JP2002006217A - Zoom lens provided with vibration-proof function and optical equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens provided with vibration proof function capable of easily maintaining a good optical performance all over the variable power area to which vibration compensation is easily given with a simple configuration, and to provide optical equipment using the zoom lens. SOLUTION: As for the zoom lens with the vibration-proof function, the zoom lens is provide with a 1st lens group whose refractive power is positive, a 2nd lens group whose refractive power is negative, an aperture diaphragm, a 3rd lens group whose refractive power is positive and a 4th lens group whose refractive power is positive in order form an object side, and at varying the power from a wide angle end to a telephoto end, at least the 1st, 3rd and 4th lens groups are moved on the optical axis so as to change an air distance between respective lens groups, and the 3rd lens group is provided with a 3rd group lens 3n composed of a single lens whose refractive power is negative positioned closest to the image side, and by moving the 3rd group lens 3n in a direction vertical to the optical axis, the image blurring caused by the vibration of the zoom lens is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens having an image stabilizing function and an optical apparatus using the same, and more particularly to a zoom lens by moving a part of a single lens in a direction perpendicular to an optical axis. Suitable for optical devices such as film cameras, video cameras, and digital cameras that stabilize the captured image by optically correcting the blur of the captured image when the lens vibrates (tilt) to obtain a still image. It is something.

[0002]

2. Description of the Related Art In recent years, photographic cameras, video cameras, digital cameras, and the like have provided an image stabilizing function for correcting blurring of a photographed image due to camera shake for the purpose of improving image quality and expanding photographing conditions. There is a demand for a zoom lens, and many optical systems having such an anti-vibration function have been proposed.

[0003] As a zoom lens having a vibration proof function,
For example, in Japanese Patent Application Laid-Open No. Hei 5-232410, in a four-unit zoom lens composed of lens units having positive, negative, positive, and positive refractive power from the object side, the entire second unit is moved in a direction perpendicular to the optical axis. A zoom lens that performs camera shake correction has been proposed. The above proposal is to correct an image forming position when a blur occurs in an optical system by decentering one entire lens group that functions during zooming.

Japanese Patent Application Laid-Open No. 9-230236 discloses a technique for correcting the image forming position when a blur occurs in an optical system by decentering a part of a lens group functioning during zooming.
In a four-unit zoom lens composed of lens units having positive, negative, positive, and positive refractive powers in order from the object side, the third lens unit is separated into lens units having positive and positive refractive powers, and one lens unit is defined as an optical axis. Image blur correction is performed by moving the image in the vertical direction. Also, in Japanese Patent Application Laid-Open No. 7-128319,
In a four-unit zoom system including a lens unit having negative, positive and positive refractive powers, the third lens unit is divided into lens units having negative and positive refractive powers, and the lens unit having positive refractive power is perpendicular to the optical axis. To perform image blur correction.

In Japanese Patent Application Laid-Open No. 7-199124,
4 consisting of 4 lens groups with negative, positive and positive refractive power
In the variable power optical system having the group configuration, the entire third unit is vibrated in a direction perpendicular to the optical axis to perform vibration reduction.

[0006]

Generally, in a configuration in which a plurality of lenses are moved in a direction perpendicular to the optical axis for image blur correction, the weight of the lens to be moved is large, and the lens frame holding the lens is also large. It becomes big.
For this reason, a large load is imposed on the camera shake drive system that performs the shake correction drive, and as a result, the camera shake drive system becomes large, and the response to the eccentricity is delayed.

The zoom lens proposed in Japanese Patent Application Laid-Open No. 9-230235 has a configuration in which one lens is decentered for camera shake correction. Therefore, the lens moved for image shake correction is lightweight. is there. However, in order to correct various aberrations mainly caused by eccentricity, the correction lens has a configuration in which a positive lens and a negative lens are bonded to each other, and there is still room for study in terms of reducing the size and weight of the shake correction lens.

According to the present invention, a relatively small and light single lens constituting a part of a zoom lens is moved in a direction perpendicular to an optical axis to reduce image blur when the zoom lens vibrates (tilts). By providing correction, it is possible to provide a zoom lens that can effectively correct image blur while reducing the size of the entire apparatus, simplifying the mechanism, and reducing the load on the driving unit, and providing an optical apparatus using the same. Aim.

[0009]

According to a first aspect of the present invention, there is provided a zoom lens having an anti-vibration function, in order from the object side, a first lens group having a positive refractive power and a second lens group having a negative refractive power. , An aperture stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, and at the time of zooming from the wide-angle end to the telephoto end, at least the first, third, and fourth lens groups. A zoom lens that changes the air gap between each lens group by moving the lens group on the optical axis, and the third lens group has a third (n) lens, which is a single lens having a negative refractive power, closest to the image side. By moving the 3n lens in a direction perpendicular to the optical axis, image blur caused when the zoom lens vibrates is corrected.

A second aspect of the present invention is characterized in that, when the Abbe number of the material of the 3n lens is ν3n, the condition of ν3n> 45 (1) is satisfied.

According to a third aspect of the present invention, in the first or second aspect, the focal length of the 3n lens is f3n, and
When the focal length of the lens group is f3, the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft, -3.5 <f3n / f3 <-1.5 (1.5) 2)

[0012]

(Equation 3)

It is characterized by satisfying the following conditions.

According to a fourth aspect of the present invention, the focal length of the i-th lens unit is fi, the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft. And when

[0015]

(Equation 4)

It is characterized by satisfying the following conditions.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the second lens group has an aspherical surface rotationally symmetric with respect to an optical axis on a lens surface closest to the object. It is characterized by:

According to a sixth aspect of the present invention, in the first aspect of the present invention, the fourth lens group includes at least one lens.
It is characterized in that the surface has an aspherical surface that is rotationally symmetric with respect to the optical axis.

According to a seventh aspect of the present invention, there is provided an optical apparatus including the zoom lens having the image stabilizing function according to any one of the first to sixth aspects.

[0020]

FIG. 1 is a sectional view of a numerical example 1 of a zoom lens having an image stabilizing function according to the present invention.

FIGS. 2, 3 and 4 show the wide-angle end of the first numerical embodiment.
FIG. 7 is an aberration diagram at a zoom position at a middle or telephoto end.

FIG. 5 is a lens cross-sectional view of a numerical example 2 of a zoom lens having an image stabilizing function according to the present invention.

FIGS. 6, 7 and 8 show the wide-angle end of Numerical Embodiment 2,
FIG. 7 is an aberration diagram at a zoom position at a middle or telephoto end.

FIG. 9 is a lens sectional view of a numerical example 3 of a zoom lens having an image stabilizing function according to the present invention.

FIGS. 10, 11 and 12 are aberration diagrams of the numerical value example 3 at the wide-angle end, the middle position, and the telephoto end at the zoom positions.

In the lens sectional views (A), (B),
(C) shows the wide-angle end, the middle, and the telephoto end, respectively. In the aberration diagrams, (a) is an aberration diagram at an image height 0 position and at 15 mm and -15 mm positions in an infinity object shooting state before blur correction (before eccentricity), and (b) is a diagram illustrating the aberration at 0.3 °. These are the position of image height 0 and the positions of 15 mm and -15 mm in the state of shooting an object at infinity at the time of image blur correction (eccentricity).

In the sectional view of the lens, L1 is a first lens unit having a positive refractive power, L2 is a second lens unit having a negative refractive power, L3 is a third lens unit having a positive refractive power, and L4 is a fourth lens unit having a positive refractive power. It is. SP denotes an aperture stop, which is arranged in front of the third lens unit L3. IP is an image plane, on which an image sensor such as a CCD, a film, and the like are arranged.

The third lens unit L3 is a third lens unit L3p having a positive refractive power.
And a third lens L3n composed of a single lens having a negative refractive power
Consists of The image blur caused when the zoom lens vibrates by moving the third lens L3n in the direction perpendicular to the optical axis is corrected. AL is an aspheric surface. At the time of zooming from the wide-angle end to the telephoto end, each lens unit is moved to the object side as indicated by the arrow. During zooming, the stop SP moves together with the third lens unit.

In the zoom lens having an image stabilizing function according to the present invention, the first lens unit having a positive refractive power is arranged in order from the object side.
A second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and at least the first, third, and fourth lenses By moving the groups on the optical axis, the air spacing between the lens groups is changed to perform magnification from the wide-angle end to the telephoto end and to correct the image plane fluctuation by zooming. Then, by moving the 3n lens L3n, which is a single lens having the negative refractive power closest to the image side in the third lens group, in the direction perpendicular to the optical axis, the zoom lens vibrates and the image forming position when blur occurs. (Image blur) is being corrected.

With the above-described configuration, by changing the air gap between the first lens unit and the second lens unit during zooming, the second lens unit mainly performs the zooming operation, and
By correcting the image plane fluctuation mainly due to the zooming by moving the lens groups, and simultaneously changing the air gap between the third lens group and the fourth lens group to correct the fluctuation of the off-axis aberration due to the zooming. I have. In this case, the second lens group may be fixed on the optical axis, thereby simplifying the zooming mechanism of the zoom lens. By arranging a lens element having a negative refractive power (third n lens) in the third lens group having a positive refractive power, various elements generated in a portion of the third lens group having a positive refractive action are provided. The aberration is canceled (corrected) by its negative refraction. Further, the image blur correction is performed by moving the lens element having the negative refractive power in the direction perpendicular to the optical axis, so that a large image position can be corrected with a small moving amount. At the same time, the lens element having the negative refractive power closest to the image side (the third lens) in the third lens group having the positive refractive power immediately after the stop is used as the image blur correcting lens, thereby reducing the diameter of the image blur correcting lens. Is easy.

Further, by constituting the lens element having the negative refractive power with one single lens, it is easy to reduce the size and weight of the lens element for correcting the image position, and to simplify the moving mechanism and drive torque. Is easy to reduce.

As described above, in this embodiment, the optical system for moving in the direction perpendicular to the optical axis in order to correct the blur of the photographed image is constituted by one relatively light single lens in the zoom lens. , Simple configuration and miniaturization of equipment,
A zoom lens having an image stabilizing function in which the addition of a driving unit is reduced is achieved.

The zoom lens having an anti-vibration function, which is the object of the present invention, can be achieved by satisfying the above conditions. However, it is necessary to reduce the size of the entire apparatus while having better optical performance. Preferably satisfies at least one of the following conditions.

(A-1) When the Abbe number of the material of the third lens is ν3n, the following condition is satisfied: ν3n> 45 (1)

In general, when a part of the optical system is decentered in parallel for correcting an image forming position when an image blur occurs as in the present invention, chromatic aberration of magnification, which is one of the eccentric aberrations, occurs. Therefore, it is desirable that the image blur correction optical system decentered at this time is color-corrected by itself. However, when the image blur correction optical system is constituted by a single lens as in the present invention, it is impossible to achromatize a single lens. Therefore, a new condition is required to suppress the occurrence of chromatic aberration during image blur correction.

Conditional expression (1) is a conditional expression that defines the Abbe number of the material of the third lens which is decentered perpendicularly to the optical axis when performing image blur correction. If the dispersion of the material of the 3n-th lens becomes large beyond the range of the conditional expression (1), the eccentricity occurs when the 3n-th lens is decentered for correcting the image forming position when the optical system is blurred. The chromatic aberration of magnification becomes large, making correction difficult, and a good image cannot be obtained.

It is more preferable that the conditional expression (1) is set to ν3n> 55 (1a).

(A-2) The focal length of the third lens unit is f3n, the focal length of the third lens unit is f3, the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft. -3.5 <f3n / f3 <-1.5 (2)

[0039]

(Equation 5)

It is characterized by satisfying the following conditions.

Conditional expressions (2) and (3) are the refractive power of the 3n lens which is decentered perpendicular to the optical axis when performing image blur correction, and the refractive power of the third lens group including the 3n lens. Is a conditional expression that defines the ratio of.

When the upper limit of conditional expression (2) is exceeded and the negative refractive power of the 3n-th lens becomes strong, the positive refractive power component other than the 3n-lens in the third lens group must be increased, and The following spherical aberration, coma aberration, and the like are greatly generated, and it becomes difficult to correct aberration at the time of image blur correction. On the other hand, when the negative refractive power of the 3n lens is weakened below the lower limit of the conditional expression (2), the amount of movement of the 3n lens in the direction perpendicular to the optical axis of the 3n lens for performing a constant image position correction increases, and 3n
Since the lens diameter of the 3nth lens increases in order to secure the peripheral light amount when the lens is moved (at the time of blur correction), it is not desirable from the viewpoint of reducing the size and weight of the image blur correction lens and reducing the load on the correction mechanism.

When the refractive power of the third lens unit is weakened beyond the upper limit of the conditional expression (3), the amount of movement of the lens unit for securing a constant zoom ratio becomes large. It is not preferable because it increases. On the other hand, the third
If the refractive power of the lens group is increased, it becomes difficult to satisfactorily correct aberrations generated in the third lens group in the entire zoom range, which is not desirable.

It is more preferable that conditional expression (2) be satisfied.
(3) is -3.0 <f3n / f3 <-2.0 (2a)

[0045]

(Equation 6)

It is preferable that

(A-3) The focal length of the i-th lens group is f
i, when the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft

[0048]

(Equation 7)

It is characterized by satisfying the following conditions.

The conditional expressions (4), (5) and (6) are mainly conditional expressions for defining the refractive power of each lens unit for realizing a compact and high-quality zoom lens.

If the upper limit of conditional expression (4) is exceeded and the refractive power of the first lens unit becomes weak, the outer diameter of the lens increases or the overall length of the lens undesirably increases. If the refractive power of the first lens unit exceeds the lower limit and the refractive power of the first lens unit becomes strong, a high-order spherical aberration will occur greatly, making it difficult to correct.

If the negative refractive power of the second lens unit exceeds the upper limit of conditional expression (5), the Petzval sum becomes too large in the negative direction, and the field curvature becomes undesirably large.
If the negative refractive power of the second lens unit is smaller than the lower limit, the amount of movement of each lens unit for securing a constant zoom ratio becomes large, and it becomes difficult to make the entire lens system compact.

If the upper limit of conditional expression (6) is exceeded and the refractive power of the fourth lens unit becomes weak, the back focus becomes long, and it becomes difficult to make the entire lens system compact. If the refractive power of the fourth lens unit exceeds the lower limit and the refractive power of the fourth lens unit becomes strong, large off-axis high-order aberrations such as curvature of field will be generated, and correction will be difficult.

More preferably, conditional expression (4),
(5), (6)

[0055]

(Equation 8)

It is preferable that

(A-4) The second lens group is characterized in that the lens surface closest to the object has an aspherical surface which is rotationally symmetric with respect to the optical axis.

In the zoom lens according to the present invention, it is preferable to effectively arrange the aspherical surfaces. This makes it easy to achieve a variable power optical system that maintains excellent optical performance with a small number of components as a whole. Become.

Specifically, by arranging an appropriate aspherical surface on the lens surface closest to the object in the second lens unit having a large variable load, various aberrations generated at the time of variable power can be satisfactorily corrected. In addition, the number of components can be reduced.

(A-5) The fourth lens group is characterized in that at least one surface has an aspherical surface rotationally symmetric with respect to the optical axis. By arranging an appropriate aspherical surface on one surface of the fourth group of lenses having a negative refractive power, the variation of off-axis aberration at the time of zooming can be corrected well, and the number of components can be reduced.

As described above, according to each embodiment of the present invention, an optical system for decentering in the vertical direction with respect to the optical axis in order to correct blurring of a photographed image is a relatively lightweight one in a zoom lens. Thus, a zoom lens having an anti-vibration function that realizes a simple configuration, miniaturization of the apparatus, and reduction of the load on the driving means is realized.

At the same time, by appropriately configuring the lens configuration of the zoom lens, a zoom lens having a simple configuration with a small number of components and having a compact image stabilizing function is realized.

Next, an embodiment of a video camera (optical apparatus) using a zoom lens having an image stabilizing function according to the present invention will be described with reference to FIG.

In FIG. 13, reference numeral 10 denotes a video camera main body, 11 denotes a photographing optical system constituted by the zoom lens of the present invention, 12 denotes an image pickup device such as a CCD for receiving a subject image by the photographing optical system 11, and 13 denotes an image pickup device. Reference numeral 12 denotes a recording unit for recording the received subject image, and reference numeral 14 denotes a finder for observing the subject image displayed on a display element (not shown). The display element includes a liquid crystal panel or the like, and displays a subject image formed on the image sensor 12.

As described above, by applying the zoom lens of the present invention to an electronic camera such as a video camera and a digital still camera, an optical device having a small size and high optical performance is realized.

Hereinafter, numerical data of numerical examples 1 to 3 of the zoom lens according to the present invention will be described.

In these numerical examples, ri is the radius of curvature of the i-th surface in order from the object side, di is the thickness of the i-th optical member or air gap in order from the object side, and ni and νi are respectively from the object side. The d of the material of the i-th optical member in order
The refractive index and Abbe number of the line.

In each numerical example, the surface indicated by AL is an aspherical surface, and the shape is defined by the following equation.

[0069]

(Equation 9)

Here, X is the amount of displacement in the direction of the optical axis on the lens surface away from the optical axis by h, R is the radius of curvature, B, C, D,
E is a fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficient, respectively.

Further, numerical values corresponding to the numerical conditional expressions in each numerical example are also shown.

[0072]

[Outside 1]

[0073]

[Outside 2]

[0074]

[Outside 3]

[0075]

According to the present invention, as described above, the relatively small and light lens constituting a part of the zoom lens is moved in the direction perpendicular to the optical axis, and the image when the zoom lens vibrates (tilts). A zoom lens and an optical apparatus using the zoom lens that can effectively correct image blur while reducing the size of the entire apparatus, simplifying the mechanism, and reducing the load on the driving unit by correcting the blur. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a lens cross-sectional view of Numerical Example 1 of the present invention.

FIG. 2 is a lateral aberration diagram of a zoom lens according to a numerical example 1 of the present invention in a reference state at a wide-angle end and during blur correction.

FIG. 3 is a lateral aberration diagram in a reference state and a blur correction at the middle of the zoom lens according to Numerical Example 1 of the present invention. FIG.

FIG. 4 is a lateral aberration diagram at the telephoto end of the zoom lens according to Numerical Example 1 of the present invention at the telephoto end and during blur correction.

FIG. 5 is a lens sectional view of a numerical example 2 of the present invention.

FIG. 6 is a lateral aberration diagram of a zoom lens according to a second numerical example of the present invention at the wide-angle end in a reference state and at the time of blur correction.

FIG. 7 is a lateral aberration diagram in a reference state and blur correction in the middle of a zoom lens according to Numerical Example 2 of the present invention.

FIG. 8 is a lateral aberration diagram at the telephoto end of the zoom lens according to Numerical Example 2 of the present invention at the telephoto end and during blur correction.

FIG. 9 is a lens cross-sectional view of Numerical Example 3 of the present invention.

FIG. 10 is a lateral aberration diagram of a zoom lens according to a third numerical example of the present invention at the wide-angle end in a reference state and at the time of blur correction.

FIG. 11 is a lateral aberration diagram at the time of a blur correction in a reference state in the middle of a zoom lens according to Numerical Example 3 of the present invention. FIG.

FIG. 12 is a lateral aberration diagram at the telephoto end of the zoom lens according to Numerical Example 3 of the present invention at the telephoto end and during blur correction.

FIG. 13 is a schematic view of a main part of an optical apparatus according to the invention.

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit SP Aperture IP Image plane d d line g g line ΔS Sagittal image plane ΔM Meridional image plane AL Aspherical surface

Continued on the front page F term (reference) 2H087 KA02 KA03 NA07 PA06 PA10 PA20 PB11 QA02 QA06 QA17 QA21 QA26 QA39 QA41 QA46 RA05 RA12 RA13 RA36 SA23 SA27 SA29 SA32 SA62 SA64 SA65 SA73 SB03 SB15 SB24 SB33

Claims (7)

[Claims] 1. An object having a positive refractive power in order from the object side.
It has one lens group, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. At the time of zooming, at least the first, third and fourth lens groups move on the optical axis to change the air gap between the lens groups, and the third lens group is closest to the image side. A third n-th lens made of a single lens having a negative refractive power;
A zoom lens having an image stabilizing function, wherein an image blur caused when the zoom lens vibrates is corrected by moving an n lens in a direction perpendicular to an optical axis. 2. The Abbe number of the material of the third n lens is ν.
2. The zoom lens having an anti-vibration function according to claim 1, wherein a condition of ν3n> 45 is satisfied when 3n is set. 3. The focal length of the 3n lens is f3n,
When the focal length of the third lens group is f3, the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft, -3.5 <f3n / f3 <-1.5 Equation 1 3. The zoom lens having an anti-vibration function according to claim 1, wherein the following condition is satisfied. 4. When the focal length of the i-th lens unit is fi, the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft. 4. The zoom lens having an image stabilizing function according to claim 1, wherein the zoom lens satisfies the following conditions. 5. The protection according to claim 1, wherein the second lens group has an aspherical surface rotationally symmetric with respect to an optical axis on a lens surface closest to the object. Zoom lens with vibration function. 6. The fourth lens group has at least one surface,
6. The zoom lens having an image stabilizing function according to claim 1, wherein the zoom lens has an aspherical surface that is rotationally symmetric with respect to the optical axis. 7. An optical apparatus comprising the zoom lens having the image stabilizing function according to claim 1. Description: