Abstract:
A driving mechanism for holding and shifting a part to be driven. The mechanism has at least three carrying elements for carrying the part elastically by exerting force upon the part in directions generally perpendicular to an axis of the part, at least one of the carrying elements being of a actuating type including a frictional actuator, the frictional actuator having a contact face for contacting the part under the pressure, the contact face oscillating at high frequency so as to make the part move in a direction almost rectangular to that of exerting the force upon the part.

Description:
[0001]    This application is based upon application No. 11-359095 filed in Japan, the contents of which are hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a driving system with elastically supporting units. More specifically, the present invention relates to the driving system for driving a driven member in a plane.  
           [0004]    2. Description of the Related Arts  
           [0005]    When a camera body is moved or shaken at time of photographing, an image-forming position or a position of object image, onto a photosensitive surface, is deviated or shifted out of position. In order to prevent such a deviation or shift of the image-forming position, there have been proposed various types of blur compensation mechanisms, in which a blur compensation lens provided in a lens barrel is moved suitably, on a basis of the detected direction and distance of the deviation caused by such a shaking of the camera body, so as to keep the deviation of the image-forming position onto the photosensitive surface within a certain range.  
           [0006]    However, the conventional blur compensation mechanisms are constructed so that two blur compensation lenses are driven independently in two directions perpendicular to each other, because they are needed to be driven precisely at high speed. Thereby, the construction thereof becomes large, and it is difficult to make the mechanism compact, especially in a direction of an optical axis, i.e. in a direction perpendicular to the driving directions in which the blur compensation lenses are driven.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, it is an object of the present invention to provide a driving system that is compact in a direction perpendicular to the driving directions in which the blur compensation lens is driven to move.  
           [0008]    In order to achieve the above object, there is provided a driving system comprising: a driven member; and at least three supporting units for supporting the driven member and for elastically urging the driven member in directions generally perpendicular to an axis thereof, at least one of the supporting units being of a driving type including a frictionally driving unit, the frictionally driving unit being restrained from moving a direction perpendicular to a direction in which the driven member is urged and having a contact portion for contacting the driven member under pressure, the contact portion vibrating at high frequency so as to move the driven member in a direction generally perpendicular to the direction in which the driven member is urged.  
           [0009]    In the construction, the driven member is supported on at least three supporting points, as the result of the balance of urging forces of the supporting units. The contact portion of the frictionally driving unit, which is included by at least one of the supporting units, can move or drive at least one of the supporting points by the vibration thereof so that the driven member is moved to and supported at new balanced position. That is, it is possible to move the driven member.  
           [0010]    In the construction, the frictionally driving unit may include, for example, a piezoelectric actuator, which is of the successively driving type, more specifically, a vibration motor or so-called ultrasonic motor in which high frequent vibration makes the driven member moved. In the case, the vibration motor may be of a stationary wave type, of which the contact portion for contacting the driven member vibrates in elliptic shape in a stationary manner. Also, it may be of a progressive wave type, which drives the driven member by means of the surface vibration in elliptic shape caused by the progressive wave. Depending on the contact of the frictionally driving unit with the driven member under pressure, it is possible to move the driven member by the small distance so as to control the movement of the driven member precisely with high resolution. Thus, after driving the driven member, it is possible to support the driven member without play.  
           [0011]    In the construction, since the supporting units support the driven member from directions perpendicular to the axis of the driven member the supporting units can be disposed only in the space which extends in driving directions, except for in the space which extends in a direction perpendicular to driving direction.  
           [0012]    Accordingly, the driving system can be made compact in the direction perpendicular to the axis of the driven member.  
           [0013]    As an embodiment, all of the supporting units may be of the driving type.  
           [0014]    In this embodiment, even if the force perpendicular to urging direction of respective supporting units is applied, sliding is caused between the driven member and the supporting units. Thus, the supporting unit cannot be forced excessively and can drive the driven member with small force at the stabile condition.  
           [0015]    As another embodiment, at least two of the supporting units may be of the driving type.  
           [0016]    In this embodiment, in the case that the driving type of supporting units are disposed not parallel to each other, it is possible to move the driven member in two directions. Meanwhile, in the case that the driving type of the supporting units are disposed parallel to each other, it is possible to rotate the driven member.  
           [0017]    As still another embodiment, the at least one of the supporting units being of the driving type may urge the driven member toward the axis of the driven member elastically so as to support the driven member.  
           [0018]    In this embodiment, urging toward the axis of the driven unit cannot cause redundant moment in the driven member. Thereby, the contact portion of the driving type of supporting units contact the driven member equally so as to drive the driven member at the stable condition.  
           [0019]    As still another embodiment, there may be provided two pairs of the supporting units beside the driven member at right angles in a plane perpendicular to the axis of the driven unit, and at least one of each of the two pairs thereof may be of the driving type.  
           [0020]    In this embodiment, each pair of the supporting units is disposed perpendicular to each other and at least one of the pairs is of the driving type. Thus, it is possible to drive the driven member in two directions without rotating it.  
           [0021]    As still another embodiment, there may be provided three of the supporting units beside the driven member at generally trisected positions in a plane perpendicular to the axis of the driven member so as to urge the driven member toward the axis of the driven member, and at least two of the supporting units being of the driving type.  
           [0022]    In this embodiment, at least two of the driving type of the supporting units, disposed about 120 degree apart, can drives the driven member in two directions by the resultant force thereof. Moreover, it is possible to rotate the driven member.  
           [0023]    As still another embodiment, the driving system may further comprise a holding unit for holding the driven member, the holding unit including: an urging member for urging the driven member in a direction parallel to the axis of the driven member; and a contacting member for contacting the driven member so as to prevent the driven member from moving in a direction of urging the driven member. In this embodiment, the holding unit can keep the position of the driven member constant in a direction parallel to the axis of the driven member.  
           [0024]    In this embodiment, the urging member may include a contact face, contacting the driven member under the pressure and urged by the supporting, the contact face tilting to (or being inclined against) both the axis of the driven member and a plane perpendicular to the axis of the driven member so as to generate a component of urging force in a direction parallel to the axis of the driven member. By means of the component of urging forces in the direction parallel the axis of the driven member, it is possible to support the driven member elastically and to make the construction of the driving system compact.  
           [0025]    Above mentioned constructions of the driving system is suitable to a blur compensating apparatus to drive an image blur compensation lens in a direction perpendicular to an optical axis thereof.  
           [0026]    Further, in order to achieve the above object, there is provided a driving system comprising: a driven member; a guide for guiding the driven member movably in a plane; a first elastic member for contacting the driven member from a first direction in the plane; a second elastic member for contacting the driven member from a second direction in the plane; and a third elastic member for contacting the driven member from a third direction in the plane, the third elastic member including a contact portion for contacting the driven member, the contact portion being restrained from moving in a direction perpendicular to the third direction in the plane and vibrating in the direction perpendicular to the third direction in the plane.  
           [0027]    As an embodiment, the second elastic member may include a second contact portion for contacting the driven member, the second contact portion being restrained from moving in a direction perpendicular to the second direction in the plane and vibrating in the direction perpendicular to the second direction in the plane.  
           [0028]    In this embodiment, the second direction may be perpendicular to the third direction.  
           [0029]    Moreover, the driving system may further comprise a forth elastic member for contacting the driven member from a forth direction in the plane, the first direction opposing the second direction, and the third direction opposing the forth direction.  
           [0030]    As another embodiment, the driven member may have a circular contact face for contacting the first elastic member, the second elastic member, and the third elastic member at generally trisected positions.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]    This and other objects and features of the present invention will become clear from the following description taken in connection with the preferred embodiments thereof with the reference to the accompanying drawings, in which:  
         [0032]    [0032]FIG. 1 is a schematic cross sectional view showing a main part of a driving system according to a first embodiment of the present invention;  
         [0033]    [0033]FIGS. 2A and 2B are schematic cross sectional views showing main parts of a driving system according to a second embodiment of the present invention;  
         [0034]    [0034]FIG. 3A is a schematic view showing a main part of an actuator employed in the driving system of FIG. 1;  
         [0035]    [0035]FIG. 3B is a schematic view showing a main part of an actuator according to a modification of the actuator of FIG. 3A;  
         [0036]    [0036]FIG. 4 is a vertical sectional view of the driving system of FIG. 1;  
         [0037]    [0037]FIG. 5 is a schematic diagram of a camera, which uses the driving system of FIG. 1;  
         [0038]    [0038]FIG. 6 is a cross sectional view showing a main part of a driving system according to a modification of the driving system of FIG. 1; and  
         [0039]    [0039]FIG. 7 is a vertical sectional view of FIG. 2.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0040]    Before the description of the preferred embodiments of the present invention proceeds, it is to be noted that like or corresponding parts are designated by like reference numerals throughout the accompanying drawings.  
         [0041]    First, referring to FIG. 1 and FIGS.  3  though  5 , a description is made below in detail on a driving system, which is provided in a camera, for driving an image shake preventing lens (or blur compensation lens)  1 , according to a first embodiment of the present invention.  
         [0042]    [0042]FIG. 1 shows the driving system. A lens frame  2  for supporting the image shake preventing lens  1  has a generally square section (i.e. four outer sides forming a square) along a plane, in which the image shake preventing lens  1  moves so as to compensate the deviation of the image-forming position onto the photosensitive surface. The four outer sides of the lens frame  2 , which form the square section, are supported by two pairs of elastically supporting units  100   a ,  6   a ;  100   b ,  6   b . Each pair thereof  100   a ,  6   a ;  100   b ,  6   b  is disposed in a direction perpendicular to each other relative to the lens frame  2 . One  100   a ,  100   b  of the each pair is of a driving type and includes an ultrasonic actuator  3   a ,  3   b , which contacts the corresponding outer side of the lens frame  2  radially and drives the lens frame  2 . Such a construction is suitable, for example, in case that there is not enough space to arrange the driving system in a direction of an optical axis inside a lens barrel.  
         [0043]    More specifically, the actuators  3   a  and  3   b  drive the lens frame  2  linearly in the directions x and y, respectively. The lens frame  2 , which supports the image shake preventing lens  1 , is urged by springs  5   a ,  5   b , via the actuator  3   a ,  3   b  and actuator bases  4   a ,  4   b , respectively. The lens frame  2  is urged by each of the springs  6   a ,  6   b  in an opposed direction relative to that of each of the springs  5   a ,  5   b . Thereby, the lens frame  2  is positioned in two directions x and y. The actuators  3   a ,  3   b  are adhesively bonded to the actuator bases  4   a ,  4   b , respectively. As an alternative to the bonding method just above described, the actuator bases  4   a ,  4   b  may have mounting grooves, with which the actuators  3   a ,  3   b  may engage.  
         [0044]    The actuator bases  4   a  and  4   b  are restrained from moving in the directions x and y by guiding grooves  8   a  and  8   b , which are formed in a fixing cylinder  8 , respectively. The actuator bases  4   a  and  4   b  are restrained from moving in a direction of the optical axis, as not shown. Thus, the actuator base  4   a  is able to move in only one direction y, and the actuator bases  4   b  is able to move in only one direction x.  
         [0045]    As schematically shown in FIG. 4, the lens frame  2  is guided by a spring  16  and a ball  17  so as to be able to move only in a plane perpendicular to the optical axis. That is, the lens frame  2  is urged in a direction of the optical axis by the spring  16  against a ball  17 , which is held by the fixing cylinder  8  and reduces the friction between the lens frame  2  and the fixing cylinder  8 , so as to be prevented from faltering. Thus, the lens frame  2  is restrained from moving in a direction of the optical axis.  
         [0046]    As for each of the actuators  3   a ,  3   b , an ultrasonic motor  50 , which is shown in FIG. 3A, is used. The reason why the ultrasonic motor is used for driving the image shake preventing lens is that the ultrasonic motor has many advantages as compared to the other types of actuators. For example, the ultrasonic motor can drive it from initial speed to final speed in a short time and therefore has high following property. The ultrasonic motor can drive it quickly in a reverse direction. The construction of the ultrasonic motor is simpler than that of the other types of actuators.  
         [0047]    The ultrasonic actuator  50  has a pair of projecting portions, tip surfaces  52   a ,  52   b  of which can oscillate or vibrate in elliptic shape in the range of ultrasonic frequency. The lens frame  2 , which contacts the tip surfaces  52   a ,  52   b  under pressure, is driven frictionally in a direction of tangent line with respect to the elliptic shape of the tip surfaces  52   a ,  52   b  oscillating.  
         [0048]    More specifically, the ultrasonic motor  50  has an elastic metal plate  52 , formed at right angles in a general shape of a “U.” That is, the elastic metal plate  52  has a main body and two projecting portions. At central parts on both main surfaces of the main body, piezoelectric elements  54   a ,  54   b  are bonded or fixed. Alternating current voltage is applied to the piezoelectric elements  54   a ,  54   b . Thereby, for example, as indicated by arrows in FIG. 3A, one  54   a  of the piezoelectric elements is expanded and contracted in a direction of thickness of the main body of the elastic metal plate  52 , and the other  54   b  thereof is expanded and contracted in a direction in which the main body thereof expands. Thus, the elastic metal plate  52  is vibrated in various resonant modes including, for example, bending vibration, and/or axial vibration. As a result of composition of such various vibrations, the tip surfaces  52   a ,  52   b  of the projecting portions are vibrated in the elliptic or oblong shape, as shown in FIG. 3A. The phases of such an elliptic vibration of the tip surfaces  52   a ,  52   b  are to be sifted generally in a half period (or cicle).  
         [0049]    Alternatively, an ultrasonic motor  60  as shown in FIG. 3B may be used in stead of the ultrasonic motor  50 . The ultrasonic motor  60  have a base portion  68  and piezoelectric elements  62  and  64 , which are connected to each other in a general shape of a triangle. The piezoelectric elements  62 ,  64  are expanded and contracted in shifting phases, so that a surface of a cylinder connected to the elements  62 ,  64  is vibrated in a elliptic shape. It is better to use a pair of two ultrasonic motors  60  as shown in FIG. 6 in order to prevent the lens frame  2  from rotating.  
         [0050]    Referring to FIG. 1, when a voltage is applied to the piezoelectric elements of the actuator  3   a  so as to vibrate the contact portion thereof contacting the lens frame  2  in the elliptic shape, the lens frame  2  is moved in a direction tangent to the ellipse, i.e. in the direction x. Meanwhile, the lens frame  2  slides over the spring  6   a . Through movement of the lens frame  2  in the direction x, urging force (or biasing force) exerted by the spring  5   b  and that exerted by the spring  6   b  are unbalanced to each other. However, the lens frame  2  is held in a stationary position (or stopping position) when the lens frame  2  stops moving, by static friction exerting between the actuator  3   a  and the lens frame  2  and by that exerting between the spring  6   a  and the lens frame  2 . Meanwhile, the lens frame  2  keeps a neutral position in the direction y by means of the spring  5   a ,  6   a . Namely, the lens frame  2  is driven in the direction x only.  
         [0051]    Similarly, the lens frame  2  is driven in the direction y by the actuator  3   b.    
         [0052]    Accordingly, the actuators  3   a ,  3   b  can control the position of the lens frame  2  in the directions x and y independently.  
         [0053]    [0053]FIG. 5 shows a block diagram of the camera, provided with the driving system. The camera uses an imaging lens (photographing lens)  40  equipped with the shake preventing lens  1 .  
         [0054]    The imaging lens  40  is provided with actuators  3   a ,  3   b  for driving the shake preventing lens  1  in directions x and y respectively, shake detectors (bluer detectors)  7   a ,  7   b , for example, which are acceleration sensors, for detecting shakes or blurs in directions x and y respectively, and a lens microcomputer  42  connected thereto. A camera body  30  includes a camera CPU  34  for controlling the operation of the camera totally. The camera CPU  34  and the lens microcomputer  42  are connected to each other so as to communicate therewith mutually. The camera body  30  has a CCD photo acceptance unit  32 , disposed on a focus plane of the imaging lens  40 . The CCD photo acceptance unit  32  transforms the light energy into electric energy photoelectrically and outputs image signal.  
         [0055]    The lens microcomputer  42  performs the operation of compensating the shake of the camera body on a basis of an instruction from the camera CPU  34 . That is, the lens microcomputer  42  receives shake information from the shake detectors  7   a ,  7   b  and then evaluates adjusting distance and direction of the shake preventing lens  1 , based on the shake information. Then, the lens microcomputer  42  controls the actuators  3   a ,  3   b  so as to drive the shake preventing lens  1  in a plane perpendicular to the optical axis, i.e. in a x-y plane. Thus, if the shake or vibration may occur, it is possible to reduce the deviation of the imaging position relative to the photosensitive surface, i.e. the plane of the CCD photo acceptance unit  32 , below a certain range.  
         [0056]    Next, referring to FIGS. 2A, 2B,  3  and  7 , a description is made below in detail on a driving system of an image shake preventing lens  9 , according to a second embodiment of the present invention.  
         [0057]    As shown in FIG. 2A, a lens frame  10  holding the image shake preventing lens (or blur compensation lens)  9  has a circular section along a plane, in which the image shake prevent lens  9  moves so as to compensate the deviation of the image-forming position onto the photosensitive surface. The outer side of the lens frame  10 , which forms the circular section, is supported by three elastically supporting members  200 , one end of each of which is rotatably supported by the fixed cylinder (or stationary cylinder).  
         [0058]    Each elastically supporting member  200  is constructed as shown in FIG. 2B. That is, an arm  12  has a hole  12   w  in an end portion thereof, through which an axis  20   k , fixed on the fixing cylinder, passes so as to support the arm  12  rotatably. The arm  12  is urged toward the lens frame  10  by means of a torsion spring  13 . The torsion spring  13  has a coil portion inside which the axis  20   k  is fitted with some play, and end portions which are hooked on a projection  12   t  of the arm  12  and a projection  20   s  of the fixing cylinder, respectively.  
         [0059]    The actuator  11  is an ultrasonic motor  50  as well as that shown in FIG. 3A according to the first embodiment of the present invention, and bonded or fixed to an actuator base  11   s , as well as the first embodiment. A projection  12   s , which is provided on the other end of the arm  12 , projects into a hole lit of the actuator base  11   s . Thereby, the actuator  11  is supported by the arm  12 , so as to be able to swing rotatably.  
         [0060]    Referring to FIG. 2A again, the actuators  11   a ,  11   b  and  11   c , which contact under the pressure with the lens frame  10  by the biasing force of the torsion coil springs  13   a ,  13   b  and  13   c  respectively, can drive the lens frame  10 . With this arrangement, the arms  12   a ,  12   b ,  12   c  rotate accordingly. Namely, it is possible to move the shake preventing lens  9  in any direction in the plane perpendicular to the optical axis by controlling driving amount of the actuators  11   a ,  11   b ,  11   c . The operation, such as shake preventing operation and so on, is similar to the first embodiment, except for a holding mechanism of the lens frame  10 .  
         [0061]    By the way, if the lens frame is driven by the actuators from a direction radial to the lens frame, it is necessary to prevent the lens frame from moving in a direction parallel to the optical axis. For example, it is necessary for the lens frame to be urged toward a stationary member by means of the spring  16 , as shown in FIG. 4, and so on. Such additional parts, which are not needed in case that the lens is driven from a direction parallel to the optical axis, may make a mechanism bigger and may increase its production cost.  
         [0062]    Therefore, as shown in FIG. 7, the lens frame  10  has a contact surface, for contacting the actuator  11 , which is tilted with respect to the optical axis. The contact surface causes axial component of the force exerted by the spring, i.e. a component thereof in a direction parallel to the optical axis. Namely, the spring  13 , which urges the actuator  11  toward the lens frame  10 , is used in order to restrain the lens frame  10  in a direction parallel to the optical axis, as well as to drive the lens frame  10 .  
         [0063]    Though FIG. 7 shows the example on a basis of the driving system as shown in FIG. 2, it is possible to similarly construct the driving system as shown in FIG. 1. In that case of FIG. 1, not only surfaces to contact the actuator  3   a ,  3   b , but those to contact the spring  6   a ,  6   b , are needed to be tilted with respect to the optical axis.  
         [0064]    As above described, by arranging the actuators in the space provided radially with respect to the shake preventing lens, the size of the driving system for driving the shake preventing lens can be reduced in the direction of the optical axis.  
         [0065]    Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various other changes and modifications are also apparent to those skilled in the art.  
         [0066]    The driving system according to the preferred embodiment can drive a part by minute distance at high speed. Thus, it is possible to apply the driving system to various apparatus.  
         [0067]    For example, it is possible to support and drive the CCD photo acceptance unit, instead of the image shake preventing lens, similarly to the first embodiment as described above, so as to compensate the deviation of the image-forming position onto the photosensitive surface.  
         [0068]    Such a driving system can be applied to so-called pixel shifting. That is, in order to increase superficial numbers of the pixels in the CCD photo acceptance unit, the driving system drives the CCD photo acceptance unit minutely so as to fill in the blanks between pixels.  
         [0069]    The driving system, such as the above mentioned second embodiment, can not only translate but rotate a part. Therefore, the driving system can be applied to the high accuracy moving stage, for example, which is used to process a cell under the microscope or which is used in the process of manufacturing the electronic parts.