JP4665877B2 - Actuator, optical scanner, and image forming apparatus - Google Patents

Description

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

In recent years, an actuator including a torsional vibrator formed by using a micromachining technique is known (for example, see Patent Document 1). Such an actuator can be used as, for example, an optical scanner for performing optical scanning such as a laser printer or a display.
For example, Patent Document 1 discloses an actuator including a one-degree-of-freedom vibration system torsional vibrator. Such an actuator has a structure in which a mirror (mass part) is supported by a torsion bar as a torsional vibrator of a one-degree-of-freedom vibration system. This structure is obtained by processing a Si single crystal substrate. An electrode is provided at a distance from the mirror. By applying a voltage (drive voltage) between the electrode and the mirror, an electrostatic attractive force is generated between them, and the torsion bar is twisted. Rotate the mirror while deforming.

  In such an actuator, a p-type diffused resistor is formed on the torsion bar. Then, while applying a voltage to the diffusion resistance, the voltage value at the diffusion resistance due to torsional deformation of the torsion bar is detected. Based on the detection result, the amount of change in the specific resistance value of the diffusion region is detected, and the rotation angle of the mirror is detected based on the result. By rotating the mirror based on such a detection result, the behavior of the mirror (for example, the rotation angle of the mirror and the frequency of vibration) can be made desired.

However, in the actuator according to Patent Document 1, since the diffusion resistance value changes due to the temperature change (particularly the temperature rise) of the diffusion resistance, it is difficult to accurately detect the behavior of the mass part. Such a temperature change is caused by, for example, heat generation of the mirror due to light that cannot be completely reflected by the mirror. Further, when a piezoelectric driving method is used as a driving method instead of the electrostatic driving method described above, the driving piezoelectric element generates heat, so that the temperature change as described above also occurs due to the heat.
Further, when forming the diffusion resistance as described above, if the formation position is slightly deviated from the set position, it is difficult for the obtained actuator to detect the behavior of the mass part with high accuracy. Therefore, since the formation of the diffused resistor requires high accuracy, a high-precision processing technique is required, and there is a problem that the cost of the actuator is increased.

JP-A-5-119280

  An object of the present invention is to provide an actuator, an optical scanner, and an image forming apparatus that can detect the behavior of a mass part with high accuracy without being affected by temperature change while reducing costs. .

Such an object is achieved by the present invention described below.
The actuator of the present invention includes a mass part,
A support part for supporting the mass part;
A connecting portion that includes at least one elastic portion that is elastically deformable, and rotatably connects the mass portion to the support portion;
Drive means for rotationally driving the mass part,
An actuator configured to rotate the mass portion while twisting and deforming the elastic portion of the connecting portion by the operation of the driving means,
Having a behavior detecting means for detecting the behavior of the mass part;
The behavior detection means includes a vibration detection element that detects vibration of a gas around the mass part as the mass part rotates, and detects the behavior of the mass part based on a detection result of the vibration detection element. It is comprised so that it may do.
Thereby, the behavior of the mass part can be detected with high accuracy without being affected by the temperature change. Such behavior detection means does not vary in detection accuracy depending on the mounting position of the vibration detection element. Therefore, the manufacturing process can be simplified and the cost of the actuator can be reduced.

In the actuator according to the aspect of the invention, it is preferable that the mass portion has a plate shape, and the vibration detection element is provided at a position not overlapping the mass portion in a plan view.
Thereby, the distance between a vibration detection element and a mass part can be made small, without a vibration detection element obstructing rotation of a mass part. Therefore, it is possible to increase the output signal of the vibration detection element and improve the detection accuracy of the mass part behavior detection.

In the actuator according to the aspect of the invention, the mass portion has a longitudinal shape extending in a direction perpendicular to the rotation center axis, and the vibration detection element has the mass portion in a plan view. It is preferable to face the end face in the longitudinal direction.
Thereby, the vibration which a vibration detection element receives can be enlarged. Therefore, it is possible to increase the output signal of the vibration detection element and improve the detection accuracy of the mass part behavior detection.

In the actuator according to the aspect of the invention, it is preferable that the mass portion is provided with a light reflecting portion having light reflectivity.
Thereby, the present invention can be applied to optical devices such as an optical scanner, an optical switch, and an optical attenuator.
In the actuator according to the aspect of the invention, it is preferable that the driving unit includes a piezoelectric element that generates a driving force for rotationally driving the mass unit.
Thereby, it is possible to increase the driving force while suppressing the driving voltage. The piezoelectric element generates heat as it is driven, but the behavior detecting means is not affected by temperature changes, so that the effect becomes remarkable when the present invention is applied to an actuator having such a driving means.

The actuator of the present invention preferably includes a housing that accommodates the mass portion, the connecting portion, and the vibration detection element.
Thereby, the vibration detection element can detect the vibration of the gas accompanying the rotation of the mass part without being influenced by the outside of the actuator. As a result, the detection accuracy of the behavior detection of the mass part can be improved.

In the actuator according to the aspect of the invention, it is preferable that a vibration absorbing portion that absorbs vibration of the gas is provided on the inner wall of the housing.
Thereby, it is possible to prevent the vibration (sound wave) of the gas from being reflected on the inner wall surface of the housing and affecting the vibration detecting element. As a result, the detection accuracy of the behavior detection of the mass part can be improved.

In the actuator of the present invention, it is preferable that the inside of the housing is an airtight space.
Thereby, the density of the gas in the housing can be kept constant. As a result, the mass portion can be stably rotated, and unintentional fluctuations in the detection result of the vibration detection element can be prevented.
In the actuator according to the aspect of the invention, it is preferable that the vibration detection element is supported by the housing.
Thereby, the influence of the vibration of mass part itself with respect to a vibration detection element can be prevented.

The actuator of the present invention preferably includes a blocking member that blocks transmission of vibration from the housing to the vibration detection element.
Thereby, the influence of the vibration of the mass part itself on the vibration detection element can be prevented more reliably.
In the actuator according to the aspect of the invention, it is preferable that the behavior detection unit is configured to detect the frequency of the mass unit based on a detection result of the vibration detection element.
Thereby, the frequency of the mass part can be detected with high accuracy.

In the actuator according to the aspect of the invention, it is preferable that the behavior detection unit includes an arithmetic circuit that obtains 1/2 of the vibration frequency detected by the vibration detection element as the rotation frequency of the mass unit.
Thereby, the frequency of the mass part can be detected with high accuracy.
In the actuator of the present invention, the arithmetic circuit outputs a high signal when the output value of the vibration detection element is equal to or higher than a set value, and outputs a low signal when the output value of the vibration detection element is equal to or lower than the setting. A rectangular wave generating circuit to output, a flip-flop circuit that alternately outputs a high signal and a low signal at a timing when the output of the rectangular wave generating circuit switches from a low signal to a high signal, and a pulse is transmitted at regular intervals. A pulse transmission circuit; and a count circuit that calculates the frequency of rotation of the mass portion by counting the number of pulses of the pulse transmission circuit when the output of the flip-flop circuit is a high signal. Is preferred.
Thereby, the frequency of the mass part can be detected with high accuracy with a relatively simple configuration.

The optical scanner of the present invention includes a mass part including a light reflecting part having light reflectivity,
A support part for supporting the mass part;
A connecting portion that includes an elastically deformable elastic portion and rotatably connects the mass portion to the support portion;
Drive means for rotationally driving the mass part,
An optical scanner configured to scan the light reflected by the light reflecting portion by rotating the mass portion while twisting and deforming the elastic portion of the connecting portion by the operation of the driving means,
Having a behavior detecting means for detecting the behavior of the mass part;
The behavior detection means includes a vibration detection element that detects vibration of a gas around the mass part as the mass part rotates, and detects the behavior of the mass part based on a detection result of the vibration detection element. It is comprised so that it may do.
As a result, even if a temperature change occurs in the mass part due to the heat that cannot be completely reflected by the light reflecting part, the behavior of the mass part is detected with high accuracy, and the mass part is driven based on the detection result. Scanning can be performed within a desired range.

An image forming apparatus according to the present invention includes a mass part including a light reflecting part having light reflectivity,
A support part for supporting the mass part;
A connecting portion that includes an elastically deformable elastic portion and rotatably connects the mass portion to the support portion;
Drive means for rotationally driving the mass part,
An optical scanner configured to scan the light reflected by the light reflecting portion by rotating the mass portion while twisting and deforming the elastic portion of the connecting portion by the operation of the driving means, An image forming apparatus in which an optical scanner forms an image by performing main scanning or sub-scanning of light,
Having a behavior detecting means for detecting the behavior of the mass part;
The behavior detection means includes a vibration detection element that detects vibration of a gas around the mass part as the mass part rotates, and detects the behavior of the mass part based on a detection result of the vibration detection element. It is comprised so that it may do.
Thereby, it is possible to obtain an excellent image by performing optical scanning in a desired range.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an actuator of the invention will be described with reference to the accompanying drawings.
1 is a plan view showing an embodiment of the actuator of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a block diagram showing a configuration of a control system of the actuator shown in FIG. 4 is a diagram showing an example of the drive voltage of the actuator shown in FIG. 1, FIG. 5 is a timing chart for explaining the behavior detection of the actuator shown in FIG. 1, and FIG. It is a graph which shows the relationship with each amplitude of a mass part and a 2nd mass part. In the following, for convenience of explanation, the front side of the paper in FIG. 1 is called “up”, the back side of the paper is called “down”, the right side is called “right”, the left side is called “left”, and the upper side in FIG. The upper side, the lower side is called “lower”, the right side is called “right”, and the left side is called “left”.

  As shown in FIGS. 1 and 2, the actuator 1 includes a base body 2 having a two-degree-of-freedom vibration system, and piezoelectric elements 31, 32, 33, 34 for driving the two-degree-of-freedom vibration system of the base body 2, It has a support substrate 4 that supports the base 2 via a bonding layer 5, a housing 7 that accommodates them, and a vibration detection element 8 that detects the vibration of gas in the housing 2. The base body 2, the support substrate 4, and the bonding layer 5 may be integrally formed.

The base body 2 includes a pair of first mass units (drive units) 21 and 22, a pair of support units 23 and 24, a second mass unit (movable unit) 25, and a pair of first elastic members. Parts 26 and 27 and a pair of second elastic parts 28 and 29.
Here, the second mass portion 25 is a mass portion, and the first elastic portion 26 and the second elastic portion 28 are elastic portions that can be elastically deformed, and these and the first mass portion 21 are supported. The connection part which connects the 2nd mass part 25 with respect to the part 23 so that rotation is possible is comprised. The first elastic portion 27 and the second elastic portion 29 are also elastic portions that can be elastically deformed, and these and the first mass portion 22 rotate the second mass portion 25 with respect to the support portion 24. The connection part connected so that movement is possible is comprised.

In such a base body 2, the second mass part 25 is centered on the left side of the second mass part 25 so as to have a symmetrical shape, and the second elastic part 28, the first mass part 21, and the support part are located on the left side. 23 is sequentially arranged, and on the right side, the second elastic portion 29, the first mass portion 22, and the support portion 24 are sequentially arranged.
The pair of first mass portions 21 and 22 each have a plate shape, and have substantially the same dimensions and the same shape.

In addition, a second mass unit 25 is provided between the pair of mass units 21 and 22, and the pair of mass units 21 and 22 are substantially bilaterally symmetric about the second mass unit 25. It is provided to become.
The second mass unit 25 has a plate shape, and a light reflection unit 251 is provided on the plate surface. Thereby, the actuator 1 can be applied to optical devices such as an optical scanner, an optical attenuator, and an optical switch.

In such first mass parts 21, 22 and second mass part 25, the first mass parts 21, 22 are connected to the support parts 23, 24 via the first elastic parts 26, 27. The second mass portion 25 is connected to the first mass portions 21 and 22 via the second elastic portions 28 and 29.
The first elastic portion 26 connects the first mass portion 21 and the support portion 23 so that the first mass portion 21 can be rotated with respect to the support portion 23. Similarly, the first elastic portion 27 connects the first mass portion 22 and the support portion 24 so that the first mass portion 22 can be rotated with respect to the support portion 24. .

In particular, the first elastic portion 26 includes two rod-like connecting members 261 and 262 that are opposed to each other via the rotation center axis of the first mass portion 21. Similarly, the first elastic portion 27 includes two rod-like connecting members 271 and 272 that are opposed to each other via the rotation center axis of the first mass portion 22.
The second elastic portion 28 connects the second mass portion 25 and the first mass portion 21 so that the second mass portion 25 can be rotated with respect to the first mass portion 21. Yes. Similarly, the second elastic portion 29 is configured so that the second mass portion 25 and the first mass portion 22 are configured so that the second mass portion 25 can be rotated with respect to the first mass portion 22. Are linked.

The first elastic portions 26 and 27 and the second elastic portions 28 and 29 are provided coaxially, and the first mass portions 21 and 22 are provided with the rotation central axis (rotation axis) as a rotation center axis. The second mass unit 25 is rotatable with respect to the support units 23 and 24 and the first mass units 21 and 22.
As described above, the base 2 includes the first vibration system including the first mass parts 21 and 22 and the first elastic parts 26 and 27, the second mass part 25, and the second elastic part 28. , 29 and a second vibration system. That is, the base body 2 has a two-degree-of-freedom vibration system including a first vibration system and a second vibration system.

The base body 2 having such a two-degree-of-freedom vibration system is made of, for example, silicon as a main material, and includes a first mass unit 21, 22, a second mass unit 25, and support units 23 and 24. The first elastic portions 26 and 27 and the second elastic portions 28 and 29 are integrally formed.
And in order to drive such a two-degree-of-freedom vibration system, on the rod-like connecting members 261, 262, 271, 272 of the first elastic portions 26, 27, piezoelectric elements 31, 32 corresponding to these are provided. , 33 and 34 are provided.

  The piezoelectric element 31 is joined to the upper surface of the rod-like connecting member 261 and is configured to expand and contract in the longitudinal direction of the rod-like connecting member 261. Thereby, the piezoelectric element 31 bends and deforms the rod-shaped connecting member 261 in the vertical direction by expansion and contraction thereof. The piezoelectric element 32 is joined to the upper surface of the rod-shaped connecting member 262 and is configured to expand and contract in the longitudinal direction of the rod-shaped connecting member 262. Thereby, the piezoelectric element 32 bends and deforms the rod-shaped connecting member 262 in the vertical direction by expansion and contraction thereof.

  In other words, the piezoelectric element 31 extends along the longitudinal direction of the rod-shaped connecting member 261 and expands and contracts in the extending direction to bend and deform the rod-shaped connecting member 261. As a result, the rod-shaped connecting member 261 can be bent and deformed by the piezoelectric element 31 more reliably with a relatively simple configuration. Similarly, the piezoelectric element 32 extends along the longitudinal direction of the rod-like connecting member 262, and expands and contracts in the extending direction to bend and deform the rod-like connecting member 262. As a result, the rod-shaped connecting member 262 can be bent and deformed by the piezoelectric element 32 more reliably with a relatively simple configuration.

  More specifically, the piezoelectric element 31 includes a piezoelectric layer 311 composed of a piezoelectric material as a main material, and a pair of electrodes 312 and 313 that sandwich the piezoelectric layer 311. The electrode 312 located on the lower side in FIG. 2 is joined to the upper surface of the rod-like connecting member 261. When the piezoelectric element 31 is configured as described above, the rod-shaped connecting member 261 can be bent and deformed by the piezoelectric element 31 with a relatively simple configuration.

The piezoelectric layer 311 covers the entire upper surface of the rod-shaped connecting member 261 and is provided so as to straddle the joint portion between the rod-shaped connecting member 261 and the support portion 23. Thereby, the driving force of the piezoelectric element 31 can be efficiently transmitted by the rod-shaped connecting member 261. As a result, the drive voltage can be further reduced, and the rod-like connecting member 261 can be bent and deformed more greatly.
Examples of the piezoelectric material include zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate (PZT), barium titanate, and various other materials. One or more of them can be used in combination, but at least one of zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate and lead zirconate titanate is mainly used. Are preferred. By configuring the piezoelectric layer 311 with such a material, the actuator 1 can be driven at a higher frequency.

  The electrode 312 is longer than the piezoelectric layer 311 and extends to the support portion 23. on the other hand. The electrode 313 has substantially the same length as that of the piezoelectric layer 311. And the electrode 313 is connected to the terminal 314 provided on the support part 23 through the wiring formed, for example by wire bonding. The power supply circuit 12 to be described later is connected to the electrode 312 and the terminal 314. Thereby, each piezoelectric element 31, 32, 33, 34 is connected to the power supply circuit 12, and an alternating voltage (driving voltage) is applied between the electrodes of each piezoelectric element 31, 32, 33, 34. Yes.

In such a piezoelectric element 31, when a voltage is applied between the electrode 312 and the electrode 313 (terminal 314), the piezoelectric layer 311 expands and contracts in parallel with the longitudinal direction of the rod-like connecting member 261 due to the piezoelectric effect. Thereby, the piezoelectric element 31 bends and deforms the rod-shaped connecting member 261 in the vertical direction by expansion and contraction thereof.
Similar to the piezoelectric element 31, the piezoelectric element 32 is configured, and when a voltage is applied between the electrode 322 and the terminal 324, a piezoelectric layer (not shown) in the piezoelectric element 32 becomes piezoelectric. Due to the effect, the rod-like connecting member 262 expands and contracts parallel to the longitudinal direction. Thereby, the piezoelectric element 32 bends and deforms the rod-shaped connecting member 262 in the vertical direction by expansion and contraction thereof.
Since such piezoelectric elements 31 and 32 are both provided on the upper surface of the base 2, the two rod-like connecting members 261 and 262 are bent and deformed in directions opposite to each other when operated to alternately expand and contract. Let As a result, the entire first elastic portion 26 composed of the two rod-like connecting members 261 and 262 is torsionally deformed.

Similarly to the piezoelectric elements 31 and 32 described above, the piezoelectric elements 33 and 34 are configured. That is, with respect to the piezoelectric element 33, when a voltage is applied between the electrode 332 and the electrode 333 (terminal 334), the piezoelectric layer 331 in the piezoelectric element 33 is parallel to the longitudinal direction of the rod-like connecting member 271 due to the piezoelectric effect. Extends and contracts. Thereby, the piezoelectric element 33 bends and deforms the rod-shaped connecting member 271 in the vertical direction by expansion and contraction thereof. Further, regarding the piezoelectric element 34, when a voltage is applied between the electrode 342 and the terminal 344, a piezoelectric layer (not shown) in the piezoelectric element 34 is parallel to the longitudinal direction of the rod-shaped connecting member 272 due to the piezoelectric effect. Extends and contracts. Thereby, the piezoelectric element 34 bends and deforms the rod-shaped connecting member 272 in the vertical direction by expansion and contraction thereof.
Since the piezoelectric elements 33 and 34 are provided on the upper surface of the base 2 in the same manner as the piezoelectric elements 31 and 32, the two rod-shaped connecting members 271 and 272 are moved in opposite directions when operated alternately. Bend and deform. As a result, the entire first elastic portion 27 composed of the two rod-like connecting members 271 and 272 is torsionally deformed.

The support substrate 4 for supporting the base 2 as described above is bonded to the base 2 via the bonding layer 5. The bonding layer 5 is made of, for example, glass, silicon, or SiO ₂ as a main material.
Further, the support substrate 4 is made of, for example, glass or silicon as a main material.
On the upper surface of the support substrate 4, an opening 41 is formed at a portion corresponding to the second mass portion 25 as shown in FIG. 2.

The opening 41 constitutes an escape portion that prevents contact with the support substrate 4 when the second mass portion 25 rotates (vibrates). By providing the opening (escape portion) 41, the deflection angle (amplitude) of the second mass portion 25 can be set larger while preventing the actuator 1 from being enlarged.
Note that the relief portion as described above is not necessarily opened (opened) on the lower surface (surface opposite to the second mass portion 25) of the support substrate 4 as long as the above-described effect can be sufficiently exerted. May be. In other words, the escape portion can be configured by a recess formed on the upper surface of the support substrate 4.

The housing 7 that houses the structure composed of the base 2, the piezoelectric elements 31 to 34, and the support substrate 4 as described above includes a side wall member 71 having a frame shape or a cylindrical shape, and an upper side of the side wall member 71. It has an upper wall member 72 provided so as to cover the opening, and a lower wall member 73 provided so as to cover the opening on the lower side of the side wall member 71.
The side wall member 71 has an internal space larger than the structure.
Although it does not specifically limit as a constituent material of the side wall member 71, For example, a metal, a silicon | silicone, glass etc. are used suitably.
An upper wall member 72 is joined to the upper side of the side wall member 71 so as to cover the opening.

In the present embodiment, the upper wall member 72 is airtightly joined to the side wall member 71.
Further, the upper wall member 72 is made of glass or the like and has optical transparency. Note that when the actuator 1 is used as a microresonator instead of an optical device, the constituent material of the upper wall member 72 is not particularly limited, and may be composed of, for example, silicon or metal.

On the other hand, a lower wall member 73 is joined to the lower side of the side wall member 71 so as to cover the opening.
In the present embodiment, the lower wall member 73 is airtightly joined to the side wall member 71. As described above, since the upper wall member 72 is also airtightly joined to the side wall member 71, the side wall member 71, the upper wall member 72, and the lower wall member 73 form an airtight space therebetween. That is, the housing space of the housing 7 is an airtight space.

  Gas is accommodated in such an airtight space, that is, the housing 7. This gas is not particularly limited, and may be air or an inert gas such as nitrogen or argon. If air is used as the gas in the housing 7, it is not necessary to manufacture the housing 7 in an airtight manner, and the cost of the actuator can be reduced because expensive gas is not used. Further, when an inert gas is used as the gas in the housing 7, the vibration characteristics of the vibration system of the base 2 can be improved, and deterioration of the vibration system can be prevented.

The constituent material of the lower wall member 73 is not particularly limited, but for example, glass, silicon, metal, or the like is preferably used.
On the upper surface of the lower wall member 73 of the housing 7, the structure including the base body 2 and the like described above is bonded with an adhesive or the like.
In addition, the vibration detection element 8 is bonded to the lower surface of the upper wall member 72 of the housing 7 with an adhesive or the like.

  The vibration detection element 8 has a function of detecting the vibration (sound wave) of the gas around the second mass unit 25 accompanying the rotation of the second mass unit 25 described above. In the present embodiment, the vibration detection element 8 is provided at a position that does not overlap the second mass unit 25 in a plan view of the plate-shaped second mass unit 25 (non-driven state). In addition, the vibration detection element 8 is in the vicinity of the second mass unit 25, and in the plan view of the second mass unit 25 in the non-driven state, the end surface in the longitudinal direction of the second mass unit 25 ( Facing the upper end surface).

Such a vibration detection element 8 is not particularly limited as long as it has the above-described function, but an element that converts sound waves into an electrical signal, that is, a microphone (microphone) can be preferably used.
The microphone is not particularly limited, and for example, a moving coil microphone, a ribbon microphone, a capacitor microphone, a carbon microphone, a piezoelectric microphone, or the like can be used. Further, the microphone is appropriately selected and designed according to the design of the actuator 1 (such as the frequency of rotation of the second mass unit 25).

As the microphone, any directional microphone such as omnidirectional, bidirectional, unidirectional, sharp directivity, and superdirectivity can be used. It is preferable to use a directional or super-directional microphone. Thereby, the detection accuracy of the vibration detection element 8 can be improved. In this case, the microphone is preferably provided so that the diaphragm (diaphragm) faces the second mass unit 25.
Since the vibration detected by the vibration detection element 8 corresponds to the rotation vibration of the second mass unit 25, the vibration of the second mass unit 25 is determined based on the detection result of the vibration detection element 8. The behavior (particularly the frequency) can be detected, and the behavior of the second mass unit 25 can be controlled to be a desired behavior based on the detected behavior.

Here, the control system of the actuator 1 will be described with reference to FIG.
In the actuator 1, as shown in FIG. 3, the vibration detection element 8 rotates the second mass unit 25 by halving the frequency of vibration detected by the vibration detection element 8 via the amplifier circuit 9. Is connected to the arithmetic circuit 10 for obtaining the frequency of the. The arithmetic circuit 10 is connected to a control circuit 11 for controlling the driving of the second mass unit 25.

The control circuit 11 is connected to a power supply circuit 12 that applies a voltage to the piezoelectric elements 31 to 34 and a light source driving circuit 13 that drives a light source 14 for optical scanning or the like.
Hereinafter, each part which comprises the control system of the actuator 1 is demonstrated sequentially.
The amplifier circuit 9 has a function of amplifying the output signal of the vibration detection element 8. Thereby, the detection accuracy of the second mass unit 25 can be improved.

The arithmetic circuit 10 has a function of obtaining ½ of the vibration frequency detected by the vibration detection element 8 as the rotation frequency of the mass portion. Thereby, the frequency of the second mass unit 25 can be detected with high accuracy.
Specifically, in this embodiment, the arithmetic circuit 10 includes a rectangular wave generation circuit 101 connected to the amplifier circuit 9, a flip-flop circuit 102 connected to the rectangular wave generation circuit 101, and a flip-flop circuit 102. A connected count circuit 103 and a pulse transmission circuit 104 connected to the count circuit 103 are provided.

The rectangular wave generation circuit 101 outputs a high signal when the output value of the vibration detection element 8 (amplification circuit 9) is equal to or greater than a set value (threshold value), and when the output value of the vibration detection element 8 is equal to or less than the setting Has a function of outputting a low signal.
The flip-flop circuit 102 has a function of alternately outputting a high signal and a low signal at a timing when the output of the rectangular wave generation circuit 101 switches from a low signal to a high signal.

The pulse transmission circuit 104 has a function of transmitting pulses at regular intervals.
The count circuit 103 has a function of calculating the frequency of rotation of the second mass unit 25 by counting the number of pulses of the pulse transmission circuit 104 when the output of the flip-flop circuit 102 is a high signal.
Since the arithmetic circuit 10 is configured in this manner, the frequency of the second mass unit 25 can be detected with high accuracy with a relatively simple configuration. The arithmetic circuit 10, the amplifier circuit 9, and the vibration detection element 8 constitute a behavior detection unit that detects the behavior (particularly the vibration frequency) of the second mass unit 25.

  The control circuit 11 to which the arithmetic circuit 10 is connected controls the power supply circuit 12 and the light source driving circuit 13 based on the arithmetic result of the arithmetic circuit 10 (that is, the vibration detected by the vibration detecting means). Thereby, the drive state of the piezoelectric elements 31 to 34 can be made desired, and as a result, the behavior of the second mass unit 25 can be made desired. Further, the light irradiated from the light source 14 and reflected by the light reflecting portion 251 can be scanned in a desired range.

The actuator 1 having the above configuration is driven as follows.
For example, a voltage as shown in FIG. 4A is applied to the piezoelectric elements 32 and 34, and a voltage as shown in FIG. 4B is applied to the piezoelectric elements 31 and 33. In other words, voltages that are 180 ° out of phase with each other are applied to the piezoelectric elements 32 and 34 and the piezoelectric elements 31 and 33. Then, the state in which the piezoelectric elements 31 and 33 are expanded and the piezoelectric elements 32 and 34 are contracted and the state in which the piezoelectric elements 31 and 33 are contracted and the piezoelectric elements 32 and 34 are expanded alternately are repeated.

Accordingly, the first elastic portions 26 and 27 are twisted and deformed, and the first mass portions 21 and 22 rotate (vibrate) with respect to the support portions 23 and 24.
At this time, since the rod-shaped connecting members 261, 262, 271, 272 are mainly bent and deformed, the entire first elastic portion 26 and the entire first elastic portion 27 are torsionally deformed. 27 can be reduced. Therefore, it can be driven with a large deflection angle.

  Further, since the driving force is obtained by the piezoelectric elements 31, 32, 33, and 34, it is possible to drive with a relatively large driving force even when driving at a low voltage. Therefore, even in low voltage driving, the spring constants of the first elastic portions 26 and 27 can be increased and driven at high frequency. In particular, since the driving force of the piezoelectric elements 31, 32, 33, and 34 is relatively high, the deflection angle can be increased even if the spring constants of the first elastic portions 26 and 27 are relatively high.

The second mass part 25 connected via the second elastic parts 28 and 29 in accordance with the vibration (drive) of the first mass parts 21 and 22 is also connected to the second elastic part 28, 29 is oscillated (rotated) so as to be inclined with respect to the plate surface of the support substrate 4 (the paper surface in FIG. 1).
When the second mass unit 25 rotates in this way, the gas around the second mass unit 25 vibrates (that is, a sound wave is generated).

  Such vibration of the gas is detected by the vibration detection element 8. At that time, the output signal of the vibration detection element 8 periodically fluctuates as shown in FIG. The end of the second mass unit 25 on the vibration detection element 8 side passes through the vicinity of the detection unit of the vibration detection element 8 twice per cycle of rotation (vibration) of the second mass unit 25. Therefore, the period t of the output signal of the vibration detection element 8 is ½ of the period T of rotation of the second mass unit 25. That is, the frequency of the output signal of the vibration detection element 8 is twice the frequency of rotation of the second mass unit 25.

The output signal of the vibration detecting element 8 is amplified by the amplifier circuit 9 as shown in FIG.
Then, the amplified signal is converted by the rectangular wave generation circuit 101 into a rectangular wave signal that rises at a period T / 2 (that is, a period t) as shown in FIG.
The rectangular wave signal output from the rectangular wave generating circuit 101 is converted by the flip-flop circuit 102 into a rectangular wave signal that rises at a period T (that is, a period 2t) as shown in FIG.

On the other hand, as shown in FIG. 5E, the pulse transmission circuit 104 transmits a pulse signal at a constant interval (pulse transmission cycle).
Then, the count circuit 103 counts the number of pulse signals from the pulse transmission circuit 104 during the period T of the rectangular wave signal output from the flip-flop circuit 102, and the count number in the pulse transmission circuit 104 is counted. By multiplying the pulse transmission period, the frequency of rotation of the second mass unit 25 is obtained.

Based on the vibration frequency thus obtained, the control circuit 11 controls the driving of the power supply circuit 12 and the light source driving circuit 13.
According to the actuator 1 as described above, the vibration detection element 8 detects the vibration (that is, sound wave) of the gas around the second mass unit 25 accompanying the rotation of the second mass unit 25, and the detection result. Therefore, the behavior of the second mass unit 25 can be detected with high accuracy without being affected by the temperature change. Such behavior detection means does not cause fluctuations in detection accuracy due to the mounting position of the vibration detection element 8, and can be manufactured separately from the structure constituting the vibration system including the second mass portion and the like. it can. Therefore, the manufacturing process can be simplified and the cost of the actuator 1 can be reduced.

In particular, the actuator 1 can detect the frequency of the second mass unit 25 with high accuracy based on the detection result of the vibration detection element 8.
The actuator 1 employs a piezoelectric driving method (having piezoelectric elements 31 to 34) as a driving means, and the piezoelectric elements 31 to 34 generate heat when driven, but the vibration detecting element 8 (behavior detection). Therefore, when the present invention is applied to the actuator 1 having such a drive means, the effect (the improvement in the accuracy of behavior detection of the second mass unit 25) becomes remarkable.

  In addition, the vibration detection element 8 is provided at a position that does not overlap the second mass part 25 in a plan view of the plate-shaped second mass part 25 (non-driven state). However, the distance between the vibration detection element 8 and the second mass unit 25 can be reduced without hindering the rotation of the second mass unit 25. Therefore, it is possible to increase the output signal of the vibration detection element 8 and improve the detection accuracy of the behavior detection of the second mass unit 25.

Further, since the vibration detection element 8 faces the end surface in the longitudinal direction of the second mass part 25 in plan view of the second mass part 25, the vibration received by the vibration detection element 8 is increased. Can do. Therefore, it is possible to increase the output signal of the vibration detection element 8 and improve the detection accuracy of the behavior detection of the second mass unit 25.
Further, since the base body 2 (vibration system) and the vibration detection element 8 are accommodated in the housing 7, the vibration detection element 8 is not affected by the outside of the actuator 1 and the rotation of the second mass unit 25 is not affected. It is possible to detect gas vibration accompanying movement. As a result, the detection accuracy of the behavior detection of the second mass unit 25 can be improved.

Moreover, since the inside of the housing 7 is an airtight space, the gas density in the housing 7 can be kept constant. As a result, the second mass unit 25 can be stably rotated, and unintentional fluctuations in the detection result (output signal) of the vibration detection element 8 can be prevented.
Further, since the vibration detection element 8 is supported by the housing 7, it is possible to prevent the influence of the vibration of the second mass part 25 itself on the vibration detection element 8.

It is preferable that a vibration absorbing portion for absorbing gas vibration is provided on the inner wall of the housing 7. Thereby, it is possible to prevent the vibration (sound wave) of the gas from being reflected on the inner wall surface of the housing 7 and affecting the vibration detecting element 8. As a result, the detection accuracy of the behavior detection of the second mass unit 25 can be improved.
In addition, it is preferable to have a blocking member that blocks transmission of vibration from the housing 7 to the vibration detecting element 8. Thereby, the influence of the vibration of the 2nd mass part 25 itself with respect to the vibration detection element 8 can be prevented more reliably. As this blocking member, for example, a member having vibration absorption such as rubber can be suitably used. For example, such a member is used between the housing 7 and the vibration detecting element 8 or between the support substrate 4 and the housing. 7, between the side wall member 71 and the upper wall member 72 of the housing 7, between the side wall member 71 and the lower wall member 73 of the housing 7, or the side wall member 71 of the housing 7 is made of rubber. This can be realized by using a member having such a vibration absorption property.

In the actuator 1, the length (maximum length) in the direction (longitudinal direction) perpendicular to the rotation center axis of the first mass portion 21 is L _1, and the first mass portion 22 is rotated. The length (maximum length) in the direction perpendicular to the central axis (longitudinal direction) is L _2, and the length in the direction perpendicular to the rotational central axis of the second mass portion 25 (maximum length) when was the L _3, in the present embodiment, the first mass portions 21 and 22 is, because it is provided independently, regardless of the size of the second mass 25 (length L ₃₎ The first mass parts 21 and 22 and the second mass part 25 do not interfere with each other, and L ₁ and L ₂ can be reduced. Thereby, the rotation angle (swing angle) of the first mass parts 21 and 22 can be increased, and as a result, the rotation angle of the second mass part 25 can be increased.

Here, it is preferable that the dimensions of the first mass parts 21 and 22 and the second mass part 25 are set so as to satisfy the relationship of L ₁ <L ₃ and L ₂ <L ₃ , respectively.
By satisfying the above relationship, L ₁ and L ₂ can be made smaller, the rotation angle of the first mass parts 21 and 22 can be made larger, and the rotation angle of the second mass part 25 can be further increased. Can be bigger.

In this case, it is preferable that the maximum rotation angle of the second mass unit 25 is configured to be 20 ° or more.
By these, the low voltage drive of the 1st mass parts 21 and 22 and the vibration (rotation) in the large rotation angle of the 2nd mass part 25 are realizable.
For this reason, when such an actuator 1 is applied to, for example, an optical scanner used in an apparatus such as a laser printer or a scanning confocal laser microscope, the apparatus can be more easily downsized.

As described above, in the present embodiment, L ₁ and L ₂ are set to be substantially equal, but it goes without saying that L ₁ and L ₂ may be different.
By the way, in such a vibration system (two-degree-of-freedom vibration system) including the mass parts 21, 22, and 25, the amplitude (deflection angle) of the first mass parts 21 and 22 and the second mass part 25, and the piezoelectric element A frequency characteristic as shown in FIG. 6 exists between the frequency of the alternating voltage applied to 31, 32, 33, and 34.

That is, the vibration system has two resonance frequencies fm ₁ [kHz] and fm ₃ [kHz] (however, fm) in which the amplitude of the first mass parts 21 and 22 and the amplitude of the second mass part 25 are increased. ₁ <fm ₃ ) and one anti-resonance frequency fm ₂ [kHz] at which the amplitude of the first mass parts 21 and 22 is substantially zero.
In this vibration system, the frequency F of the AC voltage applied to the piezoelectric elements 31, 32, 33, 34, those lower of the two resonant frequencies, i.e., preferably set to be substantially equal to fm _1. Thereby, the deflection angle (rotation angle) of the 2nd mass part 25 can be enlarged, suppressing the amplitude of the 1st mass parts 21 and 22. FIG.

In this specification, F [kHz] and fm ₁ [kHz] being substantially equal means that the condition of (fm ₁ −1) ≦ F ≦ (fm ₁ +1) is satisfied.
The average thicknesses of the first mass parts 21 and 22 are each preferably 1 to 1500 μm, and more preferably 10 to 300 μm.
The average thickness of the second mass part 25 is preferably 1 to 1500 μm, and more preferably 10 to 300 μm.

The spring constant k ₁ of the first elastic portions 26 and 27 is preferably 1 × 10 ⁻³ to 1 × 10 ⁵ Nm / rad, and is preferably 1 × 10 ⁻² to 1 × 10 ⁴ Nm / rad. Is more preferably 1 × 10 ⁻¹ to 1 × 10 ³ Nm / rad. Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased.
On the other hand, the spring constant k ₂ of the second elastic portions 28 and 29 is preferably 1 × 10 ⁻⁴ to 1 × 10 ⁴ Nm / rad, and 1 × 10 ⁻² to 1 × 10 ³ Nm / rad. More preferably, it is 1 × 10 ⁻¹ to 1 × 10 ² Nm / rad. Thereby, the deflection angle of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.

Further, it is preferable that the relationship of k ₁ > k ₂ is satisfied, where k _{1 is} the spring constant of the first elastic portions 26 and 27 and k ₂ is the spring constant of the second elastic portions 28 and 29. Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.

Furthermore, the moment of inertia of the first mass portions 21 and 22 and _{J 1,} when the moment of inertia of the second mass 25 has a _{J 2,} and _{J 1} and _{J 2,} the _{J 1} ≦ _{J 2} the relationship It is preferable to satisfy, and it is more preferable to satisfy the relationship of J ₁ <J ₂ . Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.

By the way, the natural frequency ω ₁ of the first vibration system including the first mass parts 21 and 22 and the first elastic parts 26 and 27 is the inertia moment J _{1 of} the first mass parts 21 and 22, and According to the spring constant k _{1 of} the first elastic part 26, 27, it is given by ω ₁ = (k ₁ / J ₁ ) ^1/2 . On the other hand, the natural frequency ω ₂ of the second vibration system including the second mass part 25 and the second elastic parts 28 and 29 is the inertia moment J _{2 of} the second mass part 25 and the second elasticity. With the spring constant k ₂ of the parts 28, 29, it is given by ω ₂ = (k ₂ / J ₂ ) ^1/2

It is preferable that the natural frequency ω ₁ of the first vibration system and the natural frequency ω ₂ of the second vibration system obtained in this way satisfy the relationship ω ₁ > ω ₂ . Thereby, the rotation angle (swing angle) of the second mass unit 25 can be further increased while suppressing the deflection angle of the first mass units 21 and 22.
Such an actuator 1 can be manufactured as follows, for example.
7 and 8 are views (longitudinal sectional views) for explaining the method for manufacturing the actuator 1 of the first embodiment. 7 and 8 each show a cross section corresponding to the cross section along the line AA in FIG. Hereinafter, for convenience of explanation, the upper side in FIGS. 7 and 8 is referred to as “upper” and the lower side is referred to as “lower”.

[A1]
First, as shown in FIG. 7A, an SOI substrate 6 in which an Si layer 61, an SiO ₂ layer 62, and an Si layer 63 are sequentially stacked is prepared, and one surface of the SOI substrate 6 (surface on the Si layer 61 side) is prepared. ), Electrodes 312, 322, 332, 342 and terminals 314, 324, 334, 344 are formed.
The electrodes 312, 322, 332, 342 and the terminals 314, 324, 334, 344 are formed by forming a metal film on the SOI substrate 6 and forming the electrodes 312, 322, 332, 342 and the terminals 314, 324, 334, 344. After the metal film is etched through a resist mask having a shape corresponding to the shape, the resist mask is removed.

  Examples of metal film deposition methods include chemical vapor deposition (CVD) such as plasma CVD, thermal CVD, and laser CVD, dry plating methods such as vacuum deposition, sputtering, and ion plating, electrolytic plating, immersion plating, and nothing. Wet plating methods such as electrolytic plating, thermal spraying, and joining of sheet-like members can be used. Note that the same method can also be used for forming a metal film in the following steps.

  As an etching method, for example, one or more of physical etching methods such as plasma etching, reactive ion etching, beam etching, and light-assisted etching, and chemical etching methods such as wet etching are used in combination. be able to. Note that the same method can be used for etching in the following steps.

[A2]
Next, as shown in FIG. 7B, on the electrodes 312, 322, 332, and 342, the corresponding piezoelectric layers 311 and 331 (the piezoelectric layers corresponding to the electrodes 322 and 342 are not shown). Piezoelectric layers 311, 331, etc.) are formed.
The formation of the piezoelectric layers 311, 331 and the like can be performed in the same manner as the formation of the electrodes 312, 322, 332, 342 in the step [A1] described above.

[A3]
Next, as shown in FIG. 7C, a part of the Si layer 61 of the SOI substrate 6 is removed, and the first mass parts 21, 22, the support parts 23, 24, the second mass part 25, First elastic portions 26 and 27 and second elastic portions 28 and 29 are formed. Thereby, the base 2 is obtained.
The first mass parts 21 and 22, the support parts 23 and 24, the second mass part 25, the first elastic parts 26 and 27, and the second elastic parts 28 and 29 are formed on the SOI substrate 6 with a metal film. Alternatively, a silicon oxide film is formed, and the first mass portions 21 and 22, the support portions 23 and 24, the second mass portion 25, the first elastic portions 26 and 27, and the second elastic portions 28 and 29 are formed. After etching the metal film or silicon oxide film through a resist mask having a shape corresponding to the shape, the resist mask is removed, and a part of the Si layer 61 is etched using the metal film or silicon oxide film as a mask. Can be performed.
At this time, the SiO ₂ layer as an intermediate layer of the SOI substrate 6 functions as a stop layer for the etching.
As an etching method, the same method as the above-mentioned step [A1] can be used.

[A4]
Next, as shown in FIG. 7D, a part of the Si layer 63 of the SOI substrate 6 is removed to form a recess (opening 41).
As a method for forming the recess, the same method as in the above-described step [A3] can be used.

[A5]
Next, as shown in FIG. 7E, electrodes 313 and 333 corresponding to the piezoelectric layers 311 and 331 (electrodes corresponding to the electrodes 322 and 342 are not shown). 333), and the light reflecting portion 251 is formed on the second mass portion 25.
As a method for forming the electrodes 313, 333 and the like and the light reflecting portion 251, a method similar to the above-described step [A1] can be used.

[A6]
Next, as shown in FIG. 7F, a part of the SiO ₂ layer 62 of the SOI substrate 6 is removed to form the bonding layer 5.
[A7]
On the other hand, as shown in FIG. 8A, the vibration detecting element 8 is attached to the upper wall member 72 such as a glass substrate, and as shown in FIG. 8B, the side wall member 71 and the lower wall member 73 Are joined together to produce a box.

[A8]
Next, as shown in FIG. 8C, the structure obtained in [A6] is accommodated in the box obtained in [A7], joined and fixed with an adhesive, etc. The upper wall member 72 is joined so as to cover the opening. Thereby, the actuator 1 of this embodiment is obtained.
As described above, the actuator 1 of the first embodiment is manufactured.

The actuator 1 as described above can be applied to various electronic devices, and the obtained electronic device has high reliability.
When the actuator 1 as described above is used as an optical scanner that scans the light reflected by the light reflecting portion, for example, an image forming apparatus such as a laser printer, a barcode reader, a scanning confocal laser microscope, or an imaging display. It can be suitably applied to.

  In such an image forming apparatus, the actuator 1 scans light (main scanning or sub scanning) to form an image. For example, in the case of a laser printer, the actuator 1 scans light to form a latent image on the photosensitive drum. Further, in the case of an imaging display, the actuator 1 performs main scanning, and the galvano mirror (which may be the actuator 1) performs sub scanning to form an image on the screen.

The actuator of the present invention has been described based on the illustrated embodiment, but the present invention is not limited to this. For example, in the actuator 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 rod-like connecting member has a linear shape, but the entire first elastic portion can be torsionally deformed by mainly bending the two rod-like connecting members in opposite directions. If it is a thing, the shape of a rod-shaped connection member is arbitrary. For example, the rod-like connecting member may be curved.

In the above-described embodiment, the piezoelectric element is bonded to the upper surface of the rod-shaped connecting member. However, if the rod-shaped connecting member can be bent and deformed mainly in opposite directions, the piezoelectric element is bonded to the lower surface of the rod-shaped connecting member. The arrangement of the piezoelectric elements is arbitrary.
In the above-described embodiment, a structure has been described in which the shape is substantially symmetric (symmetric) with respect to a plane that passes through the center of the actuator and is perpendicular to the rotation axis of the first mass portion and the second mass portion. However, it may be asymmetric.

In the above-described embodiment, an example in which the present invention is applied to a two-degree-of-freedom vibration system actuator has been described. However, the present invention can be applied to a one-degree-of-freedom vibration system or a vibration system actuator having three or more degrees of freedom. Needless to say, you can. That is, the connecting portion in the actuator of the present invention is not limited to the shape of the above-described embodiment as long as the connecting portion includes an elastic portion that can be elastically deformed, and the mass portion is rotatably connected to the support portion.
In the above-described embodiment, the configuration in which the light reflecting portion is provided on the upper surface of the second mass portion (the surface opposite to the support substrate) has been described. For example, the light reflecting portion is provided on the opposite surface. The structure which is provided may be sufficient and the structure provided in both surfaces may be sufficient.

It is a top 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 which shows the structure of the control system of the actuator shown in FIG. It is a figure which shows an example of the drive voltage of the actuator shown in FIG. 2 is a timing chart for explaining the behavior detection of the actuator shown in FIG. 1. It is a graph which shows the relationship between the frequency of a drive voltage, and each amplitude of a 1st mass part and a 2nd mass part. It is a figure for demonstrating the manufacturing method of the actuator shown in FIG. It is a figure for demonstrating the manufacturing method of the actuator shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Actuator 2 ... Base | substrate 21, 22 ... 1st mass part 23, 24 ... Supporting part 25 ... 2nd mass part 251 ... Light reflection part 26, 27 ... 1st elastic part 261 , 262, 271, 272... Rod-shaped connecting members 28, 29... Second elastic portions 31, 32, 33, 34... Piezoelectric elements 311, 331 ... piezoelectric layers 312, 313, 322, 332, 333, 342... Electrodes 314, 324, 334, 344... Terminal 4... Support substrate 41... Opening 5 .. Junction layer 6... SOI substrate 61 ... Si layer 62 ... SiO ₂ layer 63 ... Si layer 7 …… Housing 71 …… Side wall member 72 …… Upper wall member 73 …… Lower wall member 8 …… Vibration detection element 9 …… Amplification circuit 10 …… Calculation circuit 11 …… Control circuit 12 …… Power supply circuit 13 …… Light source drive circuit 14 …… Light source 1 1 ...... rectangular wave generating circuit 102 ...... flip-flop circuit 103 ...... counting circuit 104 ...... pulsing circuit

Claims (15)

Part by mass;
A support part for supporting the mass part;
A connecting portion that includes at least one elastic portion that is elastically deformable, and rotatably connects the mass portion to the support portion;
Drive means for rotationally driving the mass part,
An actuator configured to rotate the mass portion while twisting and deforming the elastic portion of the connecting portion by the operation of the driving means,
Having a behavior detecting means for detecting the behavior of the mass part;
The behavior detection means includes a vibration detection element that detects vibration of a gas around the mass part as the mass part rotates, and detects the behavior of the mass part based on a detection result of the vibration detection element. An actuator characterized by being configured to do so.   The actuator according to claim 1, wherein the mass portion has a plate shape, and the vibration detection element is provided at a position that does not overlap the mass portion in a plan view.   The mass portion has a longitudinal shape extending in a direction perpendicular to the rotation center axis thereof, and the vibration detection element is formed on an end surface in the longitudinal direction of the mass portion in a plan view of the mass portion. The actuator according to claim 2, which is opposed to each other.   The actuator according to claim 1, wherein the mass portion is provided with a light reflecting portion having light reflectivity.   The actuator according to claim 1, wherein the driving unit includes a piezoelectric element that generates a driving force for rotationally driving the mass unit.   The actuator according to claim 1, further comprising a housing that accommodates the mass portion, the connecting portion, and the vibration detection element.   The actuator according to claim 6, wherein a vibration absorbing portion that absorbs vibration of the gas is provided on an inner wall of the housing.   The actuator according to claim 6 or 7, wherein the inside of the housing is an airtight space.   The actuator according to claim 6, wherein the vibration detection element is supported by the housing.   The actuator according to claim 9, further comprising a blocking member that blocks transmission of vibration from the housing to the vibration detection element.   The actuator according to any one of claims 1 to 10, wherein the behavior detection unit is configured to detect a frequency of the mass unit based on a detection result of the vibration detection element.   The actuator according to claim 11, wherein the behavior detection unit includes an arithmetic circuit that obtains ½ of a vibration frequency detected by the vibration detection element as a rotation frequency of the mass unit.   The arithmetic circuit outputs a high signal when the output value of the vibration detection element is equal to or greater than a set value, and outputs a low signal when the output value of the vibration detection element is equal to or less than the setting. A flip-flop circuit that alternately outputs a high signal and a low signal at a timing when the output of the rectangular wave generation circuit switches from a low signal to a high signal, a pulse transmission circuit that transmits a pulse at regular intervals, and The actuator according to claim 12, further comprising: a counting circuit that calculates the number of rotations of the mass unit by counting the number of pulses of the pulse transmission circuit when the output of the flip-flop circuit is a high signal. . A mass part provided with a light reflecting part having light reflectivity;
A support part for supporting the mass part;
A connecting portion that includes an elastically deformable elastic portion and rotatably connects the mass portion to the support portion;
Drive means for rotationally driving the mass part,
An optical scanner configured to scan the light reflected by the light reflecting portion by rotating the mass portion while twisting and deforming the elastic portion of the connecting portion by the operation of the driving means,
Having a behavior detecting means for detecting the behavior of the mass part;
The behavior detection means includes a vibration detection element that detects vibration of a gas around the mass part as the mass part rotates, and detects the behavior of the mass part based on a detection result of the vibration detection element. An optical scanner characterized by being configured to do so. A mass part provided with a light reflecting part having light reflectivity;
A support part for supporting the mass part;
A connecting portion that includes an elastically deformable elastic portion and rotatably connects the mass portion to the support portion;
Drive means for rotationally driving the mass part,
An optical scanner configured to scan the light reflected by the light reflecting portion by rotating the mass portion while twisting and deforming the elastic portion of the connecting portion by the operation of the driving means, An image forming apparatus in which an optical scanner forms an image by performing main scanning or sub-scanning of light,
Having a behavior detecting means for detecting the behavior of the mass part;
The behavior detection means includes a vibration detection element that detects vibration of a gas around the mass part as the mass part rotates, and detects the behavior of the mass part based on a detection result of the vibration detection element. An image forming apparatus characterized by being configured to do so.

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