JP2998434B2 - 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 power optical system having an image stabilizing function, and more particularly to a variable power optical system in which a part of a lens group of the variable power optical system is rotated about a point on an optical axis as a center point. An image stabilizing function suitable for a photographic camera, a video camera, or the like that stabilizes a captured image by optically correcting a blur of the captured image when the variable power optical system vibrates (tilts) to obtain a still image. This relates to a variable power optical system having

[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, various anti-vibration optical systems having a function of preventing blurring of a captured image have been proposed.

For example, in Japanese Patent Publication No. 56-21133, some optical members are moved in a direction to cancel the vibrational displacement of an image due to vibration in response to an output signal from a detecting means for detecting a vibration state in an optical device. This stabilizes the image.

In Japanese Patent Application Laid-Open No. 61-223819, in a photographing system in which a refraction type variable apex angle prism is arranged closest to the subject, the apex angle of the refraction type variable apex angle prism is changed according to the vibration of the imaging system. The image is deflected to stabilize the image.

Japanese Patent Publication No. 56-34847, Japanese Patent Publication No. 5
In JP-A-7-7414, an optical member spatially fixed to vibration is arranged in a part of a photographing system, and a photographed image is deflected by utilizing a prism effect generated by vibration of the optical member. A still image is obtained on the image plane.

Japanese Patent Application Laid-Open No. 50-137555 discloses a telephoto lens in which a lens group on the object side is rotated about a point on the optical axis which is separated from the principal point by the focal length of the lens group as a center point. This corrects the blur of the captured image when the telephoto lens is tilted.

In Japanese Patent Application Laid-Open No. 63-115126, vibration of a photographing system is detected by using an acceleration sensor or the like, and a part of the lens group of the photographing system is moved in a direction orthogonal to the optical axis according to a signal obtained at this time. There is also a method of obtaining a still image by vibrating the image.

In addition, Japanese Patent Application Laid-Open No. Hei 2-238429 and US Pat. No. 2,959,088 disclose the first and second refractive powers of negative and positive.
A lens system consisting of two lens groups, a group and a second group, is arranged in front of the photographing system, and when the photographing system vibrates, the second group is used as an active lens group for image stabilization, and a gimbal support is provided at its focal position. We have proposed an anti-vibration optical system using the inertial pendulum method.

[0010]

Generally, a method of disposing an image stabilizing optical system in front of a photographing system and vibrating a part of a movable lens group of the image stabilizing optical system to eliminate blurring of a photographed image and obtain a still image. However, there is a problem that the entire apparatus becomes large and a moving mechanism for moving the movable lens group becomes complicated.

There is also a problem that the amount of decentering aberration generated when the movable lens group is vibrated increases, and the optical performance is greatly reduced.

An optical system that performs image stabilization using a variable apex angle prism has a problem that the amount of chromatic aberration of eccentric magnification increases during image stabilization, especially on the long focal length side (telephoto side).

On the other hand, an optical system that performs image stabilization by decentering some lenses of the photographing system in a direction perpendicular to the optical axis has the advantage that no special optical system is required for image stabilization. However, on the other hand, there is a problem that the amount of occurrence of eccentric aberration at the time of image stabilization increases.

In addition, in order to secure a necessary light amount on the imaging surface during image stabilization, it is necessary to increase the lens diameter of the lens group on the object side with respect to the movable lens group. There was a problem.

Further, in an optical system which performs vibration reduction by vibrating at least one lens unit after the variable power lens unit (magnification unit), the relationship between the amount of correction of blurring of the photographed image and the amount of movement of the movable lens unit. However, there is a problem that arithmetic means such as an arithmetic circuit is required to obtain these values, and the entire apparatus becomes complicated and costly.

If image stabilization is performed using a moving lens group such as a variator at the time of zooming, the structure becomes very complicated, and a zoom motor or the like as driving means for moving the lens group is required. There was a problem that the load increased.

According to the present invention, an image blur when the variable power optical system is vibrated (tilted) is rotated by rotating a lens group constituting a part of the variable power optical system around a rotation on the optical axis. A configuration having an image stabilizing function that satisfactorily corrects eccentric aberration while suppressing the amount of eccentric aberration generated when the lens group is decentered, while reducing the size of the entire apparatus, by reducing the size of the entire apparatus. The objective is to provide a magnification optical system.

[0018]

According to the present invention, a variable power optical system having an image stabilizing function includes a variable power optical system having a first group fixed at the time of zooming and focusing on the object side of a variable power unit. A first group having a fixed first group and a first group that rotates around a point on the optical axis to correct image blur, and includes at least one of the first group. One lens surface is formed of an aspheric surface having a shape in which the positive refractive power becomes stronger from the center to the periphery. The focal length of the first lens unit is f1b, and the rear principal point of the first lens unit to the rotation center is Where L is the distance and fT is the focal length of the entire system at the telephoto end. 0.5 <| f1b / L | <1.2 ‥‥‥‥‥‥‥ (1) 0.53 <| f1b / fT | <0.65 ‥‥‥‥‥‥‥ (2)

In particular, the variable power optical system includes, in order from the object side, a first group having a fixed positive refractive power, a second group having a negative refractive power having a zooming function, and a fixed positive lens during focusing and focusing. The third of the refractive power of
The zoom lens is characterized by having four lens groups of a fourth group having a positive refractive power and having both a correction function for correcting an image plane that fluctuates due to zooming and a focusing function.

[0020]

FIG. 1 is a schematic view showing a paraxial refractive power arrangement of an optical system according to Embodiment 1 of the present invention, and FIG. 2 is a lens sectional view of Numerical Embodiment 1 of the present invention.

FIGS. 3, 4, 5, 6, and 7 show the telephoto end corrected for the wide-angle end, the middle, the telephoto end, the telephoto end without eccentricity, and the 2 degree blur angle in the first numerical embodiment of the present invention. 8, 9, 10, 11, and 12 correct the wide-angle end, the middle, the telephoto end, the telephoto end without eccentricity, and the blur angle of 2 degrees in Numerical Embodiment 2 of the present invention. 13, FIG. 14, FIG. 15, FIG. 16, and FIG. 17 show a third embodiment of the present invention.
Wide-angle end, middle, telephoto end, telecentric end without eccentricity, and 2
FIG. 7 is an aberration diagram at a telephoto end in which a degree of blurring is corrected.

In FIG. 1, reference numeral 1 denotes a first lens unit which is fixed during zooming and focusing. The first group 1 is rotated about a fixed point on the optical axis with respect to the fixed first group 1a, and the first group 1b for image stabilization for correcting image blurring.
It is composed of two lens groups, a group 1b (movable lens group). The lens surface on the image plane side of the first lens subunit 1a is formed of an aspherical surface having a positive refractive power that increases from the center to the periphery.

Reference numeral 2 denotes a second unit having a negative refractive power which moves along the optical axis direction during zooming, and constitutes a zooming unit. The second lens unit 2 is moved, for example, as indicated by an arrow a to perform zooming from the wide-angle end to the telephoto end.

Reference numeral 3 denotes a third group having a fixed positive refractive power, and reference numeral 4 denotes a positive lens having both an image plane correction function for correcting an image plane that fluctuates with zooming and a focusing function for focusing. Is a fourth group of refractive powers.

In this embodiment, when zooming from the wide-angle end to the telephoto end with the fourth unit 4 focused on an object at infinity, the fourth unit 4 is moved on the optical axis as shown by a curve b. . When zooming from the wide-angle end to the telephoto end while focusing on the closest object, the zoom is performed by moving the optical axis as shown by a curve c.

In this embodiment, the first lens unit 1 is composed of two lens units 1a and 1b, and the first lens unit 1b is used for image stabilization by rotating around a specific point on the optical axis. The image blur when the variable magnification optical system vibrates is corrected. As a result, compared to the conventional anti-vibration optical system, anti-vibration is performed without newly adding an optical member such as a lens group or a variable apex prism for anti-vibration.

The first lens unit 1a for correcting eccentric aberration generated when the first lens unit is decentered toward the object side of the first lens unit 1b.
The group 1a is provided to satisfactorily correct eccentric aberrations generated during image stabilization, particularly eccentric coma and eccentric field curvature.

Further, in this embodiment, the first lens unit 1 constituting a part of the variable power optical system is constituted by a single block. Thus, some achromatization is performed in the first lens unit 1 so that the occurrence of eccentric magnification chromatic aberration during image stabilization is smaller than when the above-described conventional variable apex prism is used.

In this embodiment, a zoom optical system having a vibration-proof function is constituted by the four lens groups 1 to 4.

In order to obtain good optical performance while reducing the size of the entire lens system, the above-mentioned conditional expressions (1) and (2) are used.
(2) is satisfied.

Next, the technical meaning of each of the conditional expressions (1) and (2) will be described.

Conditional expression (1) is for appropriately setting the position of the center of rotation on the optical axis when rotating the first lens subunit 1b, and effectively exhibiting the vibration proof function.

If the rotation center exceeds the lower limit value of the conditional expression (1) and becomes too far from the rear principal point of the first lens unit 1b, the correction of the eccentric field curvature generated at the time of image stabilization becomes insufficient. Not so good.

If the center of rotation approaches the rear principal point of the first lens unit 1b beyond the upper limit value of the conditional expression (1), the correction of the eccentric curvature of field which occurs during image stabilization becomes excessive, and This is not good because the amount of coma aberration is too large.

Conditional expression (2) is for appropriately setting the refractive power of the first lens subunit 1b and reducing the amount of eccentric aberration generated when the first lens subunit 1c is decentered mainly for image stabilization. is there.

If the lower limit of conditional expression (2) is exceeded,
If the refractive power of b becomes too strong, it becomes difficult to reduce the amount of decentering aberration generated, which is not good.

When the value exceeds the upper limit of conditional expression (2), the first
If the refracting power of the group becomes too weak, the amount of eccentricity of the first group b becomes large at the time of image stabilization. As a result, the distance from the lens center of the first group 1b to the optical axis becomes too large and the lens diameter of the first group 1b becomes too large. Not good as it increases.

In this embodiment, the first group 1b for vibration isolation is used.
Is provided with a fixed first group 1a on the object side. The lens surface on the image plane side of the first lens subunit 1a is formed of an aspherical surface formed such that the positive refractive power increases from the center of the lens toward the periphery.

At this time, the amount of aspherical surface of the lens surface becomes larger as the inclination angle of the first lens unit 1b becomes larger with respect to the same correction angle, that is, at the time of rotation, the center of rotation of the first lens unit 1b becomes the first lens unit 1a. It is set to increase as you approach. As a result, eccentric aberrations, especially eccentric coma aberrations during vibration proofing are favorably corrected, and high optical performance is maintained.

The fixed first lens unit 1a also has a function as a protective glass so that no external force other than vibration reduction is applied directly to the variable power optical system from the outside.

SSP is a fixed stop, which is arranged between the first group 1 and the second group 2. The aperture SSP suppresses a change in the image plane illuminance ratio around the screen during image stabilization, so that an appropriate light amount distribution can be obtained on the imaging surface even during image stabilization.

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. Table 1 shows the relationship with each conditional expression in each numerical example.

Note that R23 and R in Numerical Examples 1 and 3
24, R21 and R22 in Numerical Example 2 are glass materials (parallel plane plates) such as face plates.

In Numerical Embodiments 1 to 3, R1 and R2 are a first lens unit having a function of correcting eccentric aberration during image stabilization, and R8 is a fixed stop SSP for preventing a change in image plane illuminance ratio during image stabilization.
It is.

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 ₀ being a paraxial radius of curvature, and B, C, D, and E being aspherical. Spherical coefficient

[0046]

(Equation 1) It is represented by the following equation. For example, the meaning of "D-0x" means "10- ^x ". Numerical Example 1 f = 1 to 9.46 fno = 1: 1.85 to 2.60 2ω = 53.2 ° to 6.1 ° R 1 = ∞ D 1 = 0.2659 N 1 = 1.58313 ν 1 = 59.4 R 2 = Aspherical surface D 2 = 0.31 R 3 = 5.9024 D 3 = 0.2347 N 2 = 1.80518 ν 2 = 25.4 R 4 = 3.0011 D 4 = 1.0169 N 3 = 1.62280 ν 3 = 57.1 R 5 = 19.0117 D 5 = 0.0313 R 6 = 3.8646 D 6 = 0.5632 N 4 = 1.77250 ν 4 = 49.6 R 7 = 12.5153 D 7 = 0.29 R 8 = fixed aperture D 8 = variable R 9 = 10.3513 D 9 = 0.1095 N 5 = 1.77250 ν 5 = 49.6 R10 = 1.1593 D10 = 0.3700 R11 = -2.7567 D11 = 0.1095 N 6 = 1.69680 ν 6 = 55.5 R12 = 1.5665 D12 = 0.1721 R13 = 1.9293 D13 = 0.2659 N 7 = 1.84666 ν 7 = 23.8 R14 = 8.9728 D14 = Variable R15 = Aperture stop D15 = 0.1721 R16 = 2.3868 D16 = 0.4380 N 8 = 1.58313 ν 8 = 59.4 R17 = Aspherical surface D17 = Variable R18 = 2.4818 D18 = 0.0939 N 9 = 1.84666 ν 9 = 23.8 R19 = 1.2043 D19 = 0.4693 N10 = 1.51633 ν10 = 64.2 R20 = -10.0064 D20 = 0.0235 R21 = -55.3935 D21 = 0.2659 N11 = 1.60311 ν11 = 60.7 R22 = -3.7088 D22 = 0.6258 R23 = ∞ D23 = 0.7822 N12 = 1.51633 ν12 = 64.2 R24 = ∞ R2 aspherical surface _{R 0 = ∞ K = 0 B} = -1.5671 D-04 R17 aspherical surface _{R 0 = -7.6694 K = 3.25725D +} 00 B = -5.52222D-02 C = -4.06010D-03 D = -1.53076D-02 E = -6.58462D- 03

[0047]

[Table 1] 6.629 from rotation center R3 surface 6.629 Numerical example 2 f = 1 to 7.60 fno = 1: 2.05 to 2.882 2ω = 48.0 ° to 6.6 ° R 1 = ∞ D 1 = 0.2083 N 1 = 1.51633 ν 1 = 64.2 R 2 = Aspherical surface D 2 = 0.28 R 3 = 8.6537 D 3 = 0.1528 N 2 = 1.80518 ν 2 = 25.4 R 4 = 2.6736 D 4 = 0.6945 N 3 = 1.62299 ν 3 = 58.2 R 5 = -50.9433 D 5 = 0.0278 R 6 = 2.9458 D 6 = 0.4167 N 4 = 1.80610 ν 4 = 41.0 R 7 = 9.7227 D 7 = 0.22 R 8 = Fixed diaphragm D 8 = Variable R 9 = 29.9682 D 9 = 0.0694 N 5 = 1.88300 ν 5 = 40.8 R10 = 0.8233 D10 = 0.3123 R11 = -0.9646 D11 = 0.0694 N 6 = 1.58144 ν 6 = 40.8 R12 = 1.3462 D12 = 0.2778 N 7 = 1.84666 ν 7 = 23.8 R13 = -2.5971 D13 = Variable R14 = Aperture stop D14 = 0.1667 R15 = Aspherical surface D15 = 0.4167 N 8 = 1.58313 ν 8 = 59.4 R16 = -11.4523 D16 = Variable R17 = 2.8775 D17 = 0.0694 N 9 = 1.84666 ν 9 = 23.8 R18 = 1.1272 D18 = 0.0347 R19 = 1.2844 D19 = 0.5278 N10 = 1.58313 ν10 = 59.4 R20 = aspheric D20 = 1.1112 R21 = ∞ D21 = 0.7778 N11 = 1.51633 ν11 = 64.2 R22 = ∞ R2 aspherical surface _{R 0 = ∞ K = 0 B} = -5.59792D-04 R15 Aspherical _{R 0 = 1.8533 K = -7.87402D-} 02 B = -2.81506D-02 C = -2.77357D-02 D = 1.40493D-02 R20 aspherical surface R ₀ = -2.3519 K = 0 B = 5.22976D-04 C = −5.07458D-02 D = −2.86992D-02

[0048]

[Table 2] 5.242 from center of rotation R3 5.242 Numerical Example 3 f = 1. to 9.46 fno = 1: 1.85 to 2.60 2ω = 53.2 ° to 6.1 ° R 1 = ∞ D 1 = 0.2659 N 1 = 1.58313 ν 1 = 59.4 R 2 = Aspherical surface D 2 = 0.31 R 3 = 6.0147 D 3 = 0.2347 N 2 = 1.80518 ν 2 = 25.4 R 4 = 3.0324 D 4 = 1.0168 N 3 = 1.62299 ν 3 = 58.2 R 5 = 19.2651 D 5 = 0.0313 R 6 = 3.8372 D 6 = 0.5632 N 4 = 1.77250 ν 4 = 49.6 R 7 = 12.5147 D 7 = 0.30 R 8 = Fixed aperture D 8 = Variable R 9 = 10.0075 D 9 = 0.1095 N 5 = 1.77250 ν 5 = 49.6 R10 = 1.1435 D10 = 0.3690 R11 = -2.7546 D11 = 0.1095 N 6 = 1.69680 ν 6 = 55.5 R12 = 1.5688 D12 = 0.1721 R13 = 1.9369 D13 = 0.2659 N 7 = 1.84666 ν 7 = 23.8 R14 = 9.5147 D14 = Variable R15 = Aperture stop D15 = 0.1721 R16 = Aspheric surface D16 = 0.4380 N 8 = 1.58313 ν 8 = 59.4 R17 = -7.7627 D17 = Variable R18 = 2.3759 D18 = 0.0939 N 9 = 1.84666 ν 9 = 23.8 R19 = 1.1838 D19 = 0.4693 N10 = 1.51633 ν10 = 64.2 R20 = -16.2041 D20 = 0.0235 R21 = -208.7752 D21 = 0.2659 N11 = 1.60311 ν11 = 60.7 R22 = -3.6652 D22 = 0.6257 R23 = ∞ D23 = 0.7822 N12 = 1.51633 ν12 = 64.2 R24 = ∞ R2 aspherical surface R ₀ ∞ K = 0 B = -1.30610D- 04 R16 aspherical surface _{R 0 = 2.3914 K = 3.28859D +} 00 B = -5.49762D-02 C = -3.59539D-03 D = -1.55306D- 02 E = -7.02882D-03

[0049]

[Table 3] 7.824 from surface of rotation center R3

[0050]

According to the present invention, as described above, the first lens group, which is one element of the variable power optical system, is rotated to correct the image blur when the variable power optical system vibrates (tilts). With this configuration, it is possible to achieve a variable-magnification optical system having an anti-vibration function that reduces the size of the entire apparatus while minimizing deterioration of optical performance during anti-vibration.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a paraxial refractive power arrangement of an optical system according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 3 is a diagram illustrating various aberrations at the wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 4 is a diagram showing various aberrations in the middle of the first numerical embodiment of the present invention;

FIG. 5 is a diagram illustrating various aberrations at the telephoto end in Numerical Example 1 of the present invention.

FIG. 6 is a lateral aberration diagram without decentering at the telephoto end according to Numerical Embodiment 1 of the present invention.

FIG. 7 is a lateral aberration diagram of the numerical example 1 of the present invention in a state where a 2 degree blur angle at the telephoto end is corrected.

FIG. 8 is a diagram illustrating various aberrations at the wide-angle end according to Numerical Embodiment 2 of the present invention.

FIG. 9 is a diagram showing various aberrations in the middle of Numerical Example 2 of the present invention.

FIG. 10 is a diagram showing various aberrations at the telephoto end in Numerical Example 2 of the present invention.

FIG. 11 is a lateral aberration diagram without decentering at the telephoto end in Numerical Embodiment 2 of the present invention.

FIG. 12 illustrates a second example of the second embodiment at the telephoto end in Numerical Embodiment 2 of the present invention.
Lateral aberration diagram with the degree of blurring corrected

FIG. 13 is a diagram illustrating various aberrations at the wide-angle end according to Numerical Embodiment 3 of the present invention.

FIG. 14 is a diagram showing various aberrations in the middle of Numerical Embodiment 3 of the present invention.

FIG. 15 is a diagram showing various aberrations at the telephoto end in Numerical Example 3 of the present invention.

FIG. 16 is a lateral aberration diagram without decentering at the telephoto end in Numerical Example 3 of the present invention.

FIG. 17 is a diagram illustrating a second embodiment of the third numerical embodiment of the present invention at the telephoto end.
Lateral aberration diagram with the degree of blurring corrected

[Explanation of symbols]

 Reference Signs List 1 1st group 1a 1a group 1b 1b group 2 2nd group 3 3rd group 4 4th group d d line g g line y Image height Y Maximum image height ΔM Meridional image plane ΔS Sagittal image plane

Claims (2)

(57) [Claims] 1. A variable power optical system having a fixed first lens unit at the time of zooming and focusing on an object side of a zooming unit, wherein the first lens unit is fixed on the optical axis with a fixed first lens unit. And a first lens group that corrects image blur by rotating about one point as a rotation center. At least one lens surface in the first lens group has a stronger positive refractive power from the center to the periphery. The first shape
When the focal length of the b group is f1b, the distance from the rear principal point of the 1b group to the rotation center is L, and the focal length of the entire system at the telephoto end is fT, 0.5 <| f1b / L | < 1.2 0.53 <| f1b / fT | <0.65. A variable power optical system having an anti-vibration function, characterized by satisfying the following condition. 2. The variable magnification optical system includes a first group of fixed positive refractive power, a second group of negative refractive power having a variable magnification function, and a fixed A third group of positive refractive power,
2. The image forming apparatus according to claim 1, further comprising: a fourth lens unit having a positive refractive power, which has both a correction function and a focusing function for correcting an image plane that fluctuates due to zooming. Variable power optical system with anti-vibration function.