JP2008178173A - Actuator, optical scanner, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator, which can efficiently perform the action detection of a movable board and the rotational drive, using a piezoelectric element while achieving downsizing, an optical scanner, and an image forming apparatus. <P>SOLUTION: The actuator has a pair of piezoelectric elements 51 and 52 (a pair of piezoelectric elements 53 and 54), a voltage application means 6 which applies voltage to the pair of piezoelectric elements 51 and 52 alternately and cyclically, an action detection means 7 which detects the action of the movable plate, based on the electromotive force generated by the deformation in a state that the voltage of the piezoelectric elements 51 and 52 is not applied, and a controller 8 which controls the action of the voltage application means 6, based on the detection results of the action detection means 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an actuator, an optical scanner, and an image forming apparatus.

For example, as an optical scanner for performing drawing by optical scanning with a laser printer or the like, an optical scanner using an actuator composed of a torsional vibrator is known (for example, see Patent Document 1).
Patent Document 1 discloses an actuator including a reflection mirror, a fixed frame portion for supporting the reflection mirror, and a pair of spring portions that rotatably connect the reflection mirror to the fixed frame portion. Yes. And each such spring part has comprised the structure branched into two on the way. Specifically, each spring part has a connection body, a first spring part that connects the reflection mirror and the connection body, and a second spring part that connects the fixed frame part and the connection body. . Furthermore, the second spring portion is composed of a pair of elastic bodies provided so as to face each other with respect to the rotation center axis of the reflection mirror.

  A piezoelectric element is joined to each second spring portion, and this piezoelectric element expands and contracts in the longitudinal direction of each second spring portion. Such a piezoelectric element is formed so as to cover the entire area of the second spring part to which it is joined in plan view, and the entire area of the surface on the second spring part side of each piezoelectric element is It is joined to the second spring part. Then, the actuator applies a voltage to the piezoelectric element and expands and contracts the piezoelectric element to bend and deform each second spring part, and torsionally deform the first spring part accordingly, Rotate to reflect and scan light. Thereby, drawing can be performed by optical scanning.

  In general, such an actuator is configured to detect a behavior (for example, a rotation angle) of a reflecting mirror and apply a voltage to the piezoelectric element based on the detection result. However, in the actuator of Patent Document 1, the piezoelectric element joined to each second spring portion is used only as a drive source for rotating the reflection mirror. Therefore, in order to detect the behavior of the reflection mirror, it is necessary to provide a behavior detection means (for example, a photodiode) that detects the behavior of the reflection mirror, separately from the piezoelectric element. This leads to an increase in the size of the actuator, a reduction in design freedom, and an increase in cost.

JP 2004-191953 A

  An object of the present invention is to provide an actuator, an optical scanner, and an image forming apparatus capable of efficiently performing behavior detection and rotational driving of a movable plate using a piezoelectric element while achieving downsizing.

Such an object is achieved by the present invention described below.
The actuator of the present invention includes a movable plate,
A support portion for supporting the movable plate;
A connecting portion that connects the movable plate and the support portion so that the movable plate is rotatable with respect to the support portion;
Each of the connecting portions includes a pair of longitudinal elastic members provided so as to face each other via the rotation center axis of the movable plate, and the pair of elastic members are bent and deformed in opposite directions to each other. An actuator configured to rotate the movable plate,
A pair of piezoelectric elements provided to correspond to each of the pair of elastic members;
Voltage application means for alternately and periodically applying a voltage to the pair of piezoelectric elements;
And a behavior detecting means for detecting the behavior of the movable plate based on an electromotive force generated by deformation of each piezoelectric element in a state where the voltage is not applied.
As a result, it is possible to provide an actuator capable of efficiently performing behavior detection and rotational driving of the movable plate using the pair of piezoelectric elements while reducing the size and power consumption.

In the actuator of the present invention, the behavior detection means includes an electromotive force detection unit that detects an electromotive force generated by deformation of the piezoelectric element, and the behavior of the movable plate based on the electromotive force detected by the electromotive force detection unit. It is preferable to have an analysis unit that analyzes the above and a switching unit that cuts off the input of electromotive force from the piezoelectric element to the electromotive force detection unit when necessary.
Thereby, the behavior of the movable plate can be detected with a simple configuration.

In the actuator according to the aspect of the invention, the switching unit may be configured to block the input of the electromotive force generated by deformation of one piezoelectric element of the pair of piezoelectric elements to the electromotive force detection unit, and the other piezoelectric element. It is preferable that the timing at which the input of the electromotive force generated by the deformation starts to the electromotive force detection unit substantially coincides.
Thereby, the electromotive force detection part can detect the electromotive force generated by the deformation of any one of the pair of piezoelectric elements over the entire driving time of the actuator. Therefore, the behavior of the movable plate can be detected very accurately.

In the actuator of the present invention, the voltage applying means includes a voltage waveform generating unit that generates a desired voltage waveform, and a driver that applies a voltage corresponding to the voltage waveform generated by the voltage waveform generating unit to each piezoelectric element. It is preferable to have.
Accordingly, a desired voltage can be applied to the pair of piezoelectric elements with a simple configuration.
In the actuator according to the aspect of the invention, the driver may include a period between the end of voltage application to one piezoelectric element of the pair of piezoelectric elements and a start time of voltage application to the other piezoelectric element, and the other A voltage is alternately applied to the pair of piezoelectric elements by providing a predetermined time interval between the end of voltage application to one of the piezoelectric elements and the start of voltage application to the one piezoelectric element. Is preferred.
Thereby, the said movable plate can be smoothly rotated, aiming at power saving.

The actuator of the present invention preferably includes a control unit that controls the operation of the voltage application unit based on the detection result of the behavior detection unit.
Thereby, since the said voltage application means can be operated based on the detection result of the said behavior detection means, the behavior of the said movable plate can be made into a desired thing. That is, an actuator capable of exhibiting desired vibration characteristics can be provided.

In the actuator according to the aspect of the invention, it is preferable that the piezoelectric element is bonded to the elastic members along the longitudinal direction thereof and expands and contracts in the longitudinal direction of the elastic members to bend and deform the elastic members.
In the actuator according to the aspect of the invention, it is preferable that the piezoelectric element is provided so as to be in contact with each elastic member and bend and deform each elastic member by expanding and contracting in the thickness direction of the movable plate.
In the actuator according to the aspect of the invention, it is preferable that the movable plate includes a light reflecting portion having light reflectivity on the plate surface.
Thereby, an actuator can be used for optical devices, such as an optical scanner.

The optical scanner of the present invention includes a movable plate including a light reflecting portion having light reflectivity,
A support portion for supporting the movable plate;
A connecting portion that connects the movable plate and the support portion so that the movable plate is rotatable with respect to the support portion;
Each of the connecting portions includes a pair of longitudinal elastic members provided so as to face each other via the rotation center axis of the movable plate, and the pair of elastic members are bent and deformed in opposite directions to each other. An optical scanner configured to scan the light reflected by the light reflecting portion by rotating the movable plate.
A pair of piezoelectric elements provided to correspond to each of the pair of elastic members;
Voltage application means for alternately and periodically applying a voltage to the pair of piezoelectric elements;
And a behavior detecting means for detecting the behavior of the movable plate based on an electromotive force generated by deformation of each piezoelectric element in a state where the voltage is not applied.
Accordingly, it is possible to provide an optical scanner capable of efficiently detecting the behavior of the movable plate and rotationally driving it using the pair of piezoelectric elements while reducing the size and power consumption.

An image forming apparatus of the present invention includes a movable plate including a light reflecting portion having light reflectivity,
A support portion for supporting the movable plate;
A connecting portion that connects the movable plate and the support portion so that the movable plate is rotatable with respect to the support portion;
Each of the connecting portions includes a pair of longitudinal elastic members provided so as to face each other via the rotation center axis of the movable plate, and the pair of elastic members are bent and deformed in opposite directions to each other. An image forming apparatus including an optical scanner configured to rotate the movable plate, scan the light reflected by the light reflecting portion, and form an image on an object,
A pair of piezoelectric elements provided to correspond to each of the pair of elastic members;
Voltage application means for alternately and periodically applying a voltage to the pair of piezoelectric elements;
And a behavior detecting means for detecting the behavior of the movable plate based on an electromotive force generated by deformation of each piezoelectric element in a state where the voltage is not applied.
As a result, an optical scanner capable of efficiently performing behavior detection and rotational driving of the movable plate using the pair of piezoelectric elements while achieving miniaturization and power saving is excellent. Therefore, it is possible to provide an image forming apparatus that can exhibit the drawing characteristics.

Hereinafter, preferred embodiments of an actuator, an optical scanner, and an image forming apparatus of the present invention will be described with reference to the accompanying drawings.
<First Embodiment>
First, a first embodiment of the actuator of the present invention will be described.
FIG. 1 is a perspective view showing a first embodiment of the actuator of the present invention, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 is a block diagram illustrating driving and behavior detection of the actuator shown in FIG. FIGS. 4 and 4 are timing charts showing the drive of the actuator shown in FIG. 1, and FIG. 5 is a cross-sectional view taken along the line BB in FIG. 1, illustrating the rotation of the actuator.
In the following, for convenience of explanation, the front side of the paper in FIG. 1 is referred to as “up”, the back side of the paper is referred to as “down”, the right side is referred to as “right”, and the left side is referred to as “left”. The upper side is called “upper”, the lower side is called “lower”, the right side is called “right”, and the left side is called “left”.

  The actuator 1 includes a base body 2 having a two-degree-of-freedom vibration system as shown in FIG. 1, a support substrate 3 that supports the base body 2 via a bonding layer 4, and a drive source for driving the two-degree-of-freedom vibration system. And it has the piezoelectric elements 51-54 which function as a detection element for detecting the behavior of a two-degree-of-freedom vibration system. Further, as shown in FIG. 3, the actuator 1 detects the behavior of the two-degree-of-freedom vibration system based on the voltage applying means 6 for applying a voltage to the piezoelectric elements 51 to 54 and the electromotive force generated from the piezoelectric elements 51 to 54. And a control unit 8 that controls the operation of the voltage application unit 6 based on the detection result of the behavior detection unit 7. Hereinafter, these will be described in detail.

As shown in FIG. 1, the base 2 includes a movable plate 21, a support portion 22 for supporting the movable plate 21, and a pair of connecting portions 23 and 24 that connect the movable plate 21 and the support portion 22. I have.
The connecting portion 23 is a pair of a driving member 231 provided at a distance from the movable plate 21, a shaft member 232 that connects the driving member 231 and the movable plate 21, and a pair that connects the driving member 231 and the support portion 22. The elastic members 233 and 234 are provided.

Similarly, the connecting portion 24 connects the drive member 241 provided at a distance from the movable plate 21, the shaft member 242 that connects the drive member 241 and the movable plate 21, and the drive member 241 and the support portion 22. And a pair of elastic members 243 and 244.
That is, the base 2 includes the movable plate 21, shaft members 232 and 242, drive members 231 and 241, elastic members 233, 234, 243, and 244, and a support portion 22. Hereinafter, these will be sequentially described.

The movable plate 21 has a plate shape. A light reflecting portion 211 having light reflectivity is provided on the upper surface of the movable plate 21. Driving members 231 and 241 are provided so as to face each other through the movable plate 21 in a plan view when the movable plate 21 is not driven (hereinafter, simply referred to as a “plan view of the movable plate 21”). ing.
The pair of drive members 231 and 241 are provided so as to be symmetric with respect to the movable plate 21 in plan view of the movable plate. In addition, the pair of drive members 231 and 241 have the same size and the same shape, and each has a plate shape. However, the shape of the drive members 231 and 241 is not limited to this, and may be, for example, a rod shape. Further, the pair of driving members 231 and 241 may not have the same shape.
Such a drive member 231 is connected to the movable plate 21 via the shaft member 232, and is connected to the support portion 22 via a pair of elastic members 233 and 244. Similarly, the drive member 241 is connected to the movable plate 21 via the shaft member 242 and is connected to the support portion 22 via a pair of elastic members 243 and 244.

  Each of the shaft members 232 and 242 has a longitudinal shape and is elastically deformable. The shaft member 232 connects the movable plate 21 and the drive member 231 so that the movable plate 21 can be rotated with respect to the drive member 231. Similarly, the shaft member 242 connects the movable plate 21 and the drive member 241 so that the movable plate 21 can rotate with respect to the drive member 241. The pair of shaft members 232 and 242 are provided coaxially with each other, and the movable plate 21 is connected to the drive members 231 and 241 around this shaft (hereinafter referred to as “rotation center axis X”). It rotates with respect to it.

Each of the elastic members 233, 234, 243, 244 has a longitudinal shape and can be elastically deformed. Such elastic members 233, 234, 243, 244 are provided so as to extend in directions parallel to the rotation center axis X, respectively. Further, the elastic members 233, 234, 243, 244 have the same size and the same shape.
Among these, the pair of elastic members 233 and 234 are provided symmetrically with respect to the rotation center axis X so as to face each other via the rotation center axis X in a plan view of the movable plate 21. It has been. Similarly, the pair of elastic members 243 and 244 are provided symmetrically with respect to the rotation center axis X so as to face each other via the rotation center axis X in a plan view of the movable plate 21. It has been.

The piezoelectric element 51 is bonded to the upper surface of the elastic member 233. Similarly, the piezoelectric element 52 is bonded to the upper surface of the elastic member 234, the piezoelectric element 53 is bonded to the upper surface of the elastic member 243, and the piezoelectric element 54 is bonded to the upper surface of the elastic member 244, respectively. The piezoelectric elements 51 to 54 will be described in detail later.
The support portion 22 has a frame shape and surrounds the outer periphery of the movable plate 21, the shaft members 232 and 242, the drive members 231 and 241, and the elastic members 233, 234, 243, and 244 in a plan view of the movable plate 21. Is provided. However, the shape of the support portion 22 is not limited to this as long as the movable plate 21 can be supported.

  The base 2 as described above is composed of, for example, silicon as a main material, and includes a movable plate 21, shaft members 232 and 242, drive members 231 and 241, elastic members 233, 234, 243 and 244, The support portion 22 is integrally formed. By using silicon as a main material, it is possible to realize excellent rotation characteristics and to exhibit excellent durability. Further, fine processing (processing) is possible, and the actuator 1 can be miniaturized.

  The base 2 is formed from a substrate having a laminated structure such as an SOI substrate, the movable plate 21, shaft members 232 and 242, drive members 231 and 241, elastic members 233, 234, 243, 244, and support unit 22. May be formed. At that time, the movable plate 21, the shaft members 232 and 242, the drive members 231 and 241, the elastic members 233, 234, 243 and 244 and the support portion 22 are integrated with each other so as to be integrated. It is preferable to be composed of one layer.

The base 2 as described above is bonded to the support substrate 3 via the bonding layer 4.
Such a support substrate 3 is made of, for example, glass or silicon as a main material. The support substrate 3 has a frame shape and has substantially the same shape as the support portion 22 in a plan view of the movable plate 21. The shape of the support substrate 3 is not particularly limited, and may be, for example, a shape divided into left and right as shown in FIG. 1. The shape is not a frame shape, and a recess is formed on the upper surface of the support substrate 3. (That is, the support substrate 3 may not be opened on the lower surface thereof). Further, the support substrate 3 may be omitted depending on the shape of the support portion 22 and the like.
The bonding layer 4 formed between the support substrate 3 and the base 2 is made of, for example, glass, silicon, or SiO ₂ as a main material. However, such a bonding layer 4 may be omitted. That is, the base 2 and the support substrate 3 may be directly joined.

Next, driving means and behavior detecting means of the actuator 1 will be described.
As shown in FIG. 3, the actuator 1 is a voltage application means 6 that applies a voltage to the piezoelectric elements 51 to 54, and a behavior that detects the behavior of the movable plate 21 based on the electromotive force generated by the deformation of the piezoelectric elements 51 to 54. A detection unit 7 and a control unit 8 that controls the operation of the voltage application unit 6 based on the detection result of the behavior detection unit 7 are provided. Each of (a) to (f) in FIG. 3 corresponds to the waveforms (signals) of (a) to (f) in FIG.
First, the piezoelectric elements 51 to 54 will be described. Since the piezoelectric elements 51 to 54 have the same configuration, the piezoelectric element 51 will be described as a representative, and the piezoelectric elements 52 to 54 will be described. Is omitted.

The piezoelectric element 51 is joined to the elastic member 233 so as to cover the entire upper surface of the elastic member 233 and to straddle the boundary between the elastic member 233 and the support portion 22. The piezoelectric element 51 expands and contracts in the longitudinal direction of the elastic member 233 when energized.
As shown in FIG. 2, such a piezoelectric element 51 includes a piezoelectric layer 511 composed of a piezoelectric material as a main material, and a pair of electrodes 512 and 513 that sandwich the piezoelectric layer 511. Yes.

  Examples of the piezoelectric material for forming the piezoelectric layer 511 include zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate (PZT), barium titanate, and other various types. Of these, one or more of these can be used in combination, but in particular, zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate and lead zirconate titanate Of these, those mainly comprising at least one of them are preferred. By configuring the piezoelectric layer 511 with such a material, the actuator 1 can be driven at a higher frequency.

The electrode 512 is formed so as to cover the entire area of the lower surface of the piezoelectric layer 511 and to be partially exposed on the support portion 22.
On the other hand, the electrode 513 is formed so as to cover the entire upper surface of the piezoelectric layer 511. And the electrode 513 is connected to the terminal (not shown) provided in the support part 22 via the wiring formed, for example by wire bonding.

A material for forming the electrodes 512 and 513 and the terminal is not particularly limited as long as it has conductivity.
Such a piezoelectric element 51 is expanded in the expansion / contraction direction (that is, the polarization direction) by an external force to generate one voltage (electromotive force) of a positive voltage and a negative voltage and contracts in the expansion / contraction direction. Thus, the other voltage of the positive voltage and the negative voltage is generated.

The piezoelectric element 51 as described above may be directly formed on the elastic member 233 by using a thin film forming method such as CVD, sputtering, hydrothermal synthesis, sol-gel, or fine particle spraying, or the elastic member 233 ( A piezoelectric element (for example, a bulk piezoelectric element) manufactured separately from the base body 2) may be bonded onto the elastic member 233 via a resin material (adhesive) or the like.
However, the configuration of the piezoelectric element 51 is not limited to this as long as it can expand and contract in the longitudinal direction of the elastic member 233. The terminal may not be formed on the support portion 22 or may be omitted.
Each of such piezoelectric elements 51 to 54 is connected to the voltage applying means 6 and the behavior detecting means 7.

  The voltage applying means 6 applies a voltage to the piezoelectric element 51 to bend and deform the elastic member 233 in the thickness direction of the movable plate 21, and applies a voltage to the piezoelectric element 52 to cause the elastic member 234 to move to the movable plate 21. The elastic member 243 is bent and deformed in the thickness direction of the movable plate 21 by applying a voltage to the piezoelectric element 53 by bending and deforming in the thickness direction, and the elastic member 244 is moved by applying a voltage to the piezoelectric element 54. 21 is configured to bend and deform in the thickness direction.

  As shown in FIG. 3, the voltage application means 6 is controlled in operation by the control unit 8, and a voltage waveform generation unit 61 that generates a waveform of a voltage applied to the piezoelectric elements 51 to 54, and an output from the voltage waveform generation unit 61. D / A converters 62 to 65 that convert the signal of the voltage waveform thus converted into an analog signal, a driver 66 that applies a voltage corresponding to the analog signal converted by the D / A converter 62 to the piezoelectric element 51, and D A driver 67 that applies a voltage corresponding to the analog signal converted by the / A converter 63 to the piezoelectric element 52 and a driver that applies a voltage corresponding to the analog signal converted by the D / A converter 64 to the piezoelectric element 53 68 and a driver 69 that applies a voltage corresponding to the analog signal converted by the D / A converter 65 to the piezoelectric element 54.

  Here, in the actuator 1, the voltage applied by the driver 66 to the piezoelectric element 51 and the voltage applied by the driver 68 to the piezoelectric element 53 are the same, and the voltage applied by the driver 67 to the piezoelectric element 52 and the driver 69 are the piezoelectric element. Since the voltages applied to 54 are the same, the drivers 66 and 67 will be described as a representative, and the descriptions of the drivers 68 and 69 will be omitted.

Each of the drivers 66 and 67 is driven based on, for example, a clock pulse transmitted from the control unit 8.
The driver 66 applies a voltage as shown in FIG. 4A to the piezoelectric element 51, for example. That is, the driver 66 applies a voltage to the piezoelectric element 51 intermittently and periodically. The voltage application time to the piezoelectric element 51 by the driver 66 is approximately ¼ of the rotation period of the movable plate 21 (that is, the voltage application period of the driver 66).
For example, the driver 67 applies a voltage as shown in FIG. 4D to the piezoelectric element 52. That is, the driver 67 applies a voltage to the piezoelectric element 52 intermittently and periodically. In addition, the voltage application time to the piezoelectric element 52 by the driver 67 is approximately ¼ of the rotation period of the movable plate 21 (that is, the voltage application period of the driver 67).

  As described above, the voltage applying unit 6 is configured to alternately apply a voltage to the piezoelectric elements 51 and 52 by the drivers 66 and 67. In addition, a predetermined time interval is provided between the end of voltage application to the piezoelectric element 51 by the driver 66 and the start of voltage application to the piezoelectric element 52 by the driver 67. This time interval is approximately ¼ of the rotation period of the movable plate 21. In addition, a predetermined time interval is provided between the end of voltage application to the piezoelectric element 52 by the driver 67 and the start of voltage application to the piezoelectric element 51 by the driver 66. This time interval is also substantially ¼ of the rotation period of the movable plate 21.

A voltage shown in FIG. 4A is applied to the piezoelectric elements 51 and 53 by the drivers 66 and 68, and a voltage shown in FIG. 4D is applied to the piezoelectric elements 52 and 54 by the drivers 67 and 69. Thereby, the actuator 1 is driven as follows. Note that the behavior (deformation) of the connecting portion 23 and the behavior of the connecting portion 24 during driving of the actuator 1 intersect with the center of the movable plate in a plan view of the movable plate 21 and are orthogonal to the rotation center axis X. For the convenience of explanation, the connecting portion 23 will be described as a representative, and the description of the connecting portion 24 will be omitted. For convenience of explanation, the start of voltage application to the piezoelectric element 51 by the driver 66 is “T ₁ ”, and the end of voltage application to the piezoelectric element 51 by the driver 66 is “T ₂ ”. The start of voltage application to the element 52 is “T ₃ ”, and the end of voltage application to the piezoelectric element 52 by the driver 67 is “T ₄ ”.

1. Between T _{1 and} T ₂ Between T _{1 and} T ₂ , a voltage is applied to the piezoelectric element 51, and no voltage is applied to the piezoelectric element 52. Accordingly, the piezoelectric element 51 expands in the longitudinal direction of the elastic member 233, and accordingly, the end portion on the drive member 231 side in the longitudinal direction of the elastic member 233 is displaced downward. That is, the elastic member 233 is bent and deformed downward.

On the other hand, the elastic member 234 displaces the end on the drive member 231 side in the longitudinal direction upward due to the reaction of the bending deformation of the elastic member 233. That is, the elastic member 234 is bent and deformed upward. At this time, the piezoelectric element 52 is deformed so as to contract in the longitudinal direction along with the bending deformation of the elastic member 234.
As a result, as shown in FIG. 5A, the drive member 231 tilts around the rotation center axis X and counterclockwise in FIG. By tilting the drive member 231, the shaft member 232 is twisted and deformed, and the movable plate 21 tilts about the rotation center axis X and counterclockwise in FIG. 5.

2. Between T _{2 and} T ₃ Between T _{2 and} T ₃ , no voltage is applied to each of the piezoelectric elements 51 and 52. Therefore, each of the elastic members 233 and 234 is displaced so as to return to a state where bending deformation does not occur (that is, a state where no external force is applied: a neutral state) due to its own elastic force (so-called springback). ). As a result, the drive member 231 is displaced so as to coincide with the position of the drive member 231 when the actuator 1 is not driven, as shown in FIG.

3. Between T _{3 and} T ₄ Between T _{3 and} T ₄ , no voltage is applied to the piezoelectric element 51, and a voltage is applied to the piezoelectric element 52. Accordingly, the piezoelectric element 52 expands in the longitudinal direction of the elastic member 234, and accordingly, the end of the elastic member 234 on the drive member 231 side is displaced downward. That is, the elastic member 234 is bent and deformed downward.

On the other hand, the elastic member 233 is displaced with the end on the drive member 231 side in the longitudinal direction upward due to the reaction of the bending deformation of the elastic member 234. At this time, the piezoelectric element 51 is deformed so as to contract in the longitudinal direction along with the bending deformation of the elastic member 233.
As a result, as shown in FIG. 5C, the drive member 231 tilts around the rotation center axis X and clockwise in FIG. By tilting the drive member 231, the shaft member 232 is twisted and deformed, and the movable plate 21 tilts around the rotation center axis X and clockwise in FIG. 5.

4). In between T ₄ between -T ₁ T ₄ -T _1, to each of the piezoelectric elements 51 and the piezoelectric element 52, no voltage is applied. Therefore, each of the elastic members 233 and 234 is displaced so as to return to a state where the bending deformation does not occur (neutral state) due to the elastic force of the elastic members 233 and 234. As a result, the drive member 231 is displaced so as to coincide with the position of the drive member 231 when the actuator 1 is not driven, as shown in FIG.

  The voltage application means 6 can rotate the movable plate 21 around the rotation center axis X by repeating the voltage application as described above by the drivers 66 and 67. Here, the actuator 1 has a first vibration system composed of elastic members 233 and 234 and a drive member 231, and a second vibration system composed of a shaft member 232 and the movable plate 21. It can be said that. That is, it can be said that the actuator 1 has a two-degree-of-freedom vibration system. Thereby, the rotation angle of the movable plate 21 can be increased.

Further, as described above, the time between T _{1 and} T _2, between T _{2 and} T _3, between T _{3 and} T _{4, and} between T _{4 and} T ₁ is approximately 1 / of the drive cycle of the movable plate 21. 4. Thereby, the movable plate 21 can be rotated extremely smoothly by effectively using the spring back by the elastic force of the elastic members 233 and 234. Moreover, since the voltage application time to the piezoelectric elements 51 and 52 can be shortened, power saving of the actuator 1 can be achieved. However, the voltage application (for example, waveform, application time, frequency) to the piezoelectric elements 51 and 52 by the drivers 66 and 67 is not particularly limited as long as the voltage can be alternately applied to the piezoelectric elements 51 and 52.

Next, the behavior detection means 7 will be described in detail.
As shown in FIG. 3, the behavior detection unit 7 includes an electromotive force detection unit 711 that detects an electromotive force generated by the deformation of the piezoelectric element 51, and a switching unit provided between the piezoelectric element 51 and the electromotive force detection unit 711. 73, an A / D converter 721 that converts the electromotive force detected by the electromotive force detector 711 into a digital signal, an electromotive force detector 712 that detects an electromotive force generated by deformation of the piezoelectric element 52, and the piezoelectric element 52 Is generated by deformation of the piezoelectric element 53, a switching unit 74 provided between the electromotive force detection unit 712, an A / D conversion unit 722 that converts the electromotive force detected by the electromotive force detection unit 712 into a digital signal, and the like. An electromotive force detection unit 713 for detecting an electromotive force, a switching unit 75 provided between the piezoelectric element 53 and the electromotive force detection unit 713, and an electromotive force detected by the electromotive force detection unit 713 are converted into a digital signal. A / D conversion 723, an electromotive force detection unit 714 for detecting an electromotive force generated by the deformation of the piezoelectric element 54, a switching unit 76 provided between the piezoelectric element 54 and the electromotive force detection unit 714, and an electromotive force detection unit 714. An A / D converter 724 that converts the electromotive force generated into a digital signal, and an analyzer 77 that analyzes the behavior of the movable plate 21 based on the digital signals input from each of the A / D converters 721 to 724. Have.

  Hereinafter, these will be sequentially described. However, the electromotive force generated by the deformation of the piezoelectric element 53 and the line for inputting the electromotive force generated by the deformation of the piezoelectric element 51 to the analysis unit 77 (that is, the switching unit 73, the electromotive force detection unit 711, and the A / D conversion unit 721). And the line for inputting the electromotive force generated by the deformation of the piezoelectric element 52 and the electromotive force generated by the deformation of the piezoelectric element 54 to the analyzing unit 77. Therefore, the line that inputs electromotive force generated by the deformation of the piezoelectric element 51 to the analyzing unit 77 and the line that inputs electromotive force generated by the deformation of the piezoelectric element 52 to the analyzing unit 77 are representative. The line for inputting the electromotive force generated by the deformation of the piezoelectric element 53 to the analysis unit 77 and the electromotive force generated by the deformation of the piezoelectric element 54 are input to the analysis unit 77. For the line, and a description thereof will be omitted.

The switching unit 73 includes a switch element 731 provided between the piezoelectric element 51 and the electromotive force detection unit 711, and a driver 732 that drives the switch element 731.
The switch element 731 can be switched between an ON state in which an electromotive force generated by deformation of the piezoelectric element 51 is input to the electromotive force detection unit 711 and an OFF state in which this input is blocked (blocked).

  The driver 732 operates to turn off the switch element 731 when a voltage is applied to the piezoelectric element 51 by the driver 66 of the voltage applying unit 6. Thereby, it is possible to prevent the electromotive force detection unit 711 from detecting noise generated when a voltage is applied to the piezoelectric element 51. Therefore, the electromotive force generated by the deformation of the piezoelectric element 51 can be detected more accurately by the electromotive force detection unit 711.

Such a driver 732 operates to switch between the ON state and the OFF state of the switch element 731 in synchronization with the driving of the driver 66 (that is, based on a clock pulse transmitted from the control unit 8).
Specifically, as shown in FIG. 4B, the driver 732 switches the switch element 731 from the OFF state to the ON state between T _{2 and} T ₃ (hereinafter, this switching time is referred to as “T _a ”). ), The switching element 731 is switched from the ON state to the OFF state between T _{4 and} T ₁ (hereinafter, this switching time is referred to as “T _b ”).

  When the driver 732 switches the ON / OFF state of the switch element 731 at such timing, the piezoelectric element 51 is not deformed by the electromotive force detection unit 711 (that is, substantially no electromotive force is generated). State) and a state where the deformation amount of the piezoelectric element 51 is maximized (that is, a state where the electromotive force is maximized), the electromotive force generated by the deformation of the piezoelectric element 51 can be detected. Thereby, the electromotive force detection unit 711 can detect from the rise of the electromotive force generated by the deformation of the piezoelectric element 51 until the electromotive force reaches the maximum value. Therefore, the behavior detection unit 7 can detect the behavior of the movable plate 21 more accurately.

Similarly, the switching unit 74 includes a switch element 741 provided between the piezoelectric element 52 and the electromotive force detection unit 712, and a driver 742 that drives the switch element 741.
The switch element 741 can switch between an ON state in which an electromotive force generated by deformation of the piezoelectric element 52 is input to the electromotive force detection unit 712 and an OFF state in which this input is blocked (blocked).

The driver 742 operates to turn off the switch element 741 when a voltage is applied to the piezoelectric element 52 by the driver 67 of the voltage applying means 6. Such a driver 742 operates to switch between the ON state and the OFF state of the switch element 741 in synchronization with the driving of the driver 67 (that is, based on the clock pulse transmitted from the control unit 8).
Specifically, the driver 742 is driven with a shift of 180 degrees with respect to the driving cycle of the driver 732. That is, the driver 742, as shown in FIG. 4 (e), switches the switch element 741 from the OFF state to the ON state at _{T b,} it switches the switch element 741 from the ON state to the OFF state at _{T a.}

  When the driver 742 switches the ON / OFF state of the switch element 741 at such timing, the state where the piezoelectric element 52 is not deformed and the amount of deformation of the piezoelectric element 51 is maximized by the electromotive force detection unit 712. And the electromotive force generated by the deformation of the piezoelectric element 52 can be detected. Thereby, the electromotive force detection unit 712 can detect from the rise of the electromotive force generated by the deformation of the piezoelectric element 52 until the electromotive force reaches the maximum value. Therefore, the behavior detection unit 7 can detect the behavior of the movable plate 21 more accurately.

As described above, the switch element 731, switches from the ON state at _{T b} in the OFF state, the switch element 741 is switched from the OFF state to the ON state at _{T b.} The switch element 731 is switched from the OFF state to the ON state at _{T a,} the switch element 741 is switched from the ON state to the OFF state at _{T a.}
That is, the time when the switch element 731 is turned off substantially coincides with the time when the switch element 741 is turned on, and when the switch section 741 is turned off and when the switch element 731 is turned on. Substantially matches. Thereby, the electromotive force detection units 711 and 712 can detect the electromotive force generated by the deformation of one of the piezoelectric elements 51 and 52 over the entire driving time of the actuator 1.

When the switch element 731 is in the ON state, an electromotive force generated by the deformation of the piezoelectric element 51 is input to the electromotive force detection unit 711. At this time, an analog signal as shown in FIG. 3C is input to the electromotive force detection unit 711.
The electromotive force detection unit 711 includes an amplifier circuit (not shown), and the amplifier circuit amplifies the analog signal shown in FIG. The amplified analog signal is input to the A / D converter 721 and converted into a digital signal. Such an A / D conversion method is not particularly limited, and an integration type, successive approximation type, pre-parallel type, ΔΣ type, or the like can be suitably used.

The digital signal converted by the A / D conversion unit 721 is input to the analysis unit 77. Such a digital signal is, for example, a signal of 4 bits, 8 bits, 16 bits, etc., and a multi-gradation signal corresponding to an analog signal.
On the other hand, when the switch element 741 is in the ON state, an electromotive force generated by the deformation of the piezoelectric element 52 is input to the electromotive force detection unit 712. At this time, an analog signal as shown in FIG. 3F is input to the electromotive force detection unit 712.

The electromotive force detection unit 712 includes an amplifier circuit (not shown), and the amplifier circuit amplifies the analog signal shown in FIG. The amplified analog signal is input to the A / D converter 722 and converted into a digital signal. Then, this digital signal is input to the analysis unit 77.
The analysis unit 77 analyzes the input digital signal and detects the behavior of the movable plate 21. Such an analysis unit 77 is, for example, based on a clock pulse transmitted by the control unit 8, an input digital signal generated from a signal output from the A / D conversion unit 721 (that is, generated by deformation of the piezoelectric element 51). Electromotive force) or a signal output from the A / D converter 722 (that is, an electromotive force generated by deformation of the piezoelectric element 52).

As a method for analyzing the behavior of the movable plate 21, the amount of deformation of the piezoelectric elements 51, 52 (in the thickness direction of the movable plate 21 is calculated by calculating the value of the electromotive force detected by the electromotive force detection units 711, 712. The displacement amount of the end of the piezoelectric elements 51 and 52 on the driving member 231 side) may be calculated, and the behavior of the movable plate 21 may be detected from the calculation result. For example, if an 8-bit digital output is used, it is determined which level the electromotive force detected by the electromotive force detection units 711 and 712 is higher and lower using a 256 level reference voltage. The behavior of the movable plate 21 can be analyzed from the determination result.
The behavior of the movable plate 21 detected as described above is input to the control unit 8.

The control unit 8 is configured to control the operation of the voltage waveform generation unit 61 of the voltage application unit 6 based on the behavior of the movable plate 21 detected by the behavior detection unit 7. That is, the control unit 8 is configured to perform feedback control.
The control unit 8 compares the behavior of the movable plate 21 detected by the behavior detecting means 7 with the desired behavior of the movable plate 21 and controls the operation of the voltage waveform generating unit 61 based on the error, thereby controlling the piezoelectric element. The voltage applied to each of 51 to 54 is adjusted.

  For example, when the driving frequency of the movable plate 21 is lower than the desired driving frequency, the control unit 8 causes the voltage waveform generating unit 61 to increase the frequency of the voltage applied to each of the piezoelectric elements 51 to 54. Control the operation of And the control part 8 keeps the frequency of the voltage applied to each of the piezoelectric elements 51-54 constant, when the drive frequency of the movable plate 21 detected by the behavior detection means 7 and desired drive frequency correspond. The operation of the voltage waveform generator 61 is controlled.

  For example, when the rotation angle of the movable plate 21 is smaller than the desired rotation angle, the control unit 8 increases the voltage value of the voltage applied to each of the piezoelectric elements 51 to 54. The operation of the voltage waveform generator 61 is controlled. And the control part 8 makes the voltage value of the voltage applied to each of the piezoelectric elements 51-54 constant when the rotation angle of the movable plate 21 detected by the behavior detection means 7 and the desired rotation angle coincide. The operation of the voltage waveform generator 61 is controlled so as to keep it.

  For example, when the rotation of the movable plate 21 is not symmetrical with respect to the rotation center axis X, the control unit 8 applies the voltage value of the voltage applied to the piezoelectric elements 51 and 53 and the piezoelectric elements 52 and 54. The operation of the voltage waveform generator 61 is controlled so as to increase or decrease one of the voltage values. Then, when the rotation of the movable plate 21 detected by the behavior detection means 7 is symmetric with respect to the rotation center axis X, the control unit 8 is a voltage waveform generation unit so as to keep the one voltage value constant. The operation of 61 is controlled.

Further, for example, the control unit 8 controls the operation of the voltage waveform generating unit 61 so as to deform the waveform of the voltage applied to each of the piezoelectric elements 51 to 54, or the piezoelectric elements 51 to 51 with respect to the driving cycle of the movable plate 21. It is also possible to control the operation of the voltage application generator 61 so as to change the voltage application time of each of 54.
As described above, the control unit 8 controls the operation of the voltage waveform generation unit 61, so that the actuator 1 can exhibit desired rotation characteristics.

  The voltage waveform generator 61 receives a command (signal) as described above from the controller 8 and generates a voltage to be applied to each of the piezoelectric elements 51 to 54. The voltage signal applied to the piezoelectric element 51 is converted into an analog signal by the D / A converter 62 and then applied from the driver 66 to the piezoelectric element 51. Similarly, the voltage signal applied to the piezoelectric element 52 is converted into an analog signal by the D / A converter 63, and then applied from the driver 67 to the piezoelectric element 52. The voltage signal applied to the piezoelectric element 53 is After being converted into an analog signal by the D / A converter 64, a voltage signal applied to the piezoelectric element 53 from the driver 68 and applied to the piezoelectric element 54 is converted into an analog signal by the D / A converter 65. And applied to the piezoelectric element 54 from the driver 69.

  The actuator 1 includes the piezoelectric elements 51 to 54, the voltage applying unit 6, the behavior detecting unit 7, and the control unit 8 as described above, so that the rotation of the movable plate 21 can be performed using the piezoelectric elements 51 to 54. Each of the dynamic drive and the behavior detection of the movable plate 21 can be performed very efficiently. In addition, since the pair of piezoelectric elements 51 and 52 can rotate and move the movable plate 21 and detect the behavior of the movable plate 21, the actuator 1 can be reduced in size and power consumption. In addition, the manufacturing process can be simplified, the degree of design freedom can be improved, and the cost can be reduced.

Heretofore, the first embodiment of the actuator of the present invention has been described. In the present embodiment, the switching unit 73 includes the switch element 731 and the driver 732. However, the input of the electromotive force generated by the deformation of the piezoelectric element 51 to the electromotive force detection unit 711 may be blocked when necessary. If possible, it is not particularly limited.
Moreover, although this embodiment demonstrated what the switching part 73 was provided between the piezoelectric element 51 and the electromotive force detection part 711, it is not limited to this, For example, the electromotive force detection part 711 and A / It may be provided between the D conversion unit 721 and may be provided between the A / D conversion unit 721 and the analysis unit 77. Thus, even if the switching unit 73 is provided, the same effect as described above can be exhibited.

Second Embodiment
Next, a second embodiment of the actuator of the present invention will be described.
6 is a top view showing a second embodiment of the actuator of the present invention, FIG. 7 is a cross-sectional view taken along line AA in FIG. 6, and FIG. 8 is an enlarged view of a piezoelectric element included in the actuator shown in FIG. is there. For convenience of explanation, the upper side in FIG. 7 is referred to as “upper” and the lower side is referred to as “lower”.

Hereinafter, the actuator 1A of the second embodiment will be described focusing on the differences from the actuator 1 of the first embodiment described above, and the description of the same matters will be omitted.
The actuator 1A according to the second embodiment of the present invention is substantially the same as the actuator 1 of the first embodiment except that the configuration and arrangement of the piezoelectric elements 55 to 58 and the configuration of the support substrate 3 are different. The same reference numerals are given to the same components as those in the first embodiment described above.

As shown in FIG. 7, the support substrate 3 </ b> A is joined to the plate-like base 31 </ b> A and the upper surface of the base 31 </ b> A so as to coincide with the shape of the support portion 22 in a plan view of the movable plate 21. And a wall portion 32A.
And the piezoelectric element 55 is joined to the upper surface of such base 31A and the site | part which opposes the elastic member 233. FIG. Similarly, on the upper surface of the base 31 </ b> A, the piezoelectric element 56 is disposed at a portion facing the elastic member 234, the piezoelectric element 57 is disposed at a portion facing the elastic member 243, and the piezoelectric element is disposed at a portion facing the elastic member 244. The elements 58 are joined to each other.
Hereinafter, the piezoelectric elements 55 to 58 will be described. Since the piezoelectric elements 55 to 58 have the same configuration and arrangement, the piezoelectric element 55 will be representatively described, and the piezoelectric elements 56 to 58 will be described. Omitted.

The piezoelectric element 55 has a lower end surface in the thickness direction of the movable plate 21 (that is, a vertical direction in FIG. 7) joined to the base 31 </ b> A of the support substrate 3 </ b> A and an upper end surface in contact with the lower surface of the elastic member 233. Is provided. The piezoelectric element 55 expands and contracts in the thickness direction of the movable plate 21.
As shown in FIG. 8, the piezoelectric element 55 includes a plurality of piezoelectric layers 551 having piezoelectricity and a plurality of electrode layers 552 for applying a voltage to each piezoelectric layer 551 of the movable plate 21. They are stacked alternately in the thickness direction. That is, the piezoelectric element 55 is a stacked piezoelectric element that expands and contracts in the thickness direction of the movable plate 21. Such a piezoelectric element 55 can increase the amount of displacement while reducing the drive voltage.

  The plurality of piezoelectric layers 551 are formed such that the polarization directions of adjacent piezoelectric layers 551 are opposite to each other. That is, the polarization direction of the odd-numbered piezoelectric layers 551 from the base 31 </ b> A side among the plurality of piezoelectric layers 551 is opposite to the polarization direction of the even-numbered piezoelectric layers 551. Thereby, the displacement amount of the piezoelectric element 55 can be increased more reliably while reducing the drive voltage. In this specification, “polarization direction” means that there is an excess of positive charge near one surface of the piezoelectric layer and excess negative charge near the other surface when no electric field or stress is applied to the piezoelectric layer. The direction from the surface where the negative charge of the piezoelectric layer is excessively present to the surface where the positive charge is excessively present is said.

  Each electrode layer 552 is interposed between adjacent piezoelectric layers 551. A plurality of electrode layers 552 are formed such that two adjacent electrode layers 552 have an overlapping region (active region). Among the plurality of electrode layers 552, the odd-numbered electrode layers 552 from the support substrate 3 side are connected to the common electrodes 553 provided on the side surfaces of the piezoelectric elements 55, and the even-numbered electrode layers 552 from the support substrate 3 side. Is connected to a common electrode 554 provided on the surface of the piezoelectric element 55 opposite to the surface provided with the common electrode 553.

Then, by applying a voltage between the common electrode 553 and the common electrode 554, a voltage can be applied to each piezoelectric layer 551 in the overlapping region. As a result, each piezoelectric layer 551 expands and contracts in the thickness direction of the movable plate 21.
However, the structure of the piezoelectric element 55 is not particularly limited as long as it can expand and contract in the thickness direction of the movable plate 21. The common electrodes 553 and 554 may not be provided on the side surface of the piezoelectric element 55, and may be formed on the base 31A, for example.
According to the third embodiment, the same effect as that of the first embodiment can be exhibited.

The preferred embodiment of the actuator of the present invention has been described above. The actuators 1 and 1A as described above can be used in, for example, MEMS applied sensors such as an acceleration sensor and an angular velocity sensor, and optical devices such as an optical scanner, an optical switch, and an optical attenuator.
The optical scanner of the present invention has the same configuration as the actuator of the present invention. The embodiment of the optical scanner of the present invention is the same as that of the above-described embodiment, and detailed description thereof is omitted. Such an optical scanner can be suitably applied to an image forming apparatus such as a projector, a laser printer, an imaging display, a barcode reader, and a scanning confocal microscope. As a result, an image forming apparatus having excellent drawing characteristics can be provided.

Specifically, a projector 9 as shown in FIG. 9 will be described. For convenience of explanation, the longitudinal direction of the screen S is referred to as “lateral direction”, and the direction perpendicular to the longitudinal direction is referred to as “vertical direction”.
The projector 9 includes a light source device 91 that emits light such as a laser, a dichroic mirror 92, and a pair of optical scanners 93 and 94 of the present invention (for example, an optical scanner having the same configuration as the actuator 1). ing.
The light source device 91 includes a red light source device 911 that emits red light, a blue light source device 912 that emits blue light, and a green light source device 913 that emits green light.
The dichroic mirror 92 is an optical element that combines light emitted from each of the red light source device 911, the blue light source device 912, and the green light source device 913.

Such a projector 9 combines light emitted from each of the red light source device 911, the blue light source device 912, and the green light source device 913 based on image information from a host computer (not shown) by a dichroic mirror 92. The combined light is scanned by the optical scanners 93 and 94 to form a color image on the screen S.
Specifically, first, the light synthesized by the dichroic mirror 92 is scanned in the horizontal direction by the optical scanner 93 (main scanning). The light scanned in the horizontal direction is further scanned in the vertical direction by the optical scanner 94 (sub-scanning). Thereby, a two-dimensional color image can be formed on the screen S. By using the optical scanner of the present invention as the optical scanners 93 and 94, extremely excellent drawing characteristics can be exhibited.

Although the actuator, optical scanner, and image forming apparatus of the present invention have been described based on the illustrated embodiments, the present invention is not limited to this. For example, in the actuator, optical scanner, and image forming apparatus of the present invention, the configuration of each part can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration can be added.
In the above-described embodiment, the actuator has been described as having a structure that is substantially symmetrical about the movable plate 21, but may be asymmetrical.
In the above-described embodiment, the description has been given of the case where the pair of connecting portions support the movable plate from both sides (both-end support). However, the present invention is not limited to this. It may be configured to support (cantilever support).

It is a perspective view which shows 1st Embodiment of the actuator of this invention. It is the sectional view on the AA line in FIG. It is a block diagram explaining the voltage application means and behavior detection means with which the actuator shown in FIG. 1 is provided. It is a timing chart which shows the drive of the actuator shown in FIG. FIG. 2 is a cross-sectional view taken along line BB in FIG. 1 and is a view for explaining driving of an actuator. It is a top view which shows 2nd Embodiment of the actuator of this invention. It is the sectional view on the AA line in FIG. FIG. 8 is an enlarged partial cross-sectional view of a piezoelectric element included in the actuator shown in FIG. 7. It is the schematic of the image forming apparatus using the actuator of this invention.

Explanation of symbols

  1, 1A ... Actuator 2 ... Substrate 21 ... Movable plate 211 ... Light reflection part 22 ... Support part 23, 24 ... Connection parts 231, 241 ... Drive members 232, 242 ... Shaft member 233, 234, 243, 244 ... Elastic member 3, 3A ... Support substrate 31A ... Base 32A ... Wall part 4 ... Junction layers 51 to 58 ... Piezoelectric Element 511, 551 ... Piezoelectric layer 512, 513 ... Electrode 552 ... Electrode layer 553, 554 ... Common electrode 6 ... Voltage application means 61 ... Voltage waveform generator 62-65 ... D / A converter 66-69 Driver 7 Behavior detector 711-714 Electromotive force detector 721-724 A / D converter 73-76 Switching unit 731, 741 switch Element 732, 742 ... Driver 77 ... Analysis unit 8 ... Control unit 9 ... Projector 91 ... Light source device 911 ... Red light source device 912 ... Blue light source device 913 ... Green Light source device 92 ... Dichroic mirror 93, 94 Optical scanner S ... Screen X ... Center axis of rotation

Claims (11)

A movable plate,
A support portion for supporting the movable plate;
A connecting portion that connects the movable plate and the support portion so that the movable plate is rotatable with respect to the support portion;
Each of the connecting portions includes a pair of longitudinal elastic members provided so as to face each other via the rotation center axis of the movable plate, and the pair of elastic members are bent and deformed in opposite directions to each other. An actuator configured to rotate the movable plate,
A pair of piezoelectric elements provided to correspond to each of the pair of elastic members;
Voltage application means for alternately and periodically applying a voltage to the pair of piezoelectric elements;
An actuator comprising: behavior detecting means for detecting the behavior of the movable plate based on an electromotive force generated by deformation of each piezoelectric element in a state where the voltage is not applied.   The behavior detection means includes an electromotive force detection unit that detects an electromotive force generated by deformation of the piezoelectric element, and an analysis unit that analyzes the behavior of the movable plate based on the electromotive force detected by the electromotive force detection unit. 2. The actuator according to claim 1, further comprising: a switching unit configured to block an input of an electromotive force from the piezoelectric element to the electromotive force detection unit when necessary.   The switching unit is configured to block the input of the electromotive force generated by the deformation of one piezoelectric element of the pair of piezoelectric elements to the electromotive force detection unit and the electromotive force generated by the deformation of the other piezoelectric element. The actuator according to claim 2, wherein the actuator is configured to substantially coincide with a timing at which an input to the electromotive force detection unit is started.   The voltage application unit includes a voltage waveform generation unit that generates a desired voltage waveform, and a driver that applies a voltage corresponding to the voltage waveform generated by the voltage waveform generation unit to each piezoelectric element. The actuator according to any one of 1 to 3.   The driver is configured to apply a voltage between the end of voltage application to one of the pair of piezoelectric elements and the start of voltage application to the other piezoelectric element, and to the other piezoelectric element. 5. The actuator according to claim 4, wherein a voltage is alternately applied to the pair of piezoelectric elements by providing a predetermined time interval between the end of application and the start of voltage application to the one piezoelectric element. .   The actuator according to any one of claims 1 to 5, further comprising a control unit that controls the operation of the voltage application unit based on a detection result of the behavior detection unit.   7. The piezoelectric element according to claim 1, wherein the piezoelectric element is bonded to the elastic members along a longitudinal direction thereof and expands and contracts in the longitudinal direction of the elastic members, whereby the elastic members are bent and deformed. Actuator.   7. The piezoelectric element according to claim 1, wherein the piezoelectric element is provided so as to be in contact with each of the elastic members and expands and contracts in the thickness direction of the movable plate to cause the elastic members to bend and deform. Actuator.   The actuator according to any one of claims 1 to 8, wherein the movable plate includes a light reflecting portion having light reflectivity on a plate surface thereof. A movable plate including a light reflecting portion having light reflectivity;
A support portion for supporting the movable plate;
A connecting portion that connects the movable plate and the support portion so that the movable plate is rotatable with respect to the support portion;
Each of the connecting portions includes a pair of longitudinal elastic members provided so as to face each other via the rotation center axis of the movable plate, and the pair of elastic members are bent and deformed in opposite directions to each other. An optical scanner configured to scan the light reflected by the light reflecting portion by rotating the movable plate.
A pair of piezoelectric elements provided to correspond to each of the pair of elastic members;
Voltage application means for alternately and periodically applying a voltage to the pair of piezoelectric elements;
An optical scanner comprising behavior detecting means for detecting the behavior of the movable plate based on an electromotive force generated by deformation of each piezoelectric element in a state where the voltage is not applied. A movable plate including a light reflecting portion having light reflectivity;
A support portion for supporting the movable plate;
A connecting portion that connects the movable plate and the support portion so that the movable plate is rotatable with respect to the support portion;
Each of the connecting portions includes a pair of longitudinal elastic members provided so as to face each other via the rotation center axis of the movable plate, and the pair of elastic members are bent and deformed in opposite directions to each other. An image forming apparatus including an optical scanner configured to rotate the movable plate, scan the light reflected by the light reflecting portion, and form an image on an object,
A pair of piezoelectric elements provided to correspond to each of the pair of elastic members;
Voltage application means for alternately and periodically applying a voltage to the pair of piezoelectric elements;
An image forming apparatus comprising: a behavior detecting unit configured to detect a behavior of the movable plate based on an electromotive force generated by deformation of each piezoelectric element in a state where the voltage is not applied.

Images