount in the direction perpendicular to the optical axis ÷ vibration group movement in the direction perpendicular to the optical axis). Amount) becomes smaller. Accordingly, it is not preferable to increase the movement amount of the image stabilizing group because the decentration coma aberration and the decentered image plane taole at the telephoto end are significantly deteriorated. In addition, there is a problem that the lens barrel becomes large. In addition, the effect of this invention can be made more reliable by making the upper limit of conditional expression (6) into 1.45, 1.32 and 1.20. On the other hand, if the lower limit of conditional expression (6) is not reached, the refractive power of the second lens group RG2 becomes large, and it becomes difficult to correct field curvature and coma at the wide-angle end. Further, it is not preferable because deterioration of imaging performance due to manufacturing errors such as decentration between lens groups, that is, deterioration of the decentered image plane is significant. In addition, the effect of this invention can be made more reliable by making the minimum of conditional expression (6) into 0.62, 0.80, and 0.88.

  In this variable magnification optical system ZL, the front lens group FG includes, in order from the object side, a front partial lens group FG1 having a positive refractive power and a rear partial lens group FG2 having a negative refractive power, When the lens position state changes from the wide-angle end state to the telephoto end state, it is desirable that the distance between the front partial lens group FG1 and the rear partial lens group FG2 increases. By adopting such a configuration, a large zoom ratio can be obtained, and high zoom ratio of the entire system can be achieved. Further, the zoom ratio of the first lens group RG1, the second lens group RG2, and the third lens group RG3 of the rear lens group RG can be reduced, and image formation is performed when image plane correction is performed when camera shake occurs. It is possible to improve performance.

  In the variable magnification optical system ZL, it is desirable that the rear lens group FG2 has at least one aspheric surface. Thereby, field curvature and distortion at the wide-angle end can be corrected well, and a wide angle of view at the wide-angle end is possible.

  In the variable magnification optical system ZL, it is desirable that the second lens group RG2 has at least one aspheric surface. Thereby, the spherical aberration at the telephoto end and the decentration coma aberration at the telephoto end when the image plane correction at the time of the occurrence of camera shake can be favorably corrected.

  In the zoom optical system ZL, it is desirable that the third lens group RG3 has at least one aspheric surface. As a result, it is possible to satisfactorily correct the decentered image plane taole at the wide angle end when the image plane correction at the time of occurrence of camera shake is performed while satisfactorily correcting the image plane aberration and distortion at the wide angle end.

  In the variable magnification optical system ZL, the second lens group RG2 is preferably composed of a cemented lens in which a biconcave lens and a positive meniscus lens are cemented. With this configuration, the principal point position of the second lens group RG2 can be arranged on the image side, and the principal point interval between the second lens group RG2 and the third lens group RG3 can be reduced. This makes it possible to reduce the decentered image plane tilt at the wide-angle end of the variable magnification optical system ZL when performing image plane correction when camera shake occurs. In addition, there is an effect of reducing the diameter of the third lens group RG3.

  Further, when the second lens group RG2 is composed of a cemented lens in this way, the radius of curvature of the cemented surface of the cemented lens of the second lens group RG2 is Rs, and the focal length of the second lens group RG2 is f2. It is desirable that the following conditional expression (7) is satisfied.

0.200 <Rs / (− f2) <3,000 (7)

  Conditional expression (7) defines the curvature of the cemented surface of the cemented lens of the second lens group RG2 with respect to the focal length of the second lens group RG2. Exceeding either the upper limit or the lower limit of conditional expression (7) is not preferable because it is difficult to correct spherical aberration, and decentration aberration is increased when image plane correction is performed when camera shake occurs. If the upper limit value of conditional expression (7) is exceeded, the curvature of the cemented surface becomes small and the positive spherical aberration becomes excessive, so that correction becomes difficult. In addition, the effect of this invention can be made more reliable by making the upper limit of conditional expression (7) into 1.500 and 1.000. On the other hand, if the lower limit value of conditional expression (7) is not reached, the curvature of the cemented surface increases and negative spherical aberration becomes excessive, making correction difficult. In addition, the effect of this invention can be made more reliable by making the minimum of conditional expression (7) into 0.400 and 0.800.

  In this case, when the refractive index for the d-line of the positive meniscus lens in the second lens group RG2 is Np and the refractive index for the d-line of the biconcave lens in the second lens group RG2 is Nn, the following conditional expression ( It is desirable to satisfy 8).

-0.150 <Np-Nn <0.150 (8)

  Conditional expression (8) defines the relationship between the refractive index of the biconcave lens of the second lens group RG2 with respect to the d-line and the refractive index of the positive meniscus lens with respect to the d-line. Exceeding either the upper limit or the lower limit of conditional expression (8) is not preferable because the decentered image plane taole when the image plane correction is performed at the time of occurrence of camera shake becomes large and the correction becomes difficult. In order to secure the effect of the present invention, it is preferable that the upper limit of conditional expression (8) is 0.100, 0.045, 0.020, and the lower limit of conditional expression (8) is −0. 100, −0.030 is preferable.

  Further, when the Abbe number of the biconcave lens of the second lens group RG2 is νn and the Abbe number of the positive meniscus lens of the second lens group RG2 is νp, it is desirable to satisfy the following conditional expression (9).

5.000 <νn−νp <30.000 (9)

  Conditional expression (9) defines the relationship between the Abbe number of the biconcave lens of the second lens group RG2 and the Abbe number of the positive meniscus lens. Exceeding either the upper limit or the lower limit of conditional expression (9) is not preferable because chromatic aberration generated in the second lens group RG2 becomes excessive and correction becomes difficult. In order to secure the effect of the present invention, it is preferable that the upper limit of conditional expression (9) is 25.000, 19.000, and the lower limit of conditional expression (9) is 8.000, 11. 500 is preferable.

  By satisfying the conditional expressions (7) to (9) as described above, various aberrations and decentration aberrations at the time of occurrence of camera shake can be suppressed, and good imaging performance can be obtained.

  The variable magnification optical system ZL preferably has an aperture stop S on the object side of the second lens group RG2, that is, in the vicinity of the first lens group RG1 or in the first lens group RG1. By adopting such a structure, it is possible to achieve both a reduction in the front lens diameter and good correction of various aberrations.

  9 and 10 show a configuration of an electronic still camera 1 (hereinafter simply referred to as a camera) as an optical apparatus including the above-described variable magnification optical system ZL. In the camera 1, when a power button (not shown) is pressed, a shutter (not shown) of the photographing lens (variable magnification optical system ZL) is opened, and light from a subject (not shown) is condensed by the variable magnification optical system ZL. The image is formed on an image sensor C (for example, a CCD or a CMOS) disposed on the surface I. The subject image formed on the image sensor C is displayed on the liquid crystal monitor 2 disposed behind the camera 1. The photographer determines the composition of the subject image while looking at the liquid crystal monitor 2, and then presses the release button 3 to photograph the subject image with the image sensor C and records and saves it in a memory (not shown).

  The camera 1 includes an auxiliary light emitting unit 4 that emits auxiliary light when the subject is dark, and a wide (W) for changing the magnification optical system ZL from the wide-angle end state (W) to the telephoto end state (T). ) -Tele (T) button 5 and function buttons 6 used for setting various conditions of the camera 1 are arranged. 10 illustrates a compact type camera in which the camera 1 and the variable magnification optical system ZL are integrally formed. However, as an optical device, a lens barrel having the variable magnification optical system ZL and a camera body main body are attached and detached. A possible single-lens reflex camera may be used.

  In the above description and the embodiments described below, the overall configuration shows a two-group configuration (front lens group FG and rear lens group RG), and the rear lens group shows a variable power optical system ZL with a three-group configuration. The above-described configuration conditions and the like can be applied to the front lens group FG as one group configuration, or to other group configurations such as the fourth group and the fifth group as a whole. For example, in the present embodiment, the lens system of the rear lens group RG is composed of three movable groups, but another lens group is added between each lens group, or on the image side or object side of the lens system. It is also possible to add another lens group adjacent to each other. Further, a lens or a lens group having a weak refractive power may be added to the most object side or the most image plane side.

  Alternatively, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. In this case, the focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (such as an ultrasonic motor). In particular, in the case of the variable magnification optical system ZL having a total of five groups, it is preferable that at least a part of the front lens group FG is a focusing lens group. Further, when the front lens group FG is composed of one lens group, the front lens group FG, the first lens group RG1 of the rear lens group RG, a part of the first lens group RG1, or the third lens group RG3 performs focusing. Is preferred.

  Further, in the present embodiment, in order to prevent a shooting failure due to an image blur caused by a camera shake or the like that is likely to occur in a high-magnification optical system, a blur detection system that detects a blur of the optical system and a driving unit are used as a lens system. In combination, the entire or part of one of the lens groups constituting the lens system is decentered as an anti-vibration lens group, so that the image blur (image caused by the blur of the lens system detected by the blur detection system) It is possible to correct image blur by shifting the image by vibrating the anti-vibration lens group so that it has a component in the direction perpendicular to the optical axis to correct the fluctuations in the surface position). It is. In particular, as described above, it is preferable that at least a part of the second lens group RG2 constituting the rear lens group RG is an anti-vibration lens group. Further, the first lens group RG1 of the rear lens group RG may be used as an anti-vibration lens group.

  In the above description, at least one aspheric lens is provided in either the second lens group RG2 or the third lens group RG3 of the rear lens group RG, or the rear lens group FG2 of the front lens group FG. Although the case of arrangement is shown, the lens surfaces of other lens groups may be aspherical. At this time, any one of an aspheric surface by grinding, a glass mold aspheric surface in which glass is formed into an aspheric shape by a mold, and a composite aspheric surface in which resin is formed in an aspheric shape on the surface of the glass may be used.

  The aperture stop S is preferably disposed on the object side of the second lens group RG2 as described above. However, the role of the aperture stop may be substituted by a lens frame without providing a member as an aperture stop.

  Furthermore, an antireflection film having a high transmittance in a wide wavelength region is applied to each lens surface, thereby reducing flare and ghost and achieving high optical performance with high contrast.

  In addition, in order to explain the present invention in an easy-to-understand manner, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the configuration of the variable magnification optical system ZL according to the present embodiment. The refractive power distribution of the variable magnification optical system ZL and the focal point from the wide-angle end state (W) to the telephoto end state (T). The state of movement of each lens group in the change of the distance state is indicated by an arrow below FIG. The zoom optical system ZL1 in FIG. 1 includes, in order from the object side, a front partial lens group FG1 having a positive refractive power, a rear partial lens group FG2 having a negative refractive power, and a first refractive power having a positive refractive power. The lens group RG1 includes a second lens group RG2 having a negative refractive power, and a third lens group RG3 having a positive refractive power. In the variable magnification optical system ZL1, when the lens position changes from the wide-angle end state to the telephoto end state, the air gap between the front partial lens group FG1 and the rear partial lens group FG2 increases, and the rear partial lens group FG2 The air gap between the first lens group RG1 decreases, the air gap between the first lens group RG1 and the second lens group RG2 increases from d12w to d12t, and the air between the second lens group RG2 and the third lens group RG3. The distance between the lens groups changes so that the distance decreases from d23w to d23t, and the second lens group RG2 is moved so as to have a component orthogonal to the optical axis, thereby correcting the image position when camera shake occurs. . The air gap d12w or d12t between the first lens group RG1 and the second lens group RG2 in the wide-angle end state or the telephoto end state corresponds to d3 in the table showing the values of the specifications of each embodiment, and is in the wide-angle end state. Alternatively, the air gap d23w or d23t between the second lens group RG2 and the third lens group RG3 in the telephoto end state corresponds to d4 in the table showing the values of the specifications in each embodiment.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangential plane of the apex of each aspheric surface to each aspheric surface at height y. Is S (y), r is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and An is the nth-order aspheric coefficient, and is expressed by the following equation (a). . In the following examples, “E−n” indicates “× 10 ⁻ⁿ ”.

S (y) = (y ² / r) / {1+ (1−κ × y ² / r ² ) ^1/2 }
^{+ A4 × y 4 + A6 ×} y 6 + A8 × y 8 + A10 × y 10 (a)

  In each embodiment, the secondary aspheric coefficient A2 is zero. In the table of each example, an aspherical surface is marked with * on the left side of the surface number.

[First embodiment]
FIG. 1 is a diagram showing a configuration of a variable magnification optical system ZL1 according to the first example. In the variable magnification optical system ZL1 in FIG. 1, the front lens group FG1 includes, in order from the object side, a cemented lens of a negative meniscus lens FL11 having a convex surface facing the object side and a biconvex lens FL12, and a convex surface facing the object side. And a positive meniscus lens FL13. The rear partial lens group FG2 includes, in order from the object side, a negative meniscus lens FL21 having a convex surface directed toward the object side, a biconcave lens FL22, a biconvex lens FL23, and a biconcave lens FL24, and is the most object side of the rear partial lens group FG2. The negative meniscus lens FL21 located at is a composite aspherical lens in which an aspherical surface is formed by providing a resin layer on the object-side lens surface.

  The first lens group RG1 includes, in order from the object side, a cemented lens of a negative meniscus lens RL11 and a biconvex lens RL12 having a convex surface facing the object side, and a biconvex lens RL13. The second lens group RG2 includes, in order from the object side, a cemented lens of a biconcave lens RL21 and a positive meniscus lens RL22 having a convex surface facing the object side. The biconcave lens RL21 located closest to the object side of the second lens group RG2. Is a glass mold type aspheric lens having an aspheric lens surface on the object side. The third lens group RG3 includes, in order from the object side, a negative meniscus lens RL31 (third A lens) having a concave surface directed toward the object side, a biconvex lens RL32, a biconvex lens RL33, and a negative meniscus lens RL34 having a concave surface directed toward the object side. The second biconvex lens RL32 from the object side of the third lens group RG3 is a glass mold type aspheric lens having an aspheric lens surface on the image side.

  The aperture stop S is located between the rear partial lens group FG2 and the first lens group RG1, and moves together with the first lens group RG1 upon zooming from the wide-angle end state to the telephoto end state. The flare stop FS is located between the second lens group RG2 and the third lens group RG3, and moves together with the second lens group RG2 upon zooming from the wide-angle end state to the telephoto end state. Focusing from a long distance to a short distance is performed by moving the rear partial lens group FG2 in the object direction.

  In addition, in a lens where the focal length of the entire system is f and the image stabilization correction coefficient (ratio of the moving amount of the image position on the imaging surface to the moving amount of the moving lens group in shake correction) is K, the rotational blurring of the angle θ In order to correct this, the moving lens group for blurring correction may be moved in the direction orthogonal to the optical axis by (f · tan θ) / K. In the wide-angle end state of the first embodiment, the image stabilization correction coefficient is 1.27 and the focal length is 18.4 (mm). Therefore, the second correction for correcting the rotation blur of 0.70 ° is performed. The moving amount of the lens group RG2 is 0.18 (mm). Further, in the telephoto end state of the first embodiment, the image stabilization correction coefficient is 1.88 and the focal length is 102.5 (mm), so that it is necessary to correct the rotation blur of 0.30 °. The amount of movement of the second lens group RG2 is 0.29 (mm).

  Table 1 below lists values of specifications of the first embodiment. In Table 1, f represents a focal length, FNO represents an F number, ω represents a half field angle, and Bf represents a back focus. Furthermore, the surface number is the order of the lens surfaces from the object side along the direction of travel of the light beam, the surface interval is the distance on the optical axis from each optical surface to the next optical surface, and the refractive index and Abbe number are each The value for the d-line (λ = 587.6 nm) is shown. Here, “mm” is generally used for the focal length f, the radius of curvature, the surface interval, and other length units listed in all the following specifications, but the optical system is proportionally enlarged or reduced. However, since the same optical performance can be obtained, it is not limited to this. The radius of curvature of 0.0000 indicates a plane, and the refractive index of air of 1.0000 is omitted. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 1)
Surface number Curvature radius Surface spacing Abbe number Refractive index
1 133.5109 1.8000 23.78 1.846660
2 59.3606 6.8598 60.68 1.603110
3 -727.9264 0.1000
4 49.0605 4.4000 55.52 1.696800
5 164.8896 (d1)
* 6 90.3741 0.2000 38.09 1.553890
7 90.0000 1.2500 42.72 1.834810
8 12.0286 5.6915
9 -44.7400 1.0000 42.72 1.834810
10 32.2623 0.3668
11 22.9010 5.3262 23.78 1.846660
12 -31.6117 0.3000
13 -26.6887 1.0000 42.72 1.834810
14 220.7828 (d2)
15 0.0000 0.4000
16 29.5250 1.1218 25.43 1.805180
17 15.2234 4.1000 64.12 1.516800
18 -45.5625 0.2000
19 28.7361 2.7532 82.56 1.497820
20 -50.7022 (d3)
* 21 -42.7919 1.0000 40.94 1.806100
22 16.6378 2.3929 23.78 1.846660
23 76.8561 3.0000
24 0.0000 (d4)
25 -19.1700 1.0000 60.67 1.603112
26 -33.0544 0.1000
27 98.3022 5.4705 61.18 1.589130
* 28 -19.0083 0.3546
29 44.6448 7.2500 70.45 1.487490
30 -17.0465 1.4977 34.96 1.801000
31 -831.5220 (Bf)

Wide angle end Intermediate focal length Telephoto end
f = 18.4 to 54.8 to 102.5
FNO = 3.6 to 5.1 to 5.8
ω = 38.7 to 13.8 to 7.5
Image height = 14.0 to 14.0 to 14.0
Total length = 133.416 to 159.151 to 175.754
Bf = 38.760 to 56.839 to 66.557

[Focal length of each lens group]
Lens group Start surface Focal length FG1 1 76.442
FG2 6 -12.285
RG1 15 22.309
RG2 21 -36.050
RG3 25 45.446

[Focal length of front lens group FG and rear lens group RG]
Lens group Start surface Wide angle end Intermediate focal length Telephoto end FG 1 -16.927 -27.504 -41.713
RG 15 31.503 29.379 28.410

  In the first embodiment, the sixth, twenty-first, and twenty-eighth lens surfaces are aspherical. Table 2 below shows aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 2)
κ A4 A6 A8 A10
6th surface 18.9814 1.59140E-06 -4.31690E-08 9.76030E-11 -2.05830E-13
Side 21 -6.3179 -6.85830E-06 2.93960E-08 0.00000E + 00 0.00000E + 00
28th surface 0.9924 1.13210E-05 1.12040E-08 1.10370E-10 -5.58920E-13

  In the first embodiment, the axial air distance d1 between the front partial lens group FG1 and the rear partial lens group FG2, the axial air distance d2 between the rear partial lens group FG2 and the first lens group RG1, and the first lens group RG1. The axial air distance d3 between the second lens group RG2 and the axial air distance d4 between the second lens group RG2 and the third lens group RG3 changes during zooming. Table 3 below shows variable intervals at the respective focal lengths in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(Table 3)
Wide angle end Intermediate focal length Telephoto end
d1 1.801 23.137 34.768
d2 21.427 7.747 3.002
d3 1.950 7.029 8.841
d4 10.542 5.463 3.652

  Table 4 below shows values corresponding to the conditional expressions in the first embodiment. In Table 4, r3AR1 is the radius of curvature of the object side surface of the 3A lens, r3AR2 is the radius of curvature of the image side surface of the 3A lens, and fw is in the wide angle end state of the entire variable power optical system. D12w is the distance between the first lens group RG1 and the second lens group RG2 in the wide-angle end state, d23w is the distance between the second lens group RG2 and the third lens group RG3, and d12t is in the telephoto end state. The distance between the first lens group RG1 and the second lens group RG2, d23t is the distance between the second lens group RG2 and the third lens group RG3, and fw123 is the first lens group RG1 and the second lens group in the wide-angle end state. The combined focal length of RG2 and the third lens group RG3, Δx1 is the amount of movement of the first lens group RG1 with respect to the image plane during zooming from the wide-angle end state to the telephoto end state, and f2 is the second lens group RG2. The point distance, Rs is the radius of curvature of the cemented surface of the cemented lens of the second lens group RG2, Np is the refractive index with respect to the d-line of the positive meniscus lens of the second lens group RG2, and Nn is both of the second lens group RG2. The refractive index with respect to the d-line of the concave lens, νp represents the Abbe number of the positive meniscus lens of the second lens group RG2, and νn represents the Abbe number of the biconcave lens of the second lens group RG2. The description of this symbol is the same in the following embodiments.

(Table 4)
(1) (r3AR1−r3AR2) / (r3AR1 + r3AR2) = − 0.27
(2) (-r3AR1) /fw=1.04
(3) (d12t-d12w) /fw123=0.22
(4) (d23w−d23t) /fw123=0.22
(5) | Δx1 | /fw123=0.88
(6) (−f2) /fw123=1.14
(7) Rs / (− f2) = 0.46
(8) Np-Nn = 0.04
(9) νn−νp = 17.16

  FIG. 2A shows an aberration diagram in the infinite focus state in the wide-angle end state of the first embodiment, and FIG. 3 shows an aberration diagram in the infinite focus state in the intermediate focal length state. FIG. 4A shows an aberration diagram in the infinitely focused state in the state. Further, FIG. 2B shows a meridional lateral aberration diagram when the blur correction is performed with respect to the rotation blur of 0.70 ° in the infinity photographing state at the wide-angle end state of the first example, and FIG. FIG. 4B shows a meridional lateral aberration diagram when blur correction is performed for 0.30 ° rotational blur in the infinity shooting state at the telephoto end state.

  In each aberration diagram, FNO represents an F number, Y represents an image height, d represents a d-line (λ = 587.6 nm), and g represents a g-line (λ = 435.6 nm). In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. The description of this aberration diagram is the same in the following examples. As is apparent from the respective aberration diagrams, in the first embodiment, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

[Second Embodiment]
FIG. 5 is a diagram showing a configuration of the variable magnification optical system ZL2 according to the second example. In the variable magnification optical system ZL2 of FIG. 5, the front lens group FG1 includes, in order from the object side, a cemented lens of a negative meniscus lens FL11 having a convex surface facing the object side and a positive meniscus lens FL12 having a convex surface facing the object side. , And a positive meniscus lens FL13 having a convex surface facing the object side. The rear partial lens group FG2 includes, in order from the object side, a negative meniscus lens FL21 having a convex surface directed toward the object side, a biconcave lens FL22, a biconvex lens FL23, and a biconcave lens FL24, and is the most object side of the rear partial lens group FG2. The negative meniscus lens FL21 located at is a composite aspherical lens in which an aspherical surface is formed by providing a resin layer on the object-side lens surface.

  The first lens group RG1 includes, in order from the object side, a biconvex lens RL11, and a cemented lens of a biconvex lens RL12 and a negative meniscus lens RL13 having a concave surface facing the object side. The second lens group RG2 includes, in order from the object side, a cemented lens of a positive meniscus lens RL21 having a concave surface directed toward the object side and a biconcave lens RL22, and a biconcave lens RL22 positioned closest to the image side of the second lens group RG2. Is a glass mold type aspherical lens having an aspherical lens surface on the image side. The third lens group RG3 includes, in order from the object side, a positive meniscus lens RL31 (third A lens) having a concave surface directed toward the object side, a biconvex lens RL32, and a negative meniscus lens RL34 having a concave surface directed toward the object side. The second biconvex lens RL32 from the object side of the third lens group RG3 is a glass mold type aspheric lens having an aspheric lens surface on the image side.

  The aperture stop S is located between the rear partial lens group FG2 and the first lens group RG1, and moves together with the first lens group RG1 upon zooming from the wide-angle end state to the telephoto end state. The flare stop FS is located between the second lens group RG2 and the third lens group RG3, and moves together with the second lens group RG2 upon zooming from the wide-angle end state to the telephoto end state. Focusing from a long distance to a short distance is performed by moving the rear partial lens group FG2 in the object direction.

  In the wide-angle end state of the second embodiment, the image stabilization correction coefficient is 1.31, and the focal length is 18.4 (mm). Therefore, the second correction for correcting the rotation blur of 0.70 ° is performed. The moving amount of the lens group RG2 is 0.17 (mm). In the telephoto end state of the second embodiment, the image stabilization correction coefficient is 1.95 and the focal length is 131.0 (mm). The amount of movement of the second lens group RG2 is 0.35 (mm).

  Table 5 below lists values of specifications of the second embodiment.

(Table 5)
Surface number Curvature radius Surface spacing Abbe number Refractive index
1 133.6773 1.8000 23.78 1.846660
2 66.6853 8.0000 63.38 1.618000
3 35123.1440 0.1000
4 59.1950 5.0000 55.52 1.696800
5 171.3580 (d1)
* 6 374.1390 0.2000 38.09 1.553890
7 120.0000 1.2500 49.61 1.772500
8 13.5130 6.2000
9 -86.7930 1.0000 45.30 1.795000
10 38.5865 0.1000
11 24.5713 4.6327 23.78 1.846660
12 -54.7598 0.6000
13 -31.0174 1.0028 46.58 1.804000
14 137.4344 (d2)
15 0.0000 1.5000
16 49.2997 2.5000 64.12 1.516800
17 -35.7453 0.2000
18 29.0138 3.5000 70.45 1.487490
19 -19.2874 1.0000 25.68 1.784720
20 -47.3217 (d3)
21 -42.0566 2.3500 28.69 1.795040
22 -12.7803 0.9000 45.30 1.795000
* 23 62.4551 4.0000
24 0.0000 (d4)
25 -55.0000 2.2587 70.45 1.487490
26 -28.0000 0.1394
27 49.7706 4.1000 60.68 1.603110
* 28 -31.9448 0.3846
29 757.7542 5.0000 82.56 1.497820
30 -18.3074 1.4000 37.17 1.834000
31 -176.6587 (Bf)

Wide angle end Intermediate focal length Telephoto end
f = 18.4 to 55.3 to 131.0
FNO = 3.6 to 5.1 to 5.8
ω = 38.7 to 13.8 to 6.0
Image height = 14.0 to 14.0 to 14.0
Total length = 131.945 to 162.180 to 182.661
Bf = 38.400 to 56.231 to 60.516

[Focal length of each lens group]
Lens group Start surface Focal length FG1 1 94.116
FG2 6 -13.955
RG1 15 23.868
RG2 21 -31.186
RG3 25 34.949

[Focal length of front lens group FG and rear lens group RG]
Lens group Start surface Wide angle end Intermediate focal length Telephoto end FG 1 -18.843 -30.191 -61.077
RG 15 31.938 30.439 29.078

  In the second embodiment, the sixth, twenty-third, and twenty-eighth lens surfaces are formed in an aspheric shape. Table 6 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 6)
κ A4 A6 A8 A10
6th surface 0.0000 1.79250E-05 -5.06070E-08 1.12800E-10 -1.16750E-13
Side 23 0.0000 -6.52410E-06 -8.63670E-09 0.00000E + 00 0.00000E + 00
28th surface -0.7531 -2.87950E-06 -2.57090E-09 -3.65880E-11 0.00000E + 00

  In the second embodiment, the axial air gap d1 between the front partial lens group FG1 and the rear partial lens group FG2, the axial air gap d2 between the rear partial lens group FG2 and the first lens group RG1, and the first lens group RG1. The axial air distance d3 between the second lens group RG2 and the axial air distance d4 between the second lens group RG2 and the third lens group RG3 changes during zooming. Table 7 below shows variable intervals at the respective focal lengths in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(Table 7)
Wide angle end Intermediate focal length Telephoto end
d1 1.800 28.000 50.000
d2 21.000 7.203 1.400
d3 2.400 7.787 10.380
d4 9.227 3.840 1.247

  Table 8 below shows values corresponding to the conditional expressions in the second embodiment.

(Table 8)
(1) (r3AR1−r3AR2) / (r3AR1 + r3AR2) = 0.33
(2) (−r3AR1) /fw=2.99
(3) (d12t-d12w) /fw123=0.25
(4) (d23w−d23t) /fw123=0.25
(5) | Δx1 | /fw123=0.69
(6) (−f2) /fw123=0.98
(7) Rs / (− f2) = 0.41
(8) Np-Nn = 0.00
(9) νn−νp = 16.61

  FIG. 6A shows an aberration diagram in the infinite focus state in the wide-angle end state of this second embodiment, and FIG. 7 shows an aberration diagram in the infinite focus state in the intermediate focal length state. FIG. 8A shows an aberration diagram in the infinitely focused state in the state. Further, FIG. 6B shows a meridional lateral aberration diagram when the blur correction is performed with respect to the rotational blur of 0.70 ° in the infinity photographing state at the wide-angle end state of the second example, and FIG. FIG. 8B shows a meridional lateral aberration diagram when blur correction is performed for 0.30 ° rotational blur in the infinity shooting state at the telephoto end state. As is apparent from the respective aberration diagrams, in the second example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

It is sectional drawing which shows the structure of the variable magnification optical system by 1st Example. FIG. 3A is a diagram illustrating various aberrations in an infinitely focused state according to the first example, FIG. 3A is a diagram illustrating various aberrations in a wide-angle end state, and FIG. FIG. 6 is a meridional transverse aberration diagram when shake correction is performed for rotational shake. FIG. 6 is an aberration diagram in an infinitely focused state at an intermediate focal length state in the first example. FIG. 4 is a diagram illustrating various aberrations in the infinite focus state in the first embodiment, (a) is a diagram illustrating aberrations in the telephoto end state, and (b) is 0.30 ° in the infinity photographing state in the telephoto end state. FIG. 6 is a meridional transverse aberration diagram when shake correction is performed for rotational shake. It is sectional drawing which shows the structure of the variable magnification optical system by 2nd Example. FIG. 6A is a diagram illustrating various aberrations in the infinitely focused state according to the second example, FIG. 9A is a diagram illustrating various aberrations in the wide-angle end state, and FIG. FIG. 6 is a meridional lateral aberration diagram when shake correction is performed for rotational shake. It is an aberration diagram of the infinite focus state in the intermediate focal length state of the second embodiment. FIG. 6A is a diagram illustrating various aberrations in the infinitely focused state according to the second embodiment, FIG. 9A is a diagram illustrating various aberrations in the telephoto end state, and FIG. 9B is 0.30 ° in the infinity photographing state in the telephoto end state. FIG. 6 is a meridional transverse aberration diagram when shake correction is performed for rotational shake. The electronic still camera which mounts the variable magnification optical system which concerns on this invention is shown, (a) is a front view, (b) is a rear view. It is sectional drawing along the AA 'line of Fig.9 (a).

Explanation of symbols

ZL (ZL1 to ZL2) Variable magnification optical system FG Front lens group RG Rear lens group FG1 Front partial lens group FG2 Rear partial lens group RG1 First lens group RG2 Second lens group RG3 Third lens group S Aperture stop 1 Electronic still camera ( Optical equipment)

Claims (10)

Along the optical axis, from the object side,
A front lens group and a rear lens group,
The rear lens group is
A first lens group having a positive refractive power;
A second lens group having negative refractive power;
A third lens group having a positive refractive power,
The second lens group includes two or more lenses, and is movable so that at least a part has a component in a direction substantially perpendicular to the optical axis.
The most object side surface of the third lens group is configured with a concave surface facing the object side,
When the radius of curvature of the object side surface of the 3A lens located closest to the object side of the third lens group is r3AR1, and the radius of curvature of the image side surface of the 3A lens is r3AR2, the following equation-2. 20 <(r3AR1-r3AR2) / (r3AR1 + r3AR2) <0.55
Variable magnification optical system that satisfies the above conditions. The front lens group includes, in order from the object side, a lens group having a positive refractive power and a lens group having a negative refractive power,
2. The variable power optical system according to claim 1, wherein a distance between the lens unit having the positive refractive power and the lens group having the negative refractive power is increased upon zooming from the wide-angle end state to the telephoto end state. When the curvature radius of the object side surface of the 3A lens is r3AR1, and the focal length in the wide-angle end state of the entire variable magnification optical system is fw, the following formula 0.50 <(-r3AR1) / fw <5 .00
The zoom optical system according to claim 1, wherein the zoom lens system satisfies the following condition. When zooming from the wide-angle end to the telephoto end,
In the wide-angle end state, the distance between the first lens group and the second lens group is d12w, and the distance between the second lens group and the third lens group is d23w,
In the telephoto end state, the distance between the first lens group and the second lens group is d12t, and the distance between the second lens group and the third lens group is d23t,
When the combined focal length of the first lens group, the second lens group, and the third lens group in the wide-angle end state is fw123, the following expression 0.03 <(d12t−d12w) / fw123 <0.32
0.03 <(d23w−d23t) / fw123 <0.32
The variable magnification optical system as described in any one of Claims 1-3 which satisfy | fills these conditions. At the time of zooming from the wide-angle end state to the telephoto end state, the amount of movement of the first lens group with respect to the image plane is Δx1, and the first lens group, the second lens group, and the third lens group in the wide-angle end state When the combined focal length of fw123 is fw123, the following expression 0.35 <| Δx1 | / fw123 <1.50
The zoom lens system according to any one of claims 1 to 4, which satisfies the following condition. When the focal length of the second lens group is f2, and the combined focal length of the first lens group, the second lens group, and the third lens group in the wide-angle end state is fw123, the following formula 0.50 < (−f2) / fw123 <1.60
The zoom lens system according to any one of claims 1 to 5, which satisfies the following condition.   The zooming from the wide-angle end state to the telephoto end state causes the first lens group and the third lens group to move in the object direction and have the same amount of movement with respect to the image plane. The variable power optical system described.   The variable power optical system according to claim 1, further comprising an aperture stop closer to the object side than the second lens group.   An optical apparatus having the variable magnification optical system according to claim 1. Along the optical axis, from the object side,
A front lens group and a rear lens group,
The rear lens group is
A first lens group having a positive refractive power;
A second lens group having negative refractive power;
A third lens group having a positive refractive power,
The second lens group includes two or more lenses, and is movable so that at least a part has a component in a direction substantially perpendicular to the optical axis.
The most object side surface of the third lens group is configured with a concave surface facing the object side,
When the radius of curvature of the object side surface of the 3A lens located closest to the object side of the third lens group is r3AR1, and the radius of curvature of the image side surface of the 3A lens is r3AR2, the following equation-2. 20 <(r3AR1-r3AR2) / (r3AR1 + r3AR2) <0.55
A zooming method for a zooming optical system that satisfies the above conditions.

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