JP2011081060A - Vibration-proof actuator, lens unit including the same and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration-proof actuator capable of maintaining initial vibration-proof performance over a long term. <P>SOLUTION: The vibration-proof actuator (10) which prevents image blur by translationally moving an image blur preventing lens (16) centering a prescribed control center position includes: a fixed part (12) including a fixed part plane part (12b); a movable part (14) including a movable part plane part (14b) and configured to attach the image blur preventing lens thereto; three spherical bodies (18) held between the fixed part plane part and the movable part plane part; driving means (20 and 22) driving the movable part; and a control means (36) controlling the driving means to move the image blur preventing lens to stabilize the image. The control means has an offset setting means (37) offsetting the control center position so as to change a contact position of the spherical bodies with the fixed part plane part or the movable part plane part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an anti-vibration actuator, a lens unit including the same, and a camera, and in particular, by translating an image blur prevention lens around a predetermined control center position in a plane perpendicular to the optical axis thereof. The present invention relates to a vibration-proof actuator that prevents image blur, a lens unit including the same, and a camera.

  Japanese Patent No. 3206075 (Patent Document 1) describes a shake prevention device. In this shake preventing apparatus, a lens frame to which a shake preventing lens is attached is supported by a plurality of balls so as to be movable in parallel. The lens frame is driven in the X-axis direction and the Y-axis direction by X-axis and Y-axis DC motors via gears and the like, respectively. By moving the lens frame according to the shake detected by the shake detection means, the image formed on the film is stabilized.

Japanese Patent No. 3206075

  In the shake preventing apparatus described in Japanese Patent No. 3206575, since the lens frame is supported by the ball, there is an advantage that the sliding resistance acting on the lens frame is small and the lens frame can be moved smoothly. .

  However, the ball supporting the lens frame and the plane on which the ball abuts theoretically come into contact at “points”, and the ball and the abutment surface are actually in contact with each other in a very small area. Therefore, the load per unit area acting on the contact surface is very large. Further, the plane on which the ball abuts does not have the ability to hold the lubricant, and it is difficult to maintain a good lubrication state between the ball and the abutment surface. For this reason, in the vibration-proof actuator of the type that supports the movable part with a ball as described in Japanese Patent No. 3206575, there is a problem that the contact surface with which the ball contacts is likely to be worn.

  In particular, in a monitoring video camera or the like that is moved back and forth within a predetermined imaging range by driving a motor, shakes of the same pattern are repeatedly applied to the video camera. For this reason, in an anti-vibration actuator incorporated in a video camera for monitoring or the like, the movable part is repeatedly moved along an almost same locus in order to correct the shake of the same pattern, and the ball also comes into contact accordingly. The same trajectory on the surface will be rolled repeatedly. As a result, in a video camera for monitoring or the like having a long operation time, there is a problem that a linearly-dented scratch is easily formed on the contact surface. In addition, when the ball rolls so as to cross such a linear scratch on the contact surface, the ball is prevented from rolling by the scratch, and the followability to the shake of the movable part is deteriorated. is there.

  Accordingly, an object of the present invention is to provide an anti-vibration actuator that is less likely to wear over a long period of time and can maintain an initial anti-vibration performance, and a lens unit and a camera including the same.

  In order to solve the above-described problem, the present invention provides an image stabilization actuator that prevents image blur by translating an image blur prevention lens around a predetermined control center position in a plane orthogonal to the optical axis thereof. Then, a fixed part provided with a fixed part flat part, a movable part provided with a movable part flat part, and attached with an image blur prevention lens, and sandwiched between the fixed part flat part and the movable part flat part, At least three spherical bodies that support the movable part so as to be movable in a plane parallel to the fixed part, drive means for driving the movable part with respect to the fixed part, and controlling the drive means to prevent image shake Control means for stabilizing the image by moving the lens for control, and the control means is a control center position so that the contact position between the spherical body and the fixed portion plane portion or the movable portion plane portion is changed. Has offset setting means to offset It is characterized in Rukoto.

  In the present invention configured as described above, at least three spherical bodies are sandwiched between the fixed portion plane portion of the fixed portion and the movable portion plane portion of the movable portion, and the movable portion is in a plane parallel to the fixed portion. Support in a movable manner. The control unit controls the driving unit to drive the movable unit with respect to the fixed unit and stabilize the image. The offset setting means offsets the control center position so that the contact position between the spherical body and the fixed part plane part or the movable part plane part is changed.

  According to the present invention configured as described above, since the contact position between the spherical body and the fixed part plane part or the movable part plane part is changed by the offset setting means, in the case where the movable part is at the control center position, It is possible to prevent the spherical body and the fixed part plane part or the movable part plane part from always contacting at the same position, and it is possible to suppress wear of the fixed part plane part or the movable part plane part.

In the present invention, preferably, the offset setting means offsets the control center position so that the movable portion is rotated about the optical axis.
According to the present invention configured as described above, since the control center position is offset so that the movable part is rotated about the optical axis, the control center position can be offset without adversely affecting the image. Can do.

In the present invention, preferably, the driving means is configured to be able to rotate the movable part relative to the fixed part at a control center position where the movable part is rotated around the optical axis.
According to the present invention configured as described above, the driving unit that translates the movable portion and stabilizes the image can be used as the unit that offsets the control center position.

In the present invention, preferably, the offset setting means continuously moves the control center position with the passage of time.
According to the present invention configured as described above, since the control center position is continuously moved, the time during which the control center position stays at the same position is very short, and the wear of the fixed portion plane portion or the movable portion plane portion is reduced. Can be effectively suppressed.

In the present invention, preferably, the offset setting means moves the control center position stepwise.
According to the present invention configured as described above, the offset setting means switches a predetermined number of control center positions, so that the offset setting means can be simply configured.

In the present invention, preferably, at least three drive units are arranged on substantially the same circumference, and each drive unit is configured to generate a drive force in a substantially circumferential direction.
According to the present invention configured as described above, by adjusting the driving force of each driving means, the movable portion can be translated and rotated, and each driving means only generates the same driving force. Thus, the movable part can be rotated.

Further, the present invention is a lens unit comprising a lens barrel, an imaging lens disposed in the lens barrel, and the vibration-proof actuator of the present invention attached to the lens barrel. It is a feature.
In addition, the present invention is a camera, and includes the lens unit of the present invention and a camera body to which the lens unit is attached.

  According to the vibration-proof actuator of the present invention, and the lens unit and camera including the same, it is difficult to wear over a long period of time, and the initial vibration-proof performance can be maintained.

It is sectional drawing of the video camera by embodiment of this invention. It is a front view of an anti-vibration actuator with a moving frame in the control center position. It is a front view of the vibration proof actuator in the 2nd control center position where the movement frame was offset. FIG. 4 is a side sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a cross-sectional side view taken along the line V-V in FIG. It is a figure explaining the relationship between the movement of a drive magnet, and the signal output from a Hall element. It is a figure explaining the relationship between the movement of a drive magnet, and the signal output from a Hall element. It is a block diagram which shows the signal processing in a controller. It is a figure which shows the positional relationship of the drive magnet arrange | positioned on the fixed frame, and the drive magnet arrange | positioned on the moving frame. It is a figure which shows the offset signal in the modification of this invention.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.
First, a video camera according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a video camera according to an embodiment of the present invention.

  As shown in FIG. 1, a video camera 1 according to an embodiment of the present invention includes a lens unit 2 and a video camera body 4. The lens unit 2 prevents the lens barrel 6, the plurality of imaging lenses 8 disposed in the lens barrel, and the image blur correction lens 16 among the imaging lenses from moving within a predetermined plane. The vibration actuator 10 and gyros 34a and 34b (only 34a is shown in FIG. 1) which are vibration detecting means for detecting the vibration of the lens barrel 6 are provided.

The lens unit 2 is attached to the video camera body 4 and configured to form incident light on the image sensor E.
The generally cylindrical lens barrel 6 holds a plurality of imaging lenses 8 therein, and allows focus adjustment by moving some imaging lenses 8.

  The video camera 1 according to the embodiment of the present invention detects vibrations by the gyros 34a and 34b, operates the image stabilization actuator 10 based on the detected vibrations to move the image blur correction lens 16, and the video camera body 4 The image focused on the image sensor E is stabilized. In the present embodiment, piezoelectric vibration gyros are used as the gyros 34a and 34b. In the present embodiment, the image blur correction lens 16 is constituted by a single lens, but the lens for stabilizing the image may be a plurality of lens groups.

  Next, the configuration of the vibration isolation actuator 10 will be described with reference to FIGS. FIG. 2 is a front view of the image stabilization actuator 10 at the control center position where the moving frame is the center of the image stabilization control. FIG. 3 is a front view of the vibration isolation actuator 10 at the second control center position where the moving frame is offset. 4 is a side sectional view taken along the line IV-IV in FIG. 2, and FIG. 5A is a side sectional view taken along the line V-V in FIG. FIG. 5B is a perspective view showing a magnetized state of the driving magnet.

  As shown in FIGS. 2 to 5, the vibration-proof actuator 10 includes a fixed frame 12 that is a fixed portion fixed in the lens barrel 6 and a movable portion that is supported movably with respect to the fixed frame 12. It has a certain moving frame 14 and three steel balls 18 (FIG. 4) which are movable part supporting means for supporting the moving frame 14. Further, the vibration-proof actuator 10 includes three drive coils 20a, 20b, and 20c attached to the fixed frame 12, and 3 attached to the moving frame 14 at positions corresponding to the drive coils 20a, 20b, and 20c, respectively. Drive magnets 22a, 22b, and 22c.

  Further, as shown in FIG. 5A, the vibration-proof actuator 10 is attached to the fixed frame 12 so that the moving frame 14 is attracted to the fixed frame 12 by the magnetic force of each of the drive magnets 22a, 22b, and 22c. The suction yoke 26 and the back yoke 28 attached to the back side of the drive magnet so as to effectively direct the magnetic force of the drive magnet toward the fixed frame 12 are provided. The driving coils 20a, 20b, and 20c, and the three driving magnets 22a, 22b, and 22c attached to the corresponding positions cause the moving frame 14 to translate and rotate with respect to the fixed frame 12. The drive means which can be moved is comprised.

  Further, as shown in FIG. 5 (a), Hall elements 24a, 24b, and 24c, which are magnetic sensors, are arranged inside the windings of the drive coils 20a, 20b, and 20c (FIG. 5). Only 24a is shown). Each Hall element 24a, 24b, 24c detects the magnetism of each driving magnet 22a, 22b, 22c arranged so as to face each other, and detects the position of the moving frame 14 with respect to the fixed frame 12. It is configured. These Hall elements 24a, 24b, 24c and the drive magnets 22a, 22b, 22c constitute position detecting means.

  As shown in FIG. 1, the vibration isolation actuator 10 is used for each drive based on the vibration detected by the gyros 34a and 34b and the position information of the moving frame 14 detected by the hall elements 24a, 24b and 24c. It has a controller 36 which is a control means for controlling the current flowing through the coils 20a, 20b, 20c. Further, the controller 36 includes an offset setting means 37 for offsetting the control center position for controlling the moving frame 14.

  The anti-vibration actuator 10 moves the moving frame 14 with respect to the fixed frame 12 fixed to the lens barrel 6 in a plane parallel to the image sensor E, thereby correcting the image blur attached to the moving frame 14. The lens 16 is moved so that the image formed on the image sensor E is not disturbed even when the lens barrel 6 vibrates.

  The fixed frame 12 has a generally donut plate shape, and three driving coils 20a, 20b, and 20c are disposed thereon. As shown in FIG. 2, the centers of these three drive coils 20 a, 20 b, and 20 c are arranged on the same circumference centering on the optical axis of the lens unit 2. In the present embodiment, the drive coil 20a is disposed vertically above the optical axis, and the drive coils 20b and 20c are disposed with a central angle of 120 ° from the drive coil 20a. That is, the driving coils 20a, 20b, and 20c are arranged at equal intervals on a circumference centered on the optical axis. The driving coils 20a, 20b, and 20c are arranged such that their windings are wound in a rectangular shape with rounded corners, and the center line of the rectangle coincides with the radial direction of the circumference.

  The moving frame 14 has a generally donut plate shape and is arranged in parallel to the fixed frame 12. An image blur correction lens 16 is attached to the central opening of the moving frame 14. In addition, rectangular driving magnets 22a, 22b, and 22c are embedded at positions on the circumference of the moving frame 14 corresponding to the driving coils 20a, 20b, and 20c, respectively. In the present specification, the position corresponding to the driving coil means a position where the influence of the magnetic field formed by the driving coil is substantially reached. In addition, rectangular back yokes 28 are attached to the back side of the drive magnet, that is, on the opposite side of each drive coil, so that the magnetic flux of each drive magnet is efficiently directed toward the fixed frame 12. It has been.

  In addition, rectangular suction yokes 26 are attached to the back side of each driving coil of the fixed frame 12, that is, on the opposite side of the moving frame 14. The moving frame 14 is attracted to the fixed frame 12 by the magnetic force exerted by each of the driving magnets 22a, 22b, and 22c on the attracting yoke 26 attached thereto. In the present embodiment, the fixed frame 12 is made of a nonmagnetic material so that the magnetic lines of force of the drive magnet can efficiently reach the attraction yoke 26.

  Next, the magnetic force exerted by the driving magnet will be described with reference to FIG. The drive magnets 22a, 22b, 22c, the back yoke 28, and the attracting yoke 26 each have a rectangular shape, and are arranged so that the long sides and the short sides overlap each other. The driving coils 20a, 20b, and 20c are arranged such that their sides are parallel to the long and short sides of the rectangular back yoke 28, respectively. Further, each drive magnet is oriented such that the magnetization boundary line C, which is the boundary line between the magnetic poles, coincides with the radial direction of the circumference where each drive magnet is disposed.

  Thereby, the drive magnet 22a, the back yoke 28, and the attracting yoke 26 constitute a magnetic circuit, and magnetic lines of force indicated by arrows in FIG. 5A are formed. When a current flows through the corresponding driving coil 20a, the driving magnet 22a receives a circumferential tangential driving force. For the other driving coils 20b and 20c, corresponding driving magnets 22b and 22c, a back yoke 28, and an attracting yoke 26 are arranged in the same positional relationship.

  In this specification, the magnetization boundary line C refers to the boundary line of the magnetized magnetic poles when both ends of the drive magnet are magnetized so as to be S pole and N pole, respectively. Shall. Accordingly, in the present embodiment, the magnetization boundary line C is positioned so as to pass through the midpoint of each long side of the rectangular driving magnet. Further, as shown in FIG. 5B, the polarity of the driving magnet 22a also changes in the thickness direction. In FIG. 5B, the lower left corner is the S pole, the lower right corner is the N pole, The upper left is the N pole and the upper right is the S pole.

Next, the position detection of the moving frame 14 will be described with reference to FIGS.
6 and 7 are diagrams illustrating the relationship between the movement of the driving magnet 22a and the signal output from the Hall element 24a. As shown in FIG. 6, when the sensitivity center point S of the Hall element 24a is located on the magnetization boundary line C of the driving magnet 22a, the output signal from the Hall element 24a is zero. When the driving magnet 22a is moved together with the moving frame 14, and the sensitivity center point of the Hall element 24a deviates from the magnetization boundary line of the driving magnet 22a, the output signal of the Hall element 24a changes. As shown in FIG. 6, when the driving magnet 22a moves in a direction orthogonal to the magnetization boundary line C, that is, in the X-axis direction, the Hall element 24a generates a sinusoidal signal. Therefore, when the amount of movement is small, the Hall element 24a outputs a signal that is substantially proportional to the distance of movement of the driving magnet 22a. In the present embodiment, when the moving distance of the driving magnet 22a is within about 3% of the length of the long side of the driving magnet 22a, the signal output from the Hall element 24a is the sensitivity center of the Hall element 24a. This is approximately proportional to the distance between the point S and the magnetization boundary line C of the driving magnet 22a. In the present embodiment, the vibration-proof actuator 10 operates within a range in which the output of each Hall element is substantially proportional to the distance in the normal operation region.

  As shown in FIGS. 7A to 7C, when the magnetization boundary line C of the driving magnet 22a is positioned on the sensitivity center point S of the Hall element 24a, the driving is performed as shown in FIG. 7B. When the working magnet 22a rotates, the output signal from the Hall element 24a is zero even when the driving magnet 22 moves in the direction of the magnetization boundary line C as shown in FIG. Further, as shown in FIGS. 7D to 7F, when the magnetization boundary line C of the driving magnet 22a deviates from the sensitivity center point S of the Hall element 24a, the sensitivity center point S and the magnetization boundary are separated. A signal proportional to the distance r of the line C is output from the Hall element 24a. Therefore, if the distance r from the sensitivity center point S to the magnetization boundary line C is the same, when the driving magnet 22a moves in a direction perpendicular to the magnetization boundary line C as shown in FIG. When the drive magnet 22a is translated and rotated as shown in FIG. 7 (e) and when it is translated in any direction as shown in FIG. 7 (f), a signal having the same magnitude is output from the Hall element 24a. Is done.

  Although the Hall element 24a has been described here, the other Hall elements 24b and 24c also output similar signals based on the positional relationship with the corresponding driving magnets 22b and 22c. For this reason, based on the signals detected by the Hall elements 24a, 24b, and 24c, the position where the moving frame 14 is translated and rotated with respect to the fixed frame 12 can be specified.

Next, a support mechanism for the moving frame 14 by the steel balls 18 will be described with reference to FIGS.
As shown in FIGS. 2 to 4, the three steel balls 18 are respectively disposed between the fixed frame 12 and the moving frame 14. The three steel balls 18 are arranged at intervals of a central angle of 120 °, and the steel balls 18 are arranged between the drive coils. As shown in FIG. 4, since the moving frame 14 is attracted to the fixed frame 12 by the driving magnet 22, each steel ball 18 is sandwiched between the fixed frame 12 and the moving frame 14. As a result, the moving frame 14 is supported on a plane parallel to the fixed frame 12, and the rolling motion of the moving frame 14 with respect to the fixed frame 12 in any direction is allowed by rolling while the steel balls 18 are sandwiched. Is done.

  In this embodiment, a steel sphere is used as the steel ball 18, but the steel ball 18 is not necessarily a sphere. In other words, the steel ball 18 can be used as long as the portion in contact with the fixed frame 12 and the moving frame 14 has a substantially spherical shape during the operation of the vibration isolating actuator 10. In addition, in this specification, such a form is called a spherical body. Further, the spherical body does not have to be made of steel, and can be formed of a resin or the like.

  As shown in FIG. 4, the fixed frame 12 is provided with an annular ball drop prevention wall 12 a so as to surround each steel ball 18. Therefore, each steel ball 18 comes into contact with the fixed frame 12 at the inner plane portion surrounded by each ball drop prevention wall 12a. The plane portion of the fixed frame 12 that comes into contact with each steel ball 18 constitutes the fixed portion plane portion 12b.

  Similarly, the moving frame 14 is provided with an annular ball drop prevention wall 14 a so as to surround each steel ball 18. Therefore, each steel ball 18 comes into contact with the moving frame 14 at an inner plane portion surrounded by each ball drop prevention wall 14a. A plane portion of the moving frame 14 that comes into contact with each steel ball 18 constitutes a movable portion plane portion 14b.

  Next, with reference to FIG. 8, image blur prevention control by the vibration damping actuator 10 will be described. FIG. 8 is a block diagram showing signal processing in the controller 36. The controller 36 can be composed of analog and / or digital circuits that perform the functions described below. As shown in FIG. 8, the vibration of the lens unit 2 is detected momentarily by the two gyros 34 a and 34 b and input to the buffer amplifiers 38 a and 38 b built in the controller 36. In the present embodiment, the gyro 34a is configured and arranged to detect the angular velocity of the yawing motion of the lens unit 2, and the gyro 34b is configured to detect the angular velocity of the pitching motion. The signals output from the buffer amplifiers 38a and 38b are input to the integrating circuits 40a and 40b, respectively, where the deflection angular velocity signal is converted into a deflection angle signal. The shake angle signal is input to the optical characteristic correction circuit 42, where a lens position command signal Dx indicating the amount of movement in the X direction and Y direction of the image shake correction lens 16 necessary for the shake angle of the lens unit 2 is obtained. Converted to Dy. By moving the image blur correction lens 16 momentarily according to the lens position command signal, even when the lens unit 2 vibrates, the image focused on the image sensor E in the video camera body 4 is stabilized without being disturbed. Is done.

  The lens position command signals Dx and Dy are input to the arithmetic circuits 44b and 44c, respectively. The arithmetic circuits 44b and 44c are configured to generate coil position command signals for the drive coils 20b and 20c based on the lens position command signals. The coil position command signal is obtained when each of the drive coils 20a, 20b, 20c and the corresponding drive magnets 22a, 22b, 22c when the image blur correction lens 16 is moved to the position specified by the lens position command signal. It is a signal showing the positional relationship. That is, when each driving magnet is moved to the position commanded by the coil position command signal for each driving coil, the image blur correction lens 16 is moved to the position commanded by the lens position command signal. Is done. In the present embodiment, since the driving coil 20a is provided vertically above the optical axis, the coil position command signal ra for the driving coil 20a is equal to the X-direction component Dx of the lens position command signal. On the other hand, the coil position command signals rb and rc for the drive coils 20b and 20c are generated by the arithmetic circuits 44b and 44c based on the X direction component Dx and the Y direction component Dy of the lens position command signal. The signal processing in the arithmetic circuits 44b and 44c will be described later.

  Coil position command signals ra, rb, and rc are input to coil drive circuits 46a, 46b, and 46c, respectively. The outputs of the coil drive circuits 46a, 46b, and 46c are connected to the drive coils 20a, 20b, and 20c, respectively, and a drive current flows through each of the drive coils.

  On the other hand, the amount of movement of each drive magnet relative to each drive coil is measured by the Hall elements 24a, 24b, and 24c. The movement amounts measured by the Hall elements 24a, 24b, and 24c are input to the position detection circuits 48a, 48b, and 48c. The outputs of the position detection circuits 48a, 48b and 48c are subtracted from the coil position command signals ra, rb and rc. That is, each coil drive circuit 46a, 46b, 46c drives each current corresponding to the difference between each coil position command signal ra, rb, rc and the position signal output from each position detection circuit 48a, 48b, 48c. It flows in the coils 20a, 20b, 20c for use. Therefore, when there is no difference between the coil position command signal and the output from each position detection circuit, that is, when each driving magnet reaches the position commanded by the coil position command signal, no current flows through each driving coil. The driving force acting on the driving magnet becomes zero.

  Each position detection circuit 48a, 48b, 48c is configured to receive an offset signal output from an offset setting means 37 built in the controller 36. As a result, the output signals of the position detection circuits 48a, 48b, and 48c become values shifted by the offset signal with respect to the positions actually detected by the Hall elements 24a, 24b, and 24c. Note that the offset setting unit 37 can be configured by, for example, a memory that stores an offset signal and a D / A converter that converts the offset signal stored in the memory into an analog signal.

  Next, the relationship between the lens position command signal and the coil position command signal when the moving frame 14 is translated will be described with reference to FIG. FIG. 9 is a diagram illustrating a positional relationship between the driving coils 20 a, 20 b, 20 c arranged on the fixed frame 12 and the driving magnets 22 a, 22 b, 22 c arranged on the moving frame 14. First, the center points of the three drive coils 20a, 20b, and 20c are arranged on the points Sa, Sb, and Sc on the circumference of the radius R with the point Q as the origin. The Hall elements 24a, 24b, and 24c are also arranged so that their sensitivity center points S are located on the points Sa, Sb, and Sc. Furthermore, when the moving frame 14 is at the control center position that is not offset as shown in FIG. 2, the center of the image blur correction lens 16 and the optical axis of the imaging lens 8 coincide with each other, and each drive coil corresponds. The midpoints of the magnetization boundary lines C of the respective drive magnets are also located on the points Sa, Sb, Sc, respectively, and each magnetization boundary line C is directed in the radial direction of a circle centered on the point Q. The moving frame 14 is translated around the operation center position, and image blur prevention control is executed.

  Next, the horizontal axis with the point Q as the origin is taken as the X axis, the vertical axis is taken as the Y axis, and the center point Q1 of the image stabilizing lens 16 is Dy, X in the Y axis direction, as shown by the solid line in FIG. Consider a case in which -Dx translation is performed in the axial direction. When the moving frame 14 is moved in this way, the magnetization boundary line C of each of the drive magnets 22a, 22b, and 22c is moved to the position indicated by the alternate long and short dash line in FIG. Here, the distance between the magnetization boundary line C of the driving magnet 22a and the point Sa is ra, the distance between the magnetization boundary line C of the driving magnet 22b and the point Sb is rb, and the driving magnet 22c Let rc be the distance between the magnetization boundary line C and the point Sc. The distances ra, rb, and rc correspond to the movement distances detected by the hall elements 24a, 24b, and 24c when the image stabilizing lens 16 is moved in the Y-axis direction by Dy and in the X-axis direction. . These distances ra, rb, and rc are uniquely determined with respect to the movement distances Dx and Dy in the X-axis direction and the Y-axis direction. Therefore, in order to move the image stabilizing lens 16 in the X-axis direction and the Y-axis direction by Dx and Dy, respectively, the distances ra, rb, and rc corresponding thereto may be given as coil position command signals.

図８において説明した各演算回路４４ｂ、４４ｃは、夫々上記数式１の第２、第３式に対応する演算を実行して、コイル位置指令信号ｒｂ、ｒｃを生成している。 Here, if the positive direction of each distance ra, rb, rc is defined as shown by arrows a, b, c in FIG. 9, the relationship between ra, rb, rc and Dx, Dy is as follows (Formula 1) Given in.

The arithmetic circuits 44b and 44c described with reference to FIG. 8 perform calculations corresponding to the second and third expressions of the above-described expression 1, respectively, to generate the coil position command signals rb and rc.

このように、各駆動用磁石が各駆動用コイルに対して同一距離接線方向に移動されることにより、移動枠１４は、像振れ補正用レンズ１６の光軸と撮像用レンズ８の光軸が一致した状態を保持しながら、光軸を中心に回転される。 Next, a coil position command signal when the moving frame 14 is rotated will be described. In order to rotate the moving frame 14, the same value may be given as each coil position command signal. That is, each coil position command signal for rotating the moving frame 14 clockwise by an angle θ [rad] is:

In this way, each drive magnet is moved in the tangential direction at the same distance with respect to each drive coil, so that the moving frame 14 has an optical axis of the image blur correction lens 16 and an optical axis of the imaging lens 8. It is rotated around the optical axis while maintaining the coincidence state.

  Next, the operation of the video camera 1 according to the embodiment of the present invention will be described with reference to FIGS. First, by turning on a start switch (not shown) of the camera shake prevention function of the video camera 1, the vibration isolation actuator 10 provided in the lens unit 2 is operated. The gyros 34 a and 34 b attached to the lens unit 2 detect vibrations in a predetermined frequency band every moment and output them to the controller 36. The gyro 34a outputs an angular velocity signal in the yawing direction of the lens unit 2, and the gyro 34b outputs an angular velocity signal in the pitching direction. The input angular velocity signals are converted into lens position command signals Dx and Dy via buffer amplifiers 38a and 38b, integration circuits 40a and 40b, and an optical characteristic correction circuit 42. By moving the image blur correction lens 16 momentarily to a position commanded by a lens position command signal output in time series from the optical characteristic correction circuit 42, the image sensor E of the video camera body 4 is focused. The image is stabilized.

  The horizontal lens position command signal Dx output from the optical characteristic correction circuit 42 is output as a coil position command signal ra for the drive coil 20a via the coil drive circuit 46a. The arithmetic circuit 44b receives the lens position command signal Dx in the horizontal direction and the lens position command signal Dy in the vertical direction, and generates a coil position command signal rb for the driving coil 20b based on the second formula of Formula 1. Is done. Similarly, the lens position command signals Dx and Dy are input to the arithmetic circuit 44c, and a coil position command signal rc for the driving coil 20c is generated based on the third formula of Formula 1.

  On the other hand, the Hall element 24a corresponding to the driving coil 20a outputs a detection signal to the position detection circuit 48a. The output signal of the position detection circuit 48a is subtracted from the coil position command signal ra for the drive coil 20a, and a current proportional to the difference between these is output to the drive coil 20a via the coil drive circuit 46a. Similarly, a current proportional to the difference between the detection signal of the hall element 24b and the coil position command signal rb is output to the driving coil 20b via the coil drive circuit 46b, and the detection signal of the hall element 24c and the coil position command signal rc A current proportional to the difference is output to the drive coil 20c via the coil drive circuit 46c.

  When a current flows through each driving coil, a magnetic field proportional to the current is generated. Due to this magnetic field, each driving magnet arranged corresponding to each driving coil receives a driving force in a direction approaching the position specified by the coil position command signals ra, rb, rc, and the moving frame 14 is moved. The When the driving magnet reaches the position specified by the coil position command signal by this driving force, the coil position command signal and the detection signal of the Hall element coincide with each other, so the output of the driving circuit becomes zero and the driving force also becomes zero. In addition, when each driving magnet deviates from the position specified by the coil position command signal due to a disturbance or a change in the coil position command signal, a current flows again to each driving coil. The position is returned to the position specified by the position command signal.

  By repeating the above operation every moment, the image blur correction lens 16 attached to the moving frame 14 having each driving magnet is moved so as to follow the lens position command signal. Thereby, the image focused on the image sensor E of the video camera body 4 is stabilized.

Next, the operation of the offset setting means 37 built in the controller 36 will be described with reference to FIG. 2, FIG. 3 and FIG.
In the present embodiment, the offset setting means 37 is configured to generate an offset signal having a predetermined positive value, 0, and a predetermined negative value by switching every predetermined time. As shown in FIG. 8, the offset signal of the offset setting means 37 is input to the position detection circuits 48a, 48b and 48c, respectively. When an offset signal is input to the position detection circuits 48a, 48b, and 48c, the output is shifted by an amount corresponding to the offset signal.

  When the moving frame 14 is at the control center position not offset shown in FIG. 2 and the lens position command signals Dx and Dy are both 0, as described above, each coil position command signal and the position detection circuit. The output signals of 48a, 48b, and 48c are all 0. In this state, when the offset signal output from the offset setting unit 37 changes from 0 to a predetermined value, the output signals of the position detection circuits 48a, 48b, and 48c change from 0 to a predetermined value. As a result, a drive current flows through each of the drive coils 20a, 20b, and 20c via the coil drive circuits 46a, 46b, and 46c. Here, since the shift amounts of the output signals of the position detection circuits 48a, 48b, and 48c are equal to each other, the same current flows through the driving coils 20a, 20b, and 20c.

  As shown in Equation 2, when the same current flows through each of the driving coils 20a, 20b, and 20c, the moving frame 14 is not translated, and only a rotational movement of a predetermined angle occurs. That is, the moving frame 14 is rotated around the optical axis while maintaining the position of the optical axis of the image blur correction lens 16. Thereby, the moving frame 14 is rotated to the offset control center position shown in FIG. When the moving frame 14 is moved to the position shown in FIG. 3, the output signals of the Hall elements 24a, 24b, 24c change so as to cancel the offset signal by the offset setting means 37, so that each position detection circuit 48a, 48b, The output of 48c is 0, and the current flowing through each of the drive coils 20a, 20b, 20c is also 0.

  When the lens position command signals Dx and Dy are input while the moving frame 14 is moved to the offset control center position shown in FIG. 3, the moving frame 14 is translated around the offset control center position. The image on the image sensor E is stabilized. On the other hand, when the offset signal output from the offset setting means 37 is changed to the opposite polarity, the moving frame 14 rotates counterclockwise around the optical axis from the non-offset control center position shown in FIG. It is moved to the rotated offset control center position (not shown).

  By offsetting the control center position every predetermined time by the offset setting means 37, the contact point between the steel ball 18 at the control center position, the fixed portion plane portion 12b and the movable portion plane portion 14b is changed. Thereby, the wear of the fixed part plane part 12b and the movable part plane part 14b is reduced.

  In the above description, for the sake of simplicity, the offset signal is switched when each lens position command signal is 0, but each lens position command signal is not 0, that is, the image stabilization by the image stabilization actuator 10 is performed. It is also possible to switch the offset signal during control.

Next, the influence on the image stabilization control by offsetting the control center position will be described.
In the present embodiment, the control center position is offset by about ± 1 deg (π / 180 rad) by the offset setting means 37. Further, in the present embodiment, each steel ball 18 is disposed at a position about 12 mm away from the optical axis in the radial direction. Therefore, each steel ball 18 is fixed to the fixed portion plane portion 12b and the movable portion plane portion by this offset. The contact position of 14b is moved in the circumferential direction by about 0.2 mm. Since the contact area between each steel ball 18 and the fixed portion plane portion 12b and the movable portion plane portion 14b is sufficiently small, the wear of the fixed portion plane portion 12b and the movable portion plane portion 14b is caused by the movement of the contact position of about 0.2 mm. Is effectively suppressed.
Further, each coil position command signal ra, rb, rc is calculated by Equation 1 as described above. In Equation 1, as the coefficients of the lens position command signals Dx and Dy, cos (0), cos (−π / 2), cos (2π / 3), cos (π / 6), cos (4π / 3), cos (5π / 6) is used. Here, Table 1 shows the amount of change in the value of each coefficient of Formula 1 when the control center position is offset by 1 deg (π / 180 rad).

Table 1

  As shown in Table 1, the amount of change in the value of the coefficient in Equation 1 is 0.02 or less, and the influence of the offset of about ± 1 deg on the coil position command signal is small and is about 2%. Is expected. Therefore, even when the control center position is offset, the moving frame 14 can be moved with sufficient accuracy by the same control as when the control center position is not offset.

  Alternatively, an accurate calculation formula of the coil position command signal when the control center position is offset is derived, and when the control center position is offset, the controller 36 is configured to execute the image stabilization control based on the calculation formula. May be configured. By configuring the controller in this way, it is possible to execute the image stabilization control with high accuracy even when the offset amount is set large.

According to the video camera of the embodiment of the present invention, since the contact position between the steel ball and the fixed portion plane portion or the movable portion plane portion is changed by the offset setting means, when the moving frame is at the control center position, It is possible to prevent the steel ball and the fixed part flat part or the movable part flat part from always contacting at the same position, and it is possible to suppress wear of the fixed part flat part or the movable part flat part.
Further, according to the video camera of the present embodiment, the control center position is offset so that the moving frame is rotated around the optical axis of the image blur prevention lens. Therefore, the control center position is offset during imaging. Even in the case of an image, there is almost no adverse effect on the image.

Furthermore, according to the video camera of the present embodiment, the translational movement of the image stabilizing lens for stabilizing the image and the rotational movement for offsetting the control center position are performed by the three driving coils and the driving magnet. Both can be performed.
In addition, according to the video camera of the present embodiment, the offset setting means can offset the control center position by simply switching three types of constant voltages in stages, so that the offset setting means can be simply configured. Can do.

  In the above-described embodiment, the offset setting means switches and outputs positive, negative, and zero offset signals, and the three types of control center positions are switched in stages. The position may be continuously moved over time. This modification is suitable for a camera that continuously captures images for a long time, such as a video camera for monitoring.

  For example, as shown in FIG. 10, the offset setting means can be configured so that the offset signal changes in a triangular wave shape with time. In this case, the control center position is moved clockwise little by little from the state without offset (t1 in FIG. 10), and when the offset amount reaches about 1 deg (t2), the counterclockwise movement is started. It returns to the state without offset (t3). Further, the control center position is moved counterclockwise, and when the offset amount reaches about −1 deg (t4), the clockwise movement is started and the state is returned to the state without the offset (t5). In this modification, one cycle of movement of the control center position is performed in about 10 minutes, and this movement is repeated. Thus, since the speed at which the control center position is offset is set to be extremely slow, the movement of the control center position does not adversely affect the image stabilization control.

  According to the modification configured as described above, since the control center position is continuously moved, the time during which the control center position stays at the same position is very short, and the fixed portion plane portion or the movable portion plane portion is worn. Can be more effectively suppressed.

  As mentioned above, although preferable embodiment of this invention was described, a various change can be added to embodiment mentioned above. In particular, in the above-described embodiment, the vibration-proof actuator of the present invention is applied to a video camera. However, the present invention can be applied to any camera for capturing still images or moving images, such as a digital camera or a film camera. it can. The present invention can also be applied to a lens unit used with the camera body of these cameras.

  In the above-described embodiment, the three control center positions are switched every predetermined time. However, for example, when the present invention is applied to still image shooting, the control center position is switched to prevent camera shake. You may comprise so that it may be performed when a function is turned on or when the power supply of a camera is turned on.

DESCRIPTION OF SYMBOLS 1 Video camera of embodiment of this invention 2 Lens unit 4 Video camera main body 6 Lens barrel 8 Imaging lens 10 Anti-vibration actuator 12 Fixed frame (fixed part)
12a Ball fall prevention wall 12b Fixed part plane part 14 Moving frame (movable part)
14a Ball fall prevention wall 14b Movable part plane part 16 Image blur correction lens 18 Steel ball (spherical body)
20a, 20b, 20c Driving coil 22a, 22b, 22c Driving magnet 24a, 24b, 24c Hall element 26 Suction yoke 28 Back yoke 34a, 34b Gyro 36 Controller (control means)
37 Offset setting means 38a, 38b Buffer amplifiers 40a, 40b Integration circuit 42 Optical characteristic correction circuit 44b, 44c Arithmetic circuit 46a, 46b, 46c Coil drive circuit 48a, 48b, 48c Position detection circuit

Claims (8)

An anti-shake actuator that prevents image shake by translating an image shake prevention lens around a predetermined control center position in a plane orthogonal to the optical axis,
A fixed part having a fixed part plane part;
A movable part provided with a movable part plane part, and attached with the image blur prevention lens;
At least three spherical bodies that are sandwiched between the fixed part plane part and the movable part plane part and support the movable part in a plane parallel to the fixed part;
Driving means for driving the movable part relative to the fixed part;
Control means for controlling the drive means to move the image blur prevention lens and stabilize the image,
The control means includes an offset setting means for offsetting the control center position so that a contact position between the spherical body and the fixed part plane part or the movable part plane part is changed. Vibration actuator.   The anti-vibration actuator according to claim 1, wherein the offset setting means offsets the control center position so that the movable part is rotated about the optical axis.   The said drive means is comprised so that the said movable part can be rotated with respect to the said fixed part to the said control center position in which the said movable part was rotated centering on the optical axis. Anti-vibration actuator.   4. The vibration-proof actuator according to claim 1, wherein the offset setting unit continuously moves the control center position as time passes.   The anti-vibration actuator according to any one of claims 1 to 3, wherein the offset setting means moves the control center position in a stepwise manner.   6. The drive means according to claim 1, wherein at least three of the drive means are arranged on substantially the same circumference, and each of the drive means is configured to generate a drive force in the circumferential direction. The anti-vibration actuator described in 1. A lens barrel;
An imaging lens arranged in the lens barrel;
The vibration-proof actuator according to any one of claims 1 to 6, attached to the lens barrel,
A lens unit comprising: A lens unit according to claim 7;
A camera body to which this lens unit is attached;
A camera characterized by comprising:

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