JP2006030340A - Variable power optical system having vibration isolation function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the lens system and its drive system small and to perform quick vibration isolation control with a small power, especially to make the curving variations small on the image surface when focusing while improving other aberrations too, and to provide a vibration isolation function to improve the light receiving efficiency of the imaging element in a variable power optical system having vibration isolation functions built in a configuration of 4 groups i.e. positive, negative, positive, and positive groups. <P>SOLUTION: This system has a 1st fixed positive lens group G<SB>1</SB>, a 2nd negative lens group G<SB>2</SB>having a variable power function, a 3rd positive lens group G<SB>3</SB>, a 4th positive lens group G<SB>4</SB>having a correction function of the image surface variations due to power changing and a focusing function, all arranged in this order from the object side for changing the power and focusing. The 3rd negative lens group G<SB>3</SB>is built by arranging a 3rd negative 3<SB>a</SB>lens group (a 7th lens L<SB>7</SB>) and a 3rd positive 3<SB>b</SB>lens group (a 8th lens L<SB>8</SB>) in this order from the object side. The instable photographed images due to the vibrations in the variable power optical system are corrected by moving the 3rd negative 3<SB>a</SB>lens group (a 7th lens L<SB>7</SB>) in the direction orthogonally crossing the optical axis X. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a variable magnification optical system with an image stabilization function, and more specifically, by moving a part of a lens group of the variable magnification optical system, for example, in a direction substantially orthogonal to the optical axis, the variable magnification optical system vibrates ( Cameras for photography, video cameras, electronic still cameras, or 3-CCD compatible electronic cameras, etc., in which still images are obtained by optically correcting blurring of captured images that occur during tilting), especially with a small CCD size The present invention relates to a variable magnification optical system with an anti-vibration function that is suitably used for a small digital camera or the like.

  In shooting from a moving object such as a moving automobile or hand-held shooting under slow shutter speed conditions, vibration is transmitted to the shooting optical system, resulting in camera shake and blurring of the shot image.

Conventionally, various anti-vibration optical systems have been proposed that have a function of preventing blurring of a photographed image due to vibration of the photographing optical system.
As such an anti-vibration optical system, an image stabilization system is known by moving a part of a lens group of a photographing optical system in a direction substantially orthogonal to the optical axis (for example, patents). Reference 1). The technique described in Patent Document 1 includes, in order from the object side, a positive first lens group that is fixed during zooming and focusing, a negative second lens group that includes a zooming function, and a positive first lens group. And a positive fourth lens group having both a correction function for correcting an image plane fluctuating due to zooming and a focusing function. The third lens group is a positive lens in order from the object side. A 31st lens group and a negative 32nd lens group, and when the variable magnification optical system vibrates by moving the 31st lens group or the 32nd lens group in a direction substantially orthogonal to the optical axis, It is intended to correct blur.

  However, in the technique described in Patent Document 1, since the positive lens is preceded as the lens configuration of the third lens group, the position of the principal point of the third lens group is closer to the object side, The air space between the third lens group and the fourth lens group is reduced. As a result, the amount of movement of the fourth lens group during focusing becomes small, and the refractive power of the fourth lens group needs to be further increased in order to enable focusing at a short distance. Fluctuation of the field curvature at the time of focusing increases, resulting in a decrease in resolution.

Further, in the device described in Patent Document 1, since the 32nd lens group of the negative lens is arranged on the image side of the third lens group, the light emission angle to the image pickup device such as a CCD becomes large, and the image pickup device In this case, the light receiving efficiency is reduced.
As a technique corresponding to such a problem, in the configuration of the third lens group, in order from the object side, a 31st lens group having a negative refractive power and a 32nd lens group having a positive refractive power are arranged, There is known a technique in which blurring of a captured image is corrected when a variable magnification optical system vibrates by moving a 32 lens group in a direction substantially orthogonal to the optical axis (see Patent Document 2 below).

Japanese Patent Laid-Open No. 10-232420 JP 11-237550 A

  However, in the device described in Patent Document 2, the 32nd lens group consisting of a positive lens arranged on the image side is driven for image stabilization, and the 31st lens group consisting of a negative lens is arranged on the object side. Has been. That is, since the light flux diverges at the position of the 32nd lens group due to the light beam divergence of the 31st lens group, the diameter of the 32nd lens group is inevitably increased and the weight is increased, so that it is possible to quickly prevent with a small power. There was a problem that it was difficult to perform vibration control. Today, digital cameras are strongly demanded to reduce the size and weight, and to save labor, and it is desired to develop a lens system that can perform a quick vibration control with a smaller power.

  Furthermore, in a small digital camera or the like, since the focal length of the lens is set short, the amount of movement of the focus lens is small, which is advantageous in terms of mechanism for performing macro photography (short-distance photography). There is also a strong demand for macro photography.

  On the other hand, when using an auxiliary light source such as a strobe during macro photography, it is important not to use such an auxiliary light source because the color reproduction of the reflected light from the subject is greatly reduced. The shutter speed must be slowed down, and in macro photography where image blurring is noticeable, it is particularly necessary to suppress blurring of the shot image due to camera shake. From this point of view, there is a demand for a vibration-proof optical system that can prevent blurring of a captured image more quickly with low power.

  The present invention has been made in view of the above-described circumstances, and the lens system and its driving system are small. In particular, in macro photography, it is possible to perform quick image stabilization control with low power, and curvature of field at the time of focusing. The object of the present invention is to provide a variable magnification optical system with an image stabilization function that can improve the light receiving efficiency of the image sensor, and can improve the other aberrations. .

The variable power optical system with an image stabilization function of the present invention has, in order from the object side, a first lens group having a positive refractive power that is fixed upon zooming and focusing, and a negative refractive power having a variable power function. A second lens group, a stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power having a function of correcting and focusing an image plane variation due to zooming; A variable magnification optical system,
The third lens group includes, in order from the object side, a 3a lens group having negative refractive power and a 3b lens group having positive refractive power,
The third-a lens group is moved in a direction intersecting the optical axis to correct blurring of a captured image caused by vibration of the variable power optical system. Here, it is preferable that the “intersection” angle is approximately 90 degrees.

  Moreover, it is preferable that the said 3a lens group is comprised by one lens.

  The 3a lens group preferably has at least one aspherical lens surface.

  The 3b lens group may be constituted by a cemented lens formed by cementing a positive lens and a negative lens.

  Furthermore, the 3b lens group may be composed of a single aspheric lens.

  According to the variable magnification optical system with the image stabilization function of the present invention, the 3a lens group disposed on the object side of the third lens group is driven for image stabilization. The third lens group is constituted by a lens having negative refractive power, and the third lens group is arranged by arranging a third lens group having positive refractive power on the image side of the third lens group. Since the 3a lens group can be reduced in diameter and weight can be reduced, it is possible to perform quick image stabilization control with low power. Become.

  As described above, according to the variable magnification optical system with the image stabilization function of the present invention, since the image stabilization is reliably prevented by performing quick image stabilization control with a small power, the shutter speed is decreased. Therefore, it is possible to cope with macro photography which is necessary and image blurring is conspicuous.

  Further, as the configuration of the third lens group, since the 3a lens group having a negative refractive power and the 3b lens group having a positive refractive power are arranged in order from the object side, the position of the principal point of the third lens group Is positioned on the image side, the air space between the third lens group and the fourth lens group can be widened, and the amount of movement of the fourth lens group during focusing can be increased. This facilitates focusing during close-up shooting. Further, the refractive power of the fourth lens group can be suppressed to a certain level, the fluctuation of the field curvature at the time of focusing can be reduced, and the resolution can be stabilized.

  Furthermore, in the third lens group, the 3b lens group having positive refractive power is arranged on the image side, so that the angle of emission to the CCD can be reduced, and the light receiving efficiency can be improved.

  In addition, by configuring the 3a lens group with a single lens, it becomes easier to reduce the weight, and it is possible to perform quick vibration control with less power.

  Further, by configuring the 3b lens group with a pair of cemented lenses of a positive lens and a negative lens, axial chromatic aberration can be reduced and image quality can be improved.

  Further, by providing at least one aspheric surface in the 3a lens group or providing at least one aspheric lens in the 3b lens group, it is possible to improve the correction of spherical aberration while preventing vibration. Stabilization of image quality at the time can be achieved.

Hereinafter, a variable magnification optical system with an image stabilization function according to an embodiment of the present invention will be described with reference to FIG. 1 showing Example 1 as a representative example.
The lower part of FIG. 1 shows the movement locus of each lens group from the wide-angle end to the telephoto end (the same applies to FIGS. 2 and 3). Of the movement locus of the fourth lens group, the solid line indicates the movement locus at an infinite object distance, and the broken line indicates the movement locus at a finite object distance.

As shown in FIG. 1, the variable magnification optical system with an image stabilization function according to the embodiment of the present invention is fixed in order from the object side at the time of variable magnification and focusing, three lenses L ₁ , L ₂ , L _A first lens group G ₁ having a positive refractive power composed of ₃ , a second lens group G ₂ having a negative refractive power composed of three lenses L ₄ , L ₅ and L ₆ having a zooming function, A third lens group G ₃ having positive refractive power, which includes two lenses L ₇ and L ₈ (in the second and third embodiments, which includes three lenses L ₇ , L ₈ and L ₉ ), and a variable magnification 3 lenses L ₉ , L ₁₀ , and L _{11 having} an image plane variation correction function and a focusing function (in Embodiments 2 and 3, the three lenses L ₁₀ , L ₁₁ , and L _{12 are included.} formed by disposing the fourth lens group G ₄ having from consisting) positive refractive power.

Further, a is the object side of the third lens group G ₃ diaphragm 3 is disposed, between the fourth lens group G ₄ and the image plane (CCD imaging surface) 1, a low-pass filter or an infrared cut filter The filter part 2 containing is arranged.

In this anti-vibration function variable power optical system, by moving along the second lens group G ₂ to the optical axis X, along with changing the focal length f of the entire system, the optical axis and the fourth lens group G ₄ X , The image plane variation due to zooming is corrected and focused, and the light beam is efficiently converged on the image plane 1.

Further, the third lens group G ₃ is composed of, in order from the object side, a first negative 3a lens group, and becomes a positive of the 3b lens group, the third 3a lens group seventh lens L _7, is the 3b lens group In each constructed (example 2 and example 3 by the eighth lens _{L 8,} a 3a lens group seventh lens _{L 7} is, by the eighth lens _{L 8} and the ninth lens _{L 9} is a 3b lens arrangement )

Then, in the present embodiment, by moving the seventh lens L ₇ constituting the first 3a lens group in the direction the optical axis X and substantially perpendicular, so as to correct blurring of a photographed image caused by the vibration of the variable magnification optical system It has become.

Specifically, for example, in a storage device built in the camera or the like in advance, the axis shift amount of the 3a lens group (seventh lens L ₇ ) for correcting camera shake is stored and disposed on the camera side. The amount of camera shake is detected using an angular velocity sensor, and the third a lens group (seventh lens L ₇ ) is moved to the optical axis X by an axis shift amount corresponding to the amount of camera shake using an actuator provided in the zoom optical system. And move in a direction substantially orthogonal to

Thus, as the configuration of the third lens group G _3, in order from the object side, since the sequence of the negative of the 3a lens group and a positive third 3b lens group, the position of the principal point of the third lens group G ₃ There will be located on the image side, the third lens group G ₃ can take a wide air space between the fourth lens group G _4, that a large amount of movement during focusing of the fourth lens group G ₄ Can do. This facilitates focusing during close-up shooting. Further, the refractive power of the fourth lens group G ₄ can be suppressed to a certain degree of strength, improved variation of curvature of field when focusing, it is possible to stabilize the resolution. Further, the third lens group G _3, by disposing the first 3b lens group having a positive refractive power on the image side, it is possible to reduce the emission angle of the CCD, thereby improving the light receiving efficiency.

  Further, by configuring the 3a lens group that is driven for image stabilization with a lens having negative refractive power, and disposing the 3b lens group having positive refractive power on the image side of the 3a lens group, Since the spread of the light beam at the position of the 3a lens group becomes small, the diameter and the weight of the 3a lens group can be reduced, and quick vibration control can be performed with low power.

  In addition, by configuring the 3a lens group with a single lens, weight reduction is promoted, and it is possible to perform quick image stabilization control with smaller power.

Further, in the image stabilization function zoom lens system according to this embodiment, by the combination of the third negative lens group of the lens group G ₃ and the positive lens group, to reduce the chromatic aberration, by optimizing the Petzval sum There is an effect that the curvature of field can be reduced.

Further, both surfaces of the seventh lens L ₇ , the eighth lens L ₈ and the eleventh lens L ₁₁ (in the second and third examples, the seventh lens L ₇ and the twelfth lens L ₁₂ ) are expressed by the following aspherical expression. The aspherical shape is expressed. This makes it possible to stabilize the image quality during image stabilization while improving the correction of spherical aberration.

<Example 1>
Hereinafter, a specific configuration of the variable magnification optical system with an image stabilization function according to the first embodiment of the present invention will be described.
The variable magnification optical system with an image stabilization function according to the first embodiment has a lens configuration as shown in FIG.

That is, the first lens group G ₁ includes, in order from the object side, a meniscus first lens L ₁ having a negative refractive power with a convex surface facing the object side, a biconvex second lens L ₂ , and a convex surface facing the object side. and a third lens L ₃ of meniscus shape having a positive refractive power with a first lens L ₁ and second lens L ₂ is the lens surfaces to each other has a bonded cemented lens.

The second lens group G ₂ includes, in order from the object side, a biconcave fourth lens L ₄ , a biconcave fifth lens L ₅ , and a meniscus sixth lens having positive refractive power with a convex surface facing the object side. It consists lens L _6, and has a fifth lens L ₅ and the sixth lens L ₆ are cemented lens lens surfaces are bonded together.

The third lens group G ₃ is composed of, in order from the object side, a convex surface directed toward the object side, the seventh lens L ₇ having a small _power, and consisting of the eighth lens L ₈ biconvex. Incidentally, the seventh lens _{L 7} constitute a first 3a lens group constituting the 3b-th lens group eighth lens _{L 8.}

The fourth lens group G ₄ has, in order from the object side, a meniscus ninth lens L ₉ having negative refractive power with a convex surface facing the object side, a biconvex tenth lens L ₁₀ , and a convex surface on the image side. consists eleventh lens L ₁₁ of a small meniscus of power with its, has a ninth lens L ₉ and the tenth lens L ₁₀ is a cemented lens in which the lens surfaces are bonded together.

Table 1 below shows numerical values related to the variable magnification optical system with the image stabilization function according to Example 1.
In the first row of Table 1, the radius of curvature R (mm) of each lens surface, the center thickness of each lens, and the air spacing between each lens (hereinafter collectively referred to as the axial top surface spacing) D (mm), The values of the refractive index N and the Abbe number ν in the d-line of each lens are shown.
The numbers in the table represent the order from the object side (the same applies to Tables 2 and 3).

Further, in the second row of Table 1, D ₅ , D ₁₀ , D _{15 at} each of the wide-angle end (f = 8.13 mm) and the telephoto end (f = 45.08 mm) in the column of the shaft upper surface distance D described above. , and shows the value of the variable range of _{D 20.}
Further, the third row of Table 1 shows values of the focal length f (mm), F _NO and the angle 2ω at each position in the wide-angle end (f = 8.13mm), and the telephoto end (f = 45.08mm).

Table 2 shows values of the constants KA, A ₄ , A ₆ , A ₈ , and A ₁₀ of the aspheric surface shown in the above aspheric expression. That is, the aspheric coefficient values for both surfaces of the seventh lens L ₇ , the eighth lens L ₈ and the eleventh lens L ₁₁ are shown.

FIG. 4 shows various aberrations (spherical aberration, astigmatism, distortion) at the wide-angle end (f = 8.13 mm) and the telephoto end (f = 45.08 mm) of the variable magnification optical system with image stabilization function according to Example 1 above. FIG. 6 is an aberration diagram showing chromatic aberration of magnification). Each spherical aberration diagram shows aberrations at 615 nm, 587.6 nm, and 460 nm, and each astigmatism diagram shows aberrations with respect to the sagittal image surface and the tangential image surface (FIG. 5, FIG. 5). The same applies to FIG. 6).
As is apparent from FIG. 4, according to the variable magnification optical system with the image stabilization function according to the first embodiment, good aberration correction is performed over the entire zoom region.

<Example 2>
As shown in FIG. 2, the variable magnification optical system with an image stabilization function according to the second embodiment has a lens configuration substantially the same as that of the first embodiment. However, it differs from Example 1 mainly in that the 3b lens group is a cemented lens composed of a biconvex lens L ₈ and a negative meniscus lens L ₉ having a convex surface facing the image side. Thus, by configuring the 3b lens group with a cemented lens including a positive lens and a negative lens, it is possible to reduce axial chromatic aberration and improve image quality.

Table 3 below shows numerical values related to the variable magnification optical system with the image stabilization function according to Example 2.
The first level of Table 3 shows the values of the radius of curvature R (mm) of each lens surface, the distance D (mm) between the axial top surfaces of each lens, and the refractive index N and Abbe number ν for each lens d-line.
In the second row of Table 3, D ₅ , D ₁₀ , D _{16 at} each of the wide-angle end (f = 8.16 mm) and the telephoto end (f = 45.26 mm) in the column of the axis top surface distance D described above. , and shows the value of the variable range of _{D 21.}
Further, the third row of Table 3 shows the values of the focal length f (mm), F _NO and the angle 2ω at each position in the wide-angle end (f = 8.16 mm), and the telephoto end (f = 45.26mm).

Table 4 shows values of the constants KA, A ₄ , A ₆ , A ₈ , and A ₁₀ of the aspheric surface shown in the above aspheric expression. That is, the values of the respective aspheric coefficients for both surfaces of the seventh lens L ₇ and the twelfth lens L ₁₂ are shown.

FIG. 5 shows various aberrations (spherical aberration, astigmatism, distortion) at each of the wide-angle end (f = 8.16 mm) and the telephoto end (f = 45.26 mm) of the variable magnification optical system with image stabilization function according to Example 2 above. FIG. 6 is an aberration diagram showing chromatic aberration of magnification).
As is apparent from FIG. 5, according to the variable magnification optical system with the image stabilization function according to the second embodiment, good aberration correction is performed over the entire zoom region.

<Example 3>
As shown in FIG. 3, the variable magnification optical system with an image stabilization function according to Example 3 has a lens configuration substantially the same as that of Example 2. However, the second embodiment mainly in the cemented lens of the 3b lens group, that negative meniscus lens eighth lens L ₈ is having a convex surface facing the object side, a ninth lens L ₉ is a biconvex lens Is different.

Table 5 below shows numerical values related to the variable magnification optical system with the image stabilization function according to Example 3.
The first level of Table 5 shows the values of the radius of curvature R (mm) of each lens surface, the distance D (mm) between the axial top surfaces of each lens, and the refractive index N and the Abbe number ν for each lens d-line.
In the second row of Table 5, D ₅ , D ₁₀ , D _{16 at} each of the wide-angle end (f = 8.11 mm) and the telephoto end (f = 44.97 mm) in the column of the axis top surface distance D described above. , and shows the value of the variable range of _{D 21.}
Further, the third row of Table 5 shows the values of the focal length f (mm), F _NO and the angle 2ω at each position in the wide-angle end (f = 8.11mm), and the telephoto end (f = 44.97mm).

Table 6 shows values of constants KA, A ₄ , A ₆ , A ₈ , and A ₁₀ of the aspheric surface shown in the above aspheric expression. That is, the values of the respective aspheric coefficients for both surfaces of the seventh lens L ₇ and the twelfth lens L ₁₂ are shown.

FIG. 6 shows various aberrations (spherical aberration, astigmatism, distortion) at the wide-angle end (f = 8.11 mm) and the telephoto end (f = 44.97 mm) of the variable magnification optical system with an image stabilization function according to Example 3 above. FIG. 6 is an aberration diagram showing chromatic aberration of magnification).
As can be seen from FIG. 6, the variable magnification optical system with the image stabilization function according to the third embodiment can satisfactorily correct aberrations over the entire zoom region.

Lens configuration diagram of a variable magnification optical system with an image stabilization function according to an embodiment (Example 1) of the present invention Lens configuration diagram of a variable magnification optical system with an image stabilization function according to an embodiment (Example 2) of the present invention Lens configuration diagram of a variable magnification optical system with an image stabilization function according to an embodiment (Example 3) of the present invention FIG. 6 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) at the wide-angle end and the telephoto end of the variable magnification optical system with an image stabilization function according to Example 1 of the present invention. Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) at the wide-angle end and the telephoto end of the variable magnification optical system with an image stabilization function according to Example 2 of the present invention. Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) at the wide-angle end and the telephoto end of the variable magnification optical system with an image stabilization function according to Example 3 of the present invention.

Explanation of symbols

G ₁ ~G ₄ lens group L ₁ ~L ₁₂ lens X optical axis 1 imaging surface 2 filter unit 3 stop

Claims (5)

In order from the object side, a first lens group having a positive refractive power, which is fixed during zooming and focusing, a second lens group having a negative refractive power having a zooming function, a diaphragm, and a positive refractive power A variable power optical system comprising a third lens group having a positive lens and a fourth lens group having a positive refractive power and a correction function and a focusing function of an image plane variation due to zooming,
The third lens group includes, in order from the object side, a 3a lens group having negative refractive power and a 3b lens group having positive refractive power,
A variable power optical system with a vibration proof function, wherein the 3a lens group is moved in a direction intersecting the optical axis to correct a blur of a photographed image due to vibration of the variable power optical system.   The variable-magnification optical system with an image stabilizing function according to claim 1, wherein the third-a lens group includes a single lens.   3. The variable magnification optical system with an anti-vibration function according to claim 1, wherein the third-a lens group has at least one aspherical lens surface.   4. The variable magnification optical system with an anti-vibration function according to claim 1, wherein the third lens group includes a cemented lens formed by cementing a positive lens and a negative lens. . 4. The variable magnification optical system with an image stabilization function according to claim 1, wherein the third lens group is constituted by a single aspheric lens. 5.

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