JP2007271990A - Lens drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact lens drive device capable of providing an automatic focusing function and a zoom function even in a compact apparatus such as a mobile phone. <P>SOLUTION: The lens drive device includes: a case; a lens barrel that holds a lens and moves relatively to the case by being received with a driving force; a drive force transmission section that has a rotor and transmits the rotating force of the rotor to the lens barrel, thereby driving the lens barrel; and an ultrasonic actuator that acts on the rotor to ratate the rotor. The ultrasonic actuator has an oscillator disposed in contact with the rotor at one end, is bent in the form of corner at a certain point, further extends from the corner, and is fixed to the case at another end. The oscillator is arranged so that the lens barrel is positioned on the minor angle side of the corner. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lens driving device that holds and moves a lens.

  2. Description of the Related Art In recent years, it has been widely practiced to incorporate a photographing device for photographing a subject in a small device such as a mobile phone. By providing a photographing device in a small device that is always carried around, it is possible to easily shoot anytime without having to carry a digital camera or a video camera. In addition, these small devices are generally equipped with a data communication function using wireless or infrared rays in advance, and the captured images are immediately taken on the spot to other mobile phones, personal computers, etc. There is also an advantage that can be sent to.

  However, since a photographing device incorporated in a small device such as a mobile phone is considerably small as compared with a normal digital camera, a lens, a CCD (Charge Couple Device) imaging element, a MOS (Metal Oxide Semiconductor) imaging element ( Hereinafter, these are collectively referred to as “imaging elements”), the size of the shutter, and the space for storing them is greatly limited. For this reason, these small devices have insufficient shooting functions and image quality of captured images to be used as alternative devices for digital cameras. For obtaining images instead of memos, and for standby screens such as mobile phones. As in the case of obtaining an image, the use is often limited to shooting that does not require high image quality.

  With regard to these points, in recent years, small image sensors with a large number of pixels and small lenses corresponding to these have been developed, and the quality of captured images taken using small devices has rapidly increased. It is out. In order to enhance the imaging function, which remains as a remaining issue, it is particularly desirable that these small devices are equipped with an autofocus function and a zoom function that are normally installed in digital cameras.

  In general, the autofocus function and the zoom function are realized by moving a lens in a direction along the optical axis by using rotation of a motor. Normally, an electromagnetic motor that rotates a rotor by a magnetic field is often used as a motor for driving a lens. However, an electromagnetic motor consumes a large amount of power and is relatively large. In addition, the size and weight of the entire photographing apparatus are greatly increased, and in addition to the power for executing the normal photographing function, it is necessary to secure sufficient power for driving the electromagnetic motor. Therefore, it is difficult to mount an autofocus function and a zoom function using an electromagnetic motor in a mobile phone or the like that is required to be reduced in size and weight.

  In this regard, Patent Document 1 and Patent Document 2 describe an imaging device that moves a lens using an actuator that uses piezoelectric instead of an electromagnetic motor, and Patent Document 3 and Patent Document 4 describe piezoelectric devices. The basic structure of an actuator using the above is described.

  FIG. 1 is a schematic configuration diagram of an ultrasonic actuator 10 using piezoelectricity, and FIG. 2 is a diagram for explaining an operation principle of the ultrasonic actuator 10.

  As shown in FIG. 1, the ultrasonic actuator 10 supports a piezoelectric element 11 that vibrates when voltage is applied, an elastic vibrating body 12 that is distorted by the vibration of the piezoelectric element 11, the piezoelectric element 11, and the elastic vibrating body 12. And a pressing plate 15 for pressing the spring 14 against the elastic vibrating body 12. The supporting member 13 is configured to support the elastic vibrating body 12 toward the rotor 20.

  As shown in FIG. 2, the elastic vibrating body 12 is sandwiched between two piezoelectric elements 11a and 11b. For example, when an AC voltage having the same phase is applied to each of the piezoelectric elements 11a and 11b, the piezoelectric elements 11a and 11b. 11a and 11b expand and contract in the same direction, the elastic vibrating body 12 is deformed, and the tip of the elastic vibrating body 12 is pressed against the rotor 20, whereby the tip of the elastic driving body 12 is driven in an ellipse, and the rotor 20 is driven. It will be rotated in the direction of arrow A.

By attaching such a piezoelectric ultrasonic actuator to the lens, it is possible to drive the lens with less power than an electromagnetic motor. Further, it is possible to reduce the weight of the photographing apparatus and reduce the lens driving noise. it can.
JP 2004-294759 A JP 2004-294580 A JP 2005-218179 A JP 2003-199371 A

  By the way, the distortion of the elastic vibration body 12 includes longitudinal vibration in which the elastic vibration body 12 expands and contracts, bending vibration in which the elastic vibration body 12 bends so as to wave, and coupled vibration in which the longitudinal vibration and the bending vibration are combined. As is known, in order to drive the lens at a high speed, it is necessary to rotate the rotor 20 at a high speed by coupling and vibrating the elastic vibrator 12. However, according to the techniques described in Patent Document 3 and Patent Document 4 described above, it is necessary to apply AC voltages having mutually different phases to each of the plurality of piezoelectric elements in order to couple and vibrate the elastic vibrator. There is a problem that the voltage control becomes complicated.

  In addition, a conventional ultrasonic actuator using piezoelectric elements requires a preload mechanism such as a spring 15 and a pressing plate 16 that press the elastic vibration body 12 against the rotor 13 in addition to the support member 14 that supports the elastic vibration body 12. Become. In particular, although the preload mechanism is a component that is not directly related to the distortion of the elastic vibrating body 12, it occupies the same space as the other portions, and the ultrasonic actuator is downsized. It has become a neck.

  From the above, in order to mount a mechanism for driving a lens with an ultrasonic actuator in a photographing device for a mobile phone, further miniaturization of the ultrasonic actuator, simplification of voltage control, and the like are required.

  In view of the above circumstances, an object of the present invention is to provide a small lens driving device capable of realizing an autofocus function and a zoom function even in a small device such as a mobile phone.

The lens driving device of the present invention that achieves the above object includes a case,
A lens barrel that holds the lens and receives the driving force and moves relative to the case;
A driving force transmission unit that has a rotor and transmits the rotational force of the rotor to the lens barrel to drive the lens barrel;
An ultrasonic actuator that acts on the rotor and rotates the rotor,
The ultrasonic actuator includes a vibrator that has a corner portion that is bent at one end in contact with the rotor and that extends further and is fixed to the case from the other end side. It is characterized by being deployed in a position.

  According to the lens driving device of the present invention, the ultrasonic actuator is supported by the end (the other end side) fixed to the case of the vibrator, and the fixed side end (the other end side) and the corner portion The end (one end side) in contact with the rotor is pressed against the rotor by the elasticity of the portion between them. For this reason, the preload mechanism such as the support member 13 shown in FIG. 1, the spring 14, and the pressing plate 15 is not necessary, and the ultrasonic actuator can be miniaturized. Furthermore, the lens driving device of the present invention has a corner portion where the ultrasonic actuator is bent, and the lens barrel is driven in a space vacant on the inferior angle side of the corner portion. The lens driving device does not increase in size even if it is attached, and can be mounted on a mobile phone or the like to realize an autofocus function or a zoom function.

In the lens driving device of the present invention, the vibrator is plate-shaped,
It is preferable that the actuator further includes a piezoelectric element that is in contact with a portion of the vibrator between the one end and the corner portion, vibrates by receiving an AC voltage, and transmits the vibration to the vibrator.

  According to the lens driving device of the present invention, when an AC voltage is applied to the piezoelectric element, the vibrator is distorted in a direction corresponding to the phase of the AC voltage, and the direction of a part of the distortion is converted at the corners. Multiple directions of distortion are combined and transmitted to the rotor. Therefore, the coupling vibration described above can be realized by simply applying a single-phase AC voltage to the piezoelectric element, and voltage control can be simplified.

  In the lens driving device of the present invention, it is preferable that a plurality of the piezoelectric elements are provided across a part of the vibrator between the one end and the corner portion.

  By providing a plurality of piezoelectric elements with the vibrator interposed therebetween, the size of the apparatus can be suppressed, the vibrator can be greatly distorted, and the lens held in the lens barrel can be driven at high speed.

  In the lens driving device of the present invention, it is preferable that the vibrator is a metal plate and also serves as one electrode of each of the plurality of piezoelectric elements.

  According to the preferred lens driving device of the present invention, the vibrator also serves as an electrode for applying a voltage to the piezoelectric element, so that the entire device can be reduced in size.

  In the lens driving device of the present invention, it is preferable that a portion of the one end side of the vibrator is formed to be narrower than a portion excluding the portion.

  By forming a portion of the vibrator on the side in contact with the rotor to be narrow, distortion of the vibrator is efficiently transmitted to the rotor, and the lens held in the lens barrel can be reliably driven.

  According to the present invention, an autofocus function and a zoom function can be realized even in a small device such as a mobile phone.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, prior to the description of the lens driving device of the present invention, the ultrasonic actuator applied to the lens driving device of the present invention will be described in detail.

  FIG. 3 is a schematic configuration diagram showing an example of an ultrasonic actuator applied to the lens driving device of the present invention.

  As shown in FIG. 3, the ultrasonic actuator 100 includes two piezoelectric elements 110 that vibrate upon application of an alternating voltage, an electrode 111 for applying an alternating voltage to the piezoelectric element 110, and a corner 120a. A diaphragm 120 is provided that is bent in an L shape, the upper leg 121 is in contact with the rotor 100A, and the lower leg 122 is fixed. The ultrasonic actuator 100 corresponds to an example of the ultrasonic actuator referred to in the present invention. The diaphragm 120 corresponds to an example of a vibrator according to the present invention, the rotor 100A corresponds to an example of a rotor according to the present invention, and the piezoelectric element 110 corresponds to an example of a piezoelectric element according to the present invention.

  FIG. 4 is an enlarged view of the ultrasonic actuator 100, and FIG. 5 is a diagram showing the polarization direction of the piezoelectric element 110.

  In the present embodiment, the diaphragm 120 is made of stainless steel (for example, SUS304), and the piezoelectric element 110 is made of piezoelectric ceramics (for example, PZT). The materials constituting the diaphragm 120 and the piezoelectric element 110 are not limited to these.

  In the diaphragm 120, a contact portion 121a of the upper leg 121 that comes into contact with the rotor 100A is formed with a narrow width. In addition, the two piezoelectric elements 110 are disposed with the upper leg 121 of the vibration plate 120 interposed therebetween, and the vibration plate made of metal is distorted by the vibration of the piezoelectric element 110 and the two piezoelectric elements. It also serves as a counter electrode for each of the two electrodes 111 provided in the element 110. As described above, the diaphragm 120 serves as both a vibrating body and a counter electrode, whereby the ultrasonic actuator 100 can be reduced in size.

  As shown in FIG. 5, the two piezoelectric elements 110 are polarized in the thickness direction (arrow C, arrow C ′), and the two piezoelectric elements 110 have the same phase, the same size, and the same. An alternating voltage of frequency is applied.

  6 and 7 are diagrams showing directions of distortion generated in the diaphragm 120. FIG.

  When an AC voltage is applied to the two piezoelectric elements 110, the piezoelectric elements 110 are excited and distortion occurs in the upper leg 121 of the diaphragm 120. The upper leg 121 of the diaphragm 120 is pressed against the rotor 100A shown in FIG. 3 by the elasticity of the lower leg 122, and the distortion generated in the diaphragm 120 is reliably transmitted to the rotor 100A. In this way, by bending the diaphragm 120 into an L shape, a support member that supports the piezoelectric element 110 and a preload mechanism that presses the diaphragm 120 against the rotor 100A become unnecessary, thereby reducing the number of parts and suppressing manufacturing costs. In addition, the ultrasonic actuator 100 can be significantly downsized.

  In addition, the direction of a part of the distortion generated in the upper leg 121 is changed by the corner portion 120a. As a result, distortion in a plurality of directions is generated in the diaphragm 120, and the distortions in the plurality of directions are combined and transmitted to the rotor 100A. The order of the vibration mode of the diaphragm 120 shown in FIGS. 6 and 7 is an example, and can be adjusted by changing the length of the diaphragm 120.

  FIG. 8 is a graph showing the resonance frequency of the diaphragm 120.

  In FIG. 8, the horizontal axis indicates the length X of the upper leg 121 of the diaphragm 120, and the vertical axis indicates the resonance frequency of the diaphragm 120.

  Compared with the conventional ultrasonic actuator 10 shown in FIGS. 1 and 2, the ultrasonic actuator 100 loses the symmetry of the shape because the diaphragm 120 is bent in an L shape, and longitudinal vibration is not generated. When the vibration occurs, a part of the longitudinal vibration is converted into a bending vibration. Conversely, when the bending vibration occurs, a part of the bending vibration is converted into the longitudinal vibration. Thus, in the ultrasonic actuator 100, two vibrations are always mixed.

As shown in FIG. 8, in the ultrasonic actuator 100 of this embodiment, the resonance frequency of the longitudinal vibration (L-mode) and the resonance frequency of the bending vibration (B-mode) do not coincide with each other. In the region R where the resonance frequency of vibration approaches, the nearest resonance frequency f _Low when closest to the bending vibration graph on the longitudinal vibration graph and the nearest resonance frequency when closest to the longitudinal vibration graph on the bending vibration graph f _High .

For example, when an alternating voltage having the latest resonance frequency f _Low on the longitudinal vibration (L-mode) graph shown in FIG. 8 is applied to the two piezoelectric elements 110, the diaphragm 120 is mainly expanded and contracted. It is distorted to generate a longitudinal vibration (L-mode), and the longitudinal vibration is converted into a distortion in the bending direction at the corner portion 120a to generate a bending vibration (B-mode). The longitudinal vibration and the bending vibration are coupled at the front end portion 121 of the diaphragm 120, and the rotor 100A is rotated by the resultant force T in which the expansion and contraction of the diaphragm 120 is added to the expansion and contraction of the diaphragm 120 as shown in FIG.

When an alternating voltage having the latest resonance frequency f _High on the bending vibration (B-mode) graph shown in FIG. 8 is applied to the two piezoelectric elements 110, the diaphragm 120 is mainly bent in the bending direction. The bending vibration (B-mode) is distorted and the bending vibration is converted into the distortion in the expansion / contraction direction at the corner 120a to generate the longitudinal vibration (L-mode). By combining these longitudinal vibration and bending vibration at the tip 121 of the diaphragm 120, as shown in FIG. 7, the rotor 100A is rotated by the resultant force T ′ in the direction opposite to that in FIG.

  FIG. 9 is a diagram illustrating an operation principle of rotating the rotor 100A in the forward direction.

For example, when an alternating voltage having a resonance frequency f _Low is recently applied to vibrate the piezoelectric element 110, the amplitude of distortion of the diaphragm 120 gradually increases. When the bending displacement of the diaphragm 120 is maximum in the upward direction and the expansion / contraction displacement approaches 0, the contact portion 121a of the diaphragm 120 comes into contact with the rotor 100A (step S11 in FIG. 9). At this time, the expansion / contraction speed becomes maximum in the extension direction.

  Subsequently, the diaphragm 120 extends, and the contact portion 121a strikes the outer periphery of the rotor 100A, thereby giving rotational torque to the rotor 100A. As a result, the rotor 100A rotates in the arrow M direction (step S12 in FIG. 9). At this time, the expansion / contraction displacement is maximum, the bending displacement is near 0, and the downward speed is maximum.

  When the diaphragm 120 is extended to the maximum, the diaphragm 120 is displaced in a contracting direction, but a downward bending displacement is generated, and the contact portion 121a is separated from the rotor 100A. (Step S13 in FIG. 9). At this time, the expansion / contraction displacement is 0, the bending displacement is maximum in the downward direction, and the speed in the contraction direction is maximum.

  In the state where diaphragm 120 is most contracted, diaphragm 120 expands and contracts in the direction opposite to that in step S11, but contact portion 121a is away from rotor 100A, so contact portion 121a does not hinder the rotation of rotor 100A. The rotor 100A continues to rotate with inertia (step S14 in FIG. 9).

  As described above, the rotor 100A is rotated in the forward direction (the direction of the arrow M).

  FIG. 10 is a diagram illustrating an operation principle of rotating the rotor 100A in the sub direction.

Contrary to FIG. 9, when an AC voltage having a resonance frequency f _High is applied recently to vibrate the piezoelectric element 110, when the expansion / contraction displacement of the vibration plate 120 is maximum in the extension direction, The contact portion 121a does not contact the rotor 100A (step S21 in FIG. 10). At this time, the displacement in the expansion / contraction direction is maximum, the bending displacement is near 0, and the upward speed is maximum.

  Subsequently, the diaphragm 120 contracts, and the contact portion 121a rubs around the outer periphery of the rotor 100A, thereby giving rotational torque to the rotor 100A. As a result, the rotor 100A rotates in the direction of the arrow M ′ (step S22 in FIG. 10). At this time, the expansion / contraction displacement is 0, the bending displacement is 0, and the speed in the contraction direction is maximum.

  When the displacement in the bending direction is maximum in the upward direction, the expansion / contraction displacement is minimum, and the contact portion 121a is separated from the rotor 100A. (Step S23 in FIG. 10). At this time, the expansion / contraction displacement is minimum, and the bending displacement is maximum in the upward direction.

  When the displacement in the bending direction is maximized in the downward direction, the expansion / contraction displacement approaches the maximum. However, since the contact portion 121a is separated from the rotor 100A, the contact portion 121a does not hinder the rotation of the rotor 100A, and the rotor 100A is inertial. The rotation continues (step S24 in FIG. 10).

  As described above, the rotor 100A is rotated in the sub direction (arrow M ′ direction).

As described above, according to the ultrasonic actuator 100, both the bending vibration and the longitudinal vibration are applied to the diaphragm 120 by simply applying the same AC voltage (magnitude, phase, frequency) to each of the two piezoelectric elements 110. Therefore, the rotor 100A can be rotated at high speed with simple voltage control. Further, the rotation direction of the rotor 100A can be changed by switching the frequency of the AC voltage applied to the piezoelectric element 110 to the two nearest resonance frequencies f _High and f _Low , and the rotor 100A can be efficiently rotated.

  Subsequently, an embodiment of the lens driving device of the present invention provided with the ultrasonic actuator as described above will be described.

  FIG. 11 is an external perspective view of a photographing apparatus to which an embodiment of the lens driving device of the present invention is applied.

  The photographing device 200 is a small imaging device mounted on a mobile phone. The imaging device 200 is configured by a case 210 and a front cover 220 in appearance, and the front cover 220 is attached to the case 210 by screws 230. The case 210 corresponds to an example of the case according to the present invention.

  Inside the front cover 220 and the case 210, a lens that forms an image of subject light, a drive mechanism for driving the lens, and the like are arranged. A CCD for generating is attached. In this embodiment, a CCD is used as an image pickup device for generating a subject signal. However, in an image pickup apparatus mounted on a mobile phone or the like, a MOS is also widely used as an image pickup device. You may apply.

  One embodiment of the lens driving device of the present invention is attached to the case 210 of the photographing apparatus 200, and hereinafter, description will be given focusing on various components provided inside the case 210.

  FIG. 12 is a view showing the inside of the case 210.

  As shown in FIG. 12, an L-shaped ultrasonic actuator 310 having the same configuration as the ultrasonic actuator 100 shown in FIG. 3 and a rotor 320 rotated by the ultrasonic actuator 310 are provided inside the case 210. Furthermore, a lens barrel 350 having a built-in lens is provided inside the L-shape of the ultrasonic actuator 310. The lens barrel 350 corresponds to an example of a lens barrel according to the present invention.

  FIG. 13 is an exploded perspective view of the photographing apparatus 200, and FIG. 14 is a cross-sectional view of the top surface of the photographing apparatus 200. In FIGS. 13 and 14, it is assumed that the subject light L is incident from the lower side of the figure and the lower side of the figure is referred to as the front and the upper side of the figure is referred to as the rear.

  In the photographing apparatus 200, an ultrasonic actuator 310, a rotor 320, a rotation shaft 330, a cam ring 340, a lens barrel 350, and a spring 360 are arranged in order from the rear inside the case 210, and the front cover 220 is attached by a screw 230. It is fixed to the case 210.

  A gear 321 that meshes with the teeth 341 of the cam ring 340 is attached to the rotor 320. A combination of the gear 321 and the cam ring 340 corresponds to an example of a driving force transmission unit according to the present invention.

  The rotating shaft 330 passes through the rotor 320 and is supported by the case 210 and the front cover 220. As a result, the rotor 320 is rotatably supported around the rotation shaft 330. In the ultrasonic actuator 310, the upper foot 311 is in contact with the rotor 320 and the lower foot 312 is fixed to the case 210.

  Subsequently, when the cam ring 340 is attached to the case 210 and the lens barrel 350 is attached to the cam ring 340, the teeth 341 of the cam ring 340 are engaged with the gear 321 of the rotor 320, and the rail portion 351 provided on the lens barrel 350 is the case. 210 is fitted into a guide groove 211 formed in 210.

  Further, a spring 360 is attached to the front cover 220, the front cover 220 and the case 210 are screwed together, and a CCD (not shown) is attached to the back of the case 210. As a result, as shown in FIG. 14, the lens barrel 350 is urged from the front cover 220 toward the case 210 by the spring 360.

  In the imaging apparatus 200 as described above, the autofocus function is realized by the following procedure. Here, it is assumed that the lens barrel 350 moves in the forward direction when the rotor 320 rotates in the forward direction.

  First, subject light is roughly read by the CCD to generate a subject signal, and the contrast of the subject signal is acquired by the CPU of the mobile phone provided with the imaging device 200. The acquired contrast is stored as a provisional maximum contrast.

  Subsequently, an AC voltage of a predetermined magnitude is applied to the piezoelectric element 110 (see FIG. 3) of the ultrasonic actuator 310 by the CPU of the mobile phone, and the rotor 320 is rotated in the positive direction by a predetermined angle. By rotating the gear 321 of the rotor 320 while meshing with the teeth 341 of the cam ring 340, the cam ring 340 is also rotated in the positive direction by a predetermined angle. The back surface of the rail 351 provided on the lens barrel 350 is pressed against the cam surface of the cam ring 340 by a spring 360, and the rotational force of the cam ring 340 is converted into a force along the optical axis and transmitted to the lens barrel 350. Is done. As a result, the lens barrel 350 is moved forward by a predetermined distance along the optical axis, with the rail portion 351 guided to the guide groove 211. The guide groove 211 and the rail 351 not only serve to guide the moving direction of the lens barrel 350 but also serve as a rotation stopper for the lens barrel 350.

  When the lens barrel 350 is moved, the subject light is read again by the CCD and a subject signal is generated. In the CPU, the contrast of the generated subject signal is acquired and compared with the maximum stored contrast, and when the current contrast is larger than the stored contrast, the current contrast is Saved in place of the already saved contrast.

  An AC voltage is applied to the ultrasonic actuator 310, the rotor 320 is rotated by a predetermined angle in the forward direction, the lens barrel 350 is moved forward by a predetermined distance, and the contrast value of the subject signal is acquired. The operation of comparing the contrast with the stored contrast (maximum contrast until the previous time) is continued until the current contrast becomes smaller than the stored contrast.

  Normally, the contrast of the subject signal increases as the lens approaches the in-focus position. Therefore, when the lens barrel 350 is moved by a predetermined distance along the optical axis, the lens gradually approaches the in-focus position at first. After the lens position passes through the in-focus position, the contrast gradually decreases. Since the contrast changes like a mountain in this way, the lens position where the contrast has changed from an increasing tendency to a decreasing tendency can be determined as the in-focus position. A method of acquiring a change point at which the contrast changes from an increasing tendency to a decreasing tendency and detecting the in-focus position has been widely applied as “mountain climbing AF”.

  By moving the lens to the in-focus position determined as described above, it is possible to focus on the subject with high accuracy, and it is possible to acquire a high-quality captured image that is free from out-of-focus.

  In the present embodiment, a miniaturized ultrasonic actuator 310 is applied, and as shown in FIG. 12, a lens barrel 350 is provided in a space vacant inside the L-shape of the ultrasonic actuator 310. The overall size of the device is reduced. Furthermore, the ultrasonic actuator 310 is power saving compared to a conventional electromagnetic motor, and voltage control is simpler than that of a conventional ultrasonic actuator. Function can be realized.

  Here, the example provided with the ultrasonic actuator using the piezoelectric is described above, but the ultrasonic actuator according to the present invention can rotate the rotor by using a vibrator having a bent shape. If there is, an ultrasonic actuator using a polymer or the like may be used.

  In the above description, an example in which an ultrasonic actuator having two piezoelectric elements is provided has been described. However, the ultrasonic actuator in the present invention may be an ultrasonic actuator having three or more piezoelectric elements. Alternatively, it may be an ultrasonic actuator provided with one piezoelectric element.

  In the above description, the ultrasonic actuator bent in an L shape has been described. However, the ultrasonic actuator according to the present invention may have two or more corners.

  In the above description, the ultrasonic actuator provided with the metal diaphragm that also serves as the electrode of the piezoelectric element has been described. However, the ultrasonic actuator according to the present invention uses, for example, a plastic vibrator to vibrate the vibration. Aside from the child, an electrode for applying a voltage to the piezoelectric element may be provided.

  In the above description, the example in which the lens driving device of the present invention is mounted on a mobile phone has been described. However, the lens driving device of the present invention may be mounted on a small digital camera or the like.

It is a schematic block diagram of the ultrasonic actuator using a piezoelectric material. It is a figure for demonstrating the principle of operation of an ultrasonic actuator. It is a schematic block diagram which shows an example of the ultrasonic actuator applied to the shutter apparatus of this invention. FIG. 4 is an enlarged view of the ultrasonic actuator shown in FIG. 3. It is a figure which shows the polarization direction of a piezoelectric element. It is a figure which shows the direction of the distortion which generate | occur | produces in a diaphragm. It is a figure which shows the direction of the distortion which generate | occur | produces in a diaphragm. It is a graph which shows the resonant frequency of a diaphragm. It is a figure which shows the principle of operation which rotates a rotor to a normal direction. It is a figure which shows the operation | movement principle which rotates a rotor to a subdirection. 1 is an external perspective view of a photographing apparatus to which an embodiment of a lens driving device of the present invention is applied. It is a figure which shows the inner side of a case. It is a disassembled perspective view of an imaging device. It is sectional drawing of the upper surface of an imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,100,310 Ultrasonic actuator 11,110 Piezoelectric element 12 Elastic vibration body 13 Support member 14 Spring 16 Pushing plate 20,100A, 320 Rotor 111 Electrode 120 Diaphragm 120a Corner | angular part 121 Upper leg 122 Lower leg 200 Imaging device 210 Case 220 Front cover 330 Rotating shaft 340 Cam ring 350 Lens barrel 360 Spring

Claims (5)

Case and
A lens barrel that holds the lens and receives the driving force to move relative to the case;
A driving force transmission unit that has a rotor and transmits the rotational force of the rotor to the lens barrel to drive the lens barrel;
An ultrasonic actuator that acts on the rotor to rotate the rotor,
The ultrasonic actuator includes a vibrator that has a corner portion that is bent in the middle with one end in contact with the rotor, and that extends and is fixed to the case from the other end side. A lens driving device provided in a posture in which the lens barrel is located. The vibrator is plate-shaped,
The actuator further includes a piezoelectric element that contacts a portion of the vibrator between the one end and the corner portion, vibrates upon application of an alternating voltage, and transmits the vibration to the vibrator. The lens driving device according to claim 1.   The lens driving device according to claim 2, wherein a plurality of the piezoelectric elements are provided across a part of the vibrator between the one end and the corner portion.   4. The lens driving device according to claim 3, wherein the vibrator is a metal plate and serves as one electrode of each of the plurality of piezoelectric elements.   2. The lens driving device according to claim 1, wherein a part of the one end side of the vibrator is formed to be narrower than a part excluding the part.

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