Patent Publication Number: US-2021173175-A1

Title: Lens driving device, camera module, and camera-mounted device

Description:
TECHNICAL FIELD 
     The present invention relates to an auto-focusing and shake-correcting lens driving device, and to a camera module and a camera-mounted device. 
     BACKGROUND ART 
     In general, a small-sized camera module is mounted in mobile terminals, such as smartphones. A lens driving device is applied in such a camera module (see, for example, Patent Literature (hereinafter, referred to as “PTL”) 1). This lens driving device has an autofocus function of automatically performing focusing during capturing a subject (hereinafter referred to as “AF (Auto Focus) function”) and a shake correction function of reducing an image defect by optically correcting a camera-shake (vibration) that occurs when capturing an image (hereinafter referred to as “OIS (Optical Image Stabilization) function”). 
     The lens driving device having the AF and OIS functions includes an autofocus driving part (hereinafter referred to as “AF driving part”) for moving a lens part in an optical-axis direction; and a shake-correction driving part (hereinafter referred to as “OIS driving part”) for rocking the lens part in a plane orthogonal to the optical-axis direction. In PTL 1, a voice coil motor (VCM) is applied to the AF driving part and the OIS driving part. 
     In recent years, a camera module having a plurality of (typically two) lens driving devices is put into practical use (so-called dual camera). A dual camera has various possibilities, such as allowing two images having different focal lengths to be simultaneously captured, allowing a still image and a moving image to be simultaneously captured, and the like, depending on use scenes. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] 
     Japanese Patent Application Laid-Open No. 2013-210550 
     [PTL 2] 
     WO 2015/123787 
     SUMMARY OF INVENTION 
     Technical Problem 
     As disclosed in PTL 1, however, the lens driving device using VCM may impair its operation with high precision because it is affected by external magnetism. In particular, a dual camera having lens driving devices juxtaposed with each other is more likely to cause magnetic interference between the lens driving devices. 
     PTL 2 discloses a lens driving device employed with an ultrasonic motor in the AF driving part and the OIS driving part. The lens driving device disclosed in PTL 2 can reduce the effect of external magnetism because it does not include a magnet, but has a complicated structure, which makes it difficult to reduce the size and profile of the lens driving device. 
     An object of the present invention is to provide a lens driving device, a camera module, and a camera-mounted device, which are capable of reducing the effect of external magnetism and of being reduced in size and profile thereof. 
     Solution to Problem 
     A lens driving device according to the present invention includes: 
     an autofocus part including: 
     an autofocus movable part to be disposed at an autofocus fixing part; and 
     an autofocus driving part configured to move, with respect to the autofocus fixing part, the autofocus movable part in a Z-direction extending along an optical axis, and 
     a shake-correction part including: 
     a shake-correction fixing part; 
     a shake-correction movable part including the autofocus part; and 
     a shake-correction driving part configured to move, with respect to the shake-correction fixing part, the shake-correction movable part in an X-direction and a Y direction each orthogonal to the optical axis, in which 
     the shake-correction driving part includes: 
     a first shake-correction driving part to be disposed along the X-direction and configured to move the shake-correction movable part in the X-direction; and a second shake-correction driving part to be disposed along the Y-direction and configured to move the shake-correction movable part in the Y-direction, wherein 
     the first and the second shake-correcting driving parts respectively include: 
     shake-correcting ultrasonic motors composed of: shake-correcting piezoelectric elements; 
     and shake-correcting resonance parts configured to resonate with vibrations of the shake-correcting piezoelectric elements and to convert a vibrational motion into a linear motion in the X-direction or the Y-direction, the shake-correcting ultrasonic motors being configured to be disposed at the shake-correction fixing part; and 
     shake-correcting power transmitting parts configured to couple the shake-correcting ultrasonic motors and the shake-correction movable part together and to transmit the linear motion in the X-direction or the Y-direction to the shake-correction movable part, and wherein 
     the autofocus driving part includes: 
     an auto-focusing ultrasonic motor composed of: an auto-focusing piezoelectric element; and auto-focusing resonance part configured to resonate with vibrations of the auto-focusing piezoelectric element and to convert a vibration motion into a linear motion in the Z-direction, the auto-focusing ultrasonic motor being configured to be disposed at the autofocus movable part; and 
     an auto-focusing power transmitting part configured to couple the auto-focusing ultrasonic motor and the autofocus fixing part together and to transmit the linear motion to the autofocus fixing part, and in which, 
     in a rectangle defined by two sides where the first shake-correction driving part and the second shake-correction driving part are disposed, the autofocus driving part is disposed along a side different from the two sides. 
     A camera module according to the present invention includes: 
     the lens driving device described above; 
     a lens part to be mounted at the autofocus movable part; and 
     an image capturing part configured to capture a subject image imaged by the lens part. 
     A camera-mounted device according to the present invention is a camera-mounted device that is an information device or a transporting device, the camera-mounted device including: 
     the camera module described above; and 
     an image processing part configured to process image information obtained by the camera module. 
     Advantageous Effects of Invention 
     According to the present invention, it is made possible to provide a lens driving device, a camera module, and a camera-mounted device, which are capable of reducing the effect of external magnetism and of being reduced in size and profile thereof. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  illustrate a smartphone in which a camera module according to an embodiment of the present invention is mounted. 
         FIG. 2  is a perspective view of an external appearance of the camera module. 
         FIGS. 3A and 3B  are perspective views of the camera module. 
         FIG. 4  is an exploded perspective view of a lens driving device. 
         FIG. 5  is an exploded perspective view of the lens driving device. 
         FIGS. 6A and 6B  are perspective views of an OIS driving part. 
         FIG. 7  is an exploded perspective view of an OIS movable part. 
         FIG. 8  is an exploded perspective view of the OIS movable part. 
         FIG. 9  is an exploded perspective view of the OIS movable part. 
         FIGS. 10A and 10B  are perspective views of an AF movable part. 
         FIG. 11  illustrates a power feeding system and a signal system of the lens driving device. 
         FIGS. 12A and 12B  illustrate a vehicle as a camera-mounted device in which an in-vehicle camera module is mounted. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 
       FIGS. 1A and 1B  illustrate smartphone M (camera-mounted device) in which camera module A according to an embodiment of the present invention is mounted.  FIG. 1A  is a front view of smartphone M and  FIG. 1B  is a rear view of smartphone M. 
     Smartphone M has a dual camera consisting of two back cameras OC 1  and OC 2 . In the present embodiment, camera module A is applied to back cameras OC 1  and OC 2 . 
     Camera module A has an AF function and an OIS function, and is capable of automatically performing focusing during capturing a subject and of capturing images without image blurring by optically correcting a camera-shake (vibration) that occurs when capturing images. 
       FIG. 2  is a perspective view of an external appearance of camera module A.  FIGS. 3A and 3B  are perspective views of camera module A.  FIG. 3B  illustrates a state in which  FIG. 3A  has been rotated by 180° around the Z-axis.  FIGS. 3A and 3B  omit lens part  2 . As shown in  FIGS. 2, 3A and 3B , descriptions will be given for the present embodiment with an orthogonal coordinate system (X, Y, Z). The same orthogonal coordinate system (X, Y, Z) is also used for illustration of below-mentioned figures. 
     Camera module A is mounted such that the vertical direction (or the horizontal direction) is the X-direction, the horizontal direction (or the vertical direction) is the Y-direction, and the front-rear direction is the Z-direction during actually capturing of an image with smartphone M. That is, the Z-direction is the optical-axis direction, the upper side in the figures is the light reception side in the optical-axis direction, and the lower side is the image formation side in the optical-axis direction. In addition, the X- and Y-directions orthogonal to the Z-axis are referred to as “optical-axis-orthogonal directions”, and the XY plane is referred to as “optical-axis-orthogonal plane”. 
     As shown in  FIGS. 2, 3A, and 3B , camera module A includes lens driving device  1  which can perform the AF function and the OIS function; lens part  2  including a cylindrical lens barrel that houses a lens; an image capturing part (not illustrated) configured to capture a subject image imaged by lens part  2 , cover  3  which covers the entire camera module A, and the like. 
     Cover  3  is a lidded rectangular cylindrical body in plan view in the optical-axis direction. In the present embodiment, cover  3  has a square shape in plan view. Cover  3  includes, at its upper surface, a substantially circular opening  3   a . Lens part  2  faces outside from opening  3   a . Cover  3  is fixed to base  21  (see  FIG. 4 ) of OIS fixing part  20  in lens driving device  1 , for example, by adhesion. Cover  3  contacts the upper portion (damper  23 ) of lens driving device  1 . 
     The image capturing part (not illustrated) is disposed on the image formation side of lens driving device  1  in the optical-axis direction. The image capturing part (not illustrated) includes, for example, an image sensor board and an imaging device mounted on the image sensor board. The imaging device is composed of, for example, a charge-coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or the like. The imaging device captures a subject image imaged by lens part  2 . Lens driving device  1  is mounted in the image sensor board (not illustrated) and is mechanically and electrically connected thereto. A control unit that performs driving control of lens driving device  1  may be provided on the image sensor board or on a camera-mounted device having camera module A mounted thereto (in the present embodiment, smartphone M). 
       FIGS. 4 and 5  are exploded perspective views of lens driving device  1 .  FIG. 5  illustrates a state in which  FIG. 4  has been rotated by 180° around the Z-axis. 
     As shown in  FIGS. 4 and 5 , lens driving device  1  includes OIS movable part  10 , OIS fixing part  20 , OIS driving part  30 , and OIS supporting part  40  in the present embodiment.  FIGS. 4 and 5  omit wires  25  (see  FIG. 11 ) to be formed on base  21 . 
     OIS movable part  10  rocks in the optical-axis-orthogonal plane during shake correction. OIS movable part  10  includes an AF unit having AF movable part  11 , AF fixing part  12 , and AF driving part  13  (see  FIGS. 7 to 9 ). OIS movable part  10  is disposed to be spaced apart from OIS fixing part  20  in the optical-axis direction, and is coupled with OIS fixing part  20  by OIS supporting part  40 . The configuration of OIS movable part  10  will be described later in detail. 
     OIS fixing part  20  is connected to OIS movable part  10  via OIS supporting part  40 . In the present embodiment, OIS fixing part  20  includes base  21  and spacer  22 . OIS movable part  10  is sandwiched between base  21  and spacer  22  in the optical-axis direction. 
     Base  21  is a rectangular member in plan view, and includes circular opening  21   a  at the center of base  21 . Base  21  includes, at a corner of its rectangle, OIS motor fixing portion  21   b  at which OIS driving part  30  is disposed. Base  21  also includes, at a position diagonal to OIS motor fixing portion  21   b , spacer fixing portion  21   c  at which leg portions  22   b  of spacer  22  are disposed. OIS motor fixing portion  21   b  and spacer fixing portion  21   c  are formed so as to protrude from the base surface toward the light reception side in the optical-axis direction. 
     First Hall element  51  for detecting the Z position of AF movable part  11  (see  FIGS. 7 to 9 ) and second Hall elements  52  and  53  for detecting the X and Y positions of OIS movable part  10  are disposed on base  21 . First magnet  61  is disposed on AF movable part  11  to face first Hall element  51 , and second magnets  62  and  63  are disposed on OIS movable part  10  (first stage  12 ) to face second Hall elements  52  and  53 , respectively (see  FIG. 9 ). 
     Base  21  is formed of molding material made of, for example, polyarylate (PAR), PAR alloy (e.g., PAR/PC) in which a plurality of resin materials including PAR are mixed, or liquid crystal polymer. 
     Base  21  is preferably a resin mold in which 3D-shape wires  25  (see  FIG. 11 ) are formed, a so-called Molded Interconnect Device (3D-MID). This allows complicated wires  25  to be formed without using a printed circuit board. Wires  25  include power feeding and signal line  251  for first Hall element  51 , power feeding and signal line  252  for second Hall element  52 , power feeding and signal line  253  for second Hall element  53 , power feeding line  254  for AF driving part  13 , and power feeding line  255  for OIS driving part  30 . The ends of wires  25  are pulled out to the side surfaces of base  21 . 
     Base  21  includes ball housings  21   d  and  21   e  that house each ball  41 . Ball housing  21   e  provided in the upper surface of spacer fixing portion  21   c  is dented in a circular shape and the remaining three ball housings  21   d  are each dented in an ellipsoidal form extending along the X-direction. The side surfaces of ball housings  21   d  are each formed in a tapered form so as to narrow their groove width toward the bottom. 
     Spacer  22  is a rectangular member in plan view, and has an opening  22   a  in a portion corresponding to AF movable part  11  (lens holder  111 , see  FIGS. 7 to 9 ). Spacer  22  includes, at a corner of its rectangle, leg portion  22   b  extending on the image formation side in the optical-axis direction. Leg portion  22   b  of spacer  22  is fit into spacer fixing portion  21   c  of base  21  and is adhered therein, so that OIS movable part  10  is held between base  21  and spacer  22  so as to be able to rock. Spacer  22  and OIS supporting part  40  function as a pressing portion that presses OIS movable part  10  to base  21 . Specifically, when spacer  22  is attached to base  21 , first stage  12  is pressed against second stage  16 , and second stage  16  is pressed against base  21 . At this time, balls  42  are interposed between spacer  22  and OIS movable part  10  (first stage  12 ), and balls  41  are interposed between OIS movable part  10  (second stage  16 ) and base  21 . Further, balls  43  are interposed between first stage  12  and second stage  16  (see  FIG. 7 ). With this configuration, OIS movable part  10  can be held without rattling of OIS movable part  10 . 
     Dampers  23  are disposed on the upper surface of spacer  22 . In the present embodiment, dampers  23  are each disposed at four corners on the upper surface of the spacer. Dampers  23  relieve an impact from cover  3  when the device is dropped, so that the impact resistance is improved. 
     OIS supporting part  40  supports OIS fixing part  20  so as to be spaced apart from OIS movable part  10  in the optical-axis direction. In the present embodiment, OIS supporting part  40  includes four balls  41  interposed between OIS movable part  10  and base  21 , and four balls  42  interposed between OIS movable part  10  and spacer  22 . One of balls  41  is disposed between base  21  and first stage  12 , and the remaining three are disposed between base  21  and second stage  16 . Balls  41  and  42  support OIS movable part  10  so as to be spaced apart from OIS fixing part  20 . In addition, OIS supporting part  40  includes, at OIS movable part  10 , three balls  43  interposed between first stage  12  and second stage  16  (see  FIG. 7 ). 
     The present embodiment allows OIS movable part  10  to accurately rock in the XY plane by regulating the direction in which balls  41  to  43  (a total of 11 balls) constituting OIS supporting part  40  are able to roll. The number of balls  41  to  43  that constitute OIS supporting part  40  can be appropriately changed. 
     OIS driving part  30  includes first OIS driving part  30 A configured to move OIS movable part  10  in the X-direction, and second OIS driving part  30 B configured to move OIS movable part  10  in the Y-direction. Each of first OIS driving part  30 A and second OIS driving part  30 B is an ultrasonic motor-type actuator and is fixed to OIS motor fixing portion  21   b  of OIS fixing part  20 . First OIS driving part  30 A is disposed extending along the X-direction, and second OIS driving part  30 B is disposed extending along the Y-direction. That is, first OIS driving part  30 A and second OIS driving part  30 B are disposed along the sides orthogonal to each other. In the present embodiment, first OIS driving part  30 A and second OIS driving part  30 B are fixed to motor fixing portion  21   b  of base  21 , so that OIS motors USM 2  and USM 3  come close to each other, thereby simplifying wires  255  (see  FIG. 11 ) for OIS motors USM 2  and USM 3 . 
     The configuration of OIS driving part  30  is shown in  FIGS. 6A and 6B .  FIG. 6A  illustrates a state in which the members of second OIS driving part  30 B are assembled, and  FIG. 6B  illustrates a state in which the members of second OIS driving part  30 B are disassembled. The configuration of first OIS driving part  30 A is not illustrated because it is the same as the configuration of second OIS driving part  30 B. 
     As shown in  FIGS. 6A and 6B , second OIS driving part  30 B includes OIS motor USM 3  that generates a driving force and OIS power transmission part  34  that transmits the driving force to OIS movable part  10 . Similarly, first OIS driving part  30 A includes OIS motor USM 2  that generates a driving force and OIS power transmission part  34  that transmits the driving force to OIS movable part  10 . 
     Each of OIS motors USM 2  and USM 3  includes OIS piezoelectric elements  31  and  32  and OIS resonance part  33 , and OIS electrode  35 . 
     OIS piezoelectric elements  31  and  32  are, for example, a plate element formed of ceramic material, and generate vibration by applying high frequency voltage. 
     OIS resonance part  33  is formed of conductive material, and resonates with vibrations of OIS piezoelectric elements  31  and  32  to convert a vibrational motion into a linear motion in the X- or Y-direction. 
     OIS resonance part  33  includes body portions  33   a  and arm portions  33   b . Body portion  33   a  includes two depressed portions  33   c  having a generally rectangular plate shape formed each on the right and left sides (sides along the Z-direction in  FIG. 6B ) thereof. Arm portion  33   b  is formed so as to protrude from the vertical sides (sides along the Y-direction in  FIG. 6B ) of body portion  33   a  toward the extending direction of the vertical sides, and end portion  33   d  comes in contact with OIS power transmission part  34  (hereinafter referred to as “OIS tweezer contact portion  33   d ”). 
     OIS resonance part  33  has at least two resonance frequencies and deforms due to different behaviors at the resonance frequencies. In other words, the shape of OIS resonance part  33  is set so as to deform due to the different behaviors at two resonance frequencies. The term “different behaviors” refers to behaviors of advancing and retracting OIS power transmission part  34  in the X- or Y-direction. 
     OIS piezoelectric elements  31  and  32  are laminated to body portion  33   a  of OIS resonance part  33  in the thickness direction (X-direction in  FIGS. 6A and 6B ), and then sandwiched by OIS electrode  35 , so that they are electrically connected to each other. Of wires  255  (see  FIG. 11 ) formed on base  21 , a high-pressure side wire is connected to OIS electrode  35  and a low-pressure side wire is connected to OIS resonance part  33 , so that a voltage is applied to OIS piezoelectric elements  31  and  32  to thereby generate vibration. 
     OIS power transmission part  34  is a tweezer to be connected to OIS motors USM 2  and USM 3  (hereinafter referred to as “OIS tweezer  34 ”). OIS tweezer  34  includes stage fixing portion  34   a , motor contact portions  34   b , and coupling portions  34   c . Stage fixing portion  34   a  is formed so as to bend at a right angle to the extending direction of OIS tweezer  34 , and is fixed to OIS tweezer fixing portion  12   k  of first stage  12  (see  FIGS. 8 and 9 ). Motor contact portion  34   b  is formed so as to have an almost U-shaped cross section and comes in contact with OIS tweezer contact portion  33   d  of OIS resonance part  33 . Coupling portion  34   c  is a portion that couples stage fixing portion  34   a  and motor contact portion  34   b , and is branched into two from stage fixing portion  34   a  so that the two portions are in parallel to each other. 
     The width between OIS motor contact portions  34   b  and  34   b  is set wider than the width between OIS tweezer contact portions  33   d  and  33   d  of OIS resonance part  33 . This allows OIS tweezer  34  to function as a plate spring when OIS tweezer  34  is attached to OIS motors USM 2  and USM 3 , so that a biasing force acts in a direction in which OIS tweezer contact portions  33   d  are pushed and expanded. This biasing force allows OIS tweezer  34  to be held between OIS tweezer contact portions  33   d  and  33   d , so that power from OIS resonance part  33  is efficiently transmitted to OIS tweezer  34 . 
     In the present embodiment, OIS driving part  30  is composed of OIS motors USM 2  and USM 3  and OIS power transmission parts  34 , so that the moving distance of OIS movable part  10  can be increased. 
     The present embodiment provides, between stage fixing portion  34   a  and coupling portion  34   c , bellows-shaped flexible portion  34   d  that allows moving in the X- or Y-direction. This makes it possible to prevent the movement of OIS movable part  10  by one OIS motor (e.g., OIS motor USM 2 ) from being interrupted by OIS tweezer  34  connected to the other OIS motor (e.g., OIS motor USM 3 ). That is, this can prevent OIS movable part  10  from rotating around the Z-axis, so that OIS movable part  10  can be accurately rocked in the XY plane. 
       FIGS. 7 to 9  are exploded perspective views of OIS movable part  10 .  FIG. 8  illustrates a state in which  FIG. 7  has been rotated by 180° around the Z-axis.  FIG. 9  is a lower perspective view of  FIG. 8 . 
     As shown in  FIGS. 7 to 9 , OIS movable part  10  includes AF movable part  11 , AF fixing part  12 , AF driving part  13 , and AF supporting parts  14  and  15  in the present embodiment. 
     AF movable part  11  moves in the optical-axis direction during focusing. AF movable part  11  is disposed to be spaced apart from AF fixing part  12 , and is connected with AF fixing part  12  by AF supporting parts  14  and  15 . In the present embodiment, AF fixing part  12  is composed of a first stage (hereinafter referred to as “first stage  12 ”). 
     AF movable part  11  includes lens holder  111  configured to hold lens part  2  (see  FIG. 2 ). Lens holder  111  is formed of, for example, polyarylate (PAR), PAR alloy in which a plurality of resin materials including PAR are mixed, liquid crystal polymer, or the like. Lens holder  111  includes lens housing  111   a  that is cylindrical. Lens part  2  (see  FIG. 2 ) is fixed to lens housing  111   a , for example, by adhesion. 
     Lens holder  111  includes, at the upper outer peripheral edge of lens housing  111   a , upper-spring fixing portion  111   b  for fixing AF supporting part  14 . Lens holder  111  includes, at the lower outer peripheral edge of lens housing  111   a , lower-spring fixing portion  111   c  for fixing AF supporting part  15 . Lens holder  111  includes, at one side portion along the X-direction, AF motor fixing portion  111   d  configured to fix AF driving part  13 . Lens holder  111  also has first magnet  61  for detecting the Z-position disposed so as to face first Hall element  51  in the Z-direction. In the present embodiment, first magnet  61  is disposed near AF driving part  13 . First magnet  61  has, for example, a cylindrical shape and is magnetized in the Z-direction (longitudinal direction). 
     First stage  12  supports AF movable part  111  via AF supporting parts  14  and  15 . Second stage  16  is disposed on the image formation side of first stage  12  in the optical-axis direction and is coupled to first stage  12  via balls  43 . First stage  12  moves in the X- and Y-directions during shake correction, and second stage  16  moves only in the X-direction during shake correction. 
     First stage  12  is a generally rectangular cylindrical member, and is formed of, for example, liquid crystal polymer. First stage  12  has a generally circular opening  12   a  in a portion corresponding to lens holder  111 . Opening  12   a  has depressed portion  12   b  in the area corresponding to AF driving part  13 , and AF piezoelectric element  131  (see  FIG. 10 ) on the outer side is disposed in this depressed portion  12   b , thereby achieving miniaturization. 
     First stage  12  includes, in its upper surface, four first ball housings  12   c  configured to house each ball  42 . First ball housings  12   c  are dented in a circular shape, each having, in its bottom, a ball holding hole (whose reference numeral is omitted) formed to hold ball  42  in the center of the hole. 
     First stage  12  includes, in its lower surface, three second ball housings  12   d  configured to house each ball  43  and third ball housing  12   e  configured to house ball  41 . Second ball housings  12   d  are each dented in an ellipsoidal form extending along the Y-direction. Third ball housing  12   e  is dented in a circular form. The side surfaces of second ball housings  12   d  are each formed in a tapered form so as to narrow their groove width toward the bottom. 
     First stage  12  has, at the upper surface and external side surface of one side wall along the X-direction, upper-spring fixing portion  12   f  for fixing AF supporting part  14 . First stage  12  has, at the lower surface of one side wall along the X-direction, lower-spring fixing portion  12   g  for fixing AF supporting part  15 . 
     First stage  12  has, at the lower surface of one side wall along the Y-direction, second magnets  62  and  63  for detecting the X- and Y-positions disposed so as to face second Hall elements  52  and  53  in the Z-direction. Second magnets  62  and  63  are magnetized in the Y-direction and the X-direction, respectively. 
     First stage  12  includes, at the upper peripheral edge portion of opening  12   a , AF tweezer fixing portion  12   i  in which AF power transmission part  134  is disposed. First stage  12  includes AF tweezer fastening portion  12   j  configured to fasten AF power transmission part  134 . 
     Second stage  16  is an L-shaped member and is formed of, for example, liquid crystal polymer. The inner circumferential surface of second stage  16  is formed in an arcuate form along the external shape of lens holder  111 . That is, when AF supporting part  15  is fixed to first stage  12 , second stage  16  is configured not to be positioned in the area corresponding to AF supporting part  15 . If second stage  16  is rectangularly arranged, AF supporting part  15  and second stage  16  are interfered with each other when AF movable part  11  is moved to the image formation side in the optical-axis direction. Therefore, in order to avoid such interference, the spaced distance between first stage  12  and second stage  16  needs to be increased. In contrast to this, the present embodiment provides second stage  16  having an L-shape, so that the spaced distance therebetween can be reduced, which in turn can reduce the profile of the embodiment. 
     Second stage  16  includes, in its upper surface, three first ball housings  16   a  configured to house each ball  43 . First ball housings  16   a  face second ball housings  12   d  in first stage  12 . First ball housings  16   a  are each dented in an ellipsoidal form extending along the Y-direction. The side surfaces of second ball housings  12   d  are each formed in a tapered form so as to narrow their groove width toward the bottom. 
     Second stage  16  includes, in its lower surface, three second ball housings  16   b  configured to house each ball  41 . Second ball housings  16   b  face ball housings  21   d  of base  21 . Second ball housings  16   b  are each dented in an ellipsoidal form extending along the X-direction. The side surfaces of second ball housings  16   b  are each formed in a tapered form so as to narrow their groove width toward the bottom. 
     Three balls  41  that constitute OIS supporting part  40  are sandwiched between ball housings  21   d  of base  21  and second ball housings  16   b  of second stage  16  at multipoint contact. Therefore, balls  41  stably roll in the Y-direction. 
     Balls  43  are sandwiched between first ball housings  16   a  of second stage  16  and second ball housings  12   d  of first stage  12  at multipoint contact. Therefore, balls  43  stably roll in the X-direction. 
     Balls  42  are sandwiched between first ball housings  12   c  of first stage  12  and spacer  22 . 
     AF supporting part  14  is an upper elastic supporting member that supports AF movable part  11  (lens holder  111 ) on the light reception side in the optical-axis direction (upper side) with respect to first stage  12  (AF fixing part). In the present embodiment, AF supporting part  14  is composed of two plate springs  141  and  142  (hereinafter referred to as “upper springs  141  and  142 ”). 
     Upper springs  141  and  142  have a shape conforming to the peripheral edge portion of lens housing  111   a  of lens holder  111 , and is formed of titanium copper, nickel copper, stainless steel, or the like, for example. Upper springs  141  and  142  are disposed on lens holder  111  and first stage  12  so as not to come in contact with each other. Upper springs  141  and  142  are formed by etching and machining one sheet metal, for example. 
     Upper spring  141  has lens-holder holding portion  141   a  to be fixed to lens holder  111 , stage fixing portion  141   b  to be fixed to first stage  12 , and arm portion  141   c  to be coupled between lens-holder holding portion  141   a  and stage fixing portion  141   b . Lens-holder holding portion  141   a  is formed in an arcuate form along the peripheral edge portion of lens housing  111   a  of lens holder  111 , and open end  141   a - 1  has a shape corresponding to upper-spring fixing portion  111   b  that is positioned at one end of AF motor fixing portion  111   d  of lens holder  111 . Stage fixing portion  141   b  is formed linearly along the Y-direction and a part thereof is bent vertically (bent portion  141   d ). Arm portion  141   c  is linearly formed and is elastically deformed along with the movement of AF movable part  11 . In addition, upper spring  141  extends from the bent portion  141   d  along the shape of the side wall of first stage  12 , and has wire portion  141   e  to be connected to power feeding terminal  254   a  (see  FIG. 11 ) of base  21 . The end of wire portion  141   e  is bent in the Z-direction and can follow the movement of AF movable part  11  toward the Z-direction. 
     Upper spring  142  has lens-holder holding portion  142   a  to be fixed to lens holder  111 , stage fixing portion  142   b  to be fixed to first stage  12 , and arm portion  142   c  to be coupled between lens-holder holding portion  142   a  and stage fixing portion  142   b . Lens-holder holding portion  142   a  has a shape corresponding to upper-spring fixing portion  111   b  that is positioned at the other end of AF motor fixing portion  111   d  of lens holder  111 . Stage fixing portion  142   b  is linearly formed and a part thereof is bent vertically (bent portion  142   d ). Arm portion  142   c  is formed linearly along the X-direction and is elastically deformed along with the movement of AF movable part  11 . In addition, upper spring  142  extends from the bent portion  142   d  along the shape of the side wall of first stage  12 , and has wire portion  142   e  to be connected to power feeding terminal  254   b  (see  FIG. 11 ) of base  21 . The end of wire portion  142   e  is bent in the Z-direction and can follow the movement of AF movable part  11  toward the Z-direction. 
     In the present embodiment, upper springs  141  and  142  are positioned to lens holder  111  and fixed, for example, adhesively thereto by fitting and inserting positioning bosses (whose reference numeral is omitted) of upper-spring fixing portion  111   b  of lens holder  111  into fixing holes (whose reference numeral is omitted) of lens-holder holding portions  141   a  and  142   a . Further, upper springs  141  and  142  are positioned to first stage  12  and fixed, for example, adhesively thereto by disposing bent portions  141   d ,  142   d  of magnet-holder fixing portions  141   b  and  142   b  to upper spring fixing portion  12   f  of first stage  12 . The methods of positioning and fixing upper springs  141  and  142  as described above are merely illustrative, and other known methods may be applied. 
     At this time, as shown in  FIG. 11 , lens-holder holding portion  141   a  of upper spring  141  is electrically connected to AF electrode  135  of AF driving part  13 , and lens-holder holding portion  142   a  of upper spring  142  is electrically connected to AF resonance part  133  of AF driving part  13 . Wire portions  141   e  and  142   e  are each disposed in a deformable state on the side wall of first stage  12 , and are electrically connected to power feeding terminals  254   a ,  254   b  of base  21 , respectively. Therefore, electricity is supplied to AF driving part  13  via upper springs  141  and  142 . 
     AF supporting part  15  is a lower elastic supporting member that supports AF movable part  11  (lens holder  111 ) on the image formation side in the optical-axis direction (lower side) with respect to first stage  12  (AF fixing part). In the present embodiment, AF supporting part  15  is composed of one plate spring (hereinafter referred to as “lower spring  15 ”). 
     Lower spring  15  entirely has an L-shape, and is formed of titanium copper, nickel copper, stainless steel, or the like, for example. Lower spring  15  is formed by etching one sheet metal, for example. 
     Lower spring  15  has lens-holder holding portions  15   a  and  15   b  to be fixed to lens holder  111 , stage fixing portion  15   c  to be fixed to first stage  12 , and arm portion  15   d  to be coupled between lens-holder holding portion  15   a  and stage fixing portion  15   b , and arm portion  15   e  to be coupled between lens-holder holding portion  15   b  and stage fixing portion  15   c . Lens-holder holding portion  15   a  has a shape corresponding to lower-spring fixing portion  111   c  that is positioned at one side of AF motor fixing portion  111   d  of lens holder  111 . Stage fixing portion  15   c  is linearly formed. Each of arm portions  15   d  and  15   e  is formed linearly along the X- and Y-directions, and is elastically deformed along with the movement of AF movable part  11 . 
     In the Z-direction, lower spring  15  is disposed in parallel to upper springs  141  and  142 . At this time, lens-holder holding portion  15   a , stage fixing portion  15   b , arm portion  15   c , and arm portion  15   e  of lower spring  15  correspond to lens-holder holding portion  142   a  of upper spring  142 , stage fixing portions  141   b  and  142   b  of upper springs  141  and  142 , arm portion  142   c  of upper spring  142 , and arm portion  141   c  of upper spring  141 , respectively. With this configuration, it is possible to prevent tilt from occurring when AF movable part  11  is moved in the Z-direction. 
     In the present embodiment, lower spring  15  is positioned to lens holder  111  and fixed thereto by fitting and inserting the positioning boss of lower-spring fixing portion  111   c  of lens holder  111  into the fixing hole of lens-holder holding portion  15   b . Further, lower spring  15  is positioned to first stage  12  and fixed thereto by fitting and inserting positioning bosses of lower-spring fixing portion  12   g  of first stage  12  into fixing holes of lens-holder holding portion  15   c . The methods of positioning and fixing lower spring  15  as described above are merely illustrative, and other known methods may be applied. 
     AF driving part  13  allows AF movable part  11  to move in the Z-direction. Similarly to OIS driving part  30 , AF driving part  13  is an ultrasonic motor-type actuator and is fixed to AF movable part  11  (AF motor fixing portion  111   d  of lens holder  111 ). 
     The configuration of AF driving part  13  is shown in  FIGS. 10A and 10B .  FIG. 10A  illustrates a state in which the members of AF driving part  13  are assembled, and  FIG. 10B  illustrates a state in which the members of AF driving part  13  are disassembled. 
     As shown in  FIGS. 10A and 10B , AF driving part  13  includes AF motor USM 1  that generates a driving force and AF power transmission part  134  that transmits the driving force to AF movable part  11 . 
     AF motor USM 1  includes AF piezoelectric elements  131  and  132  and AF resonance part  133 , and AF electrode  135 . 
     AF piezoelectric elements  131  and  132  are, for example, a plate element formed of ceramic material, and generates vibration by applying high frequency voltage. 
     AF resonance part  133  is formed of conductive material, and resonates with vibrations of AF piezoelectric elements  131  and  132  to convert a vibrational motion into a linear motion in the Z-direction. 
     AF resonance part  133  includes body portion  133   a  and arm portion  133   b . Body portion  133   a  includes two depressed portions  133   c  having a generally rectangular plate shape formed each on the upper and lower sides (sides along the X-direction in  FIG. 10B ) thereof. Arm portion  133   b  is formed so as to protrude from the vertical sides (sides along the Z-direction in  FIG. 10B ) of body portion  133   a  toward the extending direction of the vertical sides, and end portion  133   d  comes in contact with AF power transmission part  134  (hereinafter referred to as “AF tweezer contact part  133   d ”). 
     AF resonance part  133  has at least two resonance frequencies and deforms due to different behaviors at the resonance frequencies. In other words, the shape of AF resonance part  133  is set so as to deform due to the different behaviors at two resonance frequencies. The term “different behaviors” refers to behaviors of advancing and retracting AF power transmission part  134  in the Z-direction. 
     AF piezoelectric elements  131  and  132  are laminated to body portion  133   a  of AF resonance part  133  in the thickness direction (Y-direction in  FIGS. 10A and 10B ), and then sandwiched by AF electrode  135 , so that they are electrically connected to each other. Upper spring  141  serving as a power feeding line on the high-pressure side is connected to AF electrode  135  and upper spring  142  on a power feeding line on the low-pressure side (GND) is connected to AF resonance part  133 , so that a voltage is applied to AF piezoelectric elements  131  and  132  to thereby generate vibration. 
     AF power transmission part  134  is a tweezer to be sandwich AF motor USM 1  (hereinafter referred to as “AF tweezer  134 ”). AF tweezer  134  includes stage fixing portion  134   a , AF motor contact portions  134   b , and coupling portions  134   c . Stage fixing portion  134   a  has a generally arcuate shape and is fixed to AF tweezer fixing portion  12   i  of first stage  12 . AF motor contact portion  134   b  has a plate shape spreading out in the YZ plane and comes in contact with AF tweezer contact portion  133   d  of AF resonance part  133 . Coupling portion  134   c  couples stage fixing portion  134   a  and AF motor contact portion  134   b  together, and has a crank shape with three-dimensionally bending. Coupling portion  134   c  is disposed on the image formation side of AF tweezer fastening portion  12   j  of first stage  12  in the optical-axis direction. 
     The width between AF motor contact portions  134   b  and  134   b  is set narrower than the width between AF tweezer contact portions  133   d  and  133   d  of AF resonance part  133 . This allows AF tweezer  134  to function as a plate spring when AF tweezer  134  is attached to AF motor USM 1 , so that a biasing force acts on the side of AF driving part  13 . This biasing force allows AF driving part  13  to be held between AF motor contact portions  134   b  and  134   b , so that power from AF resonance part  133  is efficiently transmitted to AF tweezer  134 . 
     In the present embodiment, AF driving part  13  is composed of AF motor USM 1  and AF power transmission part  134 , so that the moving distance of AF movable part  11  (lens holder  111 ) can be increased. 
     In AF driving part  13 , even though AF motor USM 1  is driven so as to push down AF tweezer  134  toward the image formation side in the optical-axis direction, AF tweezer  134  does not move to the image formation side in the optical-axis direction because most of AF tweezer  134  is fixed to the upper surface of first stage  12 . Further, even though AF motor USM 1  is driven so as to push up AF tweezer  134  toward the light reception side in the optical-axis direction, AF tweezer  134  does not move to the light reception side in the optical-axis direction as well because distanced coupling portion  134   c  of AF tweezer  134  is fastened with AF tweezer fastening portion  12   j  of first stage  12 . Thus, in AF driving part  13 , AF tweezer  134  is rigidly fixed to first stage  12  (AF fixing part) and cannot move in the Z-direction. Therefore, when AF driving part  13  is driven, AF movable part  11  where AF driving part  13  is disposed moves in the Z-direction. 
     In lens driving device  1 , first magnet  61  is disposed on AF movable part  11  (lens holder  111 ) and first Hall element  51  is disposed on OIS fixing part  20  (base  21 ). First Hall element  51  primarily detects a magnetic field formed by first magnet  61 . Based on the detection result by first Hall element  51 , the position of AF movable part  11  in the Z-direction can be identified. 
     First magnet  61  and first Hall element  51  constitute a Z-position detecting part that is configured to detect movement of AF movable part  11  in the Z-direction. By providing the Z-position detecting part, a closed loop control can be achieved, so that high precision focusing can be performed. 
     In the present embodiment, since first magnet  61  has a cylindrical shape, the output of first Hall element  51  depends on the displacement (equivalent to the radius setting the reference position as its origin) with respect to the reference position (position in the XY plane at the time when shake correction is not performed) of first magnet  61 . That is, even though the position of OIS movable part  10  in the XY plane (hereinafter referred to as “XY position”) varies, the outputs of first Hall element  51  are the same. Therefore, by converting the XY position of OIS movable part  10  into a radius to be expressed by a displacement, a correction value for offsetting the influence by shake correction can be easily calculated. Thus, even though OIS movable part  10  rocks in the XY plane by shake correction to change the magnetic field that intersects with first Hall element  51 , the magnetic field can be easily corrected. 
     In lens driving device  1 , second magnets  62  and  63  are disposed on OIS movable part  10  (first stage  12 ) and second Hall elements  52  and  53  are disposed on OIS fixing part  20  (base  21 ). Second Hall element  52  primarily detects a magnetic field formed by second magnet  62 , and second hall element  53  primarily detects a magnetic field formed by second magnet  63 . Based on the detection result by second Hall elements  52  and  53 , the position of OIS movable part  10  in the XY plane can be identified. 
     Second magnets  62  and  63  and second Hall elements  52  and  53  constitute an XY-position detecting part that is configured to detect movement of OIS movable part  10  in the X- and Y-directions. By providing the XY-position detecting part, a closed loop control can be achieved, so that high precision shake correction can be performed. 
     In lens driving device  1 , when a voltage is applied to AF driving part  13 , AF piezoelectric elements  131  and  132  vibrate, and AF resonance part  133  deforms due to the behavior corresponding to the frequency. Since AF tweezer  134  is fixed to first stage  12  (AF fixing portion), AF driving part  13  moves by sliding in the Z-direction. 
     With this configuration, AF movable part  11  moves in the Z-direction, so that focusing is performed. At this time, feedback on the detection result by the Z-position detecting part makes it possible to accurately control translational movement of AF movable part  11 . 
     In lens driving device  1 , when a voltage is applied to OIS driving part  30 , OIS piezoelectric elements  31  and  32  vibrate, and OIS resonance part  33  deforms due to the behavior corresponding to the frequency. This allows OIS tweezer  34  to move by sliding in the X- or Y-direction. 
     Specifically, when first OIS driving part  30 A is driven to move OIS tweezer  34  in the X-direction, power is transmitted to first stage  12 . Balls  43  sandwiched between first stage  12  and second stage  16  cannot roll in the X-direction, but balls  41  sandwiched between second stage  16  and base  21  can roll in the X-direction. Therefore, first stage  12  and second stage  16  move together in the X-direction while maintaining their positions in the Y-direction with respect to base  21 . 
     Meanwhile, when second OIS driving part  30 B is driven to move OIS tweezer  34  in the Y-direction, power is transmitted to first stage  12 . Balls  43  sandwiched between first stage  12  and second stage  16  can roll in the Y-direction, but balls  41  sandwiched between second stage  16  and base  21  cannot roll in the Y-direction. Therefore, first stage  12  alone moves in the Y-direction while maintaining its position in the X-direction with respect to base  21 . 
     Thus, OIS movable part  10  rocks in the XY plane to perform shake correction. Specifically, the energized voltage to OIS driving part  30  is controlled based on the detection signal indicating an angle shake from a shake detecting part (e.g., gyros sensor, not illustrated) so as to offset the angle shake of camera module A. At this time, feedback on the detection result by the XY-position detecting part makes it possible to accurately control translational movement of OIS movable part  10 . 
     Thus, lens driving device  1  includes: an autofocus part that has AF movable part  11  to be disposed on first stage  12  (AF fixing part) and AF driving part  13  configured to move AF movable part  11  along the optical axis in the Z-direction with respect to first stage  12 ; and a shake-correction part that has OIS fixing part  20 , OIS movable part  10  including the autofocus part, and OIS driving part  30  configured to move OIS movable part  10  in the X- and Y-directions orthogonal to the optical axis with respect to OIS fixing part  20 . 
     OIS driving part  30  includes first OIS driving part  30 A to be disposed along the X-direction and configured to move OIS movable part  10  in the X-direction, and second OIS driving part  30 B to be disposed along the Y-direction and configured to move OIS movable part  10  in the Y-direction. 
     Each of first and second OIS driving parts  30 A and  30 B is composed of OIS piezoelectric elements  31  and  32  and OIS resonance part  33  that resonates with vibrations of OIS piezoelectric elements  31  and  32  to convert a vibrational motion into a linear motion in the X or Y-direction, and includes OIS motors USM 2  and USM 3  (shake-correcting ultrasonic motors) to be disposed on OIS fixing part  20 ; and OIS power transmission part  34  configured to couple OIS motors USM 2  and USM 3  to OIS movable part  10  and to transmit the linear motion in the X- or Y-direction to OIS movable part  10 . 
     AF driving part  13  is composed of AF piezoelectric elements  131  and  132  and AF resonance part  133  that resonates with vibrations of AF piezoelectric elements  131  and  132  to convert a vibrational motion into a linear motion in the Z-direction, and includes AF motor USM 1  (auto-focusing ultrasonic motor) to be disposed on AF movable part  11 ; and AF power transmission part  134  configured to couple AF motor USM 1  to first stage  12  and to transmit the linear motion to first stage  12 . 
     In a rectangle defined by two sides where first OIS driving part  30 A and second OIS driving part  30 B are disposed, AF driving part  13  is disposed along a side different from the two sides. 
     Lens driving device  1  can reduce the effect of external magnetism and can be reduced in size and profile thereof. Therefore, even though camera module A having lens driving device  1  is disposed close thereto like smartphone M, there is no magnetic effect, so that lens driving device  1  is suitable for use as a dual camera. 
     While the invention made by the present inventor has been specifically described based on an embodiment, it is not intended to limit the present invention to the above-mentioned embodiment, but the present invention may be further modified within the scope and spirit of the invention defined by the appended claims. 
     For example, although the embodiment has been described by mentioning smartphone M, which is a camera-equipped mobile terminal, as an example of a camera-mounted device having camera module A, the present invention is applicable to a camera-mounted device having a camera module and an image processing section that processes image information obtained with the camera module. The camera-mounted device includes an information device or a transport device. The information device includes, for example, a camera-equipped mobile phone, a note-type personal computer, a tablet terminal, a mobile game machine, a web camera, and a camera-equipped in-vehicle apparatus (e.g., a rear-view monitor apparatus or a drive recorder apparatus). The transport device includes, for example, a vehicle. 
       FIGS. 12A and 12B  illustrate a vehicle V as a camera-mounted device in which an in-vehicle camera module VC (Vehicle Camera) is mounted.  FIG. 12A  is a front view of vehicle V and  FIG. 12B  is a rear perspective view of vehicle V. In vehicle V, camera module A described in the embodiment is mounted as in-vehicle camera module VC. As shown in  FIGS. 12A and 12B , in-vehicle camera module VC may, for example, be attached to the windshield so as to face forward, or to the rear gate so as to face backward. In-vehicle camera module VC is used for rear monitoring, drive recording, collision avoidance control, automatic drive control, and the like. 
     The embodiment disclosed herein is merely an exemplification in every respect and should not be considered as limitative. The scope of the present invention is specified by the claims, not by the above-mentioned description. The scope of the present invention is intended to include all modifications in so far as they are within the scope of the appended claims or the equivalents thereof. 
     This application is entitled to and claims the benefit of Japanese Patent Application No. 2018-152250 dated Aug. 13, 2018, the disclosure of which including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     REFERENCE SIGNS LIST 
     
         
           1  Lens driving device 
           10  OIS movable part (shake-correction movable part) 
           11  AF movable part (autofocus movable part) 
           111  Lens holder 
           12  AF fixing part, first stage (autofocus fixing part) 
           13  AF driving part (autofocus driving part) 
           131 ,  132  AF piezoelectric elements (auto-focusing piezoelectric elements) 
           133  AF resonance part (auto-focusing resonance part) 
           134  AF power transmission part, AF tweezer (auto-focusing power transmitting part) 
           135  AF electrode (autofocus electrode) 
           14 ,  15  AF supporting part (auto-focusing supporting part) 
           16  Second stage 
           20  OIS fixing part (shake-correction fixing part) 
           21  Base 
           22  Spacer 
           30  OIS driving part (shake-correction driving part) 
           31 ,  32  OIS piezoelectric elements (shake-correcting piezoelectric elements) 
           33  OIS resonance part (shake-correcting resonance part) 
           34  OIS power transmission part, OIS tweezer (shake-correcting power transmitting part) 
           35  OIS electrode (shake-correction electrode) 
           40  OIS supporting part (shake-correcting supporting part) 
           41  to  43  Balls 
         USM 1  AF motor (auto-focusing ultrasonic motor) 
         USM 2 , USM 3  OIS motors (shake-correcting ultrasonic motors)