Patent Publication Number: US-2022236516-A1

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

Description:
TECHNICAL FIELD 
     The present invention relates to a lens driving apparatus, a camera module, and a camera-mounted apparatus. 
     BACKGROUND ART 
     In general, a small-sized camera module is mounted in a mobile terminal such as a smartphone. To such a camera module, a lens driving apparatus is applied which has an auto-focusing function (hereinafter referred to as “AF (Auto Focus) function”) of automatically performing focusing when a subject is photographed, and a shake-correcting function (hereinafter referred to as “OIS (Optical Image Stabilization) function”) of reducing irregularities of an image by optically correcting shake (vibration) generated during photographing (for example, Patent Literature (hereinafter referred to as “PTL”)  1 ). 
     The lens driving apparatus having the AF function and the OIS function includes: an auto-focusing driving part (hereinafter referred to as “AF driving part”) for moving a lens part in a direction of an optical axis (hereinafter referred to as “optical axis direction”); and a shake-correcting driving part (hereinafter referred to as “OIS driving part”) for swaying the lens part within 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. 
     Further, in recent years, a camera module including a plurality of (typically two) lens driving apparatuses has been put into practical use (so-called dual camera). The dual camera has various possibilities depending on the use scenes, such as two images having different focal lengths can be simultaneously captured, a still image and a moving image can be simultaneously captured, and the like. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     
         
         Japanese Patent Application Laid-Open No. 2013-210550 
       
    
     PTL 2 
     
         
         WO 2015/123787 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the lens driving apparatus utilizing the VCM as in PTL 1 is subjected to the impact of external magnetism and therefore a highly accurate operation may be impaired. In particular, in a dual camera in which lens driving apparatuses are juxtaposed, it is highly likely that magnetic interference will occur between the lens driving apparatuses. 
     PTL 2, on the other hand, discloses a lens driving apparatus in which an ultrasonic motor is applied to an AF driving part and an OIS driving part. The lens driving apparatus disclosed in PTL 2 is magnetless and is therefore capable of reducing the impact of external magnetism, but has a complicated structure and has difficulty in allowing miniaturization and a reduction in height. 
     An object of the present invention is to provide a lens driving apparatus, a camera module, and a camera-mounted apparatus that are capable of reducing the impact of external magnetism and allow miniaturization and a reduction in height. 
     Solution to Problem 
     A lens driving apparatus according to the present invention includes: 
     a first fixing part; 
     a first movable part disposed so as to be separated from the first fixing part; 
     a first support part that supports the first movable part with respect to the first fixing part; and 
     a Z-direction driving part that is disposed in the first fixing part and moves the first movable part in an optical axis direction (Z direction) with respect to the first fixing part. The Z-direction driving part includes a piezoelectric element and a resonance part, and is formed of an ultrasonic motor that converts vibration motion into linear motion. The resonance part includes a trunk part, a first arm part and a second arm part. The trunk part is a part in which the piezoelectric element is disposed. The first arm part and the second arm part extend in an identical direction from the trunk part. The first arm part and the second arm part deform when resonating with vibration of the piezoelectric element, and only the first arm part abuts on the first movable part. 
     A camera module according to the present invention includes: 
     the lens driving apparatus described above; 
     a lens part that is attached to the first movable part; and 
     an image-capturing part that captures a subject image formed by the lens part. 
     A camera-mounted apparatus according to the present invention is an information apparatus or a transport apparatus, and includes: 
     the camera module described above; and 
     an image-processing part that processes image information obtained by the camera module. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide a lens driving apparatus, a camera module, and a camera-mounted apparatus that are capable of reducing the impact of external magnetism and allow miniaturization and a reduction in height. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  illustrate a smartphone in which a camera module is mounted according to an embodiment of the present invention; 
         FIG. 2  is an external perspective view of the camera module; 
         FIGS. 3A and 3B  are external perspective views of a lens driving apparatus according to Embodiment 1; 
         FIG. 4  is an exploded perspective view of the lens driving apparatus according to Embodiment 1; 
         FIG. 5  is an exploded perspective view of the lens driving apparatus according to Embodiment 1; 
         FIGS. 6A and 6B  are perspective views of an OIS driving part; 
         FIG. 7  is an exploded perspective view of an OIS movable part according to Embodiment 1; 
         FIG. 8  is an exploded perspective view of the OIS movable part according to Embodiment 1; 
         FIG. 9  is an exploded perspective view of the OIS movable part according to Embodiment 1; 
         FIGS. 10A and 10B  are perspective views of an AF driving part according to Embodiment 1; 
         FIGS. 11A and 11B  illustrate a state in which a first stage, the AF driving part, and an AF support part are assembled according to Embodiment 1; 
         FIGS. 12A and 12B  are external perspective views of a lens driving apparatus according to Embodiment 2; 
         FIG. 13  is an exploded perspective view of an OIS movable part according to Embodiment 2; 
         FIG. 14  is an exploded perspective view of the OIS movable part according to Embodiment 2; 
         FIG. 15  is an exploded perspective view of the OIS movable part according to Embodiment 2; 
         FIGS. 16A and 16B  illustrate a state in which a first stage, an AF driving part, and an AF support part are assembled according to Embodiment 2; 
         FIG. 17  illustrates a driving unit for vibration driving; 
         FIGS. 18A and 18B  illustrate the driving unit for vibration driving; 
         FIG. 19  illustrates the driving unit for vibration driving; 
         FIG. 20  illustrates driving signals and resulting vibration amplitudes when a shape of driving pulses is adjusted; 
         FIG. 21  illustrates driving signals and resulting vibration amplitudes when a presence of driving pulses is adjusted; 
         FIG. 22  illustrates a dependence of a driving velocity on a pulse duty cycle; 
         FIG. 23  illustrates a dependence of the driving velocity on an excitation frequency; 
         FIG. 24  illustrates a flowchart for a method of driving the driving unit; and 
         FIGS. 25A and 25B  illustrate an automobile as a camera-mounted apparatus in which an in-vehicle camera module is mounted. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     Embodiment 1 
       FIGS. 1A and 1B  illustrate smartphone M (an example of the camera-mounted apparatus) in which camera module A is mounted according to an embodiment of the present invention.  FIG. 1A  is a front view of smartphone M, and  FIG. 1B  is a rear view of smartphone M. 
     Smartphone M includes a dual camera with two rear cameras OC 1  and OC 2 . In the present embodiment, camera module A is applied to rear cameras OC 1  and OC 2 . 
     Camera module A has the AF function and the OIS function, and is capable of photographing an image without image blurring by automatically performing focusing when a subject is photographed and by optically correcting shake (vibration) generated during photographing. 
       FIG. 2  is an external perspective view of camera module A.  FIGS. 3A and 3B  are external perspective views of lens driving apparatus  1  according to Embodiment 1.  FIG. 3B  illustrates a state in which  FIG. 3A  is rotated by 180° around the Z axis. As illustrated in  FIGS. 2, 3A and 3B , a description will be given using an orthogonal coordinate system (X, Y, Z) in the present embodiment. The same orthogonal coordinate system (X, Y, Z) is also used in the drawings to be described later. 
     Camera module A is mounted such that the X direction is an up-down direction (or a left-right direction), the Y direction is a left-right direction (or an up-down direction), and the Z direction is a front-rear direction in a case where photographing is actually performed with smartphone M, for example. That is, the Z direction is an optical axis direction, the upper side (+Z side) in the drawings is a light reception side in the optical axis direction, and the lower side (−Z side) in the drawings is an image formation side in the optical axis direction. Further, the X direction and the Y direction that are orthogonal to the Z axis are each referred to as “optical axis-orthogonal direction” and the XY plane is referred to as “optical axis-orthogonal plane”. 
     As illustrated in  FIGS. 2, 3A and 3B , camera module A includes: lens driving apparatus  1  that realizes the AF function and the OIS function; lens part  2  in which a lens is housed in a lens barrel having a cylindrical shape; an image-capturing part (not illustrated) that captures a subject image formed by lens part  2 ; and cover  3  that entirely covers camera module A, and the like. 
     Cover  3  is a capped square cylindrical body having a rectangular shape in plan view viewed in the optical axis direction. In the present embodiment, cover  3  has a square shape in plan view. Cover  3  includes opening  3   a  in the upper surface. Opening  3   a  has a substantially circular shape. Lens part  2  is configured to face the outside through opening  3   a , and to protrude to the light reception side from an opening surface of cover  3  in accordance with movement in the optical axis direction. Cover  3  is fixed to base  21  (see  FIG. 4 ) of OIS fixing part  20  of lens driving apparatus  1  by, for example, adhesion. 
     The image-capturing part (not illustrated) is disposed on the image formation side of lens driving apparatus  1  in the optical axis direction. The image-capturing part (not illustrated) includes, for example, an image sensor board, and an imaging element that is mounted in the image sensor board. The imaging element is formed of, for example, a charge-coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or the like. The imaging element captures a subject image formed by lens part  2 . Lens driving apparatus  1  is mounted in the image sensor board (not illustrated) and is mechanically and electrically connected to the image sensor board. A control part that controls the driving of lens driving apparatus  1  may be provided in the image sensor board or may be provided in a camera-mounted apparatus (smartphone M in the present embodiment) in which camera module A is mounted. 
       FIGS. 4 and 5  are exploded perspective views of lens driving apparatus  1  according to Embodiment 1.  FIG. 5  illustrates a state in which  FIG. 4  is rotated by 180° around the Z axis. 
     As illustrated in  FIGS. 4 and 5 , lens driving apparatus  1  includes OIS movable part  10  (second movable part), OIS fixing part  20  (second fixing part), OIS driving part  30  (XY-direction driving part), and OIS support part  40  (second support part) in the present embodiment. Note that,  FIG. 5  indicates a portion of wiring  24 , which is buried in base  21 , with a dotted line. 
     OIS movable part  10  is a portion which sways within the optical axis-orthogonal plane during shake correction. OIS movable part  10  includes an AF unit, second stage  13 , and ball  42 . The AF unit includes AF movable part  11  (first movable part), first stage  12  (first fixing part), AF driving part  14  (Z-direction driving part), and AF support part  15  (first support part) (see  FIGS. 7 to 9 ). 
     OIS fixing part  20  is a portion to which OIS movable part  10  is connected via OIS support part  40 . OIS fixing part  20  includes base  21 . 
     OIS movable part  10  is disposed so as to be separated from OIS fixing part  20  in the optical axis direction, and is coupled to OIS fixing part  20  via OIS support part  40 . Further, OIS movable part  10  and OIS fixing part  20  are urged in mutually approaching directions by OIS urging members  50  provided at four corners of lens driving apparatus  1 . 
     Note that, in the present embodiment, OIS movable part  10  in its entirety, including the AF unit, moves as a movable body with respect to the movement in the Y direction. With respect to the movement in the X direction, on the other hand, only the AF unit moves as a movable body. That is, with respect to the movement in the X direction, second stage  13  and base  21  form OIS fixing part  20 , and ball  42  functions as OIS support part  40 . 
     Base  21  is, for example, a member having a rectangular shape in plan view, which is formed of a molding material made of polyarylate (PAR), a PAR alloy (for example, PAR/PC) obtained by mixing a plurality of resin materials including PAR, or a liquid crystal polymer, and includes opening  21   a  in the center. Opening  21   a  has a circular shape. 
     Base  21  includes first base part  21   b  and second base part  21   c . First base part  21   b  forms a main surface of base  21 . Second base part  21   c  is formed at one corner of four corners of base  21 . A portion between first base part  21   b  and second base part  21   c  is formed to be recessed. Sensor board  22  is disposed in this recessed portion. First base part  21   b , second base part  21   c , and sensor board  22  form a base surface in which first base part  21   b , second base part  21   c , and sensor board  22  are flush with each other. 
     Base  21  includes OIS motor fixing part  21   d  in a portion located at a diagonal corner of second base part  21   c . Second OIS driving part  30 Y is disposed in OIS motor fixing part  21   d . OIS motor fixing part  21   d  is formed to protrude from first base part  21   b  toward the light reception side in the optical axis direction, and has a shape capable of holding second OIS driving part  30 Y. 
     Terminal metal fitting  23  and wiring  24  are disposed in base  21  by insert-molding, for example. Wiring  24  includes power supply lines to AF driving part  14  and OIS driving part  30 . Wiring  24  is exposed from openings  21   g  formed at the four corners of base  21 , and is electrically connected to OIS urging members  50 . Power supply to AF driving part  14  and first OIS driving part  30 X is performed via OIS urging members  50 . Terminal metal fitting  23  is electrically connected to wiring (not illustrated) formed in sensor board  22 . 
     Further, base  21  includes ball housing parts  21   e  and  21   f  each of which houses ball  41 . Ball housing part  21   e , which is formed in second base part  21   c , is formed to be recessed in a circular shape. Three ball housing parts  21   f  formed in first base part  21   b  are formed to be recessed in a rectangular shape extending in the Y direction. For example, ball housing part  21   f  includes side surfaces formed in a tapered shape such that the groove width narrows toward a side of the bottom surface. 
     Sensor board  22  includes wiring (not illustrated) including power supply lines and signal lines both of which are for magnetic sensors  25 X and  25 Y. Magnetic sensors  25 X and  25 Y are mounted in sensor board  22 . Magnetic sensors  25 X and  25 Y are formed of, for example, a Hall element, a tunnel magneto resistance (TMR) sensor or the like, and are electrically connected to terminal metal fitting  23  via the wiring (not illustrated) formed in sensor board  22 . In first stage  12  of OIS movable part  10 , magnets  16 X and  16 Y are disposed at positions facing magnetic sensors  25 X and  25 Y, respectively. A position detection part formed of magnetic sensors  25 X and  25 Y and magnets  16 X and  16 Y detects the positions of OIS movable part  10  in the X direction and the Y direction. Note that, it may also be configured such that the positions of OIS movable part  10  in the X direction and the Y direction are detected by an optical sensor such as a photoreflector in place of magnets  16 X and  16 Y and magnetic sensors  25 X and  25 Y. 
     OIS urging member  50  is formed of, for example, a tension coil spring, and couples OIS movable part  10  to OIS fixing part  20 . In the present embodiment, one end of OIS urging member  50  is connected to wiring  24  of base  21 , and another end of OIS urging member  50  is connected to wiring  17  of first stage  12 . OIS urging member  50  receives a tensile load when coupling OIS movable part  10  to OIS fixing part  20 , and acts so as to cause OIS movable part  10  and OIS fixing part  20  to approach each other. That is, OIS movable part  10  is held so as to be capable of swaying within the XY plane in a state of being urged in the optical axis direction (a state of being pressed against base  21 ) by OIS urging members  50 . Thus, it is possible to hold OIS movable part  10  in a stable state without rattling. 
     Further, in the present embodiment, OIS urging member  50  functions as power supply lines to AF driving part  14  and first OIS driving part  30 X. 
     OIS support part  40  supports OIS movable part  10  in a state in which OIS movable part  10  is separated from OIS fixing part  20  in the optical axis direction. In the present embodiment, OIS support part  40  includes four balls  41  interposed between OIS movable part  10  (first stage  12  and second stage  13 ) and base  21 . One ball  41  disposed in ball housing part  21   e  of base  21  is interposed between base  21  and first stage  12 . Three balls  41  disposed in ball housing parts  21   f  are interposed between base  21  and second stage  13 . 
     Further, OIS support part  40  includes three balls  42  interposed between first stage  12  and second stage  13  in OIS movable part  10  (see  FIG. 7  or the like). 
     In the present embodiment, OIS movable part  10  is configured to be capable of accurately swaying within the XY plane by regulation of directions in which balls  41  and  42  (seven balls in total) forming OIS support part  40  are rollable. Note that, the number of balls  41  and  42  forming OIS support part  40  can be changed as appropriate. 
     OIS driving part  30  is an actuator that moves OIS movable part  10  in the X direction and the Y direction. Specifically, OIS driving part  30  is formed of first OIS driving part  30 X (first XY-direction driving part) and second OIS driving part  30 Y (second XY-direction driving part). First OIS driving part  30 X moves OIS movable part  10  (only the AF unit) in the X direction. Second OIS driving part  30 Y moves OIS movable part  10  in its entirety in the Y direction. 
     First OIS driving part  30 X and second OIS driving part  30 Y are formed of an ultrasonic motor. First OIS driving part  30 X is fixed to OIS motor fixing part  12   f  of first stage  12  so as to extend along the X direction. Second OIS driving part  30 Y is fixed to OIS motor fixing part  21   d  of base  21  so as to extend along the Y direction. That is, first OIS driving part  30 X and second OIS driving part  30 Y are disposed along sides orthogonal to each other. 
       FIGS. 6A and 6B  illustrate the configuration of OIS driving part  30 .  FIG. 6A  illustrates a state in which each member of OIS driving part  30  is assembled.  FIG. 6B  illustrates a state in which each member of OIS driving part  30  is disassembled. Note that,  FIGS. 6A and 6B  illustrate second OIS driving part  30 Y, but are treated as drawings illustrating OIS driving part  30  since the main configuration of first OIS driving part  30 X, specifically the configuration thereof except for the shapes of OIS resonance part  31  and OIS electrode  33  is the same as that of second OIS driving part  30 Y. 
     As illustrated in  FIGS. 6A and 6B , OIS driving part  30  includes OIS resonance part  31 , OIS piezoelectric element  32 , and OIS electrode  33 . The driving force of OIS driving part  30  is transmitted to second stage  13  via OIS power transmission part  34 . Specifically, first OIS driving part  30 X is connected to first OIS power transmission part  34 X and second OIS driving part  30 Y is connected to second OIS power transmission part  34 Y. 
     OIS piezoelectric element  32  is, for example, a plate-like element formed of a ceramic material, and generates vibration by application of a high-frequency voltage. 
     OIS electrode  33  holds OIS resonance part  31  and OIS piezoelectric elements  32  from both sides, and applies a voltage to OIS piezoelectric elements  32 . OIS electrode  33  of first OIS driving part  30 X is electrically connected to power supply plate  18 , and OIS electrode  33  of second OIS driving part  30 Y is electrically connected to wiring  24  of base  21 . 
     OIS resonance part  31  is formed of a conductive material, and resonates with vibration of OIS piezoelectric element  32  to convert vibration motion into linear motion. In the present embodiment, OIS resonance part  31  includes trunk part  31   a , two arm parts  31   b , protrusion part  31   c , and energization part  31   d . Trunk part  31   a  has a substantially rectangular shape and is held between OIS piezoelectric elements  32 . Two arm parts  31   b  extend from upper and lower parts of trunk part  31   a . Protrusion part  31   c  extends in the Y direction from a central part of trunk part  31   a . Energization part  31   d  extends on a side opposite to protrusion part  31   c  from the central part of trunk part  31   a . Each of two arm parts  31   b  has a symmetric shape, includes a free end part that abuts on OIS power transmission part  34 , and symmetrically deforms when resonating with the vibration of OIS piezoelectric element  32 . Energization part  31   d  of first OIS driving part  30 X is electrically connected to wiring  17  of first stage  12 . Energization part  31   d  of second OIS driving part  30 Y is electrically connected to wiring  24  of base  21 . 
     Trunk part  31   a  of OIS resonance part  31  and OIS piezoelectric elements  32  are electrically connected to each other by bonding OIS piezoelectric elements  32  to trunk part  31   a  in the thickness direction and causing trunk part  31   a  and OIS piezoelectric elements  32  to be held from both sides by OIS electrode  33 . For example, one power supply path is connected to OIS electrode  33  and another power supply path is connected to energization part  31   d  of OIS resonance part  31  so that a voltage is applied to OIS piezoelectric elements  32  and vibration is generated. 
     OIS resonance part  31  has at least two resonance frequencies, and deforms in different behaviors for each resonance frequency. In other words, the entire shape of OIS resonance part  31  is set so as to deform in different behaviors with respect to the two resonance frequencies. The different behaviors refer to behaviors of advancing and retracting OIS power transmission part  34  in the X direction or the Y direction. 
     OIS power transmission part  34  is a chucking guide extending in one direction, and includes one end, which is connected to OIS driving part  30 , and another end, which is connected to second stage  13 . OIS power transmission part  34  includes OIS motor abutment part  34   a , stage fixing part  34   c , and coupling part  34   b . OIS motor abutment part  34   a  is formed to have a substantially U-shaped cross section, and abuts on the free end part of arm part  31   b  of OIS resonance part  31 . Stage fixing part  34   c  is disposed in an end part of OIS power transmission part  34 , and is fixed to OIS chucking guide fixing part  13   c  of second stage  13  (see  FIG. 8  or the like.). Coupling part  34   b  is a portion that couples OIS motor abutment part  34   a  to stage fixing part  34   c , and is formed to branch into two from stage fixing part  34   c  such that the branched portions are in parallel with each other. 
     The width between OIS motor abutment parts  34   a  is set to be wider than the width between the free end parts of arm parts  31   b  of OIS resonance part  31 . Thus, when OIS power transmission part  34  is attached to OIS driving part  30 , OIS power transmission part  34  functions as a plate spring, and an urging force acts in a direction in which arm parts  31   b  of OIS resonance part  31  are pushed and spread. This urging force causes OIS power transmission part  34  to be held between the free end parts of arm parts  31   b  of OIS resonance part  31  so that a driving force from OIS resonance part  31  is efficiently transmitted to OIS power transmission part  34 . 
     Since OIS driving part  30  only abuts on OIS power transmission part  34  in an urged state, the movement distance (stroke) of OIS movable part  10  can be lengthened without enlarging the outer shape of lens driving apparatus  1 , only by increasing the abutment portion in the X direction or the Y direction. 
     First OIS driving part  30 X is fixed to OIS movable part  10  (first stage  12 ), and is connected to second stage  13  via OIS power transmission part  34 X. During shake correction in the Y direction by second OIS driving part  30 Y, first OIS driving part  30 X moves together with OIS movable part  10 . On the other hand, second OIS driving part  30 Y is fixed to OIS fixing part  20  (base  21 ), is connected to second stage  13  via OIS power transmission part  34 Y, and is not affected by shake correction in the X direction by first OIS driving part  30 X. That is, the movement of OIS movable part  10  by one of OIS driving parts  30  is not hindered by the structure of another of OIS driving parts  30 . Accordingly, it is possible to prevent OIS movable part  10  from rotating around the Z axis, and it is possible to cause OIS movable part  10  to accurately sway within 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  is rotated by 180° around the Z axis.  FIG. 9  is a lower perspective view illustrating a state in which  FIG. 7  is rotated by 90° around the Z axis. 
     As illustrated in  FIGS. 7 to 9 , OIS movable part  10  includes AF movable part  11 , first stage  12 , second stage  13 , AF driving part  14 , AF support part  15  and the like in the present embodiment. With respect to the movement in the Y direction, OIS movable part  10  in its entirety, including first stage  12  and second stage  13 , is a movable body, whereas with respect to the movement in the X direction, second stage  13  functions as OIS fixing part  20 , and only the AF unit functions as OIS movable part  10 . Further, first stage  12  functions as an AF fixing part. 
     AF movable part  11  is a portion which moves in the optical axis direction during focusing. AF movable part  11  is disposed so as to be radially separated from first stage  12  (AF fixing part), and is connected to first stage  12  via AF support part  15 . 
     AF movable part  11  includes lens holder  111  which holds lens part  2  (see  FIG. 2 ), and AF urging member  112 . 
     Lens holder  111  is formed of, for example, polyarylate (PAR), a PAR alloy obtained by mixing a plurality of resin materials including PAR, a liquid crystal polymer, or the like. Lens holder  111  includes lens housing part  111   a  having a cylindrical shape. Lens part  2  (see  FIG. 2 ) is fixed to lens housing part  111   a  by, for example, adhesion. 
     Lens holder  111  includes upper flange  111   b  at an outer peripheral edge of an upper part of lens housing part  111   a , and lower flange  111   c  at an outer peripheral edge of a lower part of lens housing part  111   a . In the present embodiment, four upper flanges  111   b  are provided at positions corresponding to the four corners of lens driving apparatus  1 , and lower flanges  111   c  are provided downward from two upper flanges  111   b  facing each other. Upper flange  111   b  functions as a regulation part that regulates movement of lens holder  111  to the image formation side in the optical axis direction (lower side), and lower flange  111   c  functions as a regulation part that regulates movement of lens holder  111  to the light reception side in the optical axis direction (upper side). 
     Further, lens holder  111  includes ball housing part  111   d  in a peripheral surface of lens housing part  111   a . Ball housing part  111   d  houses AF support part  15 . In the present embodiment, ball housing parts  111   d  are provided at two positions in line symmetry with respect to one diagonal direction (an intermediate direction between the X direction and the Y direction) such that portions on the same side with respect to the other diagonal direction (the side opposite to the side on which AF urging member  112  is disposed) open. 
     AF urging member  112  is formed of, for example, a metal material such as titanium copper, nickel copper, and stainless steel, and is disposed so as to extend in a peripheral direction of lens holder  111 . In the present embodiment, AF urging member  112  is formed by, for example, bending a metal plate material, and includes plate spring parts  112   a  extending in directions orthogonal to each other, and coupling part  112   b  that couples plate spring parts  112   a . Plate spring part  112   a  has a symmetric shape with respect to coupling part  112   b , and end part  112   c  of plate spring part  112   a  is formed by being folded back into a substantially U-shape (hereinafter referred to as “AF motor abutment part  112   c ”). 
     AF urging member  112  is fixed to lens holder  111  by attaching coupling part  112   b  to one side of a space held between upper flanges  111   b  and lower flanges  111   c  of lens holder  111 . Plate spring parts  112   a  extend along the X direction and the Y direction. 
     First stage  12  is a portion that supports AF movable part  111  via AF support part  15 . Second stage  13  is disposed on the image formation side of first stage  12  in the optical axis direction via balls  42 . First stage  12  moves in the X direction and the Y direction during shake correction, and second stage  13  moves only in the X direction during shake correction. 
     First stage  12  is a substantially rectangular tubular member, and is formed of, for example, a liquid crystal polymer. First stage  12  includes opening  12   a  in a portion corresponding to lens holder  111 . Opening  12   a  has a substantially circular shape. In first stage  12 , two side walls corresponding to second stage  13  are formed to be thinner than the other side walls by the thickness of the second stage. 
     First stage  12  includes three ball housing parts  12   b  and ball housing part  12   c  on the lower surface. Ball housing part  12   b  houses ball  42 . Ball housing part  12   c  houses ball  41 . Ball housing part  12   b  is formed to be recessed in an oval shape extending in the X direction. Further, ball housing part  12   b  includes side surfaces formed in a tapered shape such that the groove width narrows toward a side of the bottom surface. Ball housing part  12   c  is formed to be recessed in a circular shape. Ball housing part  12   b  faces ball housing part  13   a  of second stage  13  in the Z direction. Ball housing part  12   c  faces ball housing part  21   e  of base  21  in the Z direction. 
     First stage  12  includes flange parts  12   d  at four corners of the lower part. Flange part  12   d  protrudes inwardly. When lens holder  111  is attached to first stage  12 , upper flanges  111   b  of lens holder  111  are located upward from flange parts  12   d , and lower flanges  111   c  of lens holder  111  are located downward from two flange parts  12   d  located diagonally. That is, two flange parts  12   d  are held between upper flanges  111   b  and lower flanges  111   c  of lens holder  111  in a state in which flange parts  12   d  are separated from upper flanges  111   b  and lower flanges  111   c  by the movable distance of lens holder  111 . 
     First stage  12  includes ball fixing parts  12   e  on the inner side surface of one side wall along the X direction and on the inner side surface of one side wall along the Y direction. Ball fixing part  12   e  is used for fixing AF support part  15 . First stage  12  includes OIS motor fixing part  12   f  on one outer side surface along the X direction. OIS motor fixing part  12   f  is used for fixing first OIS driving part  30 X. In first stage  12 , the outer side surface of one side wall along the Y direction is formed to be recessed inwardly, where second OIS driving part  30 Y is located when lens driving apparatus  1  is assembled. 
     Further, in first stage  12 , AF driving parts  14 A and  14 B are disposed on the inner side surface of the other side wall along the X direction and on the inner side surface of the other side wall along the Y direction, respectively. On the lower surfaces of the side walls described above, magnets  16 X and  16 Y for XY-position detection are disposed so as to face magnetic sensors  25 X and  25 Y in the Z direction, respectively. For example, magnet  16 X is magnetized in the X direction, and magnet  16 Y is magnetized in the Y direction. 
     For example, wiring  17  is buried in first stage  12  by insert-molding. Wiring  17  is exposed from notched parts of the outer surfaces of four corners of first stage  12 , and each one end of OIS urging members  50  is connected to these parts. Further, power supply plate  18  which is electrically connected to wiring  17  is disposed on the upper surface of first stage  12 . Power is supplied to AF driving part  14  and first OIS driving part  30 X via wiring  17  and power supply plate  18 . 
     Second stage  13  is an L-shaped member, and is formed of, for example, a liquid crystal polymer. Second stage  13  includes an inner peripheral surface formed in an arc shape along the outer shape of lens holder  111 . In the same manner as in first stage  12 , the outer side surface the side wall of second stage  13  along the Y direction is formed to be recessed inwardly, where second OIS driving part  30 Y is located when lens driving apparatus  1  is assembled. In the present embodiment, a reduction in the height of OIS movable part  10  is achieved by forming second stage  13  in an L-shape and by disposing second stage  13  downward from the two side walls of first stage  12  which are formed as thinner side walls. 
     Second stage  13  includes three ball housing parts  13   a  on the lower surface. Ball housing part  13   a  houses ball  41 . Ball housing part  13   a  faces ball housing part  21   f  of base  21 . Ball housing part  13   a  is formed to be recessed in an oval shape extending in the Y direction. Further, ball housing part  13   a  includes side surfaces formed in a tapered shape such that the groove width narrows toward a side of the bottom surface. 
     Further, second stage  13  includes three ball housing parts  13   b  on the upper surface. Ball housing part  13   b  houses ball  42 . Ball housing part  13   b  faces ball housing part  12   b  of first stage  12  in the Z direction. Ball housing part  13   b  is formed to be recessed in an oval shape extending in the X direction. Ball housing part  12   b  includes side surfaces formed in a tapered shape such that the groove width narrows toward a side of the bottom surface. 
     Three balls  41  that form OIS support part  40  are held by multipoint contacts between ball housing parts  21   f  of base  21  and ball housing parts  13   a  of second stage  13 . Accordingly, ball  41  stably rolls in the X direction. 
     Further, balls  42  are held by multipoint contacts between ball housing parts  13   b  of second stage  13  and ball housing parts  12   b  of first stage  12 . Thus, ball  42  stably rolls in the X direction. 
     AF support part  15  is formed of balls. In the present embodiment, three balls are arranged side by side in the Z direction. AF support part  15  is interposed in a state of being rollable between ball housing part  111   d  of lens holder  111  and ball fixing part  12   e  of first stage  12 . 
     AF driving part  14  is an actuator that moves AF movable part  11  in the Z direction. AF driving part  14  is formed of first AF driving part  14 A (first Z-direction driving part) and second AF driving part  14 B (second Z-direction driving part). In the same manner as in OIS driving part  30 , AF driving part  14  is formed of an ultrasonic motor. First AF driving part  14 A and second AF driving part  14 B are fixed to an inner peripheral surface of first stage  12  so as to be along the X direction and the Y direction, respectively. 
       FIGS. 10A and 10B  illustrate the configuration of AF driving part  14 .  FIG. 10A  illustrates a state in which each member of AF driving part  14  is assembled.  FIG. 10B  illustrates a state in which each member of AF driving part  14  is disassembled. Note that, although  FIGS. 10A and 10B  illustrate second AF driving part  14 B, the main configuration of first AF driving part  14 A, specifically the configuration thereof except for the shape of AF electrode  143  is the same as that of second AF driving part  14 B so that  FIGS. 10A and 10B  are treated as drawings illustrating AF driving part  14 . The configuration of AF driving part  14  is substantially the same as that of OIS driving part  30 . 
     As illustrated in  FIGS. 10A and 10B , AF driving part  14  includes AF resonance part  141 , AF piezoelectric element  142 , and AF electrode  143 . The driving force of AF driving part  14  is transmitted to lens holder  111  via AF urging member  112 . 
     AF piezoelectric element  142  is, for example, a plate-like element formed of a ceramic material, and generates vibration by application of a high-frequency voltage. Two AF piezoelectric elements  142  are disposed so as to hold trunk part  141   a  of AF resonance part  141  therebetween. 
     AF electrode  143  holds AF resonance part  141  and AF piezoelectric elements  142  from both sides, and applies a voltage to AF piezoelectric elements  142 . 
     AF resonance part  141  is formed of a conductive material, and resonates with vibration of AF piezoelectric element  142  to convert vibration motion into linear motion. In the present embodiment, AF resonance part  141  includes trunk part  141   a , two arm parts  141   b , protrusion part  141   c , and energization part  141   d . Trunk part  141   a  has a substantially rectangular shape and is held between AF piezoelectric elements  142 . Two arm parts  141   b  extend from upper and lower parts of trunk part  141   a  in the X direction or the Y direction. Protrusion part  141   c  extends from a central part of trunk part  141   a  in the X direction or the Y direction. Energization part  141   d  extends on a side opposite to protrusion part  141   c  from the central part of trunk part  141   a , and is electrically connected to a power supply path (wiring  17  of first stage  12 ). Two arm parts  141   b  have a symmetric shape except for each free end part, and symmetrically deform when resonating with the vibration of AF piezoelectric element  142 . The free end parts of two arm parts  141   b  have shapes different from each other such that only one free end part abuts on AF urging member  112 . Note that, the free end parts of two arm parts  141   b  may have a symmetric shape as long as only one free end part can be configured to abut on AF urging member  112  by devising the shape of AF urging member  112  or the like. 
     Trunk part  141   a  of AF resonance part  141  and AF piezoelectric elements  142  are electrically connected to each other by bonding AF piezoelectric elements  142  to trunk part  141   a  in the thickness direction and causing trunk part  141   a  and AF piezoelectric elements  142  to be held from both sides by AF electrode  143 . Power supply plate  18  is connected to AF electrode  143  and wiring  17  of first stage  12  is connected to energization part  141   d  of AF resonance part  141  so that a voltage is applied to AF piezoelectric elements  142  and vibration is generated. 
     In the same manner as in OIS resonance part  31 , AF resonance part  141  has at least two resonance frequencies, and deforms in different behaviors for each resonance frequency. In other words, the entire shape of AF resonance part  141  is set so as to deform in different behaviors with respect to the two resonance frequencies. 
     First AF driving part  14 A and second AF driving part  14 B are fixed to the inner peripheral surface of first stage  12  so as to be along the X direction and the Y direction, respectively. In the present embodiment, it is configured such that the leading end of one of two arm parts  141   b  (for example, arm part  141   b  located on the lower side) of first AF driving part  14 A and the leading end of one of two arm parts  141   b  (for example, arm part  141   b  located on the lower side) of second AF driving part  14 B are caused to abut on AF urging member  112  to move AF movable part  11  in the Z direction. Arm part  141   b  that abuts on in AF urging member  112  is referred to as “first arm part  141   b ”, and arm part  141   b  that does not abut on AF urging member  112  is referred to as “second arm part  141   b ”. Note that, when both the leading ends of two arm parts  141   b  of AF resonance part  141 , where two arm parts  141   b  are located on the upper and lower sides, respectively, are caused to abut on AF urging member  112 , two arm parts  141   b  symmetrically operate so that it is impossible to move AF movable part  11  in the Z direction by slipping. 
     In the present embodiment, AF driving part  14  causes only first arm part  141   b  to abut on AF movable part  11  (AF urging member  112 ) to move AF movable part  11  in the Z direction so that a driving force to be transmitted is halved in comparison with a case of transmitting a driving force by utilizing two arm parts  31   b  as in OIS driving unit  30 . Accordingly, the driving force for movement in the optical axis direction is ensured by providing two AF driving parts  14 . 
     It is configured such that when the AF unit is assembled and AF driving part  14  is caused to abut on AF urging member  112 , AF urging member  112  functions as a plate spring, and AF movable part  11  (lens holder  111 ) is urged to first stage  12  (AF fixing part) via AF support part  15  (see  FIGS. 11A and 11B ). 
     Specifically, first arm parts  141   b  of first AF driving part  14 A and second AF driving part  14 B abut on both end parts of AF urging member  112  so that lens holder  111  is urged to the first stage (AF fixing part) in one direction in the optical axis-orthogonal plane. In the embodiment, lens holder  111  is pressed by AF urging member  112  and is urged to the first stage (AF fixing part) in an intermediate direction between the X direction and the Y direction by AF urging member  112 . 
     This urging force causes AF urging member  112  to be pressed against the leading end of arm part  141   b  of AF resonance part  141  so that a driving force from AF resonance part  141  is efficiently transmitted to AF urging member  112 . Further, since AF urging member  112  has both a function of transmitting the driving force of AF driving part  14  and a function of urging AF movable part  11  to first stage  12 , the component configuration is simplified. 
     Further, AF support parts  15  are provided at two positions corresponding to first AF driving part  14 A and second AF driving part  14 B. Since AF movable part  11  is urged toward first stage  12  via AF support parts  15  provided at the two positions, AF movable part  11  is held in a stable attitude. 
     Since AF driving part  14  only abuts on AF urging member  112  in an urged state, the movement distance (stroke) of AF movable part  11  can be easily lengthened without impairing a reduction in the height of lens driving apparatus  1 , only by increasing the abutment portion in the Z direction. However, the movement distance of AF movable part  11  is limited to an extent that AF urging member  112  does not abut on another arm part  141   b  (for example, arm part  141   b  located on the upper side) of AF resonance part  141 , where another arm part  141   b  is not involved in movement of AF movable part  11 . 
     Further, first arm part  141   b  of AF resonance part  141  abuts on AF urging member  112  that is a metal molded article. Thus, the driving force of AF driving part  14  can be efficiently transmitted in comparison with a case where first arm part  141   b  abuts on lens holder  111  that is a resin molded article. 
     In lens driving apparatus  1 , when a voltage is applied to AF driving part  14 , AF piezoelectric element  142  vibrates, and AF resonance part  141  deforms in a behavior corresponding to the frequency. At this time, the voltage is applied such that first AF driving part  14 A and second AF driving part  14 B indicate the same behavior. The driving force of AF driving part  14  causes AF urging member  112  to slide in the Z direction, which is accompanied by movement of AF movable part  11  in the Z direction and focusing. Since AF support part  15  is formed of balls, AF movable part  11  can move smoothly in the Z direction. 
     In lens driving apparatus  1 , when a voltage is applied to OIS driving part  30 , OIS piezoelectric element  32  vibrates, and OIS resonance part  31  deforms in a behavior corresponding to the frequency. The driving force of OIS driving part  30  causes OIS power transmission part  34  to slide in the X direction or the Y direction, which is accompanied by movement of OIS movable part  10  in the X direction or the Y direction and shake correction. Since OIS support part  40  is formed of balls, OIS movable part  10  can move smoothly in the X direction or the Y direction. 
     Specifically, in a case where first OIS driving part  30 X is driven and OIS power transmission part  34  moves in the X direction, power is transmitted from first stage  12 , in which first OIS driving part  30 X is disposed, to second stage  13 . At this time, balls  41  (three balls  41  housed in ball housing parts  211 ) held between second stage  13  and base  21  cannot roll in the X direction so that the position of second stage  13  in the X direction with respect to base  21  is maintained. On the other hand, since balls  42  held between first stage  12  and second stage  13  can roll in the X direction, first stage  12  moves in the X direction with respect to second stage  13 . That is, second stage  13  forms OIS fixing part  20 , and first stage  12  forms OIS movable part  10 . 
     Further, in a case where second OIS driving part  30 Y is driven and OIS power transmission part  34  moves in the Y direction, power is transmitted from base  21 , in which second OIS driving part  30 Y is disposed, to second stage  13 . At this time, since balls  42  held between first stage  12  and second stage  13  cannot roll in the Y direction, the position of first stage  12  in the Y direction with respect to the second stage is maintained. On the other hand, balls  41  (three balls  41  housed in ball housing parts  21   f ) held between second stage  13  and base  21  can roll in the Y direction, second stage  13  moves in the Y direction with respect to base  21 . First stage  12  also follows second stage  13  to move in the Y direction. That is, base  21  forms OIS fixing part  20 , and AF unit including first stage  12  and second stage  13  forms OIS movable part  10 . 
     In this way, OIS movable part  10  sways within the XY plane and shake correction is performed. Specifically, the energizing voltage to OIS driving parts  30 X and  30 Y is controlled based on an angle shake-indicating detection signal from a shake detection part (for example, a gyro sensor; not illustrated) so as to offset an angle shake of camera module A. At this time, feedback on a detection result of an XY-position detection part formed of magnets  16 X and  16 Y and magnetic sensors  25 X and  25 Y makes it possible to accurately control translational movement of OIS movable part  10 . 
     Thus, lens driving apparatus  1  according to the embodiment includes: first stage  12  (first fixing part); AF movable part  11  (first movable part) disposed so as to be separated from first stage  12 ; AF support part  15  (first support part) that supports AF movable part  11  with respect to first stage  12 ; and AF driving part  14  (Z-direction driving part) that is disposed in first stage  12  and moves AF movable part  11  in the optical axis direction with respect to first stage  12 . AF driving part  14  includes AF piezoelectric element  142  and AF resonance part  141 , and is formed of an ultrasonic motor that converts vibration motion into linear motion. AF resonance part  141  includes trunk part  141   a , first arm part  141   b  and second arm part  141   b . Trunk part  141   a  is held between AF piezoelectric elements  142 . First arm part  141   b  and second arm part  141   b  extend in an identical direction from trunk part  141   a . First arm part  141   b  and second arm part  141   b  deform when resonating with vibration of the AF piezoelectric element, and only first arm part  141   b  abuts on AF movable part  11 . 
     Since AF driving part  14  is formed of an ultrasonic motor, lens driving apparatus  1  makes it possible to reduce the impact of external magnetism and allows miniaturization and a reduction in height. Accordingly, since there is no magnetic impact even when camera modules A including lens driving apparatus  1  are disposed close to each other as in smartphone M, lens driving apparatus  1  is extremely suitable for use as a dual camera. 
     Further, in lens driving apparatus  1 , AF movable part  11  is urged to the first stage (AF fixing part) via AF support part  15 . Thus, it is possible to efficiently transmit the driving force of AF driving part  14  to AF movable part  11 . 
     Embodiment 2 
       FIGS. 12A and 12B  are external perspective views of lens driving apparatus  1 A according to Embodiment 2.  FIG. 12B  illustrates a state in which  FIG. 12A  is rotated by 180° around the Z axis. Lens driving apparatus  1 A according to Embodiment 2 is substantially the same as lens driving apparatus  1  according to Embodiment 1 except for the configuration of OIS movable part  10 A. The same or corresponding components as those of lens driving apparatus  1  according to Embodiment 1 will be denoted with the same reference signs and descriptions thereof will be omitted. Here, OIS movable part  10 A (in particular AF movable part  51 ) will be described. 
       FIGS. 13 to 15  are exploded perspective views of OIS movable part  10 .  FIG. 14  illustrates a state in which  FIG. 13  is rotated by 180° around the Z axis.  FIG. 15  is a lower perspective view illustrating a state in which  FIG. 13  is rotated by 90° around the Z axis. 
     As illustrated in  FIGS. 13 to 15 , in Embodiment 2, OIS movable part  10 A includes AF movable part  51 , first stage  12 , second stage  13 , AF driving part  14 , AF support part  15 , and the like. With respect to the movement in the Y direction, OIS movable part  10 A in its entirety, including first stage  12  and second stage  13 , is a movable body, whereas with respect to the movement in the X direction, second stage  13  functions as OIS fixing part  20 , and only the AF unit functions as OIS movable part  10 . Further, first stage  12  functions as the AF fixing part. 
     AF movable part  51  is a portion which moves in the optical axis direction during focusing. AF movable part  51  is disposed so as to be radially separated from first stage  12  (AF fixing part), and is connected to first stage  12  via AF support part  15 . 
     AF movable part  51  includes lens holder  511  that holds lens part  2  (see  FIG. 2 ), and AF urging member  512 . 
     Lens holder  511  is formed of, for example, polyarylate (PAR), a PAR alloy obtained by mixing a plurality of resin materials including PAR, a liquid crystal polymer, or the like. Lens holder  511  includes lens housing part  511   a  having a cylindrical shape. Lens part  2  (see  FIG. 2 ) is fixed to lens housing part  511   a  by, for example, adhesion. 
     Lens holder  511  includes upper flange  511   b  at an outer peripheral edge of an upper part of lens housing part  511   a . In Embodiment 2, four upper flanges  511   b  are provided at positions corresponding to four corners of lens driving apparatus  1 A. Upper flange  511   b  functions as a regulation part that regulates movement of lens holder  511  to the image forming side in the optical axis direction (lower side). 
     One of four upper flanges  511   b  is provided with magnet housing part  511   c  that houses magnet  16 Z for Z-position detection. Magnet  16 Z is disposed in magnet housing part  511   c , and a magnetic sensor for Z-position detection (for example, a Hall element, a TMR sensor, or the like) (not illustrated) is disposed at a position of sensor board  22  (see  FIG. 4 ), where the position faces magnet  16 Z in the optical axis direction. Note that, it may also be configured such that the position of AF movable part  51  in the Z direction may be detected by an optical sensor such as a photoreflector in place of magnet  16 Z and the magnetic sensor (not illustrated). 
     Further, lens holder  511  includes ball housing part  511   d  in a peripheral surface of lens housing part  511   a . Ball housing part  511   d  houses AF support part  15 . In Embodiment 2, ball housing parts  511   d  are provided at two positions in line symmetry with respect to one diagonal direction (an intermediate direction between the X direction and the Y direction) such that portions on the same side with respect to the other diagonal direction (the side on which AF urging member  512  is disposed) open. 
     AF urging member  512  is formed of, for example, a metal material such as titanium copper, nickel copper, and stainless steel. AF urging member  512  is formed of, for example, a plate spring having a flat dumbbell shape. AF driving parts  14 A and  14 B abut on both end parts  512   a  of AF urging member  512  in the longitudinal direction. Further, the spring constant of AF urging member  512  is adjusted by thinning. 
     AF urging member  512  is disposed in space  511   e  formed between magnet housing part  511   c  and lens housing part  511   a , and is held between spacer  513  and magnet housing part  511   c . AF urging member  512  extends so as to come into contact with lens housing part  51   a.    
     First AF driving part  14 A and second AF driving part  14 B are fixed to the inner peripheral surface of first stage  12  so as to be along the X direction and the Y direction, respectively. In Embodiment 2, it is configured such that the leading end of one of two arm parts  141   b  (for example, arm part  141   b  located on the upper side) of first AF driving part  14 A and the leading end of one of two arm parts  141   b  (for example, arm part  141   b  located on the upper side) of second AF driving part  14 B are caused to abut on AF urging member  512  to move AF movable part  51  in the Z direction. Arm part  141   b  that abuts on AF urging member  512  is referred to as “first arm part  141   b ”, and arm part  141   b  that does not abut on AF urging member  112  is referred to as “second arm part  141   b ”. Note that, when both the leading ends of two arm parts  141   b  of AF resonance part  141 , where two arm parts  141   b  are located on the upper and lower sides, respectively, are caused to abut on AF urging member  112 , two arm parts  141   b  symmetrically operate so that it is impossible to move AF movable part  11  in the Z direction by slipping. 
     In Embodiment 2, AF driving part  14  causes only first arm part  141   b  to abut on AF movable part  11  (AF urging member  112 ) to move AF movable part  11  in the Z direction so that a driving force to be transmitted is halved in comparison with a case of transmitting a driving force by utilizing two arm parts  31   b  as in OIS driving unit  30 . Accordingly, the driving force for movement in the optical axis direction is ensured by providing two AF driving parts  14 . 
     It is configured such that when the AF unit is assembled and AF driving part  14  is caused to abut on AF urging member  512 , AF urging member  512  functions as a plate spring and AF movable part  51  is urged to first stage  12  (AF fixing part) via AF support part  15  (see  FIGS. 16A and 16B ). 
     Specifically, first arm parts  141   b  of first AF driving part  14 A and second AF driving part  14 B abut on both end parts of AF urging member  512  so that lens holder  111  is urged to the first stage (AF fixing part) in one direction in the optical axis-orthogonal plane. In Embodiment 2, lens holder  111  is pulled by AF urging member  512  and is urged to the first stage (AF fixing part) in an intermediate direction between the X direction and the Y direction by AF urging member  512 . 
     This urging force causes AF urging member  512  to be pressed against the leading end of arm part  141   b  of AF resonance part  141  so that a driving force from AF resonance part  141  is efficiently transmitted to AF urging member  512 . Further, since AF urging member  512  has both a function of transmitting the driving force of AF driving part  14  and a function of urging AF movable part  51  to first stage  12 , the component configuration is simplified. 
     Further, in Embodiment 2, AF urging member  512  is formed of a plate spring having a flat dumbbell shape and exerts a large urging force so that sinking due to the self-weight of AF movable part  51  is suppressed and the attitude of AF movable part  51  with respect to first stage  12  is stabilized. Accordingly, it is possible to transmit the driving force of AF driving part  14  to AF movable part  51  efficiently and the responsiveness improves. 
     Further, AF support parts  15  are provided at two positions corresponding to first AF driving part  14 A and second AF driving part  14 B. Since AF movable part  11  is urged toward first stage  12  via AF support parts  15  provided at the two positions, AF movable part  51  is held in a stable attitude. 
     Since AF driving part  14  only abuts on AF urging member  512  in an urged state, the movement distance (stroke) of AF movable part  51  can be easily lengthened without impairing a reduction in the height of lens driving apparatus  1 A, only by increasing the abutment portion in the Z direction. However, the movement distance of AF movable part  51  is limited to an extent that AF urging member  512  does not abut on another arm part  141   b  (for example, arm part  141   b  located on the lower side) of AF resonance part  141 , where another arm part  141   b  is not involved in movement of AF movable part  51 . 
     Further, first arm part  141   b  of AF resonance part  141  abuts on AF urging member  512  that is a metal molded article. Thus, the driving force of AF driving part  14  can be efficiently transmitted in comparison with a case where first arm part  141   b  abuts on lens holder  111  that is a resin molded article. 
     Thus, lens driving apparatus  1 A according to Embodiment 2 includes: first stage  12  (first fixing part); AF movable part  51  (first movable part) disposed so as to be separated from first stage  12 ; AF support part  15  (first support part) that supports AF movable part  51  with respect to first stage  12 ; and AF driving part  14  (Z-direction driving part) that is disposed in first stage  12  and moves AF movable part  51  in the optical axis direction with respect to first stage  12 . AF driving part  14  includes AF piezoelectric element  142  and AF resonance part  141 , and is formed of an ultrasonic motor that converts vibration motion into linear motion. AF resonance part  141  includes trunk part  141   a , first arm part  141   b  and second arm part  141   b . Trunk part  141   a  is held between AF piezoelectric elements  142 . First arm part  141   b  and second arm part  141   b  extend in an identical direction from trunk part  141   a . First arm part  141   b  and second arm part  141   b  deform when resonating with vibration of AF piezoelectric element  142 , and only first arm part  141   b  abuts on AF movable part  51  (AF urging member  512 ). 
     Since AF driving part  14  is formed of an ultrasonic motor, lens driving apparatus  1 A makes it possible to reduce the impact of external magnetism and allows miniaturization and a reduction in height. Accordingly, since there is no magnetic impact even when camera modules A including lens driving apparatus  1  are disposed close to each other as in smartphone M, lens driving apparatus  1 A is extremely suitable for use as a dual camera. 
     Further, in lens driving apparatus  1 A, AF movable part  51  is urged to the first stage (AF fixing part) via AF support part  15 . Thus, it is possible to efficiently transmit the driving force of AF driving part  14  to AF movable part  51 . 
     [Method of Controlling Driving Unit] 
     In lens driving apparatus  1  according to Embodiment 1 and lens driving apparatus  1 A according to Embodiment 2, AF driving part  14  and OIS driving part  30  (driving units) are controlled, for example, as follows. In the driving unit indicated below, “active element C- 1 ” corresponds to AF resonance part  141  and OIS resonance part  31 , and “passive element C- 4 ” corresponds to AF urging members  112  and  512  and OIS power transmission part  34 . 
     In principle, identical or functionally identical parts are provided with the same reference signs in the drawing described below.  FIG. 17  illustrates a driving unit including active element C- 1 . Active element C- 1  includes resonator C- 2  (corresponding to AF resonance part  141  and OIS resonance part  31 ) with a pair of arms, first arm C- 21  and second arm C- 22 . Arms C- 21  and C- 22  and attachment part C- 14  are connected to coupling part C- 20  of resonator C- 22 . Resonator C- 22  is mounted in another part, such as a base element, via attachment part C- 14 . 
     Excitation means C- 23  (corresponding to AF piezoelectric element  142  and OIS piezoelectric element  32 ) such as a piezoelectric element is disposed on coupling part C- 20 . Controller  90  is disposed so as to generate an excitation signal or excitation voltage for driving excitation means C- 23 . Sensor  91  is located so as to measure the position and/or velocity of passive element C- 4  with respect to active element C- 1 . Sensor  91  measures the position and/or velocity of passive element C- 4  based on a magnetic field that is affected by the position of passive element C- 4 . A Hall sensor can be applied to sensor  91 . 
     Excitation means C- 23  includes two separate elements disposed on both sides of excitation means C- 23 . Resonator C- 22  and excitement means C- 23  are flat elements, are stacked onto each other, and extend in parallel to reference plane C- 28  (see  FIG. 19 ). 
     Upon excitation by an alternating voltage with an excitation frequency, arms C- 21  and C- 22  vibrate and first contact part C- 31  of first arm C- 21  performs a nearly linear motion in accordance with the frequency. A linear vibration can include an orthogonal component and the entire motion can be considered to be elliptical. The direction of a linear vibration (front-rear) motion changes in accordance with the frequency. First contact part C- 31  repeatedly comes into contact with first contact region C- 41  of passive element C- 4  and drives first contact region C- 41  with respect to active element C- 1 . The same applies to second contact part C- 32  and second contact region C- 42 . 
     In accordance with the direction of the linear front-rear motion, passive element C- 4  is repeatedly pushed in a corresponding direction. In accordance with how passive element C- 4  is suspended, passive element C- 4  performs, for example, a linear motion and/or a rotary motion. In the embodiment illustrated in  FIG. 17 , passive element C- 4  rotates with respect to active element C- 1 . 
     Given specific geometric shapes of these parts and the aspect in which passive element C- 4  is disposed to move with respect to active element C- 1 , it is possible to determine, for a desired (rotary or linear) motion direction, an excitation frequency that results in, for each vibration or for each pulse and resulting pressing motion, a maximum energy transmission for the desired motion. In order to reduce the energy transmission per pulse, the excitation frequency can be changed slightly such that the same schematic direction of vibration motion, although the direction slightly changes, is maintained. This changes the abutment angle at which first contact part  31  and second contact part  32  abut on contact regions  41  and  42 , respectively, as well as the amplitude of vibrations thereof so that the energy to be transmitted per pulse decreases in comparison with the optimum angle. Thus, a slight relative change in excitation frequency can be utilized to control the movement velocity of passive element C- 4 . 
     A pre-stress force acts between first contact part C- 31  and first contact region C- 41  and between second contact part C- 32  and second contact region C- 42 , respectively. The pre-stress force is generated by the elasticity of first arm C- 21  and second arm C- 22 . When passive element C- 4  is disposed between first contact part C- 31  and second contact part C- 32 , first arm C- 21  and second arm C- 22  are pushed so as to be apart. 
     First arm C- 21  and second arm C- 22  extend from coupling part C- 20  in a substantially symmetric manner, but may differ in details of the shape thereof, in particular the contour thereof, in a case where first arm C- 21  and second arm C- 22  are manufactured from a flat material piece. Resonator axis C- 24  corresponds to an axis of symmetry at which resonator C- 22 , in particular coupling part C- 20  and first arm C- 21  and second arm C- 22 , can be mirrored, except for the aforementioned details of the arms. When coupling part C- 20  and first arm C- 21  and second arm C- 22  are excited by excitement means C- 23 , motion of coupling part C- 20  and arms C- 21  and C- 22  is substantially symmetric with respect to the same axis of symmetry. Nodes of this motion, that is, regions of minimal motion region are located on resonator axis C- 24 . Attachment part C- 14  for mounting active element C- 1  in another element is also located on resonator axis C- 24 . 
       FIGS. 18A and 18B  illustrate variations of active element C- 1  in which passive element C- 4  is omitted for clarity.  FIG. 18A  illustrates active element C- 1  as illustrated in  FIG. 17 . In  FIG. 18B , active element C- 1  is located so as to drive the passive element in a linear direction in particular within the plane in which two arms C- 21  and C- 22  are located, as indicated by a bi-directional arrow corresponding to resonator axis C- 24 . In  FIGS. 18A and 18B , excitement means C- 23  are attached to both sides of resonator C- 22 . 
       FIG. 19  illustrates a driving unit including essentially the same elements as the driving unit illustrated in  FIG. 17 . This driving unit also includes a pair of arms C- 21  and C- 22 , but only first arm C- 21  comes into contact with passive element C- 4  to drive passive element C- 4 . The motion of the driving unit is a linear motion as indicated by linear motion axis C- 26 . 
     In the embodiment described above, passive element C- 4  is disposed between arms C- 21  and C- 22 , and contact parts C- 31  and C- 32  at the end parts of the arms point inwardly toward each other. In other embodiments, albeit not illustrated, arms C- 21  and C- 22  have such a shape that contact parts C- 31  and C- 32  point outwardly away from each other. Passive element C- 4  is disposed so as to come into contact with one or both of contact parts C- 31  and C- 32  from the outside. 
     Further embodiments of driving units to which the driving method presented herein can be applied are disclosed in WO 2006/000118, U.S. Pat. No. 7,429,812, and WO 2019/068708 which are incorporated herein by reference in their entirety. 
       FIG. 20  illustrates, along time axis t that is the same time axis, three driving signals D 1 , D 2 , and D 3  and corresponding amplitudes (amplitudes A 1 , A 2 , and A 3 ) of vibration by active element C- 1 . 
     First driving signal D 1  is a rectangular signal with period length Te which is also referred to as “pulse period”. Excitation frequency fe is represented by fe=1/Te. The maximum pulse width of first driving signal D 1  is Te/2, that is, pulse duty cycle dp is 50%. 
     Assuming that the pulse sequence of first driving signal D 1  begins at start time t 0 , the corresponding amplitude (first amplitude A 1 ) of the vibration rises as subsequent pulses by excitation means C- 23  transmit mechanical energy into vibration of active element C- 1 , in particular resonator C- 22  and arms C- 21  and C- 22  thereof. After a plurality of pulses, the vibration reaches a maximum and then becomes essentially constant in a steady state. 
     In a case where the amplitude is below activation threshold At, arms C- 21  and C- 22  do not impart a driving force to passive element C- 4 . In a case where the amplitude exceeds the threshold, arms C- 21  and C- 22  impart a driving force to passive element C- 4 , and passive element C- 4  is driven with respect to active element C- 1 . 
     Second driving signal D 2  is obtained by amplitude modulation of first driving signal D 1 , with the amplitude being reduced with respect to its maximum value. Third driving signal D 3  is obtained by pulse width modulation of first driving signal D 1 , with the pulse width or pulse duty cycle being reduced with respect to its maximum value. In both cases of second driving signal D 2  and third driving signal D 3 , the mechanical energy transmitted to active element C- 1  per pulse decreases in comparison with the case of first driving signal D 1 . Correspondingly, the trajectories of second amplitude A 2  and third amplitude A 3  rise slower than that of first amplitude A 1 , and level off at lower constant or steady-state values. The time required to exceed the activation threshold is longer than that in the case of first driving signal D 1 . 
     The amplitude of vibration by active element C- 1  corresponds to a velocity at which passive element C- 4  moves with respect to active element C- 1 . Thus, the velocity of the driving unit can be controlled by controlling the energy imparted to active element C- 1  per pulse. The energy imparted to active element C- 1  per pulse depends on the shape of the pulse. This shape can be controlled by different types of modulation. As the types of modulation, pulse amplitude and/or pulse width modulation are well known, for example. 
     Further reduction of the energy transmitted per pulse may result in a situation in which the amplitude does not exceed activation threshold At at all or only occasionally exceeds activation threshold At in an uncertain manner. For this reason, it is impossible to reduce the velocity of the driving unit below a velocity threshold. In general, the velocity threshold corresponds to the amplitude threshold. The velocity threshold can be, in accordance with the physical and electrical characteristics of the driving unit, within a region of 20% to 40% of the maximum velocity. 
       FIG. 22  illustrates the above in terms of the relationship between pulse width or pulse duty cycle dp and the resulting velocity (velocity v). When the pulse duty cycle is reduced from 50% of its maximum, the velocity decreases to a threshold and becomes zero at the threshold. 
     In order to realize lower velocities, the shape of the driving signal is maintained such that the amplitude of the vibration of the active element in the steady state exceeds the activation threshold by a safety margin. As illustrated in  FIG. 21 , the driving unit intermittently operates. This drawing illustrates, along time axis t that is the same time axis, fourth driving signal D 4 , a corresponding amplitude (amplitude A 4 ) of the vibration of active element C- 1 , and a corresponding displacement (displacement S) of passive element C- 4  with respect to active element C- 1 . The time axis is compressed in comparison with the time axis of  FIG. 20 . 
     Fourth driving signal D 4  includes pulses during turn-on time Ton, and does not include any pulse during turn-off time Toff. Sequences with and without pulses are periodically repeated with pulse block period Tb equal to Ton+Toff. The pulse block period is also referred to as “excitation period”. The corresponding frequency (frequency fb)=1/Tb with which pulse blocks are repeated is referred to as “pulse block frequency”. The relationship between turn-on time Ton and pulse block period Tb, that is, Ton/Tb, is referred to as “pulse block duty cycle dpb”. 
     Thus, the driving unit intermittently operates by applying pulses to the driving unit only during turn-on periods and by omitting or suppressing pulses during turn-off periods. During the turn-on periods, which are sufficiently long for the amplitude to exceed the activation threshold, and after a corresponding delay, passive element C- 4  is driven with respect to active element C- 1 . During the turn-off periods, after a delay in which the vibration is attenuated, active element C- 1  holds passive element C- 4  in position by the pre-stress force. Displacement S increases by repetition of a series of steps and steady-state periods. The average slope of displacement illustrated in  FIG. 21  represents the average velocity of passive element C- 4  with respect to active element C- 1 . 
     In general, the velocity refers to the relative motion between active element C- 1  and passive element C- 4  viewed along a linear axis. In the case of a rotary driving unit, the angular velocity corresponds to a value obtained by dividing the velocity by the radius when active element C- 1  drives passive element C- 4 . 
     In typical applications, the pulse block period can correspond to pulse block frequency fb=1/Tb between 5 kHz and 100 kHz, typically around 25 kHz. The frequency of the pulses themselves is between 50 kHz and 1000 kHz, typically around 500 kHz. 
     As a result, the maximum velocity is around 80 mm/sec. The step for each vibration period is within a range of 0.01 to 1 μm. Forces imparted by active element C- 1  to passive element C- 4  are up to 100 mN (that is, up to 0.1 N). Voltages applied to excitement means C- 23  are around 3 V. 
     In situations in which a position of the driving unit needs to be obtained, the controller modifies, regardless of the velocity, the position step size by which the position changes in one pulse period, for example: 
     by modifying the shape of the driving pulses, thereby reducing the energy transmitted per pulse, and thus reducing the amplitude of the mechanical vibration that drives the passive element; or 
     by modifying the excitation frequency, thereby reducing the mechanical vibration to reduce the energy transmission to the amplitude, and/or thereby changing the direction of the mechanical vibration, that is, its contribution to a driving force that acts in the direction of motion of passive element C- 4 . 
       FIG. 23  illustrates the relationship between excitation frequency f and the resulting velocity (velocity v). At first frequency f 1 , resonator C- 22  is in a first operation mode or a first vibration mode, and drives passive element C- 4  at the maximal velocity in a first direction. At second frequency f 2 , resonator C- 22  is in a second operation mode, and drives passive element C- 4  at the maximal velocity in a second direction opposite to the first direction. In a case where there are slight deviations around f 1  or f 2 , respectively, corresponding to a detuning of the excitation frequency with respect to the natural frequency of active element C- 1  in each vibration mode, each velocity decreases. 
     The above examples have been described in connection with a driving signal with rectangular pulses. The same principles can be applied to even pulses having different shapes, in particular with respect to amplitude and pulse width modulation and the omission of pulses. For example, the same principles can also be applied to sinusoidal, triangular, trapezoidal or saw tooth pulses, or to pulses having arbitrary shapes. 
     Excitation frequencies f 1  and f 2 , which are optimal for motion in opposite directions, as well as excitation frequencies for different modes and directions generally depend on the individual mechanical and electrical characteristics of the driving unit, in particular resonator C- 22  and excitement means C- 23 . These characteristics vary over time, due to wear and parameter variations, depending on environmental conditions such as temperature and moisture, and also depending on the orientation of the driving unit with respect to the direction of gravity. The optimal values for the excitation frequencies also vary correspondingly. In order to determine optimal values, it is possible to operate the driving unit at different frequencies, to measure a response of a target, and to determine the frequency at which the response of the target becomes optimal. 
       FIG. 24  illustrates a flowchart for a method of operating the driving unit according to an embodiment. 
     The method starts in initialization step C- 80 . In measurement step C- 81 , an actual position of the driving unit, that is, a relative position between active element C- 1  and passive element C- 4  is determined. This position may be a rotational position or a translational position. 
     In difference calculation step C- 82 , difference d between an actual position and a set position is calculated. Difference d is represented by a position error signal. The method branches into different driving modes depending on the value of difference d. The driving unit is driven in driving signals of different parameters depending on thresholds d 1 &lt;d 2 &lt;d 3 , where thresholds d 1 , d 2  and d 3  differ from each other, and absolute value abs (d) of difference d: 
     in a case where abs (d)&gt;d 3  (“y” in determination step C- 83 ), the driving unit is driven in high-velocity driving mode C- 84 ; 
     in a case where d 2 &lt;abs (d)&lt;d 3  (“n” in determination step C- 83 , and “y” in determination step C- 85 ), the driving unit is driven in medium-velocity driving mode C- 86 ; and 
     in a case where d 1 &lt;abs (d)&lt;d 2  (“n” in determination step C- 85 , and “y” in determination step C- 87 ), the driving unit is driven in low-velocity driving mode C- 88 . 
     In either case, the excitation frequency of the driving signal in the foregoing examples, that is, f 1  or f 2 , is selected according to a direction in which the position is to be corrected, that is, the reference sign of difference d. 
     In a case where abs (d)&lt;d 1  (“n” in determination step C- 87 ), the driving unit is not driven. At this time, in braking mode  89 , passive element C- 4  is held with respect to active element C- 1  by the pre-stress force. 
     Then, the method is iteratively repeated by continuing measurement step C- 81 . 
     Values with respect to the threshold are selected when designing or ordering the driving unit. These values can be set as, for example, d 1 =1 μm, d 2 =5 μm, and d 3 =10 μl. 
     In an embodiment, in high-velocity driving mode C- 84 , the pulse duty cycle with respect to the maximal power of the driving signal is typically 50%, and the maximal pulse block duty cycle is typically 100%. 
     In an embodiment, in medium-velocity driving mode C- 86 , 
     the pulse duty cycle of the driving signal is reduced to be less than the pulse duty cycle in high-velocity driving mode C- 84 ; and/or 
     the pulse block duty cycle of the driving signal is reduced to be less than the pulse block duty cycle in high-velocity driving mode C- 84 . 
     In an embodiment, both the pulse duty cycle and the pulse block duty cycle are reduced. For example, the pulse duty cycle is 30% (not 50% of its maximum) and the pulse block duty cycle is 50% (not 100% of its maximum). 
     In an embodiment, in low-velocity driving mode C- 88 , 
     the pulse duty cycle of the driving signal is reduced to be less than the pulse duty cycle in medium-velocity driving mode C- 86 ; and/or 
     the pulse block duty cycle of the driving signal is reduced to be less than the pulse block duty cycle in medium-velocity driving mode C- 86 . 
     In an embodiment, 
     in high-velocity driving mode C- 84 , the pulse duty cycle of the driving signal is 50% and the pulse block duty cycle thereof is 100%; 
     in medium-velocity driving mode C- 86 , the pulse duty cycle of the driving signal is 30% and the pulse block duty cycle thereof is 50%; and 
     in low-velocity driving mode C- 88 , the pulse duty cycle of the driving signal is 20% and the pulse block duty cycle thereof is 10%. 
     In other embodiments, only two driving modes with different velocities are used. 
     While the invention made by the present inventors has been specifically described thus far based on the preferred embodiments, the present invention is not limited to the preferred embodiments described above and can be modified without departing from the gist thereof. 
     For example, although smartphone M that is a camera-equipped mobile terminal has been described as an example of the camera-mounted apparatus including camera module A in the preferred embodiments, the present invention is applicable to a camera-mounted apparatus that includes a camera module; and an image-processing part that processes image information obtained by the camera module. The camera-mounted apparatus encompasses information apparatuses and transport apparatuses. The information apparatuses include, for example, camera-equipped mobile phones, notebook personal computers, tablet terminals, mobile game machines, webcams, and camera-equipped in-vehicle apparatuses (such as rear-view monitor apparatuses and dashboard camera apparatuses). Further, the transport apparatuses include, for example, automobiles. 
       FIGS. 25A and 25B  illustrate automobile V as a camera-mounted apparatus in which in-vehicle camera module vehicle camera (VC) is mounted.  FIG. 25A  is a front view of automobile V, and  FIG. 25B  is a rear perspective view of automobile V. In automobile V, camera module A described in the preferred embodiments is mounted as in-vehicle camera module VC. As illustrated in  FIGS. 25A and 25B , in-vehicle camera module VC is attached to the windshield so as to face the front side, or is attached to the rear gate so as to face the rear side, for example. This in-vehicle camera module VC is used for a rear-view monitor, a dashboard camera, collision-prevention control, automated driving control, and the like. 
     Further, in the preferred embodiments, first arm part  141   b  of AF driving part  14  is caused to abut on AF urging member  112  or  512  that forms AF movable part  11  or  51 , but may be caused to directly abut on lens holder  111  or  512 . However, in the case where first arm part  141   b  of AF driving part  14  is caused to abut on AF urging member  112  or  512  that is a metal molded article, a driving force can be efficiently transmitted and the durability also improves in comparison with the case where first arm part  141   b  of AF driving part  14  is caused to abut on lens holder  111  or  512  is a resin molded article. 
     Further, it may also be configured such that an urging member which urges lens holder  111  or  512  toward first stage  12  and a member on which first arm part  141   b  of AF driving part  14  abuts are provided separately. 
     Further, in the preferred embodiments, two AF driving parts (AF driving parts  14 A and  14 B) are provided, but the number of AF driving parts  14  may be one or may be three or more as long as AF driving part(s)  14  is/are capable of exerting a driving force that allows AF movable part  11  or  51  to move in the Z direction. 
     In addition, the present invention is applicable not only to autofocus, but to a case where a movable part is moved in the optical axis direction, such as zoom. 
     Further, the support structure of AF movable part  51  using AF urging member  512  in Embodiment 2 is not limited to the case where the driving source is formed of an ultrasonic motor as in AF driving part  14 , but is also applicable to a lens driving apparatus including a driving source (for example, a voice coil motor (VCM)) other than an ultrasonic motor. 
     The embodiments disclosed herein are merely exemplifications in every respect and should not be considered as limitative. The scope of the present invention is specified not by the description provided above, but by the appended claims, and is intended to include all modifications in so far as they are within the scope of the appended claims or the equivalents thereof. 
     The disclosures of Japanese Patent Application No. 2019-089864, filed on May 10, 2019, Japanese Patent Application No. 2019-187775, filed on Oct. 11, 2019, and Japanese Patent Application No. 2019-225710, filed on Dec. 13, 2019, each including the specification, drawings and abstract, are incorporated herein by reference in their entirety. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  1 A Lens driving apparatus 
           10 ,  10 A OIS movable part (second movable part) 
           11 ,  51  AF movable part (first movable part) 
           111 ,  511  Lens holder 
           112 ,  512  AF energization member 
           12  First stage (first fixing part) 
           13  Second stage 
           14  AF driving part (Z-direction driving part) 
           141  AF resonance part 
           142  AF piezoelectric element 
           143  AF electrode 
           15  AF support part (first support part) 
           20  OIS fixing part (second fixing part) 
           21  Base 
           30  OIS driving part (XY-direction driving part) 
           31  OIS resonance part 
           32  OIS piezoelectric element 
           33  OIS electrode 
           34  OIS power transmission part 
           40  OIS support part (second support part) 
           50  OIS urging member 
         A Camera module 
         M Smartphone (camera-mounted apparatus)