Optical apparatus with movable member for shake correction

An image shake correction device capable of reducing a sliding friction force occurring with movement of a movable member, thereby reducing load on a drive unit for driving the movable member and improving the positioning accuracy of the movable member. The movable member of the correction device is supported to be movable in a yaw direction and supported to be pivotable in a pitch direction, and a ball is held between the movable member and a guide groove formed in a stationary member and extending in the yaw direction. When the movable member moves in the yaw direction, the ball rolls along the guide groove. When the movable member pivots in the pitch direction, a contact point where the movable member contacts with the ball functions as a pivotal fulcrum for the movable member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image shake correction device mounted on an optical apparatus such as a digital camera, binocular, and telescope, and relates to an optical apparatus and an image pickup apparatus each having the image shake correction device.

2. Description of the Related Art

An image shake correction device mounted on a digital camera or the like has a movable member that holds a lens or an image pickup device. The movable member must be movable independently in a left-right direction (yaw direction) and in an up-down direction (pitch direction) with respect to an optical axis.

To this end, a technique has been proposed in which a shaft formed on one of a movable member and a stationary member is engaged with an elongated hole formed in another of them (Japanese Laid-open Patent Publications Nos. H10-10597 and 2010-152020). In this technique, the movable member is supported to be movable relative to the stationary member in a first direction along the elongated hole and supported to be pivotable about the shaft in a second direction perpendicular to the first direction, so that the movable member can be movable independently in these two different directions.

However, due to a sliding friction force occurring between the shaft and the elongated hole with movement of the movable member, load on an actuator for driving the movable member increases and the positioning accuracy of the movable member is lowered.

SUMMARY OF THE INVENTION

The present invention provides an image shake correction device capable of reducing a sliding friction force occurring with movement of a movable member, thereby reducing load on a drive unit for driving the movable member and improving the positioning accuracy of the movable member, and provides an optical apparatus and an image pickup apparatus each having the image shake correction device.

According to one aspect of this invention, there is provided an image shake correction device, which comprises a stationary member, a movable member configured to be supported movably in a first direction relative to the stationary member and configured to be supported pivotably relative to the stationary member in a second direction different from the first direction, wherein a first guide groove extending in the first direction is formed in one of the stationary member and the movable member, a rolling member configured to be held between the first guide groove and another of the stationary member and the movable member, wherein the rolling member rolls along the first guide groove when the movable member moves in the first direction and a contact point where the movable member contacts with the rolling member functions as a pivotal fulcrum for the movable member when the movable member pivots in the second direction, an urging unit configured to urge the stationary member and the movable member in directions to hold the rolling member, and a drive unit configured to drive the movable member in the first and second directions.

With this invention, it is possible to reduce a sliding friction force occurring with movement of the movable member, whereby load on the drive unit for driving the movable member can be reduced and the positioning accuracy of the movable member can be improved.

DESCRIPTION OF THE EMBODIMENTS

The present invention will now be described in detail below with reference to the drawings showing preferred embodiments thereof.

FIG. 1schematically shows in perspective view a lens barrel serving as an optical apparatus on which an image shake correction device according to a first embodiment of this invention is mounted.

As shown inFIG. 1, the image shake correction device10of this embodiment is disposed inside the lens barrel20of the optical apparatus (e.g., a digital camera), and corrects image shakes caused by camera shakes in yaw and pitch directions (hereinafter respectively referred to as the Y and P directions). It should be noted that the Y and P directions are perpendicular to each other in this embodiment, but this is not limitative.

Angle displacement detection devices21y,21pdetect shake angle displacements22y,22pof the camera in the Y and P directions and output angle displacement signals, respectively. Based on these angle displacement signals supplied from the detection devices21p,21y, computation circuits23p,23yrespectively compute target drive signals.

In accordance with the target drive signals supplied from the computation circuits23p,23y, a drive unit of the image shake correction device10causes a movable barrel12that holds a correction lens11to move in a plane perpendicular to an optical axis, thereby correcting a shake of an image formed on an image plane of an image pickup apparatus24.

It should be noted that in this embodiment, position sensors that detect Y- and P-direction positions of the movable barrel12can be provided for execution of closed-loop control to make output signals of the position sensors coincident with respective ones of the target drive signals. Alternatively, open-loop control can be carried out without using the position sensors.

Next, a description will be given of the image shake correction device10with reference toFIGS. 2 to 5.FIG. 2shows the image shake correction device10in exploded perspective view,FIG. 3shows the correction device10as seen from one side in the optical axis direction,FIGS. 4 and 5Aare section views respectively taken along lines A-A and B-B inFIG. 3, andFIG. 5Bshows C part ofFIG. 5Ain enlarged view.

As shown inFIGS. 2 to 5, the image shake correction device10of this embodiment includes the movable barrel12that holds the correction lens11and includes a stationary base plate13, balls14to16, a first actuator17, and a second actuator18.

The movable barrel12(which is an example of a movable member of this invention) is formed with a central circular hole12afor holding the correction lens11, and is supported to be movable relative to the stationary base plate13in a plane perpendicular to the optical axis. The movable barrel12has a surface facing the stationary base plate13and formed into a flat plane perpendicular to the optical axis. At a central portion of the flat plane surface of the movable barrel12, a cylindrical portion12d(seeFIG. 4) is formed coaxially with the central hole12aso as to project toward the stationary base plate13.

The movable barrel12is also formed with rectangular holes12b,12con both sides of the central hole12aas seen in the Y direction. A first magnet17bthat cooperates with a first coil17ato constitute the first actuator17is fitted and fixed to the hole12b, and a second magnet18bthat cooperates with a second coil18ato constitute the second actuator18is fitted and fixed to the hole12c. It should be noted that in this embodiment the correction lens11is used as an optical system for image shake correction. Alternatively, an image pickup device (such as a CCD sensor or a CMOS sensor) that is movable in a direction perpendicular to the optical axis can be used.

The stationary base plate13(which is an example of a stationary member of this invention) is formed into a rectangular plate elongated in the Y direction and is disposed parallel to the movable barrel12. The stationary base plate13is formed with a central circular hole13c, which is larger in diameter than the cylindrical portion12dof the movable barrel12. The cylindrical portion12dis axially inserted into the hole13c, whereby a movable range of the movable barrel12relative to the stationary base plate13is restricted. At an outer periphery of the base plate13, there is provided a mounting portion (not shown) to which the lens barrel that supports a taking lens group is fixed.

When the movable barrel12is at a reference position (initial position) shown inFIGS. 3 and 4, the correction lens11held by the movable barrel12is disposed coaxially with the hole13cof the stationary base plate13.

The stationary base plate13is also formed with an elongated hole13along in the P direction and an elongated hole13blong in the Y direction on both sides of the central hole13cas seen in the Y direction. The first coil17aof the first actuator17is fitted and fixed to the elongated hole13a, and the second coil18aof the second actuator18is fitted and fixed to the elongated hole13b.

When the movable barrel12is at the reference position shown inFIGS. 3 and 4, a line connecting the centers of the first and second coils17a,18apasses through the center of the correction lens11(i.e., the optical axis), and the centers of the first and second magnets17b,18bare aligned in position with the centers of the first and second coils17a,18a, respectively.

The stationary base plate13is further provided with cylindrical ball receiving portions13g,13hin respective ones of which balls15,16are disposed to be rollable. The ball receiving portions13g,13hare disposed symmetrical to each other with respect to the longitudinal axis of the stationary base plate13. In this embodiment, the ball receiving portions13g,13hare located between the elongated hole13band the central hole13c, i.e., between the center of the second actuator18and the center of the correction lens11(the optical axis) as seen in the longitudinal direction of the stationary base plate13, thereby enabling the balls15,16to support the movable barrel12at near the center of gravity of the movable barrel12. It should be noted that the ball receiving portions13g,13hare formed to have inner diameters larger than the diameters of the balls15,16and corresponding to the movable range of the movable barrel12.

A guide groove13d, which is a V-shape in cross section and extends in the Y direction, is formed in the stationary base plate13at a position opposite from the hole13cwith respect to the elongated hole13a. The guide groove13dhas its center located on an extension of a line connecting the centers of the first and second coils17a,18a. When the movable barrel12is at the reference position shown inFIGS. 3 and 4, the center of the correction lens11(i.e., the optical axis) is disposed on an extension of the longitudinal axis of the guide groove13d.

In this embodiment, the guide groove13dis disposed on the side opposite from the second actuator18as seen in the longitudinal direction of the stationary base plate13with respect to the central hole13cin which the correction lens11is received. In other words, the ball14in the guide groove13dis disposed on the side opposite from the second actuator18with respect to the correction lens11in the hole13cas seen in the longitudinal direction of the base plate13. Accordingly, the movable barrel12can have a large pivot radius when driven by the second actuator18to pivot about a contact point with the ball14, i.e., about a pivotal fulcrum. It should be noted that the guide groove13dis an example of a first guide groove of this invention.

The guide groove13dof the stationary base plate13has inclined surfaces13e,13feach being in contact with the ball14at one point, so that the ball14is in contact at two points with the guide groove13d. In this embodiment, the ball14is also in contact with the movable barrel12at one point. In a state held between the movable barrel12and the stationary base plate13, the ball14is supported by three points to be rollable in the Y direction.

The balls15,16are each in contact with the movable barrel12at one point and in contact with the stationary base plate13at one point. In a state held between the movable barrel12and the stationary base plate13, each of the balls15,16is supported by two points to be rollable in the movable range of the movable barrel12.

In this embodiment, the first and second actuators17,18(an example of drive devices of a drive unit of this invention) are each implemented by a voice coil motor.

When electric power is supplied to the coil17aof the first actuator17, a force is applied to the magnet17bof the first actuator17in a direction perpendicular to the longitudinal axis of the coil17a(i.e., in the Y direction in this embodiment).

FIG. 6shows a state where forward power is applied to the first coil17aof the first actuator17. It should be noted that an illustration of the movable barrel12is omitted inFIG. 6for convenience of description.

In the state shown inFIG. 6, a Lorentz force is generated between the coil17aand magnet17bof the first actuator17, so that a force f1acting in the Y direction (i.e. in a first direction) is applied to the magnet17bfixed to the movable barrel12. As a result, the movable barrel12moves in a R direction while causing the balls14to16to roll, so that the center of the correction lens11held by the movable barrel12moves to a position denoted by symbol P1.

When electric power is supplied to the coil18aof the second actuator18, a force is applied to the magnet18bof the second actuator18in a direction perpendicular to the longitudinal axis of the coil18a(i.e., in the P direction in this embodiment).

FIG. 7shows a state where forward power is applied to the second coil18aof the second actuator18. It should be noted that an illustration of the movable barrel12is omitted inFIG. 7for convenience of description.

In the state shown inFIG. 7, a Lorentz force is generated between the coil18aand magnet18bof the second actuator18, so that a force f2acting in the P direction is applied to the magnet18bfixed to the movable barrel12. As a result, the movable barrel12pivots by an angle of θ about a contact point with the ball14(i.e., about a pivotal fulcrum) while causing the balls15,16to roll, so that the center of the correction lens11held by the movable barrel12moves to a position denoted by symbol P2. Hereinafter, the direction of arcuate movement of the correction lens11at that time will be referred to as the second direction. With the combined movement of the movable barrel12in the first and second directions, the center of the correction lens11can move to an arbitrary position on the plane perpendicular to the optical axis.

The stationary base plate13and the movable barrel12are urged by an urging unit (schematically denoted by arrow Z inFIG. 4) in directions toward each other to hold the balls14to16therebetween, so that a holding force is applied to the balls14to16. As a result, for example, the ball14is prevented from being detached from the guide groove13dwith movement of the movable barrel12. Also, the contact point between the ball14and the movable barrel12is prevented from being displaced with movement of the movable barrel12. As the urging unit, there can be mentioned, for example, a unit that utilizes urging forces of springs and a unit that utilizes magnetic attraction forces of magnets, but these are not limitative.

According to this embodiment, the movable barrel12can move in two different directions while being rollably supported by the balls14to16, as described above. More specifically, the movable barrel12moves in the first direction while causing the balls14to16to roll, and pivots in the second direction about the contact point with the ball14, i.e., about the pivotal fulcrum, while causing the balls15,16to roll. It is therefore possible to reduce a sliding friction force occurring with movement of the movable barrel12. As a result, loads on the actuators17,18for driving the movable barrel12can be reduced and the positioning accuracy of the movable barrel12can be improved.

It should be noted that in this embodiment, an example has been described in which voice coil motors are used as the actuators17,18. Alternatively, it is possible to use stepping motors, ultrasonic motors using piezoelectric elements, ultra-magnetostriction actuators, or the like.

In this embodiment, the first actuator17generates a driving force acting in the direction coincident with the direction in which the ball14is guided by the guide groove13d, but this is not limitative. In a case that the acting direction of the driving force of the actuator17does not coincide with the direction in which the ball14is guided, power supplies to the actuators17,18can simultaneously be controlled such that the resultant force of driving forces of these actuators acts in a desired direction to move the correction lens11in the plane perpendicular to the optical axis.

Next, an image shake correction device according to a second embodiment of this invention will be described with reference toFIGS. 8A and 8B. It should be noted that like elements similar to those of the first embodiment are denoted by like numerals, and a description thereof will be omitted.

FIG. 8Ashows in section view an essential part of the image shake correction device according to the second embodiment, andFIG. 8Bshows D part ofFIG. 8Ain enlarged view.

In this embodiment, the movable barrel12is formed with a guide groove12eof a V-shape in cross section, which is similar to the guide groove13dformed in the stationary base plate13. When the movable barrel12is at the reference position shown inFIGS. 3 and 4, the guide groove12eis disposed facing the guide groove13dof the stationary base plate13as seen in the optical axis direction and extends in the same direction as the guide groove13d(seeFIG. 8A). As shown inFIG. 8B, the guide groove12ehas inclined surfaces12f,12gthat form therebetween a groove angle (open angle) 2α greater than a groove angle 2β formed between the inclined surfaces13e,13fof the guide groove13dformed in the stationary base plate13. It should be noted that the guide groove12eis an example of a second guide groove of this invention.

The ball14is in contact with each of the inclined surfaces12f,12gof the guide groove12eat one point, so that the ball14is in contact at two points with the guide groove12e. Thus, the ball14is supported at four points to be rollable in the Y direction in a state held between the movable barrel12and the stationary base plate13.

In this embodiment, the ball14is made in contact at two points with the guide groove12eof a V-shape in cross section which is formed in the movable barrel12and similar to the guide groove13dof the stationary base plate13, and the groove angle 2α formed between the inclined surfaces12f,12gof the guide groove12eis made greater than the groove angle 2β formed between the inclined surfaces13e,13fof the guide groove13dformed in the stationary base plate13. In other words, the depth of the guide groove12eis made shallower than that of the guide groove13d.

As described above, the ball14is held between the guide grooves12eand13d, so that only rolling friction is produced. It is therefore possible to reduce load for pivoting the movable barrel12. It is also possible to prevent the pivot center of the movable barrel12from being displaced, even if external impact is applied to the movable barrel12. Thus, a highly accurate, highly reliable image shake correction device can be provided. In respect of other construction, function, and effect, this embodiment is the same as the first embodiment.

Next, an image shake correction device according to a third embodiment of this invention will be described with reference toFIGS. 9A and 9B. It should be noted that like elements similar to those of the first embodiment are denoted by like numerals, and a description thereof will be omitted.

FIG. 9Ashows in section view an essential part of the image shake correction device according to the third embodiment, andFIG. 9Bshows E part ofFIG. 9Ain enlarged view.

In this embodiment, a rotary member19is supported to be rotatable relative to the movable barrel12about an axis passing through the center of the ball14and extending parallel to the optical axis. The rotary member19is formed with a guide groove19aof a V-shape which is similar to the guide groove13dformed in the stationary base plate13. The guide groove19ais disposed facing the guide groove13dof the stationary base plate13as seen in the optical axis direction, and extends in the same direction as the guide groove13d.

It should be noted that in this embodiment, inclined surfaces19b,19cof the guide groove19aform therebetween a groove angle 2α equivalent to the groove angle 2β formed between the inclined surfaces13e,13fof the guide groove13dformed in the stationary base plate13. However, the groove angle 2α can be made greater than the groove angle 2β, as with the second embodiment.

The ball14is made in contact at one point with each of the inclined surfaces19b,19cof the guide groove19a. Thus, the ball14is in contact at two points with the guide groove19a. When held between the movable barrel12and the stationary base plate13, the ball14is supported by four points to be rollable in the Y direction. The movable barrel12is supported to be pivotable relative to the rotary member19about an axis extending parallel to the optical axis.

In this embodiment, the V-shaped guide groove19ais formed in the rotary member19supported to be rotatable relative to the movable barrel12, and the ball14is made in contact at two points with the guide groove19aof the rotary member19. Furthermore, the movable barrel12is supported to be pivotable about the axis extending parallel to the optical axis.

Thus, load for pivoting the movable barrel12can be largely reduced. In addition, the pivotal fulcrum for the movable barrel12can be prevented from being displaced, even if external impact is applied to the movable barrel12. It is therefore possible to provide a highly accurate, highly reliable image shake correction device and an optical apparatus having the image shake correction device.

In this embodiment, since the movable barrel12is supported to be pivotable relative to the rotary member19, the contact position between ball14and the guide groove19acan be prevented from being displaced, even if the pivot angle θ of the movable barrel12is made large. It is therefore possible to position the correction lens11in a wider range. In respect of other construction, function, and effect, this embodiment is the same as the first embodiment.

It should be noted that this invention is not limited in construction to the examples described in the embodiments, and various changes and modifications may be made in terms of material, shape, size, form, number, installation position, etc. without departing from the spirit and scope of the invention.

For example, although in the embodiments the lens barrel has been described as an example of the optical apparatus with image shake correction device, this invention is also applicable to other optical apparatus such as digital camera, digital video camera, interchangeable lens for digital single-lens reflex camera, and binocular, and is further applicable to an image pickup unit of electronic equipment such as a cellular phone or a game machine.

This application claims the benefit of Japanese Patent Application No. 2011-079556, filed Mar. 31, 2011, which is hereby incorporated by reference herein in its entirety.