JP2816714B2 - Vibration compensation zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention can compensate for an undesired tilt of a photographing lens at the time of photographing, for example, blurring of a photographed image due to hand vibration or vibration caused by the camera itself. The present invention relates to a photographing lens, and more particularly to a vibration compensation unit unique to a zoom lens having a variable focal length.

[Problems to be Solved by Conventional Techniques and Inventions] When photographing from an automobile or an aircraft, or when using a long focal length lens, image deterioration due to blurring of a photographed image is likely to be remarkable. Various proposals have been made for means for compensating for blur.

In principle, the simplest vibration compensation means in a lens system composed of a plurality of groups 1 and 2 as shown in FIG. 27 (A) is to move the lens group 1 closest to the object side of the lens system from its optical axis. A configuration in which a still image is obtained on the image plane 3 by decentering is considered.

As shown in FIG. 27 (B), when the optical axis of the lens system is tilted from the initial position indicated by the broken line to the position indicated by the dashed line, if it is displaced together with the lens system, it is at the position indicated by the broken line. By moving the object-side lens group 1 to the position shown by the solid line, blur compensation can be performed.

In this case, it is clear that the object-side lens group 1 should be moved in the direction perpendicular to the optical axis by the same amount as the amount of blur of the image formed by the lens group 1, and the movement amount Δ
Y can be represented by ΔY = f1 · ωt, where f1 is the focal length of the vibration compensation lens and ωt is the tilt angle of the entire lens system.

However, the lens group closest to the object side of the photographing optical system usually has a large effective diameter, and this is even more remarkable in the case of a telephoto lens having the highest focus. However, there is a drawback that the size becomes large.

Therefore, in a lens system composed of a plurality of groups, for example, JP-A-62-203119 or JP-A-62-47011
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. H11-260, there has been proposed an apparatus in which a still image is obtained by deflecting a lens on the more image side.
That is, as shown in FIG. 27 (C), when the optical axis of the lens system is tilted from the initial position indicated by the broken line to the position indicated by the dashed line, the image at the position indicated by the broken line is displaced together with the lens system. The blur compensation can be performed by displacing the side lens group 2 to the position shown by the solid line.

In such a configuration, assuming that the combined focal length f1 of the lens unit on the object side of the lens unit moved for compensation, the inclination angle ωt of the entire lens system, and the image magnification mc of the vibration compensation lens unit, The movement amount ΔY of the vibration compensating lens group in the in-plane direction perpendicular to the optical axis is determined by the following equation: ΔY = f1 · M · ωt where M = mc / (1−mc). Image deviation can be suppressed to zero.

However, if the lens group that moves for focusing is a vibration compensating lens group as disclosed in Japanese Patent Application Laid-Open No. Sho 62-47011, problems such as a complicated mechanism and a reduction in autofocus speed occur.

Further, in the zoom lens, the positional relationship between the variable power lens group and the vibration compensation lens group becomes a problem.

In other words, when the vibration compensating lens group is disposed closer to the object side than the variable power lens group, since the vibration compensation is completed by the vibration compensating lens group, the vibration compensating lens for the tilt angle of the entire lens system with respect to the entire zooming focal length. Only a single compensation coefficient indicating the ratio of the amount of movement of the group is determined, and control is facilitated.

However, in the case of a zoom lens, since the lens on the object side of the zoom lens group is generally a focusing lens group,
The same problem as described above occurs.

On the other hand, when the vibration compensation lens group is arranged on the image side of the variable power lens group, the compensation coefficient is generally a function of the composite focal length of the lens group on the object side of the vibration compensation lens group. Therefore, an arithmetic process for calculating the amount of movement for compensation is required.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and a lens group on the image side of a variable power lens group is set as a vibration compensation lens group by controlling the magnification of the vibration compensation lens group. Nevertheless, an object of the present invention is to provide a vibration compensation zoom lens in which the compensation coefficient does not change even if the focal length of the entire system changes.

[Means for Solving the Problems] A vibration compensation zoom lens according to the present invention is composed of three or more lens groups, and a variable power lens group or at least one lens group located on the image side therefrom is replaced with another lens. The vibration compensating lens group is displaceable with respect to the lens group. It is characterized by satisfying.

mc = 1 / {1+ (f1 / A)} mc = 1 / [1+ {f1 / (X−B)}] where A and B are arbitrary constants, and X is a vibration compensation lens group. This is the distance to the image plane.

If the taking lens or camera is tilted during the exposure time, hold the vibration compensation lens group so as not to follow the displacement of the other lens groups, or move the vibration compensation lens group in an in-plane direction almost perpendicular to the optical axis. A moving mechanism is provided to forcibly move the vibration compensating lens group to compensate for blurring of the captured image.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an arrangement of a vibration compensating lens according to the first embodiment, and shows an image plane 30 of a lens group 10 having a focal length f1.
A vibration compensation lens group 20 is arranged adjacent to the side. The movement amount ΔY of the vibration compensating lens 20 is represented by ΔY = f1 · M · ωt where M = mc / (1−mc), where ωt is the tilt angle of the entire lens system. That is, by moving the vibration compensating lens 20 in the in-plane direction substantially perpendicular to the optical axis by ΔY, it is possible to reduce blurring of the captured image.

Here, f1 · M is a constant A, and the lateral magnification mc of the vibration compensating lens group is set to the relationship of f1. If mc = 1 / {(1+ (f1 / A)}..., F1 is changed by zooming. Also in this case, the value of the movement amount ΔY with respect to the value of the tilt angle ωt does not change.

The vibration compensation lens group 20 can perform blur compensation by moving in an in-plane direction perpendicular to the optical axis. However, when the tilt angle of the entire lens system is small, the vibration compensation lens group 20 is paraxial. The same effect can be obtained even with a rotational movement about the fixed point 0. In the case of rotational movement, the mechanism is easily simplified.

Therefore, when the vibration compensating lens group 20 is a thin lens and the tilt angle ωt is close to 0, the tilt angle ωt and the moving amount Δ
The relationship with Y is as shown in FIG. 1, and the entire lens system has an angle ω about a point 0 which is a distance A away from the vibration compensation lens group 20 (the sign is + in the traveling direction of the light beam).
When tilted by t, the relative amount of displacement of the vibration compensation lens group 20 relative to the entire lens system and the image plane 30 fixed with respect to the spatial coordinates is ΔY.

In other words, when the point 0 away from the vibration compensation lens group 20 by A is a fixed point with respect to the space coordinates where the object (subject) exists, when the entire lens system rotates around the point 0,
If the vibration compensating lens group 20 stays at the original position with the coordinates fixed to the object, the vibration compensating lens group 20 moves by ΔY in the coordinate system fixed with respect to the image plane 30, and the rotation is caused by the rotation. The effect will be compensated.

In addition, as a method of relatively displacing the position of the vibration compensation lens group 20 by rotation, a known method such as a method of fixing the vibration compensation lens group with respect to spatial coordinates by a gyro can be used.

Here, the fact that A is a constant means that the point 0 generally moves integrally with the vibration compensation lens group during zooming.

However, in practice, it is more convenient to use the format in which the zero point is located at a location where the distance from the image plane is constant. This is because a point that is immovable with respect to vibration, that is, a point that is fixed with respect to the spatial coordinates where the object (subject) exists, is strongly affected by the fixed position when the camera, lens, or the like is fixed by a tripod or the like. This is because it is difficult to imagine that the lens is displaced by the movement of the vibration compensation lens group accompanying zooming.

Claim 2 is obtained by modifying the formula from such a viewpoint.
This is an equation according to. Here, the relationship between the movement amount ΔY of the vibration compensation lens group 20 and the tilt angle ωt of the entire lens system is as follows: ΔY = (X−B) · ωt. In this state, as shown in FIG. 2, B is the distance from the fixed point 0 to the image plane, X is the distance from the vibration compensation lens group to the image plane, and the entire lens system has an angle ωt around the fixed point 0. When rotated, the movement amount of the vibration compensation lens group fixed with respect to the space coordinates is ΔY.

As described above, if the entire lens system is made rotatable about the fixed point 0 and the angle of the vibration compensation lens group with respect to the object is controlled so as not to change, compensation can be performed even when the focal length of the entire lens system changes. The mechanism can always perform the best blur compensation without changing the compensation coefficient.

Further, as shown in FIGS. 3A to 3C, an image position correcting lens group 40 for correcting an image position so as to form an image on an image plane 30 at a fixed distance from the vibration compensating lens group 20 may be provided. This eliminates the need for providing a mechanism for moving the vibration compensation lens group 20 in the optical axis direction, which is advantageous in simplifying the vibration compensation mechanism. In this case, the position of the variable power lens group 11 is determined so as to satisfy the condition with respect to the front focal position of the vibration compensating lens group 20 according to the change in the combined focal length f1.

The image position correction lens group 40 may be a single lens group, or may be a two-group configuration including a compensate group having an almost afocal emission like a normal zoom lens and a master group for image formation. .

Next, three examples of a mechanism for configuring the vibration compensation lens system will be described.

The mechanism shown in FIG. 4 includes a mount 50 to which a tripod 51 is fixed below, and a telephoto lens 60 having the above-described vibration compensation function.
And a camera body 65 to which this lens is attached.

The lens barrel of the telephoto lens 60 that houses the lens group includes a movable lens barrel 61 that is displaceable with respect to the gantry 50 and a fixed lens barrel 62 that is fixed to the gantry 50.

The movable barrel 61 has a fixed point on the subject side supported by the gantry 50 via a gimbal bearing 70, and a base end side fixed to the camera body 65.

As shown in FIG. 5, the gimbal bearing 70 is rotatably attached to a support piece 52 provided in a U-shape at the tip of the gantry 50. This gimbal bearing 70 is a movable lens barrel
A first shaft 72 rotatably connecting the ring 71 to the movable lens barrel 61;
And a second shaft 73 for rotatably connecting the support piece 52 and the support piece 52.

Here, when the optical axis direction of the lens is set as the x-axis and y and z axes orthogonal to each other are set in a plane perpendicular to the x-axis, the first axis 72 becomes y
The second axis 73 provides the degree of freedom about the z-axis to the movable barrel 61 around the axis.

The camera body 65 is attached to the gantry 50 via a buffer mechanism 66 having a spring 66a and a buffer cylinder 66b.

The movable barrel 61 can be displaced with respect to the gantry 50 by the two positions supported by the gimbal bearing 70 and the buffer mechanism 66.

On the other hand, the fixed lens barrel 62 is provided in a cylindrical shape surrounding the outer periphery of the base end of the movable lens barrel 61, and a lens frame 63 protruding inward is provided at the upper and lower positions on the inner circumference. Lens frame 63
Penetrates through an opening 61a formed in the movable lens barrel 61, and holds the vibration compensation lens group 20 in the movable lens barrel 61. Therefore,
Only the vibration compensation lens group 20 in the lens system is directly fixed to the gantry 50.

Here, since the distal end side of the telephoto lens 60 is configured to be more easily movable than the tripod 51 and the gantry 50, the neutral position of the optical axis of the vibration compensating lens group 20 may vary depending on the posture of the lens. May deviate from the optical axis, but the effect on performance is small.

Strictly speaking, the fulcrum and the vibration compensating lens group should not be affected by camera vibration,
50) is required to be completely fixed. However, since some vibrations can actually be absorbed, the effect on the imaging performance can be almost ignored.

The conventional vibration compensating lens could not correct the effect of high frequency blur caused by driving the shutter and the mirror, but in the example of FIG. 4, the vibration compensating lens group 20 is fixed to the gantry 50. Specifically, the occurrence of blur on the screen can be completely prevented.

FIG. 6 shows a modification of FIG. 4,
The vibration compensating lens group 20 includes a spring 64 inside the movable barrel 61.
Supported by This configuration is effective when the vibration cycle of the vibration compensation lens group 20 is sufficiently longer than the vibration cycle of the telephoto lens 60 and the camera body 65.

FIG. 7 shows a mechanism for driving the vibration compensating lens group 20 in the YZ direction by an actuator 80 provided in the movable lens barrel 61. The displacement due to the vibration of the entire lens is detected as a displacement angle of the lens barrel by an acceleration sensor 81 provided between the movable lens barrel 61 and the gantry 50. Then, based on the detection result, the actuator 80 is controlled so that the vibration compensating lens group does not move relative to the stationary system (the gantry 50) during the vibration.

In the vibration compensating lens of the present invention, the vibration compensating lens group 20
Is a relatively lightweight lens group close to the image side, the mass of the object to be controlled by the actuator 80 is small, and high-frequency control is also possible.

In the above embodiment, the telephoto lens 60 and the camera body
Only the configuration in which the entire camera including the camera 65 is mounted on the gantry 50 is shown, but this configuration is actually equivalent to a configuration in which the fixed point 0 is fixed to a stationary system using a gyro or the like.

<< Lens Configuration Example 1 >> FIGS. 8 to 16 show lens configuration examples satisfying the condition of claim 1 of the present invention.

Shown here is a three-group configuration with a focal length of 50-100 mm,
The lens system has an F number of 4.0 to 5.6, and the focal length, that is, the magnification, can be changed by displacing the second group II and the third group III in the optical axis direction as a variable power lens group. The third group III functions as a vibration compensation lens group.
It is.

This lens system is set so that the constant A in the above equation is -120. Therefore, the magnification mc is represented by mc = 1 / {1- (f1 / 120)}, and the moving amount ΔY of the vibration compensation lens group with respect to the tilt angle ωt of the entire lens system is irrespective of the change in the focal length of the entire system. ΔY = −120 · ωt.

Here, the direction of the optical axis at a tilt angle of 0 is defined as the x-axis, and the y and z axes orthogonal to each other are determined in a plane perpendicular to the x-axis, and the tilt of the optical axis is assumed to occur in the xy plane.

The specific numerical configuration of the above lens is as shown in the following table.

Symbols in the table are Fno: F number, f: focal length at d line (wavelength 588 nm), w: half angle of view, r: radius of curvature of each lens surface, d: lens thickness or air space, n: d line Is the refractive index of the lens, and ν is the Abbe number of the lens.

However, d6 and d16 change with the movement of the second and third lens groups, and the change of these intervals according to each focal length is as shown in Table 2.

Table 2. f d6 d16 f1 mc 50 30.935 6.518 35.294 1.417 60 21.690 6.056 40.000 1.500 70 15.085 5.644 44.211 1.583 80 10.133 5.270 48.000 1.667 90 6.280 4.935 51.409 1.750 100 3.199 4.628 54.545 1.833 The respective aberrations in this state are as shown in FIG. The arrangement when the focal length is 100 mm is shown in FIG. 10, and each aberration in this state is as shown in FIG.

FIG. 12 shows a state of movement of the vibration compensating lens group when the entire lens system is tilted by 1 ° at a focal length of 50 mm.

In general, when a lens with a focal length of 100 mm is tilted by 1 °, a point image will be blurred by about 1.75 mm. However, in this lens system, the vibration compensation lens group is perpendicular to the optical axis regardless of the focal length from 50 mm to 100 mm. By shifting the image in the in-plane direction by 2.094 mm, it is possible to reduce the amount of blur of the point image as shown in FIGS. 13 and 14.

FIGS. 13 and 14 show spot diagrams at three positions with different image heights in the y direction at focal lengths of 50 mm and 100 mm, respectively. (A), (b),
(C) The intersections of the dashed lines in the figure show the point image position by the principal ray when the tilt angle is 0, and the image plane and x
The three points (y, z) = (0, 0), (21.6, 0), and (-21.6, 0) in the yz coordinates set with the light point with the axis as the origin are shown.

As shown in the figure, even in the peripheral portion of the screen where the image quality is most deteriorated due to the occurrence of the field curvature or the like after the correction, the blur amount of the point image can be suppressed to about 0.2 mm in diameter.

FIG. 15 shows astigmatism after the movement of the vibration compensation lens group when the focal length is 50 mm, and FIG. 16 shows astigmatism after correction when the focal length is 100 mm.

<< Lens Configuration Example 2 >> FIGS. 17 to 26 show lens configuration examples satisfying the condition of claim 2 of the present invention.

Shown here is a 4-group configuration with a focal length of 100 to 300 mm,
The lens system has an F number of 5.6, and the second group II functions as a variable power lens group and a vibration / compensation lens group.

This lens system is set so that the constant B in the above equation becomes 238.658. Accordingly, the magnification mc is represented by mc = 1 / [1+ {f1 / (X−238.658)}], and the required movement amount ΔY of the vibration compensation lens group with respect to the tilt angle ωt of the entire lens system is ΔY = (X− 238.658) · ωt.

Here, the direction of the optical axis at a tilt angle of 0 is defined as the x-axis, and the y and z axes orthogonal to each other are determined in a plane perpendicular to the x-axis, and the tilt of the optical axis is assumed to occur in the xy plane.

The specific numerical configuration of the above lens is as shown in the following table.

 The symbols in the table are the same as in the first embodiment.

The distance changes with the focal length change is d5, d1
0 and d13, and the change of these intervals according to each focal length is as shown in Table 4.

Note that, in this example, the combined focal length f1 of the lens unit on the object side of the vibration compensating lens unit is equal to the focal length of the first unit I, and is a constant that does not change due to zooming, and f1 = 139.71 mm.

FIG. 17 shows a state where the focal length is 100 mm, and each aberration in this state is as shown in FIG. Focal length 30
The arrangement at 0 mm is shown in FIG. 19, and each aberration in this state is as shown in FIG.

FIGS. 21 and 22 show the focal lengths of 100 mm and 300 mm, respectively.
10 shows the movement state of the vibration compensating lens group (second group II) when the entire lens system is inclined by 1 ° in the state shown in FIG.

Table 4. By shifting the compensating lens group in an in-plane direction perpendicular to the optical axis, the amount of blur of the point image can be reduced.
As shown in FIGS. 23 to 26, it is possible to reduce the size.

FIGS. 23 and 24 show spot diagrams at three positions with different image heights in the y direction at focal lengths of 100 mm and 300 mm, respectively. (A), (b),
(C) The intersections of the dashed lines in the figure show the point image position by the principal ray when the tilt angle is 0, and the image plane and x
Three points (y, z) = (0,0), (21.6,0), and (−21.6,0) in the yz coordinates set with the intersection point with the axis as the origin are shown.

FIG. 25 shows astigmatism after the movement of the vibration compensation lens group when the focal length is 100 mm, and FIG. 26 shows astigmatism after correction when the focal length is 300 mm.

As shown in the figure, the point image blur amount can be suppressed to a diameter of about 0.2 mm even in the peripheral portion of the screen where the image quality is most deteriorated due to the occurrence of the curvature of field after the correction.

[Effects] As described above, according to the present invention, a vibration that can displace a lens group having a relatively small diameter, such as a variable power lens group or a lens group located on the image side, with respect to other lens groups. Even when the compensation lens group is used and the focal length of the entire system is changed, uniform control can be performed with the ratio of the compensation displacement amount to the tilt angle of the optical system being fixed.

Therefore, the load on the compensating mechanism is kept small, and the calculation when determining the moving amount is facilitated.

[Brief description of the drawings]

FIGS. 1 to 3 are explanatory views relating to the principle of the vibration compensation zoom lens according to the present invention, and FIG.
The drawings correspond to claim 2 and FIGS. 3 (A) to 3 (C) are explanatory views respectively corresponding to claim 3. 4 to 6 are structural views showing a first embodiment of the vibration compensating lens according to the present invention. FIG. 4 is a side view partially broken away, and FIG. FIG. 6 is a view from the direction of the arrow L in the figure, and FIG. 6 is an explanatory view showing a modification of the holding mechanism of the vibration compensation lens group. FIG. 7 is a block diagram showing a second embodiment of the vibration compensating lens according to the present invention. 8 to 16 show a first example of the vibration compensating lens according to the present invention.
FIG. 8 shows a focal length.
FIG. 9 is a sectional view of the lens at 50 mm, FIG.
FIG. 11 is a cross-sectional view of a lens at a focal length of 100 mm, FIG. 11 is an aberration diagram thereof, and FIG. 13 (a), (b) and (c) are spot diagrams in the state of FIG. 12, and FIGS. 14 (a), (b) and
(C) is a similar spot diagram at a focal length of 100 mm, FIG. 15 is an astigmatism diagram in the state shown in FIG. 12,
FIG. 16 is a similar astigmatism diagram when the focal length is 100 mm. 17 to 26 show a second lens configuration example of the vibration compensation lens according to the present invention. FIG. 17 is a lens cross-sectional view at a focal length of 100 mm, FIG.
FIG. 19 is a sectional view of a lens at a focal length of 300 mm, FIG. 20 is an aberration diagram thereof, and FIG. And FIG. 22 is a sectional view of the lens after movement of the vibration compensating lens group when the entire lens system is tilted by 1 ° at a focal length of 300 mm, and FIGS. 24 (a), (b), and the spot diagram in the state of FIG.
(C) is a spot diagram in the state of FIG. 22,
FIG. 25 is a diagram showing astigmatism in the state shown in FIG. 21, and FIG. 26 is a diagram showing astigmatism in the state shown in FIG. FIGS. 27A to 27C show the principle of a conventional vibration compensating lens. 10: Variable magnification lens group, 20: Vibration compensation lens group 30: Image plane, 40: Image position correction lens group

Claims (5)

(57) [Claims] 1. A vibration compensating lens group comprising at least three lens groups and located on the image side of the variable power lens group, and being displaceable with respect to other lens groups.
The image magnification mc of the vibration compensation lens group is mc = 1 / {1+ (f1 / A)} with respect to the combined focal length f1 of the lens group on the object side of the vibration compensation lens group. A vibration compensation zoom lens characterized by satisfying the following relationship: 2. A vibration compensating lens group comprising at least three lens groups and located on the image side of the variable power lens group and being displaceable with respect to other lens groups.
The image magnification mc of the vibration compensation lens group is mc = 1 / [1+ {f1 / (X−B)}] with respect to the combined focal length f1 of the lens group on the object side of the vibration compensation lens group. B is an arbitrary constant, and X is a distance from the vibration compensation lens group to the image plane. 3. The apparatus according to claim 1, further comprising an image position correcting lens group which keeps a distance from the vibration compensating lens group to an image plane closer to the image side than the vibration compensating lens group. The vibration compensation zoom lens described. 4. A moving mechanism for moving the vibration compensation lens group in a plane substantially perpendicular to the optical axis with respect to a dynamic inclination of the entire optical system. 4. The vibration compensation zoom lens according to any one of the above items. 5. The moving mechanism according to claim 4, wherein the moving mechanism includes a mechanism for compensating for a dynamic tilt of the entire optical system and rotating the lens group about one point on the optical axis. Vibration compensation zoom lens.