JP3070592B2 - Variable power optical system with anti-vibration function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-magnification optical system having a function of correcting blurring of a photographed image due to vibration, that is, a so-called anti-shake function. The present invention relates to a variable-magnification optical system having a vibration-proof function with a mechanically simple configuration for preventing a decrease in optical performance when moving in a direction perpendicular to the above to exert a vibration-proof effect.

[0002]

2. Description of the Related Art When an image is taken from a moving object such as a car or an aircraft in progress, vibration is transmitted to a photographing system, and the photographed image is blurred.

Conventionally, a vibration proof optical system having a function of preventing blurring of a photographed image is disclosed in, for example, JP-A-50-80147, JP-B-56-21133, and JP-A-61-223819. Proposed.

Japanese Patent Application Laid-Open No. 50-80147 discloses that in a zoom lens having two afocal magnification systems, the first magnification system has an angular magnification of M ₁ and the second magnification system has an angular magnification of M _2. In this case, zooming is performed in each zooming system so as to have a relationship of M ₁ = 1−1 / M _2, and image blur is corrected by spatially fixing the second zooming system. Is stabilizing.

Japanese Patent Publication No. 56-21133 discloses that some optical members are moved in a direction to cancel the vibrational displacement of an image due to vibration in accordance with an output signal from a detecting means for detecting the vibration state of an optical device. To stabilize the image.

Japanese Patent Application Laid-Open No. 61-223819 discloses a photographing system in which a refraction type variable apex prism is arranged closest to the subject.
The image is deflected by changing the apex angle of the refraction type variable apex angle prism in accordance with the vibration of the photographing system to stabilize the image. In addition, JP-B-56-34847, JP-B-57-741
In Japanese Patent Publication No. 4 (1999), an optical member that is spatially fixed to vibration is arranged in a part of the imaging system, and the captured image is deflected by utilizing the prism action generated by the vibration of this optical member. I have a still image above.

Further, vibration of the photographing system is detected using an acceleration sensor, and a still image is formed by vibrating a part of the lens group of the photographing system in a direction perpendicular to the optical axis in accordance with a signal obtained at this time. There are also ways to get it.

In general, a movable lens group for correcting image blur is small and light in a mechanism for obtaining a still image by vibrating a part of the lens group of the image capturing system to eliminate blur of the captured image. There is a demand for an imaging system with a simple configuration that simplifies the relationship between the correction amount and the movement amount of the movable lens and shortens the calculation time for conversion.

Further, if the movable lens group is decentered, eccentric coma, eccentric astigmatism, and eccentric curvature of field are generated. If image blur is corrected, the image becomes blurred due to eccentric aberration. For example, if a large amount of eccentric distortion occurs, the amount of movement of the image on the optical axis and the amount of movement of the peripheral image differ. For this reason, if the movable lens group is decentered in order to correct the image blur on the image on the optical axis, a phenomenon similar to the image blur occurs in the peripheral portion, causing a significant decrease in optical characteristics. It is becoming.

As described above, when a movable lens group is moved in a direction perpendicular to the optical axis to be in an eccentric state in a photographic system for image stabilization, particularly in a variable power optical system, the amount of eccentric aberration is small and the optical performance is reduced. It is required to have a small number and a simple mechanism.

However, it is generally very difficult to obtain a photographing system that satisfies all of the above conditions. In particular, decentering a part of the photographing system having a refractive power greatly degrades the optical performance. There was a drawback that good images could not be obtained.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a small and lightweight lens is used as a movable lens group when a part of the movable lens group of the variable power optical system is moved in a direction perpendicular to the optical axis to correct image blurring. In addition to simplifying the mechanism of the movable lens group when selecting the group and driving it eccentrically, the amount of the above-described various eccentric aberrations generated when the movable lens group is moved and parallel decentered is reduced and improved. It is an object of the present invention to provide a variable power optical system having an anti-vibration function capable of obtaining optical performance.

[0013]

Means for Solving the Problems In order from the object side, there are provided two lens groups, a first group having a positive refractive power and a second group having a negative refractive power, wherein both the first group and the second group are arranged. In a variable power optical system that performs zooming from the wide-angle end to the telephoto end by moving to the object side,
The group includes, in order from the object side, an eleventh lens unit having a negative refractive power and a stop, and a twelfth lens unit having a positive refractive power. One of the lens units P in the first lens unit is arranged in a direction orthogonal to the optical axis. The lens unit is driven to be eccentric, and the other lens units in the first unit are fixed, and the blurring of the photographed image caused when the variable power optical system vibrates is corrected. To f11 and f
12. Assuming that the focal length at the wide-angle end of the entire system is fw, −9.0 <f11 / fw <−1.0 (1) 0.5 <f12 / fw <1.0 (1) 2) Satisfy the following conditions.

[0014]

1 to 3 are lens sectional views of Numerical Examples 1 to 3 of a variable power optical system according to the present invention, which will be described later.

In the figure, I is a first lens unit having a positive refractive power, and II is a second lens unit having a negative refractive power. By moving the first lens unit I and the second lens unit II to the object side as indicated by arrows. Zooming is performed from the wide-angle end to the telephoto end.

The first lens unit has a negative refractive power.
1, a stop SP, and a twelfth lens group I-2 having a positive refractive power.

In the present embodiment, the camera shake and the blurring of the photographed image caused by the vibration of the variable power optical system are caused by the twelfth lens group in the embodiment shown in FIGS. 1 and 2, and the eleventh lens group in the embodiment shown in FIG. The group or the twelfth group is used as a movable lens group, and is corrected by parallel eccentric drive in a direction perpendicular to the optical axis.

On the other hand, in each of the embodiments shown in FIGS. 1, 2 and 3, the focus moves the eleventh lens group (indicated by in FIG. 3) disposed in front of the stop SP on the optical axis. Have gone. In particular, in the embodiment shown in FIG. 3, a lens group (a lens group indicated by) consisting of a positive lens and a negative lens on the object side is integrally moved on the optical axis to reduce the driving force of the focus group and to reduce the screen in focus. The fluctuation of the peripheral light amount is reduced.

As described above, in this embodiment, the movable lens group to be driven eccentrically and the focusing lens group are separated to prevent the mechanical complexity, and the drive system of each lens group is simplified. I have.

In the present embodiment, the blur amount δ of the photographed image is detected by a blur detecting means such as an acceleration sensor or an angular acceleration sensor inside the camera, and based on the eccentric sensitivity S of the movable lens group inherent to the variable power optical system. Then, the parallel eccentric drive amount E of the movable lens group for correcting the blur of the photographed image is obtained from the equation E = δ / S. Then, for example, the movable lens group is eccentrically driven by a predetermined amount by a driving unit using a stacked piezo element or the like, thereby correcting the blur of the captured image.

In particular, in this embodiment, the variable power optical system is constructed as described above, and a part of the first lens group is a movable lens group for correcting blurring of a photographed image, and a direction orthogonal to the optical axis is set. Eccentric driving so that the amount of eccentric driving is always constant irrespective of the focal length.

Next, the relationship between the amount of image blur and the amount of movement of the movable lens group for correcting the amount of blur in the variable power optical system will be described.

Now, the first group of the variable power optical system is extended to a general case, and is composed of three lens groups Ia, Ib and Ic in order from the object side. The following describes the case in which it is performed.

The focal length of the lens group Ia is fIa, and the lens group is
The photographing magnifications at the wide-angle end of Ib, the lens group Ic, and the second group are βIbW, βIcW, and βIIW, respectively, and similarly, the photographing magnifications at the telephoto end are βIbT, βIcT, and βIIT.

Now, the eccentric drive amounts of the movable lens group at the wide-angle end and the telephoto end when the camera is tilted by an angle θ are expressed by EW, respectively.
b, ETb

[0026]

(Equation 1) Becomes To make the eccentric drive amount of the movable lens group constant regardless of the focal length, EWb = ETb

[0027]

(Equation 2) Becomes Further, βIbW = βIbT (a). The movable lens group for image blur correction is a lens group Ia.
When the photographing magnifications at the wide-angle end and the telephoto end of the lens unit Ia are βIaW and βIaT, respectively, the eccentric drive amounts EWa and ETa at the wide-angle end and the telephoto end are

[0028]

(Equation 3) Becomes From EWA = ETa, the following condition is obtained: βIaW = βIaT (b).

Further, when the movable lens group for image shift correction is selected as the lens group Ic, the photographing magnifications at the wide angle end and the telephoto end of the lens group Ic are βIcW and βIcT, and the combined focal length of the lens groups Ia and Ib is fIab. Then, the eccentric drive amounts EWc and ETc at the wide-angle end and the telephoto end are

[0030]

(Equation 4) Becomes From EWc = ETc, the following condition is obtained: βIcW = βIcT (c).

The lens units Ia, Ib, and Ic in the first unit are always (a),
The conditional expressions (b) and (c) hold. For this reason, even if an arbitrary lens group in the first lens group is selected as the movable lens group, the camera can be moved at the angle θ.
The amount of eccentric drive of the movable lens group when tilted can be constant regardless of the focal length of the entire system.

In the present embodiment, by using the above optical properties, a variable power optical system having a simple configuration which prevents the mechanism from being complicated when the movable lens group is eccentrically driven is achieved.

Next, the features of the lens configuration in this embodiment will be described in order.

(A) The first group is divided into two lens groups, an eleventh group and a twelfth group, with a diaphragm interposed therebetween, one of which is a movable lens group and the other is a focusing lens group. As a result, when the camera is a lens shutter, it is easy to unitize the shutter and the focus actuator, and a variable power optical system having a mechanically simple structure without mechanical interference is achieved.

In particular, in the present embodiment, the first lens unit is composed of two lens units, an eleventh lens unit having a negative refractive power and a twelfth lens unit having a positive refractive power, and the eleventh lens unit or the twelfth lens unit is driven eccentrically. As a result, good optical performance with little eccentric aberration and mainly field curvature aberration is maintained.

Next, regarding the occurrence of eccentric aberration when the movable lens group is moved in a direction perpendicular to the optical axis in an arbitrary refractive power arrangement to correct image blurring, from the viewpoint of aberration theory, the 23rd Applied Physics Explained based on the method presented by Matsui in the academic lecture (1962).

When one lens unit P of the variable power optical system is decentered in parallel by E, the aberration amount ΔY1 of the entire system is the aberration amount ΔY before the decentering and the eccentric aberration caused by the eccentricity as shown in the equation (a). And the sum with the quantity ΔY (E). Here, the aberration amount ΔY is represented by spherical aberration (I), coma aberration (II), astigmatism (III), Petzval sum (P), and distortion (Y).

The eccentric aberration ΔY (E) is expressed by the first-order eccentric coma (IIE) and the first-order eccentric astigmatism (III) as shown in the equation (C).
E) Primary eccentric field curvature (PE), Primary eccentric distortion (VE
1) First-order eccentric distortion (VE2), and first-order origin movement (ΔE).

Further, the aberrations from (ΔE) to (VE2) in equations (d) to (i) are caused by the angle of incidence of the light beam on the lens group P in the variable power optical system for decentering the lens group P in parallel.

[0040]

[Outside 1] , The aberration coefficients I _P , II _P , III _P ,
The aberration coefficients when P _P and V _P and the lens group similarly arranged on the image plane side of the lens group P as one lens group Q are I _q , II _q , III _q , P _q , _Expressed using V _q .

[0041]

[Outside 2]

[0042]

[Outside 3] More in order to reduce the occurrence of decentering aberration from expression aberrations coefficient I _P of the first lens _{group, II P, III P, P} P, or a small value V _P, or formula (a) - ( As shown in equation (i), it is necessary to set various aberration coefficients in a well-balanced manner so as to cancel each other.

For example, taking the eccentric curvature of field PE as an example, (α
_P′ −α _P ) is positive, P _q is negative, α _P is negative, P _P is positive, and the eccentric curvature of field PE is canceled out by the P group (lens group Ib) and the q group (second group II). Accordingly, the eccentric field curvature PE can be reduced.

Other decentering aberrations can be similarly canceled out by the P group and the q group. If the lens unit Ia having a negative refractive power (the eleventh unit I-1) is used as a movable lens unit for correction instead of the lens unit Ib having a positive refractive power, α _P = 0 and P _q ≒ 0. In this case, the eccentric curvature of field PE can be similarly reduced.

In this embodiment, when the first lens unit has two lens units each having a positive refractive power, when the object-side lens unit Ia is a movable lens unit for correction, α _P
= 0 and P _q ≒ 0, so that the eccentric curvature of field PE can be similarly reduced. In addition, when the lens group Ib is used as a movable lens group for correction, since the light beam enters the lens group Ib in a converged state, the effective diameter of the lens in the lens group Ib can be reduced, and the lens group Ib It has features such as easy weight reduction.

(B) The first unit is composed of, in order from the object side, an eleventh unit having a negative refractive power and a twelfth lens unit having a positive refractive power, and moving the eleventh unit on the optical axis. Focus, and the twelfth lens group is eccentrically driven to correct the blur of the photographed image.

When the focal lengths of the 11th and 12th units are f11 and f12, respectively, and the focal length at the wide-angle end of the entire system is fW, the above-mentioned conditional expressions (1) and (2) are satisfied. Like that.

As a result, good optical performance is maintained while obtaining a predetermined sensitivity (the ratio of the amount of image movement to the amount of eccentricity of the movable lens group).

By disposing the focus lens group on the object side of the movable lens group, fluctuations in aberrations caused by fluctuations in the object distance, particularly fluctuations in astigmatism, are reduced, and fluctuations in the eccentric drive amount of the movable lens group are eliminated. The eccentric drive amount is set to be constant regardless of the distance.

If the refractive power of the 11th lens unit becomes too strong beyond the lower limit value of the conditional expression (1), when focusing by the 11th lens unit, the aberration variation accompanying focusing increases. On the other hand, if the refractive power of the 11th lens group becomes too weak beyond the upper limit, a large amount of coma is generated over the entire screen, which is not good.

Conditional expression (2) relates to the refractive power of the twelfth lens group which is a movable lens group. If the lower limit value is exceeded, spherical aberration will be insufficiently corrected on the wide-angle side, and decentering coma will increase on the telephoto side. Conversely, if the upper limit is exceeded, the twelfth lens group
This is not good because the sensitivity when the group is driven in parallel eccentricity becomes too small and the entire lens system becomes large.

(C) The eleventh unit has at least one negative lens, the radius of curvature of the object-side lens surface of the object-side negative lens Na is RNa, and the twelfth unit is at least two positive lenses. A positive lens Pa on the object side
The curvature radii of the lens surfaces on the object side and the image plane side are respectively RPa
1, RPa2, the radius of curvature of the object-side and image-side lens surfaces of the positive lens Pb on the image side is RPb1, RPb2, and the thickness of the entire twelfth lens unit on the optical axis is D12L. 1 <RNa / fW <-0.25 (3) -1.2 <RPa2 / RPa1 <-0.3 (4) | RPb2 / RPb1 | <0.8 (5) 0.1 <D12L / fW <0.55 (6) The following condition is satisfied.

By specifying the lens shapes and the like of the predetermined lenses in the eleventh and twelfth groups in this manner, the optical performance of the entire screen is favorably maintained.

Conditional expression (3) is mainly for favorably correcting coma and astigmatism. If the lower limit is exceeded, a lot of coma and higher-order aberrations are generated. If the upper limit is exceeded, astigmatism will be insufficiently corrected at an intermediate zoom position, which is not good.

Conditional expression (4) is mainly for correcting decentered coma and higher-order aberrations in a well-balanced manner. When the curvature of the lens surface on the object side becomes tighter than the lower limit, the spherical aberration generated in the twelfth lens unit increases, and the eccentric coma increases on the telephoto side. If the curvature of the lens surface on the image plane side exceeds the upper limit value, a large amount of high-order aberration is generated, which is not preferable.

Conditional expression (5) is mainly for favorably correcting decentered astigmatism. If the conditional expression is not satisfied and the curvature of the lens surface on the object side increases, astigmatism generated in the twelfth lens unit increases, and it becomes difficult to satisfactorily correct decentering astigmatism especially on the telephoto side. .

Conditional expression (6) mainly relates to the length of the twelfth lens unit on the optical axis in order to favorably correct eccentric distortion. When the value exceeds the lower limit, a large amount of decentering distortion occurs on the wide angle side, and when the value exceeds the upper limit, the size of the twelfth lens unit increases, which is not good.

(D) The twelfth group has at least one negative lens Nb, and the second group has at least one positive lens Pc. The negative lens Nb and the positive lens When the Abbe numbers of the material of Pc are νNb and νPc, respectively, the following condition is satisfied: νNb <40 (7) νPc <42 (8)

Thus, the variation of the chromatic aberration of magnification due to the magnification change and the chromatic aberration of eccentric magnification when the twelfth lens unit is driven eccentrically are corrected well.

If conditional expressions (7) and (8) are not satisfied, the chromatic aberration of magnification and the chromatic aberration of eccentric magnification both increase, which is not preferable.

(E) In the present embodiment, the two lenses on the object side of the eleventh group are constituted by a positive lens and a negative lens, and focusing is performed by moving these two lenses on the optical axis. This is preferable because the weight of the focus lens group can be reduced and fluctuation of the peripheral light amount due to focus can be reduced.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass.

The aspheric surface has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R is a paraxial radius of curvature,
When A, B, C, D, and E are each aspheric coefficients

[0064]

(Equation 5) It is represented by the following equation.

Table 1 shows the relationship between the above-mentioned conditional expressions and Numerical Examples 1 to 3.

[0066]

[Outside 4]

[0067]

[Outside 5]

[0068]

[Outside 6] When the numerical examples are expressed in units of "mm", the eleventh unit shown in FIG. 3 or the lens unit consisting of two positive lenses and the negative lens shown in FIG. Feeding distance when focusing on () (∞
１1 m). Here, W and T are the wide-angle end and the telephoto end. The amount of extension is "minus sign" when it is extended to the object side.
It is represented by

[0069]

[0070]

[Table 1]

[0071]

According to the present invention, good optical performance can be maintained by correcting the blurring of an image by eccentrically driving a part of the small and light lens group of the variable power optical system as a movable lens group as described above. In addition, the parallel eccentric driving amount of the movable lens group is made independent of the value of the focal length, and a variable power optical system having a vibration proof function with a simplified mechanism can be achieved.
In addition, a variable power optical system having a simple image stabilizing function that makes the amount of parallel eccentric drive of the movable lens group independent of the object distance by using the lens group arranged on the object side of the movable lens group as the focus lens group. It is possible to achieve.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

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

FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 4 is an aberration diagram of a reference state according to Numerical Example 1 of the present invention.

FIG. 5 is an aberration diagram of a reference state according to Numerical Example 1 of the present invention.

FIG. 6 is an aberration diagram of a reference state according to Numerical Example 1 of the present invention.

FIG. 7 is an aberration diagram of a reference state according to Numerical Example 1 of the present invention.

FIG. 8 is an aberration diagram when a first shake correction is performed in the twelfth lens unit of Numerical Embodiment 1 of the present invention.

FIG. 9 is an aberration diagram obtained when one shake correction is performed in the twelfth lens unit of Numerical Embodiment 1 of the present invention.

FIG. 10 is an aberration diagram of a reference state in Numerical Example 2 of the present invention.

FIG. 11 is an aberration diagram of a reference state in Numerical Example 2 of the present invention.

FIG. 12 is an aberration diagram of a reference state according to Numerical Example 2 of the present invention.

FIG. 13 is an aberration diagram of a reference state according to Numerical Example 2 of the present invention.

FIG. 14 is an aberration diagram when a first shake correction is performed in the twelfth lens unit in Numerical Example 2 of the present invention.

FIG. 15 is an aberration diagram when a first shake correction is performed in the twelfth lens group in Numerical Example 2 of the present invention.

FIG. 16 is an aberration diagram of a reference state in Numerical Example 3 of the present invention.

FIG. 17 is an aberration diagram of a reference state in Numerical Example 3 of the present invention.

FIG. 18 is an aberration diagram of a reference state in Numerical Example 3 of the present invention.

FIG. 19 is an aberration diagram of a reference state in Numerical Example 3 of the present invention.

FIG. 20 is an aberration diagram when a first shake correction is performed in the twelfth lens group in Numerical Example 3 of the present invention.

FIG. 21 is an aberration diagram when a first shake correction is performed in the twelfth lens group in Numerical Example 3 of the present invention.

FIG. 22 is an aberration diagram obtained when one shake correction is performed in the eleventh group in Numerical Example 3 of the present invention.

FIG. 23 is an aberration diagram when a first shake correction is performed in the eleventh lens group in Numerical Example 3 of the present invention.

[Explanation of symbols]

 I First lens group II Second lens group I-1 11th lens group I-2 12th lens group SP Aperture W Wide-angle end T Telephoto end M Meridional image plane S Sagittal image plane

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Claims (3)

(57) [Claims] 1. An optical system comprising two lens groups, a first group having a positive refractive power and a second group having a negative refractive power, in order from the object side, and moving both the first group and the second group to the object side. In the variable power optical system for performing zooming from the wide-angle end to the telephoto end, the first unit includes, in order from the object side, an eleventh unit having a negative refractive power, a stop, and a twelfth unit having a positive refractive power. When one lens group P in the first group is eccentrically driven in a direction perpendicular to the optical axis, and the other lens group in the first group is fixed, the vibration occurs when the variable power optical system vibrates. When the blurring of the photographed image is corrected, the focal lengths of the 11th and 12th groups are f11 and f12, respectively, and the focal length at the wide-angle end of the entire system is fw: -9.0 <f11 / fw < A variable power optical system having an anti-vibration function, which satisfies a condition of -1.0 0.5 <f12 / fw <1.0. 2. The eleventh unit has at least one negative lens, the radius of curvature of the object-side lens surface of the object-side negative lens Na is RNa, and the twelfth unit is at least 2 lenses.
And the radius of curvature of the object-side positive lens Pa on the object side and the radius of curvature of the lens surface on the image plane side are RPa1 and R, respectively.
Pa2, the curvature radii of the object-side and image-side lens surfaces of the image-side positive lens Pb are RPb1 and RPb2, and the thickness of the entire twelfth lens unit on the optical axis is D12L. -1.1 < RNa / fw <-0.25-1.2 <RPa2 / RPa1 <-0.3 | RPb2 / RPb1 | <0.8 0.1 <D12L / fw <0.55 A variable power optical system having an image stabilizing function according to claim 1. 3. The twelfth group has at least one negative lens Nb, and the second group has at least one positive lens Pc, and the negative lens Nb and the positive lens Pc 3. The variable power optical system according to claim 2, wherein the following condition is satisfied: νNb <40 and νPc <42, where Abbe numbers of the materials are νNb and νPc, respectively.