JP2011158599A - Large-aperture telephoto zoom lens with vibration-proof function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact large-aperture telephoto zoom lens with a vibration-proof function, which has an angle of view of 13 degrees or below at a telephoto end, a variable power ratio of approximately 2.7 times, an open F-value of approximately 2.8 in the entire zooming area, is able to increase a focusing speed, sufficiently exhibits a camera shake correction effect, and has a satisfactory optical performance. <P>SOLUTION: The large-aperture telephoto zoom lens with the vibration-proof function includes, in order from an object side, a first lens group L1 of positive refractive power, second lens group L2 of negative refractive power, a third lens group L3 of positive refractive power, and a fourth lens group L4 of positive refractive power. The fourth lens group L4 includes, in order from the object side, a front group Gr4f of positive refractive power, a middle group Gr4m of negative refractive power, and a rear group Gr4r of positive refractive power. By moving the middle group Gr4m substantially vertically relative to an optical axis, an image is moved substantially vertically relative to an optical axis. The zoom lens satisfies predetermined conditions. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a zoom lens used in a digital camera, a silver salt camera, a video camera, and the like. In particular, the angle of view at the telephoto end is 13 degrees or less, the zoom ratio is about 2.7 times, and the zoom is wide open. The present invention relates to a large-aperture telephoto zoom lens having an image stabilization function with an F value of about 2.8.

Conventionally, a large-aperture telephoto zoom lens having an anti-vibration function having a field angle on the telephoto side of 13 degrees or less, a zoom ratio of about 2.7 times, and an open F value in the entire zoom range of about 2.8 is shown below. Patent literature is disclosed.

JP 2003-090958 A

JP 2002-162564 A

JP 2009-198656 A

JP 2009-086535 A

JP 2009-156893 A

The lens optical system of Patent Document 1 has a long total length and a sufficient amount of peripheral light, and it has been a problem to reduce the total length and improve the peripheral light amount.

Patent Documents 2 and 3 disclose a lens optical system having a short overall length, but the examples in Patent Document 2 and Patent Document 3 have a complicated mechanism because there are three lens groups that move during zooming. Became a problem.

The lens optical system of Patent Document 3 has a problem that the focusing speed becomes slow because the second lens unit L2 that is large and heavy is moved during focusing.

The lens optical systems of Patent Document 4 and Patent Document 5 move the lightweight lens during focusing, so that the focusing speed can be increased, but the total length of the lens optical system is long, and shortening of the total length has been a problem. .

Furthermore, the lens optical system of Patent Document 5 has a small amount of change on the image plane with respect to the amount of movement of the image stabilization lens group in the direction perpendicular to the optical axis, and it is difficult to perform sufficient image stabilization. .

The present invention solves the above-mentioned problems, has an angle of view of 13 degrees or less at the telephoto end, a zoom ratio of about 2.7 times, an open F value in the entire zoom range of about 2.8, and an in-focus speed. An object of the present invention is to provide a large-aperture telephoto zoom lens that can be made faster, exhibits a sufficient camera shake correction effect, has good optical performance, is compact, and has an anti-vibration function.

In order to solve the above-mentioned problem, the first invention according to the present invention has a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, and a positive refractive power in order from the object side. A third lens unit L3 having a positive refractive power and a fourth lens unit L4 having a positive refractive power, moving the second lens unit L2 and the third lens unit L3 along the optical axis, By moving the third lens unit L3 from the object side to the image side along the optical axis, focusing is performed from infinity to a close object, and the fourth lens unit L4 has positive refractive power in order from the object side. A front group Gr4f having a negative refractive power, a rear group Gr4r having a positive refractive power, and moving the middle group Gr4m in a direction substantially perpendicular to the optical axis. Move in a direction substantially perpendicular to the axis, and Providing a large-diameter telephoto zoom lens system with a vibration reduction function and satisfying.
(1) 0.27 <| f2 / fW | <0.36
f2: focal length of the second lens unit L2 fW: focal length of the entire lens system at the wide angle end

The second invention according to the present invention provides a large-aperture telephoto zoom lens having an anti-vibration function characterized by further satisfying the following conditions.
(2) 0.7 <f3 / fW <1.0
f3: focal length of the third lens unit L3

The third invention according to the present invention provides a large-aperture telephoto zoom lens having an image stabilization function characterized by further satisfying the following conditions.
(3) 0.18 <| f4m / fT | <0.28
f4m: fourth lens group middle group Gr4m focal length fT: focal length of the entire lens system at the telephoto end

In addition, the fourth invention according to the present invention is further adapted to contrast AF or the like in which the in-focus direction cannot be identified by vibrating at least one lens or one lens unit W1 at high speed along the optical axis. Provided is a large-aperture telephoto zoom lens having an anti-vibration function characterized by being able to identify a focal direction.

Further, the fifth invention according to the present invention can perform more rapid focusing by causing at least one lens or one lens unit W1 to vibrate at a high speed even during focus driving, thereby capturing moving images. In addition, a large-aperture telephoto zoom lens having a suitable anti-vibration function is provided.

According to the present invention, a zoom lens used in a digital camera, a silver salt camera, a video camera, etc., has a telescopic end angle of view of 13 degrees or less, a zoom ratio of about 2.7 times, and a zoom range. A large-aperture telephoto zoom lens with an open F value of about 2.8, which can increase the focusing speed, exhibit a sufficient camera shake correction effect, good optical performance, and a compact, anti-vibration function. Can be provided.

Sectional view of the zoom lens of Embodiment 1 at infinity at the wide-angle end Longitudinal aberration diagram in the infinite state at the wide angle end of the zoom lens of Example 1 Longitudinal aberration diagram in the infinity state at the intermediate focal length of the zoom lens of Example 1 Longitudinal aberration diagram in the infinite state at the telephoto end of the zoom lens of Example 1 Lateral aberration diagram in the standard state at the infinity state at the wide-angle end of the zoom lens of Example 1 Transverse aberration diagram in the standard state at the infinity state at the intermediate focal length of the zoom lens of Example 1 Transverse aberration diagram in the standard state at infinity at the telephoto end of the zoom lens of Example 1 Lateral aberration diagram when the zoom lens in the infinite state at the wide angle end of the zoom lens of Example 1 is shaken in a state tilted by 0.15 °. FIG. 6 is a lateral aberration diagram when the zoom lens of the first embodiment is shaken in a state where the zoom lens is tilted by 0.15 ° at an infinite distance at an intermediate focal length. Lateral aberration diagram of the zoom lens of Example 1 when the zoom lens in the infinite state at the telephoto end is tilted by 0.15 ° and is shaken. Sectional view of the zoom lens of Embodiment 2 in the infinity state at the wide-angle end Longitudinal aberration diagram in the infinite state at the wide angle end of the zoom lens of Example 2 Longitudinal aberration diagram in the infinite state at the intermediate focal length of the zoom lens of Example 2 Longitudinal aberration diagram of the zoom lens of Example 2 in the infinite state at the telephoto end Lateral aberration diagram in the standard state at infinity at the wide-angle end of the zoom lens of Example 2 Transverse aberration diagram in the standard state at the infinity state at the intermediate focal length of the zoom lens of Example 2 Transverse aberration diagram in the standard state at infinity at the telephoto end of the zoom lens of Example 2 Lateral aberration diagram of the zoom lens of Example 2 when the zoom lens in the infinity state at the wide-angle end is shaken by 0.15 ° and is shaken. Lateral aberration diagram when the zoom lens of Example 2 in the infinite state at the intermediate focal length is shaken with the lens tilted by 0.15 ° Lateral aberration diagram of the zoom lens according to the second exemplary embodiment when the zoom lens in the infinity state at the telephoto end is anti-vibrated in a state tilted by 0.15 °. FIG. 5 is a lens cross-sectional view of the zoom lens according to the third exemplary embodiment in an infinite state at the wide-angle end. Longitudinal aberration diagram in the infinite state at the wide-angle end of the zoom lens of Example 3 Longitudinal aberration diagram in the infinite state at the intermediate focal length of the zoom lens of Example 3 Longitudinal aberration diagram of the zoom lens of Example 3 in the infinite state at the telephoto end Lateral aberration diagram in the standard state at infinity at the wide-angle end of the zoom lens of Example 3 Transverse aberration diagram in the standard state at the infinity state at the intermediate focal length of the zoom lens of Example 3 Lateral aberration diagram in the standard state at infinity at the telephoto end of the zoom lens of Example 3 Lateral aberration diagram of the zoom lens according to the third exemplary embodiment when the zoom lens in the state of infinity at the wide-angle end is shaken by 0.15 °. Lateral aberration diagram of the zoom lens according to the third exemplary embodiment when the zoom lens in the infinite state at the intermediate focal length is shaken by 0.15 °. Lateral aberration diagram of the zoom lens of Example 3 when the zoom lens in the infinity state at the telephoto end is tilted by 0.15 ° and is shaken.

The large-aperture telephoto zoom lens having an anti-vibration function according to the present invention includes, in order from the object side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, and a first lens unit having a positive refractive power. A third lens unit L3 and a fourth lens unit L4 having positive refracting power. The second lens unit L2 and the third lens unit L3 are moved along the optical axis to perform zooming, and By moving the three lens units L3 from the object side to the image side along the optical axis, focusing is performed from infinity to a short-distance object. Thus, the focusing speed can be increased by using the light-weight third lens group L3, which does not have a large lens diameter and can reduce the number of components, as the focus lens group.

Further, the fourth lens unit L4 includes, in order from the object side, a front group Gr4f having a positive refractive power, a middle group Gr4m having a negative refractive power, and a rear group Gr4r having a positive refractive power. By moving the group Gr4m in a direction substantially perpendicular to the optical axis, the image is moved in a direction substantially perpendicular to the optical axis. Thereby, the influence of the camera shake on the zoom lens of the photographer is corrected.

In the lens optical system of the large-aperture telephoto zoom lens having the image stabilization function of the present invention, the distance between the conjugate points with the first lens unit L1 and the third lens unit L3 is shortened by shortening the focal length of the second lens unit L2. Since the zoom lens can be shortened, the overall length of the zoom lens can be made compact. However, if the focal length of the second lens unit L2 is too short, a pincushion-type distortion aberration is greatly generated on the telephoto side. Therefore, it is desirable to satisfy the following conditions.
(1) 0.27 <| f2 / fW | <0.36
f2: focal length of the second lens unit L2 fW: focal length of the entire lens system at the wide angle end

Conditional expression (1) defines the ratio between the focal length of the second lens unit L2 and the focal length of the entire zoom lens system at the wide angle end.

When the upper limit of conditional expression (1) is exceeded, the focal length of the second lens unit L2 becomes relatively longer than the focal length of the entire zoom lens system at the wide-angle end, and the pincushion type on the telephoto side is particularly long. Although distortion can be easily corrected, the distance between the conjugate points with the first lens unit L1 and the third lens unit L3 becomes too long, leading to an increase in the overall length of the zoom lens.

When the lower limit of conditional expression (1) is exceeded, the focal length of the second lens unit L2 becomes relatively shorter than the focal length of the entire zoom lens system at the wide angle end, and the first lens unit L1 and the third lens unit 3 Since the distance between the conjugate points with the lens unit L3 is shortened, the overall length of the zoom lens can be made compact. However, the pincushion distortion on the telephoto side becomes large, and correction becomes difficult. Further, since the second lens group L2 has the strongest refractive power among the respective groups, when the refractive power is further increased beyond the lower limit value, the manufacturing sensitivity of the eccentricity of the second lens group 2 is increased, Performance degradation around the telephoto side is inevitable.

Further, in the large-aperture telephoto zoom lens having the image stabilization function according to the present invention, if the amount of movement of the focus lens group during focusing is small, the entire length of the zoom lens can be made compact. Furthermore, if the amount of movement of the focus lens group during focusing is small, the movement time of the focus lens group can be shortened, and the focusing speed can be increased. In order to realize this, it is desirable to satisfy the following conditions.
(2) 0.7 <f3 / fW <1.0
f3: focal length of the third lens unit L3

Conditional expression (2) defines the ratio between the focal length of the third lens unit L3 and the focal length of the entire zoom lens system at the wide angle end.

When the upper limit value of conditional expression (2) is exceeded, the focal length of the third lens unit L3 becomes relatively longer than the focal length of the entire zoom lens system at the wide-angle end, and astigmatism variation during focusing is However, the amount of movement of the focus lens unit necessary for focusing increases, and this amount of movement must be ensured between the third lens unit L3 and the fourth lens unit L4, and the total length of the zoom lens is reduced. It cannot be made compact. Further, since the movement amount of the focus lens group is large, the movement time of the focus lens group until focusing is increased, and the focusing speed cannot be increased.

When the lower limit value of conditional expression (2) is exceeded, the focal length of the third lens unit L becomes relatively shorter than the focal length of the entire zoom lens system at the wide-angle end, and the focus lens unit necessary for focusing is reduced. Since the amount of movement is reduced, the overall length of the zoom lens can be made compact, and the focusing speed can be increased. However, the focal length of the third lens group becomes too short, so that the object from infinity to a close object can be reduced. At the time of focusing, aberration fluctuations in which astigmatism greatly falls to minus occur, and it is difficult to correct this.

Further, in the large-aperture telephoto zoom lens having the image stabilization function of the present invention, it is desirable that the following conditions are satisfied in order to exhibit a sufficient camera shake correction effect.
(3) 0.18 <| f4m / fT | <0.28
f4m: focal length of the fourth lens group middle group Gr4m fT: focal length of the entire lens system at the telephoto end

Conditional expression (3) defines the ratio between the focal length of the middle lens group Gr4m in the fourth lens unit L4 and the focal length of the entire zoom lens system at the telephoto end.

When the upper limit value of conditional expression (3) is exceeded, the focal length of the middle lens group Gr4m in the fourth lens unit L4 is relatively long with respect to the focal length with the entire zoom lens system at the telephoto end. It is difficult to secure a sufficient camera shake correction effect.

When the lower limit value of conditional expression (3) is exceeded, the focal length of the middle lens group Gr4m in the fourth lens unit L4 is relatively short with respect to the focal length of the entire zoom lens system at the telephoto end, and sufficient camera shake is achieved. Although a correction effect can be secured, it is difficult to satisfactorily correct astigmatism on the telephoto side.

Further, in the large-aperture telephoto zoom lens having the image stabilization function of the present invention, contrast AF or the like in which the in-focus direction cannot be identified by vibrating at least one lens or one lens unit W1 at high speed along the optical axis. It is desirable that the wobbling operation can be performed so that the in-focus direction of the focus lens group can be discriminated.

Further, W1 is desirably a part of a focus lens group that easily secures a vibration space. When wobbling the entire focus lens group, the heavier lens is vibrated at high speed, so the actuator needs to be enlarged, and the entire zoom lens system is enlarged, or the lens 1 is used to reduce the weight of the focus lens group. Restrictions such as having to be composed of a single sheet occur.

Therefore, a lightweight lens or lens unit that can be controlled with a small actuator is adopted as a lens component for wobbling, and the in-focus direction is identified by vibrating at high speed in the optical axis direction, and the entire focus lens group is in the in-focus direction. By repeating the movement, it is possible to perform quick focusing.

In addition, in the large-aperture telephoto zoom lens having an image stabilization function according to the present invention, it is possible to focus more quickly by oscillating W1 at high speed even during focus driving, and it is also possible to handle moving image shooting. .

Hereinafter, Numerical Example 1 to Numerical Example 3 according to the large-aperture telephoto zoom lens having the image stabilization function of the present invention will be described.

In each numerical example, f in [general specifications] indicates a focal length, Fno indicates an F number, and 2ω indicates an angle of view. The number in [Lens Specification] is the lens surface number of the lens from the object side, R is the radius of curvature of the lens surface, D is the distance between the lens surfaces, nd is the refractive index of d-line, and νd is the Abbe number of d-line. Indicates. Bf represents the back focus, and Obj represents the distance from the subject to the first lens surface. In the drawing, d-line, g-line, and C-line are aberrations with respect to respective wavelengths, ΔS indicates a sagittal image plane, and ΔM indicates a meridional image plane.

L1 First lens unit L1
L2 Second lens unit L2
L3 Third lens unit L3
L4 Fourth lens unit L4
Gr4f 4th lens group front group Gr4f
Gr4m Fourth lens group middle group Gr4m
Gr4r fourth lens group rear group Gr4r
W1 Wobbling lens unit W1
SP Aperture stop d d line g g line C C line ΔS sagittal image plane ΔM meridional image plane

Claims (5)

In order from the object side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, and a fourth lens having a positive refractive power Group L4,
Zooming is performed by moving the second lens unit L2 and the third lens unit 3 along the optical axis;
By moving the third lens unit L3 from the object side to the image side along the optical axis, focusing from infinity to a short distance object is performed,
The fourth lens group L4 includes, in order from the object side, a front group Gr4f having a positive refractive power, a middle group Gr4m having a negative refractive power, and a rear group Gr4r having a positive refractive power, and the middle group Gr4m Is moved in a direction substantially perpendicular to the optical axis to move the image in a direction substantially perpendicular to the optical axis,
A large-aperture telephoto zoom lens having an anti-vibration function characterized by satisfying the following conditions.
(1) 0.27 <| f2 / fW | <0.36
f2: focal length of the second lens unit L2 fW: focal length of the entire lens system at the wide angle end
The large-aperture telephoto zoom lens having a vibration-proof function according to claim 1, wherein the following conditions are satisfied.
(2) 0.7 <f3 / fW <1.0
f3: focal length of the third lens unit L3
The large-aperture telephoto zoom lens having an image stabilization function according to claim 1, wherein the following condition is satisfied.
(3) 0.18 <| f4m / fT | <0.28
f4m: focal length of the fourth lens group middle group Gr4m fT: focal length of the entire lens system at the telephoto end
The in-focus direction can be identified by contrast AF or the like in which the in-focus direction cannot be identified by causing at least one lens or one lens unit W1 to vibrate at high speed along the optical axis. A large-aperture telephoto zoom lens having an image stabilization function according to any one of 3).
5. The large-aperture telephoto zoom lens having an anti-vibration function according to claim 1, wherein at least one lens or one lens unit W1 is vibrated at high speed during focus driving.

Images