JP5103876B2 - Two-dimensional optical scanning device - Google Patents

Description

  The present invention relates to a two-dimensional optical scanning device that scans a light beam two-dimensionally.

In recent years, various optical scanning devices using MEMS (Micro Electro Mechanical System) technology have been proposed for the purpose of downsizing the optical scanning device.
On the other hand, the applicant of the present application excites two vibration modes by exciting a three-degree-of-freedom torsional vibration system with a piezoelectric bimorph, and torsionally vibrates a mirror disposed in the center in two directions. An optical scanning device configured to perform the optical scanning is proposed (see Patent Document 1).

Also, a one-dimensional optical scanning device has been proposed that uses a piezoelectric bimorph for excitation and vibration detection (see Patent Document 2).
Further, the mirror portion can be vibrated by generating an electrostatic force between the comb teeth provided on both sides of the mirror portion formed of silicon and the comb teeth disposed on the fixed side opposite to the comb teeth. The angle of a mirror part is detected by the change of the electrostatic capacity in between (refer patent document 3).
JP-A-7-199099 JP-A-9-101474 JP 2004-245890 A

  By the way, in the technique described in Patent Document 1, a piezoelectric bimorph actuator and a displacement enlarging mechanism for obtaining a torsional excitation force are employed in order to vibrate a three-degree-of-freedom torsional vibrator. However, since the piezoelectric element used for the piezoelectric bimorph actuator is ceramic, it has high rigidity. For this reason, even if a displacement magnifying mechanism is used, a sufficient amount of displacement cannot be obtained, and it has been difficult to obtain a large amplitude at a low voltage.

  In the technique described in Patent Document 2, a piezoelectric bimorph is used as a detection element, and the displacement of the rotation angle of the mirror is converted into the bending displacement of the piezoelectric element by the principle of an insulator. However, since the piezoelectric element has high rigidity, it is difficult to be deformed, and it is difficult to obtain a signal having a good S / N ratio. That is, it is difficult to accurately detect the angular displacement of the mirror portion.

  In the technique disclosed in Patent Document 3, the mirror and the comb teeth on both sides of the mirror vibrate integrally. Therefore, when the angular amplitude of the mirror increases, the mirror side comb teeth (hereinafter referred to as the mirror portion comb teeth) are fixed. The period in which the side comb teeth (hereinafter referred to as “fixed side comb teeth”) face each other is only an instant of the periodic motion. That is, since the time during which the excitation force within the cycle is applied is short, a large excitation force cannot be applied and a large scanning angle cannot be obtained. Further, even if the voltage is increased to increase the scanning angle, discharge occurs between the comb teeth, and therefore there is a limit to the magnitude of the applied voltage. In the capacitance detection between the comb teeth, the capacitance is detected while the mirror side comb teeth and the fixed side comb teeth face each other, but the angular displacement becomes large and the mirror side comb teeth are fixed. When the side comb teeth do not face each other, the capacitance becomes zero. For this reason, during periodic movement, the capacitance can be detected only in the moment when the mirror comb teeth and the fixed comb teeth face each other, and the angular displacement of the mirror section can be detected accurately over the entire period of the periodic movement. It was difficult to do.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a two-dimensional optical scanning apparatus that can obtain a large excitation force at a low voltage and can accurately detect an angular displacement. To do.

The two-dimensional optical scanning device according to claim 1, which has been made to achieve the above object, has a plate-like third rigid member having a reflecting surface for reflecting light, and a predetermined gap with respect to the third rigid member. A plate-like second rigid body member provided via a plate, a plate-like first rigid body member provided via a predetermined gap with respect to the second rigid body member, and a predetermined value for the first rigid body member The plate-like 0th rigid body member provided through the gap, the third rigid body member, and the second rigid body member are coupled, and twisted when a rotational torque is applied, and depending on the rotational angle of this twisting The third rigid member is twisted with a third central axis passing through the center of gravity of the third rigid member as a rotation axis, and an elastic body that generates rotational torque in a direction opposite to the direction of twisting. A third elastically deformable member for torsional vibration, the second rigid member, and the 1 is composed of an elastic body that is connected to a rigid member, twisted when rotational torque acts, and has a magnitude corresponding to the rotational angle of the twist and generates rotational torque in a direction opposite to the direction of twisting; A second elastic deformation member that twists and vibrates the second rigid member with a second central axis passing through the center of gravity of the third rigid member and the second rigid member as a rotation axis; the first rigid member; It is composed of an elastic body that is connected to the 0th rigid member and is twisted when a rotational torque is applied, and has a magnitude corresponding to the rotational angle of the twist and generates a rotational torque in a direction opposite to the direction of the twist. A first elastically deforming member that twists and vibrates the first rigid member with a first central axis passing through the center of gravity of the third rigid member, the second rigid member, and the first rigid member as a rotation axis; The third rigid body part The second rigid member, the first rigid member, the third elastic deformation member, the second elastic deformation member, and the first elastic deformation member are twisted at a large rotation angle when an inherent periodic external force is applied. A three-degree-of-freedom coupled vibration system that torsionally oscillates is configured, and is further provided on the zeroth rigid body member, and is provided on the first rigid body member and the zeroth combtooth electrode portion formed in a combtooth shape. A first comb-like electrode portion formed in a comb-teeth shape that can mesh with the zeroth comb-like electrode portion, and a periodic electrical signal is input to the zeroth comb-like electrode portion. The first external force application means for applying the inherent periodic external force to the three-degree-of-freedom coupled vibration system, and the second comb-like electrode portion provided in the zeroth rigid member and formed in a comb-teeth shape And a third comb provided in the first rigid member and formed in a comb-like shape that can mesh with the second comb-like electrode portion And a torsional vibration of the first rigid member based on a change in capacitance between the second comb-shaped electrode portion and the third comb-shaped electrode portion. First angle detecting means for detecting an angle of the amplitude, and the angle of the torsional vibration amplitude of the third rigid member and the second rigid member is an amplitude of the torsional vibration amplitude of the first rigid member. The torsional vibration of the first rigid member is sufficiently large with respect to the angle so that the amplitude of the torsional vibration of the first rigid member is substantially equal to the plate thickness of the first rigid member. The period is configured such that there is no period in which the 0th comb-shaped electrode portion and the first comb-shaped electrode portion do not face each other during the period .

  In the two-dimensional optical scanning device according to claim 1, configured as described above, the third rigid member, the second rigid member, the first rigid member, the third elastic deformation member, the second elastic deformation member, and the first elastic deformation. The member constitutes a three-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when an inherent periodic external force is applied.

Therefore, the two-dimensional optical scanning device is a three-degree-of-freedom torsional vibrator having a zero-th rigid member as a fixed end and a degree of freedom in twisting with respect to the first central axis, the second central axis, and the third central axis. ing.
This three-degree-of-freedom torsional vibrator has theoretically three vibration modes. That is, the three vibration modes have different resonance frequencies, and the ratio of the angular amplitude of the torsional vibration of each frame to each resonance frequency is different (this is called a vibration mode). Hereinafter, these three vibration modes are referred to as vibration mode 1, vibration mode 2, and vibration mode 3, respectively.

  The first external force acting means generates an electrostatic force between the 0th comb-shaped electrode portion and the first comb-shaped electrode portion by inputting a periodic electrical signal to the 0th comb-shaped electrode portion. And a periodic external force specific to the three-degree-of-freedom coupled vibration system is applied.

  Further, the first angle detection means is adapted to detect a change in capacitance between the second comb-shaped electrode portion provided on the 0th rigid member and the third comb-shaped electrode portion provided on the first rigid member. Based on this, the amplitude angle of the torsional vibration of the first rigid member is detected.

  Then, if a periodic excitation force having a frequency corresponding to each of vibration mode 1, vibration mode 2, and vibration mode 3 is applied by the first external force acting means, the respective vibration modes can be excited. In addition, if a plurality of periodic excitation forces with a plurality of frequencies are superimposed and applied, a plurality of vibration modes can be excited simultaneously.

Here, for example,
The resonance frequency f1 of vibration mode 1 is 1000 Hz,
The resonance frequency f2 of vibration mode 2 is 5000 Hz,
The resonance frequency f3 of vibration mode 3 is 40000 Hz,
The amplitude ratio r1 of the first rigid member, the second rigid member, and the third rigid member in the vibration mode 1 is “1: −20: 0.5”,
The amplitude ratio r2 of the first rigid member, the second rigid member, and the third rigid member in the vibration mode 2 is “1: 0.01: −50”,
The amplitude ratio r3 of the first rigid member, the second rigid member, and the third rigid member in the vibration mode 3 is “1: 0.02: −0.03”,
The operation of the three-degree-of-freedom torsional vibrator will be described.

  The amplitude ratio in each vibration mode is described from the left in the order of the first rigid member, the second rigid member, and the third rigid member. For example, when the amplitude of the first rigid member is “1”, the amplitude ratio r1 indicates that the amplitude of the second rigid member is “−20” and the amplitude of the third rigid member is “0.5”. Show.

  Further, in the resonance state of the 3-DOF torsional vibrator, the phase angle between the rigid members is theoretically 0 degree or 180 degrees. Therefore, when describing the amplitude ratio, the sign is “+” when the phase angle difference is 0 degree, and the sign is “−” when the difference is 180 degrees. For example, in the amplitude ratio r1, the phase angle difference between the first rigid member and the third rigid member is 0 degree, and the phase angle difference between the first rigid member and the second rigid member is 180 degrees. Indicates.

  When the resonance frequency and amplitude ratio of each vibration mode are designed as described above, in vibration mode 1, the second rigid member and the third rigid member connected to the second rigid member are largely torsionally vibrated at 1000 Hz. To do. In vibration mode 2, the third rigid body member mainly vibrates largely at 5000 Hz.

  For this reason, the laser beam is reflected by the reflecting surface of the third rigid member, and the vibration mode 1 and the vibration mode 2 are simultaneously excited, so that the vibration mode 2 is in the main scanning direction (5000 Hz) and the vibration mode 1 is sub-scanned. Laser light can be scanned two-dimensionally in the direction (1000 Hz).

  Since the two-dimensional optical scanning device of the present invention constitutes a three-degree-of-freedom coupled vibration system, the angle of the torsional vibration amplitude of the third rigid member and the second rigid member is the same as that of the first rigid member. It is configured to be sufficiently large with respect to the angle of the amplitude of torsional vibration.

  For example, the amplitude ratio r1 in the vibration mode 1 is “1: −20: 0.5”. That is, if the amplitude of the first rigid member is “1”, the amplitude of the second rigid member is “20”, and the angle of the torsional vibration amplitude of the second rigid member is the torsional amplitude of the first rigid member. It is sufficiently large with respect to the angle of the amplitude of vibration.

  The amplitude ratio r2 in the vibration mode 2 is “1: 0.01: −50”. That is, when the amplitude of the first rigid member is “1”, the amplitude of the third rigid member is “50”, and the angle of the torsional vibration amplitude of the third rigid member is the torsional amplitude of the first rigid member. It is sufficiently large with respect to the angle of the amplitude of vibration.

Furthermore, the amplitude of the torsional vibration of the first rigid member is configured to be substantially equal to the plate thickness of the first rigid member.
For this reason, there is no period in which the 0th comb-shaped electrode portion and the first comb-shaped electrode portion do not face each other during one period of torsional vibration of the first rigid body member, and the 0th comb An electrostatic force always acts between the tooth-like electrode part and the first comb-like electrode part.

  On the other hand, when the amplitude of the torsional vibration of the first rigid body member is larger than the plate thickness of the first rigid body member, the 0th comb-like electrode portion and the first torsional vibration of the first rigid body member There is a period in which the first comb-shaped electrode part does not face the electrode, and no electrostatic force acts between the 0th comb-shaped electrode part and the first comb-shaped electrode part during this period.

  That is, when the amplitude of the first rigid member is equal to or less than the plate thickness of the first rigid member, the excitation force acts in all sections of one cycle of torsional vibration, but when the amplitude becomes larger than that, the excitation force is increased. The acting section is narrowed. That is, when the amplitude of the first rigid member becomes larger than the plate thickness of the first rigid member, an electric signal is input to the 0th comb-like electrode portion even in a section where no excitation force is applied. For this reason, power is consumed wastefully, and a large excitation force cannot be obtained at a low voltage.

  Further, as the amplitude of the first rigid member becomes smaller than the plate thickness of the first rigid member, the change in the area where the 0 comb-shaped electrode portion and the first comb-shaped electrode portion face each other becomes smaller. As a result, the amount of change in the electrostatic force acting between the 0th comb-shaped electrode portion and the first comb-shaped electrode portion is reduced, and a large excitation force cannot be obtained.

  Therefore, when the amplitude of the first rigid member is substantially equal to the plate thickness of the first rigid member, the amount of change in the electrostatic force is maximum, and the section in which the excitation force acts is maximum. That is, by making the torsional vibration amplitude of the first rigid member approximately equal to the plate thickness of the first rigid member, a large excitation force can be obtained at a low voltage.

  In addition, since the amplitude of the torsional vibration of the first rigid member is substantially equal to the plate thickness of the first rigid member, the second comb-like electrode portion and the first rigid body member during one cycle of the torsional vibration of the first rigid member. There is no period in which the third comb-shaped electrode portion does not face the third comb-shaped electrode portion, and the capacitance between the second comb-shaped electrode portion and the third comb-shaped electrode portion is the same as that of the first rigid member. It changes in a one-to-one relationship with respect to the angle. For this reason, a highly accurate angle signal is obtained, and the first angle detection means can accurately detect the angular displacement of the first rigid member. As described above, in the resonance state of the three-degree-of-freedom torsional vibrator, the phase angle between the rigid members is theoretically 0 degree or 180 degrees. For this reason, the angular displacement of the second rigid member and the third rigid member can be detected by detecting the angular displacement of the first rigid member.

Next, the two-dimensional optical scanning device according to claim 2 is an eighth rigid member having a reflecting surface for reflecting light, and a seventh rigid body provided with a predetermined gap with respect to the eighth rigid member. A member, a sixth rigid member provided through a predetermined gap with respect to the seventh rigid member, a fifth rigid member provided through a predetermined gap with respect to the sixth rigid member, The fourth rigid member provided through a predetermined gap with respect to the fifth rigid member, the eighth rigid member, and the seventh rigid member are connected to each other and twisted when a rotational torque acts, and this twist And an elastic body that generates rotational torque in a direction opposite to the direction of twisting, with the eighth central axis passing through the center of gravity of the eighth rigid member as the rotational axis. An eighth elastically deforming member for torsionally vibrating the eight rigid member; The seventh rigid member and the sixth rigid member are connected to each other, and twisted when rotational torque is applied, and rotational torque is generated in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. A seventh elastically deforming member that is constituted by an elastic body and that twists and vibrates the seventh rigid member about a seventh central axis that passes through the center of gravity of the eighth rigid member and the seventh rigid member; The sixth rigid member and the fifth rigid member are connected to each other, and twisted when rotational torque is applied, and rotational torque is generated in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. A sixth elastic member configured by an elastic body and torsionally vibrates the sixth rigid member with a sixth central axis passing through the center of gravity of the eighth rigid member, the seventh rigid member, and the sixth rigid member as a rotation axis; A deformable member; An elastic member that connects the body member and the fourth rigid member and twists when rotational torque acts, and generates rotational torque in a direction opposite to the direction of the twist with a magnitude corresponding to the rotational angle of the twist. The fifth rigid member is twisted about a fifth central axis passing through the center of gravity of the eighth rigid member, the seventh rigid member, the sixth rigid member, and the fifth rigid member. A fifth elastic member that vibrates, the eighth rigid member, the seventh rigid member, the sixth rigid member, the fifth rigid member, the eighth elastic deformable member, the seventh elastic deformable member, The sixth elastic deformable member and the fifth elastic deformable member constitute a four-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when an inherent periodic external force is applied. A fourth comb provided in a rigid member and formed in a comb-teeth shape A tooth-like electrode part; and a fifth comb-like electrode part provided in the fifth rigid member and formed in a comb-like shape that can mesh with the fourth comb-like electrode part, and has the four degrees of freedom. A second external force acting means for applying the inherent periodic external force to the coupled vibration system; a sixth comb-like electrode portion formed on the fourth rigid member and formed in a comb-like shape; and the fifth rigid body A seventh comb-shaped electrode portion provided on the member and formed in a comb-tooth shape that can mesh with the fourth comb-shaped electrode portion, and the sixth comb-shaped electrode portion and the seventh comb-tooth electrode Second angle detection means for detecting the angle of the amplitude of torsional vibration of the fifth rigid member based on a change in capacitance between the sixth rigid member and the sixth electrode, The angle of the torsional vibration amplitude of the seventh rigid member and the eighth rigid member is larger than the angle of the torsional vibration amplitude of the fifth rigid member; The amplitude of the torsional vibration of 5 rigid member is set to be substantially equal to the thickness of said fifth rigid member, between the one period of the torsional vibration of the fifth rigid member, the fourth comb The tooth-shaped electrode portion and the fifth comb-shaped electrode portion are configured so as not to have a period in which they do not face each other.

In the two-dimensional optical scanning device according to claim 2 , configured as described above, the eighth rigid member, the seventh rigid member, the sixth rigid member, the fifth rigid member, the eighth elastic deformation member, and the seventh elastic deformation member. The sixth elastic deformable member and the fifth elastic deformable member constitute a four-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when an inherent periodic external force is applied.

  For this reason, the two-dimensional optical scanning device has four degrees of freedom having a degree of freedom of twisting with respect to the fifth central axis, the sixth central axis, the seventh central axis, and the eighth central axis with the fourth rigid member as a fixed end. It is a torsional vibrator.

  Then, the second external force acting means generates an electrostatic force between the fourth comb-shaped electrode portion and the fifth comb-shaped electrode portion by inputting a periodic electric signal to the fourth comb-shaped electrode portion. And a periodic external force specific to the four-degree-of-freedom coupled vibration system is applied. As a result, the four-degree-of-freedom twisted vibrator can be brought into a resonance state.

  In addition, the second angle detection means is adapted to change the electrostatic capacitance between the sixth comb-shaped electrode portion provided on the fourth rigid member and the seventh comb-shaped electrode portion provided on the fifth rigid member. Based on this, the amplitude angle of the torsional vibration of the fifth rigid member is detected.

  Further, since the two-dimensional optical scanning device of the present invention constitutes a 4-degree-of-freedom coupled vibration system, the angle of the torsional vibration amplitude of the sixth rigid member, the seventh rigid member, and the eighth rigid member is The fifth rigid member is configured to be sufficiently large with respect to the angle of the amplitude of torsional vibration.

  Furthermore, the amplitude of the torsional vibration of the fifth rigid member is configured to be approximately equal to the plate thickness of the fifth rigid member. Therefore, similarly to the two-dimensional optical scanning device according to the first aspect, a large excitation force can be obtained with a low voltage, and the angular displacement of the fifth rigid member can be accurately detected.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view showing a configuration of a two-dimensional optical scanning device 100 according to a first embodiment to which the present invention is applied, FIG. 2A is an enlarged view of a region R1 in FIG. 1, and FIG. 3 is an enlarged view of a region R2 in FIG. 1, and FIG.

  The two-dimensional optical scanning device 100 is manufactured by processing an SOI (Silicon On Insulator) wafer by a semiconductor process. As shown in FIG. 3, the SOI wafer has a three-layer structure. In this embodiment, the SOI layer 11 having a thickness of 50 μm, the silicon oxide film layer 12 having a thickness of 1 μm, and the base silicon having a thickness of 400 μm. Layer 13.

  As shown in FIG. 1, the two-dimensional optical scanning device 100 performs trench etching from the surface of the SOI layer to the silicon oxide film layer, and a circular third frame 104 having a mirror surface portion of an aluminum thin film formed on the surface. The octagonal second frame 103 provided with a predetermined gap with respect to the third frame 104 by the formed groove (hereinafter referred to as a trench groove) 103a and the trench groove 103b, and the trench groove 102a and the trench groove 102b A rectangular first frame 102 provided to the second frame 103 via a predetermined gap and a rectangular first frame 102 provided to the first frame 102 via a predetermined gap by the trench groove 101a. Frame 101.

  Further, in the region where the third frame 104, the second frame 103, and the first frame 102 are formed, a recess 108 formed by etching and removing the base silicon layer 13 and the silicon oxide film layer 12 from the back surface. (See FIGS. 1 and 3). That is, the third frame 104, the second frame 103, and the first frame 102 are configured by the SOI layer 11.

  Further, an SOI layer 107 (hereinafter referred to as a third torsion spring) provided between the third frame 104 and the second frame 103 through a predetermined gap with respect to the second frame 103 by the trench groove 103a and the trench groove 103b. 107) and are connected at two locations facing each other. These two third torsion springs 107 are provided on a central axis k that passes through the center of gravity of the third frame 104. Thereby, the third frame 104 is configured to be able to torsionally vibrate with the central axis k as the rotation axis.

  Similarly, an SOI layer 106 (hereinafter referred to as a second twist) provided between the second frame 103 and the first frame 102 with a predetermined gap with respect to the first frame 102 by the trench groove 102a and the trench groove 102b. Are connected at two locations facing each other. These two second torsion springs 106 are provided on a central axis j that passes through the center of gravity of the third frame 104 and the second frame 103. As a result, the first frame 102 is configured to be capable of torsional vibration with the central axis j as the rotation axis.

  Further, an SOI layer 105 (hereinafter referred to as a first torsion spring 105) provided between the first frame 102 and the 0th frame 101 via a predetermined gap with respect to the 0th frame 101 by the trench groove 101a. Are connected at two locations facing each other. These two first torsion springs 105 are provided on a central axis i that passes through the center of gravity of the third frame 104, the second frame 103, and the first frame 102. Thus, the first frame 102 is configured to be able to torsionally vibrate about the central axis i as a rotation axis.

  The 0th frame 101 is formed with a connecting portion 113 to which the end portion 105a of the first torsion spring 105 on the side not connected to the first frame 102 is connected. The connecting portion 113 is formed of an SOI layer that is electrically insulated from other regions of the 0th frame 101 by the trench groove 101a.

  Accordingly, the connecting portion 113 and the first frame 102 are electrically connected via the first torsion spring 105. Similarly, the first frame 102 and the second frame 103 are electrically connected via a second torsion spring 106, and the second frame 103 and the third frame 104 are electrically connected via a third torsion spring 107.

  In addition, the first torsion spring 105, the second torsion spring 106, and the third torsion spring 107 are twisted when a rotational torque is applied, and have a magnitude corresponding to the rotational angle of the twist and a direction opposite to the twist direction. Is configured to generate rotational torque.

Therefore, by fixing the 0th frame 101, the third frame 104, the second frame 103, and the first frame 102 constitute a three-degree-of-freedom structure.
Hereinafter, the first frame 102, the second frame 103, the third frame 104, the first torsion spring 105, the second torsion spring 106, the third torsion spring 107, and the connecting portion 113 are collectively referred to as a vibrator region 114.

  Further, on the left edge 102c and the right edge 102d of the first frame 102, as shown in FIGS. 2A and 2B, comb teeth 112 formed in a comb shape (FIG. 2A). And a comb tooth portion 110 (see FIG. 2B). Then, the 0th frame 101 has comb teeth formed in a comb tooth shape that meshes with the comb teeth portion 112 at a predetermined interval at positions facing the comb teeth portion 112 and the comb tooth portion 110 of the first frame 102. A comb-tooth portion 109 (see FIG. 2B) formed in a comb-teeth shape that meshes with the portion 111 (see FIG. 2A) and the comb-tooth portion 110 at a predetermined interval is provided.

Hereinafter, the comb tooth portion 110 and the comb tooth portion 112 are collectively referred to as a movable side comb tooth portion, and the comb tooth portion 109 and the comb tooth portion 111 are collectively referred to as a fixed side comb tooth portion.
In addition, the connecting portion 113 is provided with a terminal portion 115. The terminal portion 115 forms a contact hole by removing a silicon oxide film (refer to the silicon oxide film 21 in FIG. 3) formed on the SOI layer of the connecting portion 113 by etching, and forms a contact hole in the contact hole. It is formed by depositing an aluminum thin film (see aluminum thin film 22 in FIG. 3). By applying a voltage via the terminal portion 115, the entire SOI layer in the vibrator region 114 can be made equipotential.

  Further, a silicon oxide film is formed on the SOI layer in the region 117 separated and formed by the trench groove 116, and an aluminum thin film 118 is formed on the silicon oxide film so as to cover the surface of the comb tooth portion 109. (See the aluminum thin film 23 in FIG. 3). By applying a voltage to the aluminum thin film 118, it is possible to apply a voltage to the surface of the comb tooth portion 109. A terminal portion 119 is provided in the region 117. Thereby, a voltage can be applied also to the SOI layer of the comb-tooth part 109 by applying a voltage through the terminal part 119. An excitation force can be applied to the vibrator region 114 by applying a periodic voltage to the region 117.

  Here, the term “terminal portion” refers to a contact hole formed by removing a silicon oxide film (see the silicon oxide film 21 in FIG. 3) formed on the SOI layer by an etching process. It shall refer to what is formed by depositing an aluminum thin film (see aluminum thin film 22 in FIG. 3).

  Further, a silicon oxide film (see the silicon oxide film 21 in FIG. 3) is formed on the SOI layer in the region 121 separated and formed by the trench groove 120, and the comb tooth portion 111 is formed on the silicon oxide film. An aluminum thin film 122 is formed so as to cover the surface (see the aluminum thin film 23 in FIG. 3). By using the aluminum thin film 122 as an electrode, the electrostatic capacitance between the comb tooth portion 111 and the comb tooth portion 112 can be detected. Further, a terminal portion 123 is provided in the region 121, and the capacitance between the SOI layer of the comb tooth portion 111 and the comb tooth portion 112 can be detected using the terminal portion 123 as an electrode.

  In addition, the region 125 separated and formed by the trench groove 124 is provided to electrically separate the region 117 and the region 121. Note that a terminal portion is provided on substantially the entire surface of the region 125. By grounding this terminal portion, the SOI layer in the region 125 can be held at the ground potential.

Next, the operation principle of the two-dimensional optical scanning device 100 will be described.
The two-dimensional optical scanning device 100 is a three-degree-of-freedom twisted vibrator having the zeroth frame 101 as a fixed end and a twist degree of freedom with respect to the central axes i, j, and k.

  A three-degree-of-freedom torsional vibrator theoretically has three vibration modes. That is, the three vibration modes have different resonance frequencies, and the ratio of the angular amplitude of the torsional vibration of each frame to each resonance frequency is different (this is called a vibration mode). Hereinafter, these three vibration modes are referred to as vibration mode 1, vibration mode 2, and vibration mode 3, respectively.

  When a voltage is applied to the comb tooth portion 109, an electrostatic force is generated between the comb tooth portion 110 and the comb tooth portion 110. Further, while the first frame 102 vibrates for one period, the comb tooth portion 110 comes closest to the comb tooth portion 109 twice. For this reason, if a periodic electrostatic force close to twice the resonance frequency is applied, the three-degree-of-freedom torsional vibrator can be brought into a resonance state (hereinafter, an excitation force for making the resonance state is referred to as a periodic excitation force). Further, every time the comb tooth portion 110 comes closest to the comb tooth portion 109, a periodic excitation force can be applied.

  If a periodic excitation force having a frequency corresponding to each of vibration mode 1, vibration mode 2, and vibration mode 3 is applied, the respective vibration modes can be excited. In addition, if a plurality of periodic excitation forces with a plurality of frequencies are superimposed and applied, a plurality of vibration modes can be excited simultaneously.

Here, for example,
The resonance frequency f1 of vibration mode 1 is 1000 Hz,
The resonance frequency f2 of vibration mode 2 is 5000 Hz,
The resonance frequency f3 of vibration mode 3 is 40000 Hz,
The amplitude ratio r1 of the first frame 102, the second frame 103, and the third frame 104 in the vibration mode 1 is “1: −20: 0.5”,
The amplitude ratio r2 of the first frame 102, the second frame 103, and the third frame 104 in the vibration mode 2 is set to “1: 0.01: −50”,
The amplitude ratio r3 of the first frame 102, the second frame 103, and the third frame 104 in the vibration mode 3 is “1: 0.02: −0.03”,
The operation of the three-degree-of-freedom torsional vibrator will be described.

  The amplitude ratio in each vibration mode is described in the order of the first frame 102, the second frame 103, and the third frame 104 from the left. For example, when the amplitude of the first frame 102 is “1”, the amplitude ratio r1 indicates that the amplitude of the second frame 103 is “−20” and the amplitude of the third frame 104 is “0.5”. Show.

  In the resonance state of the three-degree-of-freedom torsional vibrator, the phase angle between the frames is theoretically 0 degree or 180 degrees. Therefore, when describing the amplitude ratio, the sign is “+” when the phase angle difference is 0 degree, and the sign is “−” when the difference is 180 degrees. For example, in the amplitude ratio r1, the phase angle difference between the first frame 102 and the third frame 104 is 0 degree, and the phase angle difference between the first frame 102 and the second frame 103 is 180 degrees. Indicates.

  When the resonance frequency and amplitude ratio of each vibration mode are designed as described above, in the vibration mode 1, the second frame 103 and the third frame 104 connected to the second frame 103 are largely torsionally vibrated at 1000 Hz. To do. Further, in the vibration mode 2, the third frame 104 is largely torsionally vibrated at 5000 Hz.

  For this reason, the laser beam is reflected by the mirror surface portion of the third frame 104 and the vibration mode 1 and the vibration mode 2 are simultaneously excited, so that the vibration mode 2 is in the main scanning direction (5000 Hz) and the vibration mode 1 is sub-scanned. Laser light can be scanned two-dimensionally in the direction (1000 Hz).

  The resonance frequency and amplitude ratio of each vibration mode can be obtained by deriving the equation of motion of the three-degree-of-freedom torsional vibrator and calculating the eigenvalue and eigenvector. The eigenvalue corresponds to the resonance frequency, and the eigenvector for each eigenvalue corresponds to the amplitude ratio. What is necessary is just to design the inertia moment of each frame and the spring constant of each torsion spring so that a desired eigenvalue and eigenvector can be obtained.

  In the two-dimensional optical scanning device 100, the angle of the torsional vibration amplitude of the third frame 104 and the second frame 103 is sufficiently larger than the angle of the torsional vibration amplitude of the first frame 102. The torsional vibration amplitude of one frame 102 is designed to be substantially equal to the plate thickness of the first frame 102.

Next, the configuration of the drive circuit 200 that drives the two-dimensional optical scanning device 100 will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the drive circuit 200. As shown in FIG.
As shown in FIG. 4, the drive circuit 200 includes a laser light generation unit 201 that generates laser light, a signal generation unit 202 that generates an electrical signal for vibrating the two-dimensional optical scanning device 100, and two-dimensional optical scanning. An amplitude detection unit 203 that detects the vibration amplitude of the apparatus 100 and a control circuit 204 that controls the laser light generation unit 201 and the signal generation unit 202 based on the amplitude detected by the amplitude detection unit 203 are configured.

  Among these, the laser light generation unit 201 includes a laser drive circuit 212 that transmits a drive signal to the semiconductor laser 211 based on an instruction from the control circuit 204, based on an instruction from the control circuit 204.

  The signal generator 202 generates an electric signal having a frequency for exciting the vibration mode 1 (hereinafter referred to as mode 1 excitation signal RS1) and an electric signal having a frequency for exciting the vibration mode 2 (hereinafter referred to as mode 2 excitation signal RS2). A signal generator 221 for adding, an adder 222 for adding two frequency electrical signals (mode 1 excitation signal RS1 and mode 2 excitation signal RS2) inputted from the signal generator 221, and the electricity added by the adder 222 An amplifier 223 that amplifies the signal and outputs it to the two-dimensional optical scanning device 100, and when the current value of the electric signal amplified by the amplifier 223 becomes excessive, the electric signal is input to the two-dimensional optical scanning device 100. And an overcurrent cutoff circuit 224 that cuts off the current.

  The excessive current cutoff circuit 224 is provided to prevent the comb teeth 109, 110, 111, and 112 from being damaged. That is, since the comb-tooth portions are opposed to each other with a very small gap of several microns, there is a risk that when an excessive current flows in, sparks are generated and destroyed due to local heat generation. In addition, if an abrupt potential difference occurs due to operational mistakes, radio noise, lightning, etc., there is a possibility of such an accident. A weak glow discharge is generated immediately before the occurrence of a spark, and a current that is abnormally larger than the steady value is generated between the comb teeth. Therefore, the circuit is shut off as soon as an abnormal current is detected, thereby preventing the comb teeth from being damaged.

  The signal generator 202 configured in this manner gives the first frame 102 an excitation force (see FIG. 5A) on which the frequencies of the vibration mode 1 and the vibration mode 2 are superimposed. Hereinafter, the frequency of vibration mode 1 is referred to as vibration mode frequency f1, and the frequency of vibration mode 2 is referred to as vibration mode frequency f2.

  As a result, as shown in FIG. 5B, the first frame 102 is vibrated at the vibration mode frequency f2 (see vibration waveform SD1), and the second frame 103 vibrates at the vibration mode frequency f1 (see vibration waveform SD2). In both cases, the third frame 104 vibrates at the vibration mode frequency f2 (see the vibration waveform SD3).

  The amplitude detector 203 converts the capacitance change between the comb teeth into a voltage signal, and the voltage signal (see FIG. 5C) converted by the CV converter is the vibration mode frequency f1. Frequency (see FIG. 6 (a), hereinafter referred to as mode 1 detection signal MK1) and vibration mode frequency f2 (see FIG. 6 (b), hereinafter referred to as mode 2 detection signal MK2). Separation filter 232, rectifier circuit 233 for converting to a DC voltage proportional to the vibration amplitude of mode 1 detection signal MK1, and outputting the signal to signal generator 221, and converting to a DC voltage proportional to the vibration amplitude of mode 2 detection signal MK2 The signal generator 22 outputs a phase difference signal indicating the phase difference by measuring the phase difference between the rectifier circuit 234 output to the generator 221 and the mode 1 detection signal MK1 and mode 2 detection signal MK2. A phase difference measurement circuit 235 that outputs to the control circuit 204, a binarization circuit 236 that converts the mode 1 detection signal MK1 into a pulse signal and outputs it to the control circuit 204, and a mode 2 detection signal MK2 that converts the pulse signal into a pulse signal and outputs it to the control circuit 204 And a binarizing circuit 237.

  Based on the signal output from the amplitude detection unit 203 configured as described above, the signal generation unit 202 adjusts the gain of the signal generator 221, and between the mode 1 excitation signal RS 1 and the mode 2 excitation signal RS 2. Adjust the phase difference.

  Specifically, the signal generator 221 automatically adjusts the gain of the signal generator 221 so that the DC voltage input from the rectifier circuit 233 and the rectifier circuit 234 becomes a constant value. Thereby, the vibration amplitude of the first frame 102 and the second frame 103 can be controlled to be constant.

  Further, the signal generator 221 automatically calculates the phase difference between the mode 1 excitation signal RS1 and the mode 2 excitation signal RS2 so that the phase difference indicated by the phase difference signal input from the phase difference measurement circuit 235 is constant. adjust. Thereby, the phase difference between the vibration of the first frame 102 and the vibration of the second frame 103 can be controlled to be constant.

  Further, based on the pulse signal output from the amplitude detector 203, the control circuit 204 adjusts the semiconductor laser 211, the laser drive circuit 212, and the optical modulator (non-modulator) in synchronization with the vibration timing of the two-dimensional optical scanning device 100. Image generation can be performed by driving (shown).

  In the two-dimensional optical scanning device 100 configured as described above, the third frame 104, the second frame 103, the first frame 102, the third torsion spring 107, the second torsion spring 106, and the first torsion spring 105 are inherently provided. A three-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when a periodic external force is applied is configured.

  Further, by inputting a periodic electrical signal to the comb tooth portion 109, an electrostatic force is generated between the comb tooth portion 109 and the comb tooth portion 110, and a periodic external force unique to the three-degree-of-freedom coupled vibration system. Act.

  Further, the torsional vibration of the first frame 102 based on the change in electrostatic capacitance between the comb tooth portion 111 provided on the 0th frame 101 and the comb tooth portion 112 provided on the first frame 102. Detect the angle of the amplitude.

  Since the two-dimensional optical scanning device 100 constitutes a three-degree-of-freedom coupled vibration system, the angle of the torsional vibration amplitude of the third frame 104 and the second frame 103 is the torsion of the first frame 102. It is configured to be sufficiently large with respect to the angle of the vibration amplitude.

  In the present embodiment, the amplitude ratio r1 in the vibration mode 1 is “1: −20: 0.5”. In other words, if the amplitude of the first frame 102 is “1”, the amplitude of the second frame 103 is “20”, and the angle of the torsional vibration amplitude of the second frame 103 is the torsion of the first frame 102. It is sufficiently large with respect to the angle of the amplitude of vibration.

  The amplitude ratio r2 in the vibration mode 2 is “1: 0.01: −50”. That is, if the amplitude of the first frame 102 is “1”, the amplitude of the third frame 104 is “50”, and the angle of the torsional vibration amplitude of the third frame 104 is the torsion of the first rigid member. It is sufficiently large with respect to the angle of the amplitude of vibration.

  The amplitude of the torsional vibration of the first frame 102 is configured to be approximately equal to the plate thickness of the first frame 102. Therefore, a large excitation force can be obtained at a low voltage, and the angular displacement of the third frame 104, the second frame 103, and the first frame 102 can be detected with high accuracy.

The reason for this will be described below.
First, since the first frame 102 is torsionally vibrated, the angular displacement θ ₁ of the first frame 102 can be expressed by a sine function. When the amplitude angle of the first frame 102 is “A” and the frequency is “f”, the angular displacement θ ₁ is expressed by Expression (1). In addition, "t" in Formula (1) represents time.

θ ₁ = A · sin (2πft) (1)
Here, when θ ₁ is divided by A to be a normalized angle, “2πft” repeats a change from 0 to 2π radians. In other words, since the change from 0 degree to 360 degrees is repeated in terms of angle, it can be expressed in terms of phase angle. Accordingly, the normalized angle can be expressed as “normalized angle = sin (phase angle)” as shown in FIG.

  Since the first frame 102 is torsionally vibrated with the central axis i as the rotation axis, the comb teeth 112 and the comb teeth 110 also perform a circular motion with the center axis i as the rotation center. If the radius of rotation is sufficiently large with respect to the thickness of the first frame 102, linear motion can be regarded approximately. Therefore, for simplification of calculation, the following calculation is performed by approximating that the comb tooth portion 112 and the comb tooth portion 110 linearly move in the plate thickness direction.

  Here, the electrostatic force between the comb teeth depends on the capacitance between the comb teeth. In general, the capacitance C between the parallel plates is expressed by Expression (2). In Expression (2), “ε” represents the dielectric constant of vacuum, “S” represents the facing area, and “d” represents the facing distance.

C = ε · S / d (2)
And about the comb-tooth part 109-112, the dielectric constant (epsilon) of vacuum and opposing distance d are unchanged, and the opposing area S changes with the movement of the comb-tooth part 112 and the comb-tooth part 110. FIG.

Further, when the plate thickness of the comb teeth is “w” and the length of the portion where the comb teeth portions are opposed to each other is “L”, the facing area S is expressed by Expression (3).
S = L × w (3)
Further, since the comb tooth portion 112 and the comb tooth portion 110 linearly move in the plate thickness direction, when the movement amount of the comb tooth portion 112 and the comb tooth portion 110 is “x”, the facing area S is expressed by the equations (4), ( 5).

S = L (w− | x |), (when “0 ≦ x ≦ w”) (4)
S = 0, (when “w <x”) (5)
Here, Formula (5) represents the facing area S when there is no overlapping portion of the facing surface of the comb tooth portion.

  According to the equations (2) and (5), the capacitance C becomes “0” when “w <x”, but actually, even if there is no overlapping portion between the comb teeth portions, The electric capacity does not become “0”. However, here, it is set to “0” for simplification of calculation.

Next, a ratio H (hereinafter, referred to as a normalized inter-comb portion opposing area H) of the opposing area S and the opposing area S when “x = 0” (hereinafter, referred to as the maximum opposing area S _max ) is expressed by an equation ( 6) and (7).
H = S / _Smax = L (w− | x |) / Lw = (w− | x |) / w = 1− | x | / w (when “0 ≦ x ≦ w”) (6)
H = 0, (when “w <x”) (7)
Further, as described above, the calculation is performed by approximating that the first frame 102 vibrates linearly. For this reason, the movement amount x is expressed by a sine function. Here, when the amplitude of the sine motion is expressed by a multiple a of the thickness of the comb teeth, the movement amount x is expressed by the following equation (8).

x = awsin θ (8)
Accordingly, the normalization area H between the comb teeth is expressed by the equations (9) and (10).
H = (1- | awsin θ |) / w = 1-a | sin θ |, (when “0 ≦ x ≦ w”) (9)
H = 0, (when “w <x”) (10)
Here, the normalizing area H between the comb teeth when the multiple a = 1, 1.5, 2, 4 will be described with reference to FIG. FIG. 7B is a graph in which the phase angle is taken on the horizontal axis and the opposed area H between the normalized comb teeth is taken on the vertical axis.

  As shown in FIG. 7 (b), when the multiple a = 1, that is, when the amplitude of the movable comb tooth portion is substantially equal to the plate thickness of the first frame 102, the normalized inter-comb tooth facing area H is When the phase angle is 0 degree, the maximum is 90 degrees, and the maximum is 0. When the phase angle is 90 degrees, the phase angle is “0” (see curve SM1 in the figure). That is, the excitation force acts in the range of 0 to 90 degrees. That is, the excitation force acts while increasing or decreasing in the entire section of one cycle of torsional vibration.

  Further, when the multiple a = 1.5, that is, when the amplitude of the movable comb-tooth portion is about 1.5 times the plate thickness of the first frame 102, the normalizing inter-comb-tooth facing area H is the phase angle. Becomes smaller toward 45 degrees and becomes “0” at 45 degrees (see curve SM2 in the figure). That is, the excitation force acts in the range of 0 to 45 degrees. In other words, the excitation force acts while increasing or decreasing in a section approximately half of one period of torsional vibration.

  Further, when the multiple a = 2, that is, when the amplitude of the movable comb tooth portion is about twice the plate thickness of the first frame 102, the opposed area H between the normalized comb tooth portions has a phase angle of 30 degrees. And becomes “0” at 30 degrees (see curve SM3 in the figure). That is, the excitation force acts in the range of 0 degrees to 30 degrees. In other words, the excitation force acts while increasing or decreasing in the interval of approximately 1/3 of one period of torsional vibration.

  Further, when the multiple a = 4, that is, when the amplitude of the movable comb teeth is about four times the plate thickness of the first frame 102, the opposing area H between the normalized comb teeth faces the phase angle of 20 degrees. And becomes “0” at 20 degrees (see curve SM4 in the figure). That is, the excitation force acts in the range of 0 degrees to 20 degrees. That is, the excitation force acts while increasing / decreasing in an interval of approximately 1 / 4.5 of one cycle of torsional vibration.

  Accordingly, when the amplitude of the movable comb tooth portion is substantially equal to the plate thickness of the first frame 102, the excitation force acts while increasing / decreasing in all sections of one period of torsional vibration. The section where the force acts is narrowed and the excitation force is reduced. That is, when the amplitude of the movable comb tooth portion becomes larger than the plate thickness of the first frame 102, an electric signal is input to the comb tooth portion 109 even in a section where no excitation force is applied. For this reason, power is consumed wastefully, and a large excitation force cannot be obtained at a low voltage.

  Here, when the amplitude of the movable comb-tooth portion is smaller than the plate thickness of the first frame 102, the normalization area H between the normal comb teeth is not “0”, and the normalization area between the normal comb-tooth portions. The amount of change in H is small. As a result, the amount of change in the electrostatic force acting between the comb tooth portion 109 and the comb tooth portion 110 becomes small, and a large excitation force cannot be obtained.

  Accordingly, when the amplitude of the movable comb tooth portion is substantially equal to the plate thickness of the first frame 102, the amount of change in the normalizing inter-comb tooth facing area H is the maximum, and the section in which the excitation force acts is the maximum. It becomes. When the excitation force is applied in this state, the excitation force is maximized, and excitation with a low voltage is possible.

  In addition, the amplitude detection unit 203 detects a change in electrostatic capacitance between the comb tooth portion 111 and the comb tooth portion 112. At this time, since the angular amplitude of the first frame 102 is approximately equal to the plate thickness of the first frame 102, the same principle as that when applying the excitation force is used. The capacitance changes in a one-to-one relationship with the angle of the first frame 102, and a highly accurate angle signal is obtained. For this reason, the angular displacement of the first frame 102 can be detected with high accuracy. As described above, in the resonance state of the three-degree-of-freedom torsional vibrator, the phase angle between the rigid members is theoretically 0 degree or 180 degrees. Therefore, the angular displacement of the second frame 103 and the third frame 104 can be detected by detecting the angular displacement of the first frame 102.

  Further, by holding the region 125 at the ground potential, noise mixed in the region 121 can be reduced. The comb-tooth portion 109 is supplied with power for excitation, and may become a noise source. Moreover, since the electrostatic capacitance of the comb-tooth part 111 is comparatively small, mixing of noise brings about the fall of S / N ratio. Therefore, it is preferable to reduce noise in the region 125.

  Further, as described above, since the torsional vibration amplitude of the first frame 102 is designed to be substantially equal to the plate thickness of the first frame 102, low-voltage driving is possible. For this reason, the number of comb teeth of the comb teeth for vibration (comb teeth 109, 110) is reduced, and the number of comb teeth of the angle detection comb teeth (comb teeth 111, 112) is increased. Also good. As a result, the capacitance between the comb teeth for angle detection (between the comb teeth 111 and the comb teeth 112) increases, and an angle detection signal with a high accuracy and a high S / N ratio can be obtained. it can.

  In the embodiment described above, the 0th frame 101 is the 0th rigid body member in the present invention, the 1st frame 102 is the 1st rigid body member in the present invention, the 2nd frame 103 is the 2nd rigid body member in the present invention, the 3rd frame 104. Is the third rigid member in the present invention, the first torsion spring 105 is the first elastic deformation member in the present invention, the second torsion spring 106 is the second elastic deformation member in the present invention, and the third torsion spring 107 is the third in the present invention. The elastic deformation member, the comb tooth portion 109, the comb tooth portion 110, the signal generator 221, the adder 222, and the amplifier 223 are the first external force acting means in the present invention, and the comb tooth portion 109 is the 0th comb-like electrode in the present invention. The comb tooth portion 110 is the first comb-like electrode portion in the present invention, the comb tooth portion 111, the comb tooth portion 112, and the amplitude detecting portion 203 are the first angle detecting means in the present invention, the comb tooth portion 1. Reference numeral 1 denotes a second comb-like electrode portion in the present invention, comb-tooth portion 112 denotes a third comb-like electrode portion in the present invention, a central axis i denotes a first central axis in the present invention, and a central axis j denotes a second comb in the present invention. The central axis and the central axis k are the third central axis in the present invention.

(Second Embodiment)
A second embodiment of the present invention will be described below with reference to the drawings.
FIG. 8 is a plan view showing a configuration of a two-dimensional optical scanning device 300 according to the second embodiment to which the present invention is applied.

  The two-dimensional optical scanning device 300 is manufactured by processing an SOI wafer by a semiconductor process. As shown in FIG. 3, the SOI wafer has a three-layer structure. In this embodiment, the SOI layer 11 having a thickness of 50 μm, the silicon oxide film layer 12 having a thickness of 1 μm, and the base silicon having a thickness of 400 μm. Layer 13.

  As shown in FIG. 8, the two-dimensional optical scanning device 300 includes a circular fourth frame 305 having a mirror surface portion of an aluminum thin film formed on the surface thereof, and a predetermined gap with respect to the fourth frame 305 by a trench groove. A third frame 304 having a circular shape provided to the third frame 304 by a trench groove, and a second frame 303 having an octagonal shape provided to the second frame 303 by a trench groove. A rectangular first frame 302 provided via a predetermined gap, and a rectangular zeroth frame 301 provided via the trench groove with respect to the first frame 302 via a predetermined gap.

  The region where the fourth frame 305, the third frame 304, the second frame 303, and the first frame 302 are formed is formed by etching away the base silicon layer and the silicon oxide film layer from the back surface. A recess 320 is formed. That is, the fourth frame 305, the third frame 304, the second frame 303, and the first frame 302 are configured by an SOI layer.

  Further, an SOI layer 309 (hereinafter referred to as a fourth torsion spring 309) provided between the fourth frame 305 and the third frame 304 through a predetermined gap with respect to the third frame 304 by a trench groove, It is connected at two locations facing each other. These two fourth torsion springs 309 are provided on a central axis l that passes through the center of gravity of the fourth frame 305. Accordingly, the fourth frame 305 is configured to be capable of torsional vibration with the central axis l as the rotation axis.

  In addition, an SOI layer 308 (hereinafter referred to as a third torsion spring 308) provided between the third frame 304 and the second frame 303 through a predetermined gap with respect to the second frame 303 by a trench groove, It is connected at two locations facing each other. These two third torsion springs 308 are provided on a central axis k that passes through the center of gravity of the fourth frame 305 and the third frame 104. As a result, the third frame 304 is configured to be capable of torsional vibration with the central axis k as the rotation axis.

  Also, an SOI layer 307 (hereinafter referred to as a second torsion spring 307) provided between the second frame 303 and the first frame 302 via a predetermined gap with respect to the first frame 302 by a trench groove. It is connected at two locations facing each other. These two second torsion springs 307 are provided on a central axis j that passes through the center of gravity of the fourth frame 305, the third frame 304, and the second frame 303. As a result, the second frame 303 is configured to be capable of torsional vibration with the central axis j as the rotation axis.

  In addition, an SOI layer 306 (hereinafter referred to as a first torsion spring 306) provided between the first frame 302 and the 0th frame 301 via a predetermined gap with respect to the 0th frame 301 by a trench groove. It is connected at two locations facing each other. These two first torsion springs 306 are provided on a central axis i that passes through the center of gravity of the fourth frame 305, the third frame 304, the second frame 303, and the first frame 302. Thus, the first frame 302 is configured to be able to torsionally vibrate with the central axis i as the rotation axis.

  In addition, the first torsion spring 306, the second torsion spring 307, the third torsion spring 308, and the fourth torsion spring 309 are twisted when a rotational torque is applied, and are twisted with a magnitude corresponding to the rotation angle of the torsion. The rotational torque is generated in the direction opposite to the direction.

Accordingly, by fixing the 0th frame 301, the fourth frame 305, the third frame 304, the second frame 303, and the first frame 302 constitute a four-degree-of-freedom structure.
Further, the left and right edges of the first frame 302 are provided with comb teeth 113 and comb teeth 311 formed in a comb shape. The 0th frame 301 has comb teeth formed in a comb tooth shape that meshes with the comb teeth portion 313 at a predetermined interval at positions facing the comb teeth portion 313 and the comb teeth portion 311 of the first frame 302, respectively. A comb tooth portion 310 formed in a comb tooth shape that meshes with the portion 312 and the comb tooth portion 311 at a predetermined interval is provided.

  In the two-dimensional optical scanning apparatus 300, the angle of the torsional vibration amplitude of the fourth frame 305, the third frame 304, and the second frame 303 is set to the angle of the torsional vibration amplitude of the first frame 302. On the other hand, it is designed to be sufficiently large so that the torsional vibration amplitude of the first frame 302 is substantially equal to the plate thickness of the first frame 302.

The configuration other than the above is the same as that of the two-dimensional optical scanning device 100 of the first embodiment.
In the two-dimensional optical scanning device 300 configured as described above, the fourth frame 305, the third frame 304, the second frame 303, the first frame 302, the fourth torsion spring 309, the third torsion spring 308, and the second torsion spring. 307, the first torsion spring 306 constitutes a four-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when an inherent periodic external force is applied.

  Further, by inputting a periodic electric signal to the comb tooth portion 310, an electrostatic force is generated between the comb tooth portion 310 and the comb tooth portion 311 so that a periodic external force inherent to the four-degree-of-freedom coupled vibration system is generated. Act.

  Further, the torsional vibration of the first frame 302 based on a change in electrostatic capacitance between the comb tooth portion 312 provided in the 0th frame 301 and the comb tooth portion 313 provided in the first frame 302. Detect the angle of the amplitude.

  Since the two-dimensional optical scanning device 300 constitutes a four-degree-of-freedom coupled vibration system, the angle of the torsional vibration amplitude of the fourth frame 305, the third frame 304, and the second frame 303 is the first. The frame 302 is configured to be sufficiently large with respect to the angle of the amplitude of torsional vibration.

  The amplitude of the torsional vibration of the first frame 302 is configured to be approximately equal to the plate thickness of the first frame 302. Therefore, a large excitation force can be obtained at a low voltage, and angular displacements of the fourth frame 305, the third frame 304, the second frame 303, and the first frame 302 can be detected with high accuracy.

  In the embodiment described above, the 0th frame 301 is the fourth rigid member in the present invention, the first frame 302 is the fifth rigid member in the present invention, the second frame 303 is the sixth rigid member in the present invention, and the third frame 304. Is the seventh rigid member in the present invention, the fourth frame 305 is the eighth rigid member in the present invention, the first torsion spring 306 is the fifth elastic deformation member in the present invention, and the second torsion spring 307 is the sixth elastic deformation in the present invention. The third torsion spring 308 is the seventh elastic deformation member in the present invention, the fourth torsion spring 309 is the eighth elastic deformation member in the present invention, the comb tooth portion 310, the comb tooth portion 311, the signal generator 221 and the adder 222. And the amplifier 223 are the second external force acting means according to the present invention, the comb tooth portion 310 is the fourth comb electrode portion according to the present invention, and the comb tooth portion 311 is the fifth comb according to the present invention. The electrode portion, the comb tooth portion 312, the comb tooth portion 313, and the amplitude detection portion 203 are the second angle detecting means in the present invention, the comb tooth portion 312 is the sixth comb tooth electrode portion, and the comb tooth portion 313 in the present invention. In the present invention, the seventh comb electrode portion, the central axis i is the fifth central axis in the present invention, the central axis j is the sixth central axis in the present invention, the central axis k is the seventh central axis in the present invention, and the central axis l. Is the eighth central axis in the present invention.

As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, As long as it belongs to the technical scope of this invention, a various form can be taken.
For example, in the first embodiment, the adder 222 adds two frequency electrical signals (mode 1 excitation signal RS1 and mode 2 excitation signal RS2) to generate a signal in which the two frequency electrical signals are superimposed. In this case, the signal applied to the two-dimensional optical scanning device 100 is shown. However, when a plurality of electric signals are added and applied, the voltage of the added electric signal becomes a value obtained by adding the voltages of the plurality of electric signals. If this voltage is too high, it causes a dielectric breakdown. For example, if an electric signal having an amplitude of 60V and an amplitude of 40V is added, the peak voltage of the added electric signal is 100V. For this reason, it is desirable that the peak voltage of the electrical signal does not increase.

Therefore, the mode 1 excitation signal RS1 and the mode 2 excitation signal RS2 may be applied to the two-dimensional optical scanning device 100 without being added.
Specifically, for example, the mode 1 excitation signal RS1 is applied to the comb tooth portion 109 provided on the left edge 102c side of the first frame 102, and the mode is applied to the comb tooth 109 provided on the right edge 102d side. The two excitation signals RS2 may be applied. By doing in this way, since the peak voltage of the electric signal applied to each of the left and right comb teeth 109 can be kept low, it is possible to avoid dielectric breakdown due to excessive voltage.

  Moreover, in the said 1st Embodiment, what detected the angular displacement of the 1st flame | frame 102 using the comb-tooth part 111 and the comb-tooth part 112 was shown. However, as shown in FIG. 9A, the parallel light source 401 that irradiates the first frame 102 with parallel light (see the light NK indicated by the broken line in the figure) and the reflected light reflected by the surface of the first frame 102. An optical position detecting element 402 (for example, PSD or the like) that receives light (refer to light HK indicated by a broken line in the drawing) and detects the arrival position of the received reflected light may be provided. That is, when the first frame 102 vibrates, the arrival position of the reflected light on the optical position detection element 402 changes, so that the twist angle of the first frame 102 can be accurately detected. The parallel light source 401 is the light irradiation means in the present invention, and the optical position detection element 402 is the arrival position detection means in the present invention.

  Further, the angular displacement of the first frame 102 may be detected by measuring the strain amount of the torsion spring. Specifically, by performing ion doping treatment on the surface of the first torsion spring 105, doping regions 411 and 412 are formed and used as strain gauges as shown in FIG. 9B. Thereby, the torsion angle of the first torsion spring 105 can be detected.

  In the above embodiment, the image generation (display) using the two-dimensional optical scanning device has been described as an example. However, the application of the two-dimensional optical scanning device of the present invention is not limited to this, It can be applied to a wide range of applications such as head-up displays, projectors, rear pro displays, QR code readers, range finders, object detection sensors, and laser radars.

2 is a plan view showing a configuration of a two-dimensional optical scanning device 100. FIG. 4 is an enlarged view of regions R1 and R2 of the two-dimensional optical scanning device 100. FIG. 2 is a diagram illustrating a cross-sectional structure of the two-dimensional optical scanning device 100. FIG. 2 is a block diagram showing a configuration of a drive circuit 200. FIG. It is a figure which shows the waveform of an exciting force, and the waveform of the vibration of each flame | frame. It is a figure which shows the waveform of the signal detected by the amplitude detection part. It is a figure which shows the phase angle characteristic of the normalization angle and the opposing area H between normalization comb teeth parts. 2 is a plan view showing a configuration of a two-dimensional optical scanning device 300. FIG. It is a figure explaining angle detection of the 1st frame 102 of another embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... SOI layer, 12 ... Silicon oxide film layer, 13 ... Base silicon layer, 21 ... Silicon oxide film, 22, 23 ... Aluminum thin film, 100 ... Two-dimensional optical scanning device, 101 ... 0th frame, 102 ... 1st frame , 103 ... second frame, 104 ... third frame, 105 ... first torsion spring, 106 ... second torsion spring, 107 ... third torsion spring, 108 ... recess, 109, 110, 111, 112 ... comb tooth part, DESCRIPTION OF SYMBOLS 200 ... Drive circuit, 201 ... Laser light generation part, 202 ... Signal generation part, 203 ... Amplitude detection part, 204 ... Control circuit, 211 ... Semiconductor laser, 212 ... Laser drive circuit, 221 ... Signal generator, 222 ... Adder 223 ... Amplifier, 224 ... Excessive current cutoff circuit, 231 ... CV conversion circuit, 232 ... Frequency separation filter, 233, 234 ... Rectifier circuit, 235 ... Phase difference measurement circuit 236, 237 ... binarization circuit, 300 ... two-dimensional optical scanning device, 301 ... 0th frame, 302 ... 1st frame, 303 ... 2nd frame, 304 ... 3rd frame, 305 ... 4th frame, 306 ... 1st frame 1 torsion spring, 307... 2nd torsion spring, 308... 3 torsion spring, 309. Position detecting element, 411, 412 ... doping region

Claims (2)

A plate-like third rigid member having a reflecting surface for reflecting light;
A plate-like second rigid member provided through a predetermined gap with respect to the third rigid member;
A plate-like first rigid body member provided via a predetermined gap with respect to the second rigid body member;
A plate-like 0th rigid body member provided through a predetermined gap with respect to the first rigid body member;
The third rigid member and the second rigid member are connected to each other and twisted when a rotational torque is applied, and the rotational torque is in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. A third elastic deformation member configured to generate and torsionally vibrate the third rigid member with a third central axis passing through the center of gravity of the third rigid member as a rotation axis;
The second rigid member and the first rigid member are connected to each other and twisted when a rotational torque is applied, and the rotational torque is in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. A second elastically deformable member configured to generate and torsionally vibrate the second rigid member about a second central axis passing through the center of gravity of the third rigid member and the second rigid member; ,
The first rigid member and the zeroth rigid member are connected and twisted when a rotational torque is applied, and the rotational torque is in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. The first rigid body member is torsionally oscillated with a first central axis that is formed of an elastic body and passes through the center of gravity of the third rigid member, the second rigid member, and the first rigid member as a rotation axis. A first elastic deformation member, and the third rigid member, the second rigid member, the first rigid member, the third elastic deformation member, the second elastic deformation member, and the first elastic deformation member, A three-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when an inherent periodic external force is applied,
Further, a 0th comb-shaped electrode portion provided in the 0th rigid body member and formed in a comb-tooth shape, and a comb tooth provided in the first rigid body member and meshable with the 0th comb-toothed electrode portion. A first comb-like electrode portion formed in a shape, and by inputting a periodic electrical signal to the 0th comb-like electrode portion, the inherent period of the three-degree-of-freedom coupled vibration system First external force application means for applying an external force,
A second comb-like electrode portion provided on the 0th rigid member and formed in a comb-like shape; and a comb-teeth shape provided on the first rigid member and engageable with the second comb-like electrode portion. A third comb-shaped electrode portion formed on the basis of a change in capacitance between the second comb-shaped electrode portion and the third comb-shaped electrode portion. First angle detecting means for detecting the angle of the amplitude of the torsional vibration of
An angle of torsional vibration amplitude of the third rigid member and the second rigid member is sufficiently large with respect to an angle of torsional vibration amplitude of the first rigid member;
The amplitude of the torsional vibration of the first rigid member is substantially equal to the plate thickness of the first rigid member, and the first rigid member has the first torsional vibration during one cycle of the torsional vibration of the first rigid member. A two-dimensional optical scanning device characterized in that there is no period in which the 0 comb-shaped electrode portion and the first comb-shaped electrode portion do not face each other. An eighth rigid member having a reflective surface for reflecting light;
A seventh rigid member provided through a predetermined gap with respect to the eighth rigid member;
A sixth rigid member provided through a predetermined gap with respect to the seventh rigid member;
A fifth rigid member provided through a predetermined gap with respect to the sixth rigid member;
A fourth rigid member provided through a predetermined gap with respect to the fifth rigid member;
The eighth rigid member and the seventh rigid member are connected to each other and twisted when a rotational torque is applied, and the rotational torque is in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. An eighth elastic deformation member configured to generate and torsionally vibrate the eighth rigid member with an eighth central axis passing through the center of gravity of the eighth rigid member as a rotation axis;
The seventh rigid member and the sixth rigid member are connected to each other and twisted when a rotational torque is applied, and the rotational torque is in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. A seventh elastic deformation member configured to generate and torsionally vibrate the seventh rigid member with a seventh central axis passing through the center of gravity of the eighth rigid member and the seventh rigid member as a rotation axis;
The sixth rigid member and the fifth rigid member are connected to each other and twisted when a rotational torque is applied, and the rotational torque is in a direction corresponding to the rotational angle of the twist and in a direction opposite to the twisted direction. The sixth rigid member is configured to twist and vibrate with a sixth central axis passing through the center of gravity of the eighth rigid member, the seventh rigid member, and the sixth rigid member as a rotation axis. 6 elastically deformable members;
The fifth rigid member and the fourth rigid member are connected to each other and twisted when a rotational torque is applied, and the rotational torque is in a direction corresponding to the rotational angle of the twist and in the direction opposite to the twisted direction. The fifth rigid member is formed of an elastic body that generates, with a fifth central axis passing through the center of gravity of the eighth rigid member, the seventh rigid member, the sixth rigid member, and the fifth rigid member as a rotation axis. A fifth elastic member for torsional vibration, the eighth rigid member, the seventh rigid member, the sixth rigid member, the fifth rigid member, the eighth elastic deformable member, and the seventh elastic member. The deformable member, the sixth elastic deformable member, and the fifth elastic deformable member constitute a four-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when an inherent periodic external force is applied,
Further, a fourth comb-like electrode portion provided on the fourth rigid member and formed in a comb-like shape, and a comb tooth provided on the fifth rigid member and engageable with the fourth comb-like electrode portion. A second comb-like electrode portion formed in a shape, and a second external force acting means for applying the inherent periodic external force to the four-degree-of-freedom coupled vibration system,
A comb-like electrode portion provided on the fourth rigid body member and formed in a comb-like shape; and a comb-tooth shape provided on the fifth rigid member and engageable with the fourth comb-like electrode portion. A fifth comb member formed on the basis of a change in capacitance between the sixth comb electrode portion and the seventh comb electrode portion. Second angle detection means for detecting the angle of the amplitude of the torsional vibration of
The angle of the torsional vibration amplitude of the sixth rigid member, the seventh rigid member, and the eighth rigid member is sufficiently large with respect to the amplitude of the torsional vibration amplitude of the fifth rigid member,
The amplitude of the torsional vibration of the fifth rigid member is substantially equal to the plate thickness of the fifth rigid member, and the first rigid member has the first torsional vibration during one period of the torsional vibration of the fifth rigid member. The two-dimensional optical scanning device is configured such that there is no period in which the four comb-shaped electrode portions and the fifth comb-shaped electrode portion do not face each other.

Images