JP4889026B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device that deflects a light beam from a light source by a mirror member. More specifically, the mirror member supported by a pair of torsion springs is reciprocally oscillated with the torsion spring as a torsion rotating shaft. The present invention relates to an optical scanning device.

  An optical scanning device in which a movable electrode is provided on a mirror member supported by a pair of torsion springs, and the mirror member is reciprocally oscillated with a torsion spring as a rotational axis by using an electrostatic force between the movable electrode and the fixed electrode as a driving force. Is known (see, for example, Patent Documents 1 and 2). Such an optical scanning device can maximize the deflection angle of the mirror member when the drive frequency is matched with the resonance frequency of the mirror member.

  In the optical scanning device described in Patent Document 1, the mirror member is provided with one or a plurality of pieces that can be easily cleaved by laser beam irradiation, and the moment of inertia of the mirror member is obtained by cleaving the pieces. By adjusting the resonance frequency, the resonance frequency can be adjusted.

  In the optical scanning device described in Patent Document 2, a flat tuning electrode provided on the substrate surface facing the back surface of the mirror member (stage) or an electrode provided on the back surface of the mirror member is engaged. The resonance frequency can be adjusted by adjusting the voltage applied to the comb-shaped tuning electrode provided on the substrate surface.

  An optical scanning device using a piezoelectric element for driving a mirror member is also known. For example, in Patent Document 3, two pairs of piezoelectric unimorph diaphragms on which piezoelectric elements are formed are connected to a mirror member, and an AC voltage having an opposite phase is applied to the piezoelectric elements of each pair of piezoelectric unimorph diaphragms. An optical scanning device that reciprocally vibrates a member about a torsion spring as a rotation axis is described.

  An optical scanning device that drives a mirror member with electromagnetic force is also known. For example, in Patent Document 4, a mirror surface and a coil pattern are formed on a movable part supported by a pair of spring parts, and this movable part is placed in a bias magnetic field by a permanent magnet, and the coil pattern is energized. An optical scanning device (optical deflection element) configured to reciprocally oscillate the movable portion and an optical writing device such as a laser printer using the optical scanning device are described.

  Although the structure and behavior of the vibration system are different from those of the optical scanning device described above, a vibrator in which a mirror-like vibration part and a fixed part are connected via an elastic deformation part (torsion spring), and its fixing Patent Document 5 discloses an optical scanning device (optical scanning) that includes a vibration device (for example, a piezoelectric element) that applies high-frequency vibration in a direction orthogonal to the elastic deformation portion in the portion and causes the vibrator to resonate and vibrate. In this optical scanning device, the resonance characteristics of the vibrator can be adjusted by heating or deforming the elastic deformation portion by a resistance heating element or a piezoelectric element provided in the elastic deformation portion and changing the spring constant of the elastic deformation portion. .

JP 2003-84226 A JP 2005-128551 A JP 2005-128147 A Japanese Patent No. 3585595 Japanese Patent No. 2981600

  In an optical scanning device in which a mirror member is reciprocally oscillated using a pair of torsion springs as a rotational axis, the displacement angle of the mirror member becomes maximum when the resonance frequency of the mirror member coincides with the drive frequency. However, the resonance frequency varies due to variations in the dimensions of the torsion spring and mirror member in the manufacturing process, and a sample in which a desired drive frequency deviates from the resonance frequency band is generated at a certain rate.

Using a Si substrate having a thickness of 200 μm, a mirror member 202 as shown in FIG. 35 is supported by a pair of torsion springs 201, and comb-like electrodes 203 for generating electrostatic torque for driving the mirror member 202, An optical scanning apparatus having 204 on the free end of the mirror member 202 and the frame part 200 was made as a prototype. The size of the mirror member 202 is 2 mm in length and 1 mm in width, and the vibration space of the mirror member 202 is sealed under reduced pressure. The resonant frequency was measured for this prototype optical scanning device. The drive voltage applied to the electrodes 203 and 204 is 40 (V).
FIG. 36 shows the distribution of the measured resonance frequency. From this figure, it can be seen that the average resonance frequency is 3076.105 (Hz) and the variation is ± 41 (Hz, 3σ).
The vibration angular frequency characteristics were measured for one sample (resonance frequency 3080 Hz) whose resonance frequency is close to the average value and two samples (resonance frequencies 3050 Hz and 3100 Hz) where the resonance frequency is close to the boundary of the variation ± 41 (Hz). The result is shown in FIG. The horizontal axis is the drive frequency, and the vertical axis is the maximum deflection angle. From this figure, it can be seen that the fluctuation angular frequency characteristic shifts on the frequency axis as the resonance frequency varies. When these three samples are driven at an average resonance frequency (3080 Hz), the variation of the swing angle is about 2 ° to about 15 °. Such variations in the resonance frequency and accompanying variations in the deflection angle are a major obstacle when applying the optical scanning device.

  For example, when such an optical scanning device is used as an optical deflector of an optical writing device described in Patent Document 4, variations in shake angles cause a reduction in image quality. Further, the maximum deflection angle required in this case is determined by the distance between the photoconductor and the optical deflector (see FIG. 7 of Patent Document 4). For example, in an optical writing apparatus capable of handling paper size A4, a maximum deflection angle of ± 25 ° is required when the distance between the photosensitive member and the optical deflector is 300 (mm). In order to drive an optical scanning device having a variation in resonance frequency and deflection angle as described above at an average resonance frequency and to vibrate a 2 mm × 1 mm mirror member with a maximum deflection angle of ± 25 °, between the drive electrodes The applied drive voltage needs to be considerably higher than 40 (V), which is also not preferable.

  The present invention has been made in view of the above points, and an object thereof is to provide an improved optical scanning device of a type in which a mirror member reciprocally vibrates about a torsion spring as a rotational axis. Has resonance frequency adjustment means that can continuously adjust the resonance frequency within a sufficient range, and even when the mirror member is relatively large, it can resonate and resonate the mirror member with a large swing angle with a low driving voltage. The object is to provide a possible optical scanning device.

  The optical scanning device according to the present invention is of a type in which a mirror member supported on a frame member by a pair of torsion springs reciprocally vibrates about the torsion spring as a torsion rotating shaft.

According to the first and second aspects of the present invention, each of the torsion springs is connected to the frame member by a pair of connecting members in the vicinity of the connecting end with the frame member. A piezoelectric element for generating a driving torque for the mirror member by being deformed is provided, and a comb-shaped first electrode and a second electrode for acting as an electrostatic spring for adjusting the resonance frequency of the mirror member The first electrode is provided on the torsion spring, and the second electrode is provided on the frame member. According to the first aspect of the present invention, the length from the fixed end of the torsion spring to the frame member to the coupling end of the mirror member is L, and the length of the torsion spring near the fixed end is 2L / The first electrode and the second electrode are provided only within the range of 3. In the invention according to claim 2, the length of the first electrode is shorter as it is closer to the mirror member, and the length of the second electrode is constant.
According to such a configuration, the resonance frequency of the mirror member is adjusted in a sufficiently wide range by changing the voltage applied between the first and second electrodes, as will be described in detail later in connection with the embodiment. In addition, it is possible to generate a large mirror member driving torque by applying a relatively low voltage to the piezoelectric element. Therefore, the mirror member can be reciprocally oscillated with a large swing angle at a desired resonance frequency. Furthermore, a short circuit between the first electrode and the second electrode due to higher-order mode vibration during the vibration of the mirror member is less likely to occur.

According to the invention described in claim 3 , in the configuration according to the invention described in claim 1 or 2 , the first silicon substrate of the SOI substrate in which the first and second silicon substrates are bonded via the insulating film is provided. The frame member, the torsion spring, the mirror member, the connecting member, the first electrode, and the second electrode are integrally formed, and a vibration space for the mirror member is formed on the second silicon substrate. Is done.

According to a fourth aspect of the present invention, in the configuration according to the first or second aspect of the present invention, a comb-teeth shape for acting as an electrostatic spring for adjusting the resonance frequency of the mirror member together with the first electrode. The third electrode is provided in a positional relationship such that the third electrode is shifted in the thickness direction from the second electrode and meshes with the first electrode.
As will be described later in detail in connection with the embodiment, the resonance frequency of the mirror member can be adjusted in a wider range by adding the third electrode.

According to a fifth aspect of the present invention, in the configuration according to the fourth aspect of the present invention, the first silicon substrate of the SOI substrate in which the first and second silicon substrates are bonded via the insulating film, The frame member, the torsion spring, the mirror member, the connecting member, the first electrode, and the second electrode are integrally formed, and the third electrode and the mirror member are formed on the second silicon substrate. The vibration space is integrally formed.

According to a sixth aspect of the present invention, in the configuration according to the fourth or fifth aspect of the present invention, the second electrode and the first electrode have the same thickness. By adopting such a thickness relationship, the spring constant of the electrostatic spring between the first and third electrodes can be increased and the resonance frequency adjustment range can be expanded, as will be described later in connection with the embodiment. it can.

According to a seventh aspect of the present invention, in the configuration according to any one of the first to sixth aspects, the vibration frequency detection electrode of the mirror member includes the free end of the mirror member and the frame. It is formed at a corresponding part of the member. Such a configuration facilitates automatic detection and adjustment of the resonance frequency of the mirror member, as will be described later in connection with the embodiment.

According to an eighth aspect of the present invention, in the configuration according to the third aspect of the invention, the electrode for detecting the displacement angle of the mirror substrate is a corresponding portion between each free end of the mirror member and the second silicon substrate. Formed. According to such a configuration, as will be described later in connection with the embodiment, it is possible to easily perform control to change the voltage applied between the first and second electrodes in accordance with the displacement angle of the mirror member. Is possible.

  According to the present invention, the resonance frequency can be continuously adjusted within a sufficient range, and even when the mirror member is relatively large, it is possible to resonate and resonate the mirror member with a large swing angle with a low driving voltage. For example, an improved optical scanning device suitable as an optical polarizer of an optical writing device disclosed in Patent Document 4 can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings referred to in the following description, the same or similar reference numerals are used for the same or corresponding elements in order to reduce duplication of description.

[First Embodiment]
An optical scanning device according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic exploded perspective view of the optical scanning device according to the present embodiment. This optical scanning device has an overall structure in which a second substrate 2 is bonded to a first substrate 1. Although not shown, the substrate 1 and the substrate 2 are insulated by an insulating film. As will be described later, this optical scanning device is manufactured using an SOI (Silicon On Insulator) substrate made of Si substrate / insulating film / Si substrate. The materials of the substrates 1 and 2 will be described later in relation to the manufacturing method.

  A movable plate (mirror member) 3 having a mirror surface on the surface is integrally formed on the substrate 1 in a form supported by a frame portion 5 by a pair of torsion springs 4. The movable plate 3 can reciprocate with the torsion spring 4 as a torsional rotation shaft. The substrate 2 serves as a reinforcing member for the substrate 1, and a vibration space of the movable plate 3 is formed in the substrate 2.

  The vicinity of the fixed end of each torsion spring 4 to the frame portion 5 is connected to the frame portion 5 by a pair of connecting members (cantilevers) 7 orthogonal to the torsion spring 4. A piezoelectric element 8 is formed on each connecting member 7 as schematically shown in FIG. The piezoelectric element 8 is for generating a driving torque for the movable plate 3 by expanding and contracting in the length direction of the connecting member 7 to deform the connecting member 7. Reference numeral 11 denotes an electrode pad for each piezoelectric element 8.

  Each torsion spring 4 is formed with a comb-shaped first electrode 9. A comb-like second electrode 10 is formed in the frame portion 5 in a positional relationship to mesh with the first electrode 9. The first electrode 9 and the second electrode 10 serve to act as electrostatic springs for adjusting the resonance frequency of the movable plate (mirror member) 3. 12 is an electrode pad for the first electrode 9, and 13 is an electrode pad for the second electrode 10. By forming the separation groove 14 in the fixed portion 15 of each torsion spring 4 of the frame portion 5, the torsion spring 4, the first electrode 9 and the second electrode 10 are electrically separated.

  In order to clarify the structure and material of the optical scanning device, the manufacturing method will be described here. 3A and 3B are explanatory diagrams of processes, and schematically show a cross-sectional shape corresponding to the cross section A-A ′ of FIG. 1.

  Step (a): On the surface of the SOI substrate where the first Si substrate 100 and the second Si substrate 102 are bonded via the insulating layer 101, the thermal oxide films 103 and 104 are made to have a thickness of 0.5 μm, for example, for insulation. Form. Note that the first Si substrate 100 is a low-resistance substrate (conductor), and the substrate itself can also serve as an electrode without forming a metal.

  Step (b): On the first Si substrate 100 side, the lower electrode film 105 for the piezoelectric element 8 (FIG. 2) for generating driving torque, and the piezoelectric material film that expands and contracts in the longitudinal direction of the connecting member 7 by applying a voltage. 106 and the upper electrode film 107 are formed in this order. Examples of film thickness and materials are as follows. As the lower electrode film 105, a Ti film having a thickness of 0.05 μm and a Pt film having a thickness of 0.15 μm are formed in this order. A 3 μm thick zirconate titanate (PZT) film is formed as the piezoelectric material film 106. A Pt film having a thickness of 0.15 μm is formed as the upper electrode film 107. As a film formation method, a sputtering method can be used for the lower electrode film and the upper electrode film. A sputtering method, a CVD (Chemical Vapor Deposition) method, an ion plating method, or the like can be used for the piezoelectric material film.

  Step (c): A resist pattern 108 for dry etching the upper electrode film 107 and the piezoelectric material film 106 is formed.

  Step (d): The upper electrode film 107 and the piezoelectric material film 106 are dry-etched by RIE (Reactive Ion Etching), and then the resist is removed.

  Step (e): A resist pattern 109 for dry etching the lower electrode film 105 and the thermal oxide film 103 is formed.

  Step (f): The lower electrode film 105 and the thermal oxide film 103 are dry etched by RIE, and then the resist is removed. Thus, the piezoelectric element 8 was formed.

  Step (g): A reflective film 110 is formed as a mirror surface of the movable plate (mirror member) 3. Specifically, for example, a 0.05 μm thick Ti film, a 0.05 μm thick Pt film, and a 0.1 μm thick Au film are formed in this order. Here, these films are formed by a sputtering method using a stencil mask. At this time, electrode pads 12 and 13 for electrodes 9 and 10 for electrostatic springs are also formed.

  Step (h): A resist pattern 111 for forming the movable plate (mirror member) 3, the electrodes 9 and 10 for electrostatic springs, the connecting member (cantilever) 7 and the separation groove 14 by dry etching is formed.

  Step (i): Dry etching is performed by RIE, and then the resist is removed. Thus, the movable plate (mirror member) 3, the electrodes 9 and 10 for the electrostatic spring, the connecting member (cantilever) 7 and the separation groove 14 are patterned until reaching the insulating layer 101 of the SOI substrate.

  Step (j): A resist pattern 112 for forming the oscillating space 6 of the movable plate (mirror member) 3 by dry etching is formed on the thermal oxide film 104 on the second Si substrate 102 side of the SOI substrate. .

  Steps (k), (l): The thermal oxide film 104 is dry etched by RIE, and then the second Si substrate 102 and the insulating layer 101 are dry etched by RIE. Thereby, the optical scanning device was completed.

  In the above description, the thicknesses of the electrodes 9 and 10 for the electrostatic spring and the connecting member (cantilever) 7 are the same as the thickness of the first Si substrate 100, but are not limited thereto. The electrostatic torque can be increased as the thickness of the electrodes 9 and 10 for electrostatic springs increases. However, if the connecting member (cantilever) 7 is too thick, there is a concern that it is difficult to be deformed by the piezoelectric element 8. When there is this concern, for example, it is also possible to add an etching process only to the connecting member (cantilever) 7 in the final process to reduce the thickness of the connecting member (cantilever) 7.

  Next, driving of the optical scanning device will be described. The piezoelectric material film (PZT film) of the piezoelectric element 8 expands and contracts in the longitudinal direction of the connecting member (cantilever) 7 by applying a voltage between the upper electrode and the lower electrode. Sine wave voltages P1 and P2 having opposite phases are applied to the piezoelectric element 8 on one connecting member (cantilever) 7 and the piezoelectric element 8 on the other connecting member (cantilever) 7, respectively. Then, as schematically shown in FIG. 4, in a certain cycle of the applied sine wave voltage, one pair of connecting members (cantilevers) 7 (the left side in FIG. 4) is deformed in a convex direction because the upper surface side extends. The other connecting member (cantilever) 7 (the one on the right side in FIG. 4) is deformed in the concave direction because the upper surface side contracts, and as a result, torque Tpzt acts on the torsion spring 4. In the next cycle of the applied sine wave voltage, each connecting member (cantilever) 7 is deformed in the reverse direction, and a reverse torque Tpzt acts on the torsion spring 4. Thus, the movable plate (mirror member) 3 reciprocally vibrates at the frequency F of the applied sine wave voltage with the torsion spring 4 as a torsional rotation axis. If the frequency F of the applied sine wave voltage is matched with the resonance frequency of the movable plate (mirror member) 3, the movable plate (mirror member) 3 can be reciprocally oscillated with a large deflection angle with small energy. It is also possible to drive by applying a pulse voltage to the piezoelectric element 8 instead of the sine wave voltage.

  Next, the resonance frequency adjusting action by the comb-like electrodes 9 and 10 will be described with reference to FIGS.

  FIG. 5 schematically shows a pair of the first electrode 9 and the second electrode 10 acting as an electrostatic spring for adjusting the resonance frequency. However, the first electrode 9 is rotated by an angle θ. The first electrode 9 is grounded, and the voltage V is applied to the second electrode 10. The applied voltage V is constant regardless of the displacement angle θ of the movable plate 3 (this is the same as the displacement angle of the first electrode 9). A torque Ts1 is applied between the electrodes 9 and 10 to pull the electrode 9 back to the center line 18 of the electrode 10.

  FIG. 6 shows the relationship between the torque Ts1 and the displacement angle θ. The finite element method was used to calculate this torque. In FIG. 6, the torque Ts1 acting between the electrodes 9 and 10 increases linearly in proportion to the displacement angle θ up to an angle ± θ1 at which the engagement between the electrodes is lost. Acts as a return force. When the angle ± θ1 is exceeded, the torque Ts1 starts to decrease. If the inclination of the torque line when the displacement angle θ is in the range of −θ1 <θ <θ1 is Ks1, the torque Ts1 is given by the following equation.

電極９，１０間の静電容量をＣとすると、トルクＴs1は次式で与えられる。

If the capacitance between the electrodes 9 and 10 is C, the torque Ts1 is given by the following equation.

すなわち、トルクＴs1は印加電圧Ｖの２乗に比例し、したがってＫｓ１は印加電圧Ｖの２乗に比例する。

That is, the torque Ts1 is proportional to the square of the applied voltage V, and thus Ks1 is proportional to the square of the applied voltage V.

  FIG. 7 is a graph showing the relationship between the torque Ts1 and the displacement angle θ of the torque Tm by the torsion spring 4. The torque Tm and the torque Ts1 have the same direction of action with respect to the displacement angle θ, and the return force acting on the movable plate 3 is a torque obtained by adding the torque Ts1 and the torque Tm. The slopes Ks1 and Km of the torque lines in FIG. 7 are the spring constant of the electrostatic spring by the electrodes 9 and 10 and the spring constant of the torsion spring 4.

  From the above, an inertia (I) expressing the movable plate 3, a torsion spring having a spring constant Km, an electrostatic spring having a spring constant Ks1, and a dashpot C composed of a viscous resistance C as shown in FIG. The optical scanning device can be expressed by a degree model. With this model, the equation of motion of the movable plate 3 in a state where the electrostatic torque Ts1 is applied is given by the following equation.

−θ1＜θ＜θ1では、Ｔｓ１＝Ｋｓ1・θと表すことができるから、

Since −θ1 <θ <θ1 can be expressed as Ts1 = Ks1 · θ,

すなわち、バネ定数（Ｋm＋Ｋs1）、慣性Ｉの自由振動となる。よって、共振振動数ｆは次式で表される。

In other words, the spring constant (Km + Ks1) and the inertia I free vibration. Therefore, the resonance frequency f is expressed by the following equation.

前述の通りＫｓ1は印加電圧Ｖの２乗に比例する。よって、印加電圧Ｖを増減することによって共振周波数ｆを調節可能である。

As described above, Ks1 is proportional to the square of the applied voltage V. Therefore, the resonance frequency f can be adjusted by increasing or decreasing the applied voltage V.

The applied voltage V and resonance frequency calculated when the shape of the movable plate (mirror member) 3 is 4 mm (long side) × 1 mm (short side), the thickness of the substrate 1 is 200 μm, and the gap between the electrodes 9 and 10 is 6 μm. The relationship is shown in FIG.
Resonance frequency when applied voltage V = 0 (V): 3050 (Hz)
Torsion spring constant Km: 9.71232 × 10 ³ (dyn · cm / rad)
Electrostatic spring constant Ks1: 0.03 (dyn · cm / rad / V ² )
Movable plate inertia moment I: 2.56 × 10 ⁻⁵ (g · cm ² )

  As can be seen from FIG. 9, in this example, when 100 (V) is applied between the electrodes 9 and 10, the resonance frequency is about 50 (Hz) than when no voltage is applied (when the applied voltage is 0 (V)). Can only raise. That is, the resonance frequency can be adjusted in the range of about 50 (Hz) by changing the applied voltage from 0 (V) to 100 (V). This adjustment range can be said to be sufficiently wide if, for example, the variation in resonance frequency shown in FIG. 36 is taken into consideration.

  Although specific numerical values are not presented, it is possible to generate a relatively large driving torque Tpzt by driving the piezoelectric element 8 with a lower voltage compared to the electrostatic method in which the mirror member is driven by the electrostatic torque acting between the electrodes. . Further, even if there is a variation in the resonance frequency due to a manufacturing process or the like, the resonance frequency can be easily adjusted to coincide with a desired drive frequency. Therefore, even when the size of the movable plate 3 is relatively large, the optical scanning device according to the present embodiment can resonate and reciprocate the movable plate 3 at a desired drive frequency with a large deflection angle even with a low drive voltage. Therefore, for example, it can be suitably used as an optical polarizer of the optical writing device of Patent Document 4.

[Second Embodiment]
An optical scanning device according to a second embodiment of the present invention will be described with reference to FIGS.

  FIG. 10 is a schematic perspective view of the optical scanning device according to the present embodiment. As shown in the figure, this optical scanning device has an overall configuration in which a substrate 1 and a substrate 2 are joined, and an SOI composed of Si substrate / insulating film / Si substrate is manufactured by the same manufacturing process as in the first embodiment. It can be manufactured using a substrate. Reference numeral 21 denotes an interlayer insulating film of the SOI substrate. The structure relating to the substrate 1 is the same as that in the first embodiment. A vibration space (9) of the movable plate (mirror member) 3 is formed on the substrate 2 as in the case of the first embodiment. However, as shown in FIGS. The third embodiment is different from the first embodiment in that a comb-like third electrode 22 for adjusting the resonance frequency is further formed immediately below the second electrode 10. 11 shows the AA cross section of FIG. 10, and FIG. 12 shows the BB cross section of FIG. The second electrode 10 and the third electrode 22 are insulated by the insulating film 21. In FIG. 10, reference numeral 19 denotes an electrode pad for the third electrode 22, and a through hole is formed in the substrate 1 corresponding to this.

  In this optical scanning device, the movable plate (mirror member) 3 has a pair of torsion springs 4 by a driving torque generated by a piezoelectric element 8 (not shown in FIG. 10) formed on a connecting member (cantilever) 7. The reciprocating vibration with the twisting rotation axis as in the case of the first embodiment.

  Next, the resonance frequency adjusting action by the electrodes 9, 10, and 22 will be described. The electrostatic torque Ts1 acting between the first electrode 9 and the second electrode 10 has been described with respect to the first embodiment. Here, electrostatic torque acting between the first electrode 9 and the third electrode 22 will be described.

  FIG. 13 shows one set of the first electrode 9 and the second and third electrodes 10 and 22. The electrode 9 is rotated by an angle θ. The first electrode 9 is grounded, and a constant voltage V is applied to the third electrode 22 regardless of the displacement angle of the movable plate 3. At this time, a torque Ts2 is applied between the electrodes 9 and 22 to pull the electrode 9 back to the center line 23 of the electrode 22. FIG. 14 shows an outline of the result of calculating the torque Ts2 by changing the displacement angle θ. This calculation was based on the finite element method. FIG. 14 also shows the torque Ts1 acting between the first electrode 9 and the second electrode 10 and its spring constant Ks1, the torque Tm of the torsion spring 4 and its spring constant Km. These torques and spring constants have already been described in relation to the first embodiment.

  In FIG. 14, the torque Ts2 increases linearly in proportion to the displacement angle θ until the angle ± θ2 at which the electrodes 9 and 22 are not engaged, and the center line 23 of the electrode 22 with respect to the movable plate 3. Acts as a force to return. When the angle ± θ2 is exceeded, the torque Ts2 starts to decrease. Assuming that the slope of the torque line in the range of −θ2 <θ <θ2 is Ks2, the torque Ts2 at the displacement angle θ is given by the following equation.

電極９，２２間の静電容量をＣとするとき、トルクＴs2は次式で与えられる。

When the capacitance between the electrodes 9 and 22 is C, the torque Ts2 is given by the following equation.

このように、トルクＴs2は印加電圧Ｖの２乗に比例し、したがって、トルク曲線の傾きすなわちバネ定数Ｋｓ2は印加電圧Ｖの２乗に比例する。図１４に示されるように、トルクＴs2は、トルクＴm，Ｔs1とは、変位角θに対して作用方向が逆である。よって、可動板３を表す慣性Ｉ、バネ定数Ｋｍのトーションバネ、バネ定数Ｋs1の静電バネ、バネ定数Ｋs2の静電バネ、粘性抵抗ＣからなるダッシュポットＣで構成される図１５に示すような一自由度モデルにより光走査装置を表現することができ、トルクＴs1,Ｔs2が共に作用した状態での可動板３の運動方程式は次式で与えられる。

Thus, the torque Ts2 is proportional to the square of the applied voltage V. Therefore, the slope of the torque curve, that is, the spring constant Ks2 is proportional to the square of the applied voltage V. As shown in FIG. 14, the torque Ts2 has a direction of action opposite to the torques Tm and Ts1 with respect to the displacement angle θ. Therefore, as shown in FIG. 15, which is constituted by a dashpot C comprising an inertia I representing the movable plate 3, a torsion spring having a spring constant Km, an electrostatic spring having a spring constant Ks 1, an electrostatic spring having a spring constant Ks 2, and a viscous resistance C. The optical scanning device can be expressed by a single-degree-of-freedom model, and the equation of motion of the movable plate 3 with the torques Ts1 and Ts2 acting together is given by the following equation.

−θ1＜θ＜θ1では、Ｔs1＝Ｋs1・θ、Ｔs2＝Ｋs2・θ と表すことができるから、

Since −θ1 <θ <θ1 can be expressed as Ts1 = Ks1 · θ and Ts2 = Ks2 · θ,

すなわち、バネ定数（Ｋm＋Ｋs1−Ｔs2）、慣性Ｉの自由振動となる。よって、共振周波数ｆは次式で与えられる。

In other words, the spring constant (Km + Ks1-Ts2) and inertia I free vibration. Therefore, the resonance frequency f is given by the following equation.

前述の通り、Ｋs1、Ｋs2は印加電圧Ｖの２乗に比例して変化するので、印加圧Ｖを変化させることにより共振周波数ｆを調整することができる。すなわち、電極９，１０間の印加電圧を増加させると静電バネ定数Ｋs1が増加して共振周波数ｆが上昇し、電極９，２２間の印加電圧を増加させると静電バネ定数Ｋs2が増加して共振周波数ｆが低下する。

As described above, since Ks1 and Ks2 change in proportion to the square of the applied voltage V, the resonance frequency f can be adjusted by changing the applied pressure V. That is, when the applied voltage between the electrodes 9 and 10 is increased, the electrostatic spring constant Ks1 is increased and the resonance frequency f is increased, and when the applied voltage between the electrodes 9 and 22 is increased, the electrostatic spring constant Ks2 is increased. As a result, the resonance frequency f decreases.

The shape of the movable plate 3 is 4 mm (long side) × 1 mm (short side), the thicknesses of the substrates 1 and 2 are 200 μm, the gap between the electrodes 9 and 10 and the gap between the electrodes 9 and 22 are 6 μm, FIG. 16 shows the result of calculating the resonance frequency when a voltage is applied only to one of the electrodes 9 and 22. In FIG. 16, the applied voltage between the electrodes 9 and 10 is represented as a positive polarity, and the applied voltage between the electrodes 9 and 22 is represented as a negative polarity. May have the same polarity.
Resonance frequency when applied voltage = 0 (V): 3100 (Hz)
Torsion spring constant Km: 9.71232 × 10 ³ (dyn · cm / rad)
Electrostatic spring constant Ks1: 0.03 (dyn · cm / rad / V ² )
Electrostatic spring constant Ks2: 0.015 (dyn · cm / rad / V ² )
Movable plate inertia moment I: 2.56 × 10 ⁻⁵ (g · cm ² )

  As can be seen from FIG. 16, in this example, by changing the voltage applied to the electrode 10 or 22 in the range of 0 (V) to 100 (V), the resonance frequency f is adjusted with a width of about 75 (Hz). Is possible. This adjustment range is wide enough to compensate for variations in the resonance frequency as shown in FIG. 36, for example. As described above, the optical scanning device according to the present embodiment has a sufficiently wide resonance frequency adjustment range, and can generate a relatively large driving torque by applying a low driving voltage applied to the piezoelectric element. Therefore, even when the movable plate 3 is relatively large, the movable plate 3 can be reciprocally oscillated with a large swing angle at a desired driving frequency. It is suitable as an optical polarizer of the insertion device.

  In the present embodiment, the thicknesses of the substrates 1 and 2 are the same, and thus the thicknesses (sizes in the height direction) of the electrodes 10 and 22 are the same. The merit of doing this will be described. 17 and 18 are explanatory diagrams thereof.

  When a voltage is applied between the first electrode 9 and the third electrode 22, as shown in FIGS. 17 and 18, the electrostatic force that tries to draw the first electrode 9 into the center line 23 of the third electrode 22. It has already been described that the torque Ts2 acts and this torque Ts2 is given by the above-described equation (7).

  When the thicknesses of the substrates 1 and 2 (thicknesses of the electrodes 10 and 22) are the same (FIG. 17), and when the substrate 2 (electrode 22) is thicker than the substrate 1 (electrode 10) (FIG. 18), In the former, the change in the capacitance C between the electrodes becomes steeper and dC / dθ becomes larger. Therefore, the former can obtain a larger electrostatic torque Ts2 with the same applied voltage, and thus the resonance frequency adjustment range is widened. There is an advantage that you can.

[Third Embodiment]
An optical scanning device according to a third embodiment of the present invention will be described with reference to FIGS.

  FIG. 19 is a schematic perspective view of the optical scanning device according to the present embodiment. The overall configuration of the optical scanning device is the same as that of the first embodiment (or the second embodiment), and the difference is that the electrodes 9 and 10 (or electrodes) constituting an electrostatic spring for adjusting the resonance frequency. 9, 10, 22) is only a point having a trapezoidal planar shape.

  The planar shape of the electrodes 9, 10 (or 9, 10, 22) in the first embodiment (or the second embodiment) is shown in the upper part of FIG. 20, and the electrodes 9, 10 (or 9, 10 in the present embodiment). , 22) are shown in the lower part of FIG. In the present embodiment, each electrode has the maximum width W2 at the base end, the width decreases as it approaches the tip (free end), and the tip (free end) has the minimum width W1. The electrode pitch P is the same as in the first (or second) embodiment.

  When the electrode shape is as shown in the upper part of FIG. 20, resonance vibration as schematically shown in FIG. 21 is likely to occur in the electrode 9 when the movable plate 3 vibrates, and the electrode 9 and the electrode 10 (or 22) There is a risk of short circuit between them. In the present embodiment, since the electrode shape is as shown in the lower part of FIG. 20, the electrode 9 has high rigidity and is less likely to cause resonance vibration, and a short circuit between the electrode 9 and the electrode 10 (or 22) can be prevented. Only the electrode 9 may have a trapezoidal planar shape as described above, and the width of the electrode 10 (22) may be the same from the proximal end to the distal end.

  Now, when the movable plate (mirror member) 3 vibrates, high-order mode vibrations schematically shown by broken lines in FIG. 22 also occur. This higher-order mode vibration has a frequency that is about twice the resonance frequency, and the vibration direction is the direction indicated by the arrow in FIG. Due to this higher-order mode vibration, the torsion spring 4 is deformed as indicated by a broken line, whereby the electrode 9 provided closer to the movable plate 3 is tilted as shown schematically in FIG. 22) Easily short-circuited. On the other hand, the electrode 9 far from the movable plate 3 has a small inclination because there is little deformation of the torsion spring 3 at that position, and short-circuiting with the electrode 10 (or 22) hardly occurs. Next, an embodiment in consideration of this will be described.

[Fourth Embodiment]
FIG. 24 is a schematic perspective view of an optical scanning device according to the fourth embodiment of the present invention. The overall configuration of this optical scanning device is the same as that of the first embodiment (or the second embodiment). The difference is that, as shown in the figure, electrodes 9 and 10 (or 9, 9) for adjusting the resonance frequency are used. 10, 11) is not provided in a range where the distance from the movable plate 3 is within L / 3, but is provided only at a position closer to the fixed end 15 of the torsion spring 4 than that. Here, L is the length of the torsion spring 3. In other words, the electrodes 9, 10 (or 9, 10, 11) are provided only within the range of the length 2L / 3 from the fixed end of the torsion spring 4. Since the electrode 9 provided in such a positional relationship has a small inclination due to the higher-order mode vibration described with reference to FIG. 23, the occurrence of a short-circuit between the electrodes can be effectively prevented. The electrodes 10 and 22 may not necessarily be provided without following such restrictions. However, the electrodes 10 and 22 provided in a portion not engaged with the electrode 9 are meaningless because they do not act as electrostatic springs. is there.

[Fifth Embodiment]
The optical scanning apparatus according to the fifth embodiment of the present invention has the same overall configuration as that of the first or second embodiment, but as shown schematically in FIG. The length of the electrode 9 provided on the electrode 9 is set to be shorter as the electrode 9 is closer to the movable plate 3. In this embodiment, the length L1 of the electrode 9 provided on the fixed end side of the torsion spring 4 is the maximum, and the length L2 of the electrode 9 provided near the movable plate 3 is the minimum, provided at the intermediate position. The length of the electrode 9 is set to be smaller than L1 and larger than L2. Thus, since the length of the electrode 9 located closer to the movable plate 3 having a large inclination due to higher-order mode vibration is shorter, the short circuit between the electrode 10 (or 10, 22) and the electrode 9 is effectively prevented. Can be prevented.

[Sixth Embodiment]
The sixth embodiment of the present invention will be described with reference to FIGS.

  FIG. 26 is a schematic perspective view of the optical scanning device according to the present embodiment. In this optical scanning device, an electrode 30 is formed at the free end of the movable plate (mirror member) 3 as an electrode for vibration frequency detection, and an electrode 31 is formed on the frame portion 5 side correspondingly. These electrodes 30 and 31 can also be comb-shaped electrodes. A separation groove 32 for electrically separating the electrode 31 is formed in the frame portion 5, and an electrode pad 33 for the electrode 30 is also formed. Other configurations of the optical scanning device are the same as those of the first embodiment. However, a part of the structure on the substrate 1 is omitted in FIG. The resonance frequency adjusting electrodes 9 and 10 may be shaped or arranged as in the third to fifth embodiments, and this embodiment is also included in this embodiment. Further, the embodiment in which the resonance frequency adjusting electrode 22 is provided as in the second embodiment is also included in the present embodiment. However, when the electrode 22 is added, control for selectively applying a voltage to the electrode 10 and the electrode 22 is necessary.

  The optical scanning device according to the present embodiment can automatically adjust the resonance frequency to a target frequency. FIG. 27 is a block diagram illustrating an example of a circuit system that performs automatic resonance frequency adjustment and normal driving for the optical scanning device.

  In FIG. 27, 101 is a microcomputer (hereinafter referred to as CPU), 102 is a digital / analog converter, 103 is a voltage controlled oscillator (VCO), 104 is a pulse shaping circuit, 105 and 108 are AND gates, and 107 is a flip-flop. 106 are mono multivibrators. C1 indicates the capacitance between one electrode 30 and 31, and C2 indicates the capacitance between the other electrode 30 and 31. Reference numerals 109 and 110 denote C / V converters that convert the capacitances C1 and C2 into voltage levels. Reference numeral 111 denotes an adder that adds the converted voltage signals of the C / V converters 109 and 110. Reference numeral 112 denotes a synchronous detection circuit, and 113 denotes an amplifier. Reference numeral 120 denotes a piezoelectric element drive circuit that applies a drive pulse having an opposite phase to each pair of piezoelectric elements 8 for driving the movable plate 3, and 121 denotes an adjustment voltage application circuit that applies a voltage to the resonance frequency adjusting electrode 10. .

  First, the operation of automatically adjusting the resonance frequency to the target frequency by adjusting the voltage applied to the electrode 10 will be described. FIG. 28 is a flowchart for explaining the overall flow of this operation.

  The CPU 101 initializes the voltage value register RV to 0, and sets the value of the voltage value register RV in the adjustment voltage application circuit 121 (step S1). Therefore, at this stage, the adjustment voltage application circuit 121 applies 0 (V) to the electrode 10.

  The CPU 101 calls a resonance frequency detection routine (step S2). Although details of this routine will be described later, the detected resonance frequency is held in a register RF described later. The CPU 101 performs a comparison determination between the absolute value of the difference between the value of the register RF (resonance frequency) and the target frequency Fo and a predetermined threshold value TH (step S3). If it is determined that the absolute value of the difference exceeds the threshold value TH (step S3, No), further adjustment is necessary. Therefore, the value of the voltage value register RV is increased by dV, and the voltage value register RV after the increase is increased. Is set in the adjustment voltage application circuit 121, the voltage applied to the electrode 10 is increased by dV (step S4), and the resonance frequency detection routine is called again (step S2).

  While the determination result of step S3 is No, the processing loop of steps S2 to S4 is repeated. If the determination result in Step S3 is Yes, it means that the adjustment of the resonance frequency to the target frequency Fo has been completed, so this operation ends. The value of the voltage value register RV at this time indicates the voltage value to be applied to the electrode 10 in order to adjust the resonance frequency to the target frequency Fo.

  FIG. 29 is a flowchart for explaining the resonance frequency detection routine called in step S2 of FIG. Hereinafter, a description will be given with reference to FIG.

  The CPU 101 sets the signal C to the H level (step S11), initializes the register RC, which is a counter of the number of repetitions, to 0 (step S12), and temporarily holds the peak value of the output voltage of the amplifier 113. The register RGLf is initialized to 0 (step S13), the minimum value Fmin is set in the register RF for holding the driving frequency, and the frequency data Df corresponding to the value of the register RF (here, Fmin) is converted into a digital / analog converter. It outputs to 102 (step S14). A voltage corresponding to the frequency data Df is input from the digital / analog converter 102 to the VCO 103, and the VCO 103 generates a sine wave having a constant amplitude of the frequency Df. The pulse shaping circuit 104 shapes the sine wave into a rectangular pulse having an H level in the positive half wave section and an L level in the negative half wave section. This rectangular pulse is input to AND gates 105 and 108.

  Next, the CPU 101 outputs one H level reset pulse B (step S15). The flip-flop 107 is reset by this reset pulse B, and its Q bar output changes from L level to H level. Since the signal C is at the H level, when the output of the pulse shaping circuit 104 is at the H level, the output of the AND gate 105 changes to the H level, thereby setting the flip-flop 107 and returning the Q bar output to the L level. The output of the AND gate 105 returns to the L bell. The output of the AND gate 105 is connected to the trigger input of the mono multivibrator 106, and the mono multivibrator is changed by the transition from the L level to the H level (or the transition from the H level to the L level) of the AND gate 105. 106 is triggered, and the output of the mono multivibrator 106 becomes H level for the set time. During this H level period, the piezoelectric element drive circuit 120 applies a positive voltage to one of the paired piezoelectric elements 8 and a negative voltage to the other piezoelectric element 8. As a result, the connecting member (cantilever) 7 is deformed as schematically shown in FIG. After the set time, the voltage application to the piezoelectric element 8 is cut off, and the movable plate (mirror member) 3 oscillates and oscillates freely at the frequency shown in the equation (5).

  During this vibration, the capacitances C1 and C2 between each pair of electrodes 30 and 31 change sinusoidally at the same frequency as the vibration of the movable plate 3 as schematically shown in FIG. The conversion voltage signal by the / V converters 109 and 110 changes. A signal (capacitance detection signal) obtained by adding the converted voltage signals is input from the adder 111 to the synchronous detector 112. The synchronous detector 112 synchronously detects the capacitance detection signal using the sine wave of the frequency Df generated by the VCO 103 as a synchronous signal. The detection output signal of the synchronous detector 112 has the highest level when the frequency of the electrostatic capacitance detection signal (vibration frequency of the movable plate 3) matches the frequency Df, and the level decreases as the deviation between the two frequencies increases. The detection output signal is amplified by the amplifier 113 and input to the analog / digital conversion port (A / D) of the CPU 101 as a GLf signal.

  The CPU 101 reads the peak level of the GLf signal as a digital value after a predetermined delay time from the output of the reset pulse B (step S16). This delay time is a time required until the voltage of the smoothing capacitor of the low-pass filter is stabilized after the low-pass filter in the synchronous detector 112 is reset by the reset pulse B.

  The CPU 101 determines whether or not the read GLf value and the value of the register RGLf (initial value is 0) or more (step S17). If the GLf value is greater than or equal to the value of the register RGLf (step S17, Yes), the GLf value is set in the register RGLf (step S18), and the value of the register RC is incremented by 1 (step S19). If the value of the register RC after the increment is less than the set value PN (step S20, No), an update is performed to increase the value of the register RF by dF, and the frequency data Df corresponding to the value of the register RF after the update is obtained. The data is output to the digital / analog converter 102 (step S21). This increases the frequency of the sine wave generated by the VCO 103 by dF.

  The CPU 101 generates a reset pulse B, drives the piezoelectric element 8 to vibrate the movable plate 3, and then reads the peak level of the GLf signal as a digital value after a predetermined time (step S16). If the current frequency Df is closer to the resonance frequency of the movable plate 3 than the previous time, the GLf value should be higher than the previous time (step S17, Yes), and therefore the steps go through steps S18, S19, and S20. In S21, the value of the register RF is updated to increase by dF, the frequency of the sine wave generated by the VCO 103 is increased by dF, the reset pulse B is output again (step S15), and after a predetermined time, the GLf signal The peak level is read as a digital value (step S16).

  As described above, the movable plate 3 is excited while gradually increasing the frequency of the sine wave generated by the VCO 103 by dF, and the GLf signal peak level at that time is compared with the previous GLf signal peak level. When the frequency Df of the sine wave generated by the VCO 103 and the resonance frequency of the movable plate 3 are closest, the peak level of the GLf signal becomes the highest. Next, when the frequency DF is increased by dF, the peak level of the GLf signal is Lower than level. That is, the determination result in step S17 is No, and the process returns from the resonance frequency detection routine to the main routine shown in FIG. When the absolute value of the difference between the resonance frequency detected this time, that is, the value of the register RF and the target frequency Fo is larger than the threshold value TH (step S3, No), the CPU 101 performs an update to increase the value of the register RV by dV, The updated value of the register RV is set in the adjustment voltage application circuit 121 (step S4). Thus, since the voltage applied to the resonance frequency adjusting electrode 10 increases by dV, the resonance frequency of the movable plate 3 increases accordingly. The CPU 101 calls the resonance frequency detection routine again to restart the resonance frequency detection process (step S2).

  As described above, the resonance frequency is detected while sequentially increasing the voltage applied to the electrode 10 in increments of dV to check the deviation from the target frequency Fo, and the absolute value of the difference between the resonance frequency and the target frequency Fo is equal to or less than the threshold value TH. If so (step S3), it is determined that the resonance frequency has been adjusted to the target frequency Fo, and the resonance frequency adjustment processing is terminated. If it is determined in step S20 of FIG. 29 that the value of the register RC has reached the maximum number of repetitions PN, it is determined that the resonance frequency detection has failed, and the resonance frequency adjustment process is stopped.

  Next, a normal driving operation of the optical scanning device will be described. The CPU 101 sets the signal C to the L level and outputs frequency data Df corresponding to the target frequency Fo to the digital / analog converter 102, thereby generating a sine wave of the target frequency Fo in the VCO 103. Further, the value of the register RV at the end of the resonance frequency adjustment process is set in the adjustment voltage application circuit 121, and the voltage corresponding to the register value is applied to the electrode 10, whereby the resonance frequency of the movable plate 3 is changed to Fo. Adjust to. Since the signal C is at the L level, the rectangular pulse having the frequency Fo shaped by the pulse shaping circuit 104 is input to the piezoelectric element driving circuit 120 through the AND gate 108. The piezoelectric element driving circuit 120 applies a positive voltage to one of the paired piezoelectric elements 8 and a negative voltage to the other piezoelectric element 8 during the H level period of the input rectangular pulse, and during the L level period of the rectangular pulse. Then, a voltage having a reverse polarity is applied to the piezoelectric elements 8. Thus, the movable plate 3 (mirror member) 3 reciprocally vibrates at the resonance frequency Fo using the torsion spring 4 as a torsion rotating shaft. The piezoelectric element driving circuit 120 can be configured to switch between a power source and the piezoelectric element 8 in accordance with a rectangular pulse, for example.

  When the electrode 22 is provided in addition to the electrode 10 for adjusting the resonance frequency as in the second embodiment, which of the electrode 10 and the electrode 22 is used at the time of resonance frequency adjustment and normal driving? It is necessary to instruct the adjustment voltage application circuit 121 on the CPU 101 side.

[Seventh Embodiment]
As described in connection with the first embodiment, the torque Ts1 acting between the electrodes 9 and 10 is saturated from the vicinity of ± θ1 as shown in FIG. The electrostatic spring constant Ks1 decreases. When the movable plate 3 is vibrated with a large displacement angle exceeding ± θ1, the decrease of the electrostatic spring constant Ks1 in the range where the displacement angle exceeds ± θ1 is suppressed, and the electrostatic spring constant Ks1 is substantially reduced in a wider displacement angle range. It is preferable to keep it constant. As a method for realizing this, it is conceivable to perform control so as to increase the voltage applied between the electrodes 9 and 10 during a period in which the displacement angle exceeds ± θ1. The seventh embodiment of the present invention described here enables such control.

  FIG. 31 is a schematic exploded perspective view of the optical scanning device according to the present embodiment. The overall configuration of this optical scanning device is the same as that of the first embodiment, but an electrode 40 is formed at each free end of the movable plate 3 as an electrode for detecting the displacement angle of the movable plate 3, Two electrodes 41 are formed on the substrate 2 side so as to correspond to the electrodes 40. The electrodes 40 and 41 may have a comb shape. In the substrate 2, separation grooves 42 for electrically separating the respective electrodes 41 are formed, and electrode pads 42 for the respective electrodes 41 are formed. The substrate 1 has through holes 43 corresponding to the electrode pads 42. Other configurations are the same as those of the optical scanning device according to the first embodiment, but a part of the structure of the substrate 1 is omitted in the drawing. The electrodes 9 and 10 for electrostatic springs may be shaped or arranged as in the third to fifth embodiments, and such an embodiment is also included in this embodiment.

  FIG. 32 schematically shows the relationship between the displacement angle of the movable plate 3 and the electrodes 40 and 41. It can be seen that the vibration of the movable plate 3 causes the other electrode 40, 41 to move away when the one electrode 40, 41 approaches. Therefore, the capacitance between one electrode 40 and 41 and the capacitance between the other electrode 40 and 41 increase or decrease in a complementary manner.

  FIG. 33 shows an example of a circuit that detects the displacement angle of the movable plate 3 using the electrodes 40 and 412. In the figure, C1 is a capacitance between one electrode 40, 41, and C2 is a capacitance between the other electrode 40, 41. Reference numeral 130 denotes a voltage generator that applies a high-frequency minute alternating voltage to each electrode 41 (non-grounded ends of the capacitances C1 and C2). R1 to R6 are resistors, and 131 is a differential amplifier (op amp). The difference between the currents flowing through the capacitances C1 and C2 is amplified by the differential amplifier 131. Since the capacitances C1 and C2 increase and decrease in a complementary manner according to the change in the displacement angle of the movable plate 3, the level of the output voltage signal of the differential amplifier 131 changes substantially in proportion to the displacement angle θ as shown in FIG. .

  Therefore, by determining whether or not the displacement angle exceeds ± θ1 based on the output voltage signal of the differential amplifier 131, the determination result is given to a circuit (not shown) for applying a voltage to the electrode 10. In this circuit, the voltage V1 is applied to the electrode 10 during a period in which the displacement angle is within the range of ± θ1, but control is performed such that a higher voltage V2 is applied during the period in which the displacement angle exceeds ± θ1. It can be carried out. By such control, it is possible to suppress a decrease in the electrostatic spring constant Ks1 at a displacement angle exceeding ± θ1.

  Although the embodiments of the present invention have been described above, it is needless to say that the structure, dimensions, material, manufacturing process, and the like of the optical scanning device according to the present invention can be appropriately changed as necessary. The optical scanning device according to the present invention is suitable as an optical polarizer of an optical writing device as shown in Patent Document 4, but can be suitably used for various other applications.

1 is a schematic divided perspective view of an optical scanning device according to a first embodiment of the present invention. It is a schematic diagram for demonstrating the piezoelectric element for a drive provided in a connection member. It is process explanatory drawing corresponding to the A-A 'cross section of FIG. It is process explanatory drawing following FIG. 3-1. It is a schematic diagram which shows the mode of a deformation | transformation of the connection member by a piezoelectric element. It is a schematic diagram for demonstrating the resonance frequency adjustment torque Ts1. It is a graph which shows the relationship between torque Ts1 for resonance frequency adjustment, and displacement angle (theta). It is a graph which shows the relationship between torque Tm by resonance frequency adjustment torque Ts1, the torsion spring, and displacement angle (theta). It is a figure which shows the 1 degree-of-freedom model expressing the optical scanning device which concerns on the 1st Embodiment of this invention. It is a graph which shows the relationship between the voltage for resonance frequency adjustment, and resonance frequency. It is a schematic perspective view of the optical scanning device which concerns on the 2nd Embodiment of this invention. It is typical sectional drawing which expands and shows the AA cross section of FIG. It is typical sectional drawing which expands and shows the BB cross section of FIG. It is a schematic diagram for demonstrating torque Ts2 by the 3rd electrode for resonance frequency adjustment. It is a graph which shows the relationship between torque Tm by resonance frequency adjustment torque Ts1, Ts2, and the torque Tm by a torsion spring, and displacement angle (theta). It is a figure which shows the one-degree-of-freedom model expressing the optical scanning device which concerns on the 2nd Embodiment of this invention. It is a graph which shows the relationship between the voltage for resonance frequency adjustment, and resonance frequency. It is a schematic diagram for demonstrating the relationship between the magnitude | size relationship of the thickness of a 1st board | substrate and the thickness of a 2nd board | substrate, and the effect | action of the electrode for resonance frequency adjustment. It is a schematic diagram for demonstrating the relationship between the magnitude | size relationship of the thickness of a 1st board | substrate and the thickness of a 2nd board | substrate, and the effect | action of the electrode for resonance frequency adjustment. FIG. 6 is a schematic perspective view of an optical scanning device according to a third embodiment of the present invention. It is a schematic diagram for demonstrating the planar shape of the electrode for resonance frequency adjustment. It is a schematic diagram for demonstrating the resonant vibration of the electrode provided in the torsion spring generated at the time of vibration of a movable plate. It is a schematic diagram for demonstrating the higher mode vibration which generate | occur | produces at the time of the vibration of a movable plate. It is a schematic diagram for demonstrating the inclination of the electrode provided in the torsion spring by higher mode vibration. It is a schematic perspective view of the optical scanning device which concerns on the 4th Embodiment of this invention. It is a typical perspective view for demonstrating the optical scanning device which concerns on the 5th Embodiment of this invention. It is a schematic perspective view of the optical scanning device which concerns on the 6th Embodiment of this invention. It is a block diagram which shows an example of the circuit system which performs resonance frequency automatic adjustment and normal drive with respect to an optical scanning device. It is a flowchart which shows the flow of resonance frequency automatic adjustment operation. It is a flowchart of a resonance frequency detection processing routine. It is a figure which shows the change of the electrostatic capacitance between the electrodes for vibration frequency detection at the time of exciting an optical scanning device. It is a schematic perspective view of the optical scanning device concerning a 7th embodiment of the present invention. It is a schematic diagram for explanation of an operation of a displacement angle detection electrode. It is a circuit diagram which shows an example of the circuit which detects a displacement angle from the electrostatic capacitance between the electrodes for displacement angle detection. It is a graph which shows the relationship between the output voltage signal level of a circuit shown in FIG. 33, and a displacement angle. FIG. 3 is a schematic perspective view of an electrostatic drive type optical scanning device that was experimentally manufactured for examining variations in resonance frequency. It is a graph which shows the dispersion | variation in the measured resonance frequency. It is a graph which shows the measured deflection angular frequency characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 Movable plate (mirror member)
4 Torsion spring 5 Frame 7 Connecting member (cantilever)
8 Piezoelectric elements for driving 9, 10, 22 Resonance frequency adjusting electrodes 30, 31 Vibration frequency detecting electrodes 40, 41 Displacement angle detecting electrodes

Claims (8)

An optical scanning device in which a mirror member supported by a frame member by a pair of torsion springs reciprocally vibrates with the torsion spring as a torsional rotation shaft,
Each of the torsion springs is connected to the frame member by a pair of connecting members at a position near the coupling end with the frame member,
Each of the connecting members is provided with a piezoelectric element for generating a driving torque for the mirror member by deforming it.
In order to act as an electrostatic spring for adjusting the resonance frequency of the mirror member, the comb-shaped first electrode is in a positional relationship where the comb-shaped first electrode meshes with the first electrode. An electrode is provided on each of the frame members,
The length from the fixed end of the torsion spring to the frame member to the coupling end with the mirror member is L, and the length of the torsion spring is within the range of 2L / 3 near the fixed end. An optical scanning device comprising: one electrode and the second electrode. An optical scanning device in which a mirror member supported by a frame member by a pair of torsion springs reciprocally vibrates with the torsion spring as a torsional rotation shaft,
Each of the torsion springs is connected to the frame member by a pair of connecting members at a position near the coupling end with the frame member,
Each of the connecting members is provided with a piezoelectric element for generating a driving torque for the mirror member by deforming it.
In order to act as an electrostatic spring for adjusting the resonance frequency of the mirror member, the comb-shaped first electrode is in a positional relationship where the comb-shaped first electrode meshes with the first electrode. An electrode is provided on each of the frame members,
The length of the first electrode is shorter as it is closer to the mirror member, and the length of the second electrode is constant. The frame member, the torsion spring, the mirror member, the connecting member, the first electrode, and the first silicon substrate of the SOI substrate in which the first and second silicon substrates are bonded via an insulating film 3. The optical scanning device according to claim 1, wherein the second electrode is integrally formed, and a vibration space of the mirror member is formed in the second silicon substrate. A comb-like third electrode for acting as an electrostatic spring for adjusting the resonance frequency of the mirror member together with the first electrode is shifted in the thickness direction from the second electrode, and the first electrode The optical scanning device according to claim 1, wherein the optical scanning device is provided in a positional relationship to mesh with the electrode. The frame member, the torsion spring, the mirror member, the connecting member, the first electrode, and the first silicon substrate of the SOI substrate in which the first and second silicon substrates are bonded via an insulating film 5. The light according to claim 4, wherein the second electrode is integrally formed, and the vibration space of the third electrode and the mirror member is integrally formed on the second silicon substrate. Scanning device. The optical scanning device according to claim 4, wherein the second electrode and the first electrode have the same thickness. The optical scanning device according to claim 1, wherein an electrode for detecting a vibration frequency of the mirror member is formed at a corresponding portion of each free end of the mirror member and the frame member. . 4. The optical scanning device according to claim 3, wherein an electrode for detecting a displacement angle of the mirror substrate is formed at a corresponding portion of each free end of the mirror member and the second silicon substrate.

Images