JP2006115683A - Electrostatic actuator and optical scanning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a uniaxial and biaxial deflection electrostatic actuator and optical scanning device having a simple electrode wiring structure. <P>SOLUTION: The electrostatic actuator comprises a moving member that is supported to a holding member by a beam member and that can be oscillated in the plane and perpendicular directions of the holding member, and electrode portions provided on the holding member, that faces the moving member on which the beam member is not provided and insulated from the moving member and the beam member. In this electrostatic actuator, driving voltages are impressed between the electrodes, and the moving member is made to rock by electrostatic attractive force, caused by floating potential that corresponds to a potential difference of half the drive voltage generated in the plane of the moving member. Thus, the formation of wiring on the moving member becomes unnecessary, and thereby the electrode wiring structure becomes simple. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrostatic actuator and an optical scanning device, and more particularly to a micro optical system and a mirror scanning device to which micromachining technology is applied.

  Conventionally, optical scanning devices used in optical writing systems such as digital copying machines and laser printers, optical reading devices such as barcode readers, or projection-type image display devices swing micro optical systems that apply micromachining technology. Several configurations have been proposed. As one of them, in the oscillating mirror described in Non-Patent Document 1, a mirror substrate supported by two beams provided on the same straight line is provided between an electrode provided at a position facing the mirror substrate. The two beams are reciprocally oscillated around the torsional rotation axis with the electrostatic attraction force.

The oscillating mirror formed by such micromachining technology is simpler in structure than a conventional optical scanning device using a polygon mirror rotating using a motor, and can be formed in a batch in a semiconductor process. It is easy to manufacture, and the manufacturing cost is low, and since it is a single anti-slope, there are no variations in accuracy due to multiple surfaces. As another example of such an electrostatically driven oscillating mirror, Patent Document 1 proposes an S-shaped beam to reduce rigidity and obtain a large deflection angle with a small driving force. No. 2 proposes a beam whose thickness is thinner than that of a mirror substrate or a frame substrate. Patent Document 3 or Non-Patent Document 2 proposes a technique in which the fixed electrode is arranged at a position that does not overlap the vibration direction of the mirror portion. Further, Non-Patent Document 3 proposes a method in which the counter electrode is installed to be inclined from the center position of the mirror deflection, thereby reducing the drive voltage without changing the mirror deflection angle. In these conventional examples, in an electrostatic actuator in which a movable member is held from both sides by two beams, and the movable member is reciprocally oscillated by electrostatic attraction using this beam as a torsional rotation axis, electrodes for generating electrostatic force are opposed to each other. It was necessary to provide one of the electrodes in the movable member. Therefore, wiring must be formed on the electrode in the movable member, but in many cases, a beam is used as a wiring path.
Patent No. 2,924,200 Japanese Patent Laid-Open No. 7-92409 Patent No. 3,011,144 IBM J. Res.Develop vol.24 (1980) The 13th annual International Workshop on MEMS2000 (2000) 473-478 The 13th annual International Workshop on MEMS2000 (2000) 645-650

  However, any of the conventional electrostatic actuators and optical scanning devices described above has the drawback that the design of the electrode wiring is complicated and the formation method thereof is also complicated. In particular, it is very difficult to design an electrode wiring in a biaxial deflection optical scanning device.

  The present invention has been made to solve these problems, and it is an object of the present invention to provide a simple uniaxial and biaxial deflection electrostatic actuator and optical scanning device having an electrode wiring structure.

  In order to solve the above problems, an electrostatic actuator according to the present invention is provided with a movable member that is supported on a holding member by a beam member and that can swing in a direction perpendicular to the planar direction of the holding member, and a beam member. The electrode member is provided on a holding member facing the movable member that is not, and is insulated from the movable member and the beam member. The electrostatic actuator of the present invention applies a driving voltage between the electrode portions, and swings the movable member by an electrostatic attractive force due to a floating potential corresponding to a potential difference that is half of the driving voltage generated on the plane of the movable member. Therefore, it is not necessary to form wiring on the movable member, and the electrode wiring structure is simplified.

  Further, the end of the movable member not provided with the beam member and the end of the holding member facing the end of the movable member are each formed in a comb shape, and the comb shape is formed so as to mesh with each other. Since the electric torque can be increased, it can be operated at a low voltage.

  Furthermore, since the movable member, the beam member, and the holding member are processed and formed from the same substrate, the dimensions can be formed with high accuracy, so that an electrostatic actuator with high displacement accuracy can be provided.

  The frequency of the drive signal of the electrostatic actuator is set equal to the resonance frequency of the movable member determined by the spring constant of the beam member and the inertia of the movable member held by the beam member, or equal to twice the resonance frequency. To do. Therefore, a large deflection angle can be obtained with a small applied voltage.

  Furthermore, an electrostatic actuator as another invention is supported by a first beam member on a first holding member, and a movable member capable of swinging in a direction perpendicular to the planar direction of the first holding member, A second holding member that supports the first holding member with the second beam member, and a second holding member provided with the first beam member and the second beam member, the movable member, And an electrode portion insulated by the second beam member. Then, the electrostatic actuator of the present invention applies different driving voltages between the electrode portions, and applies to the electrode portion provided on the second holding member facing the movable member not provided with the first beam member. The movable member is swung by an electrostatic attractive force due to a floating potential corresponding to the potential difference between the applied drive voltages, and is provided on the second holding member facing the first holding member not provided with the second beam member. The first holding member is swung by an electrostatic attractive force corresponding to the potential difference between the drive voltages applied to the electrode portions. Therefore, it is possible to provide an electrostatic actuator capable of biaxial displacement that eliminates the need for wiring formation on the movable member and the first holding member and simplifies the electrode wiring structure.

  In addition, the end of the movable member not provided with the first beam member and the end of the first holding member facing the end of the movable member are each formed in a comb shape, and are formed so that the comb shapes are engaged with each other. The end of the first holding member that is not provided with the second beam member and the end of the second holding member that faces the end of the first member are each comb-shaped, and the comb-shaped By being formed so as to engage with each other, the electrostatic torque of the electrostatic attractive force generated in the movable member and the first holding member can be increased, so that it can be operated at a low voltage.

  Furthermore, since the movable member, the first and second beam members, and the first and second holding members are processed and formed from the same substrate, the dimensions can be formed with high accuracy, so that the biaxial displacement has high displacement accuracy. The electrostatic actuator can be provided.

  In addition, since the substrate is a substrate formed using single crystal silicon as a material, an electrostatic actuator with few defects and a long lifetime can be provided.

  Further, the frequency of the drive signal of the electrostatic actuator is equal to or equal to the resonance frequency of the movable member determined by the spring constant of the first beam member and the inertia of the movable member held by the first beam member. Is set to be equal to twice. Therefore, a large deflection angle can be obtained with a small applied voltage.

  Furthermore, an optical scanning device according to another invention has a mirror member formed on the surface of the movable member of the electrostatic actuator, and deflects and scans a light beam incident on the mirror member in a rotation direction about the beam member. There is a feature. Therefore, an optical scanning device having a simple structure, high deflection accuracy, and long life can be provided.

  According to another aspect of the present invention, there is provided an optical scanning device in which a mirror member is formed on the surface of the movable member of the biaxial displacement electrostatic actuator, and the light beam incident on the mirror member is transmitted to the first and second beam members. A characteristic is that biaxial deflection scanning is performed in the rotational direction of the axis. Therefore, it is possible to provide a biaxial deflecting optical scanning device that has a simple structure, high deflection accuracy, and a long lifetime.

  Further, by operating the electrostatic actuator and the optical scanning device of the present invention in a reduced pressure atmosphere, the movable member held in a reduced pressure environment by appropriate packaging or the like is not subjected to viscous resistance due to air. Therefore, the driving voltage can be further reduced.

  In the electrostatic actuator of the present invention, the beam member is provided on the rotation center axis of the movable member, and an electrode for generating an electrostatic force is formed on the holding member at a rotationally symmetric position about the rotation center of the movable member. Since the movable member becomes a floating potential and an electrostatic force acts between the movable member and the electrode, rotational torque is generated and the rotary member operates as a rotary actuator. Therefore, it is not necessary to form a wiring on the movable member, and an electrostatic actuator with a simple electrode wiring structure can be provided.

  FIG. 1 is a diagram showing a configuration of an optical scanning device according to a first embodiment of the present invention. FIG. 1A is a plan view, and FIG. 1B is a diagram of FIG. It is AA 'line sectional drawing. In the optical scanning device 100 of the present embodiment shown in FIG. 4A, the movable member 101 is supported at its center by two beam members 102 and 103 provided on the same straight line. The beam members 102 and 103 have a cross-sectional size, shape, and length that are set so that the deflection angle required by the movable member 101 is obtained, and a common holding member provided outside the movable member 101 104 is fixed. Comb shapes are formed on the end surfaces 113 and 115 on both sides of the movable member 101, which are not supported by the beam members 102 and 103, in close proximity to the holding member 104, and are formed on the holding member 104. It is formed so as to mesh with the electrodes 112 and 114. On the movable member 101, a mirror 111 having a sufficient reflectance with respect to the light to be used is formed. The holding member 104 has a two-layer structure integrated with the holding member 119 via an insulating material 118 as shown in FIG. On the holding member 104, a current path 106 and a contact part 116 for applying a voltage to the comb-like electrode 112, and a current path 105 and a contact part 117 for applying a voltage to the comb-like electrode 114 are formed. The two contact portions 116 and 117 are insulated from each other by insulating slits 107, 108, 109, and 110.

  Next, a description will be given with reference to FIG. 2 which is a plan view showing driving states of the conventional optical scanning device and the optical scanning device according to the first embodiment. 2A shows an optical scanning device having a conventional structure, and FIG. 2B shows an optical scanning device according to the first embodiment. In the optical scanning device 200 having the conventional structure shown in FIG. 2A, the electrode portions 201 and 202 generate an electrostatic force, and the electrode portions 201 and 202 in the movable member 207 are connected from the contact portion 203 via the beam member 206. Wiring is formed on one electrode, and the actuator drive voltage is applied between the contact parts 203 and 204 and between the contact parts 203 and 205 with the contact part 203 as a common electrode (in this case, ground). On the other hand, in the optical scanning device 100 of the first embodiment shown in FIG. 2B, the drive voltage is applied between the contact portion 116 and the contact portion 117. Since the movable member 101 is in a floating state, a floating potential corresponding to half of the potential difference applied between the contact portion 116 and the contact portion 117 is generated in this portion.

  Here, the floating potential will be described. In an equivalent circuit in which a floating potential is generated as shown in FIG. 3, the capacitance between the electrode A and the plate member is C1, and the electrostatic capacitance between the electrode B and the plate member is The capacitance is C2, the capacitance between the electrode C and the plate member is C3, the capacitance between the electrode D and the plate member is C4, the potential of the electrode A is V1, and the potential of the electrode B is V2, the potential of electrode C is V3, and the potential of electrode D is V4. The plate-like member is connected to the power source only through the capacitances C1, C2, C3, and C4, and is not directly fixed to any potential, and the potential Vm of the plate-like member is floating. is there. For each electrode potential (V1, V2, V3, V4, Vm) and each capacitance (C1, C2, C3, C4), the following equation is determined. The potential Vm of the plate member here is a floating potential.

  Vm = (C1 · V1 + C2 · V2 + C3 · V3 + C4 · V4) / (C1 + C2 + C3 + C4)

  Thus, an electrostatic attractive force corresponding to the difference between the floating potential induced in the movable member 101 and the voltage applied to each of the contact portions 116 and 117 is generated, and the movable member 101 rotates the beam members 102 and 103 by this attractive force. It is rotationally displaced as an axis. When driving the actuator in the optical scanning device of this embodiment, the drive voltage can be either a DC signal or an AC signal. In the case of an AC signal, it is effective to make the frequency equal to the resonance frequency of the movable member determined by the spring constant of the beam member of the actuator and the inertia of the movable member, and to use the gain of resonance. Further, although the drive signal in FIG. 2B is described as a sine waveform, the signal waveform of the drive signal is not limited to a sine wave, and can be selected according to the purpose, such as a rectangular wave or a sawtooth waveform. .

  Next, a method of manufacturing the optical scanning device in the first embodiment will be described with reference to manufacturing process diagrams of FIGS. 4-7, the same referential mark as FIG. 1 shows the same component. 4 (a), FIG. 5 (a), FIG. 6 (a), and FIG. 7 (a) are plan views, FIG. 4 (b), FIG. 5 (b), and FIG. FIGS. 7B and 7B are sectional views taken along lines AA ′ in FIGS. 4A, 5A, 6A, and 7A, respectively. .

  First, for the formation of the movable member 101, the beam members 102 and 103, and the holding member 104, an SOI substrate made of low-resistance single crystal silicon that can be easily used as a conductive material with high precision fine processing is used. Two silicon substrates 401 and 402 having a double-side polished surface having a thickness of 50 μm were bonded together via a silicon oxide film 403 having a thickness of 5 μm to form an SOI substrate. Using a technique of photolithography and dry etching known as a silicon microfabrication technique from this SOI substrate, a holding member 104 (3 mm × 3 mm), beam members 102 and 103 (width 20 μm, length 500 μm), movable member 101 (1 mm × 1 mm), comb-like shapes 112, 113, 114, 115 (length 100 μm, interval 5 μm, pitch 50 μm), insulating slit portions 107, 108, 109, 110 (width 5 μm) were formed.

  Next, as shown in FIG. 5B, the central portion (portion surrounded by a dotted line in the figure) of the other silicon substrate 402 of the SOI substrate is removed to form a space in which the movable member 101 is rotationally displaced. . Then, as shown in FIG. 6B, the silicon oxide film 403 (except for the insulating slits 107, 108, 109, and 110) in the portion where the silicon is removed and the silicon oxide film 403 appears on the surface. The portion surrounded by the dotted line in the figure) was removed by dry etching. Finally, as shown in FIGS. 7A and 7B, a mirror part 111 (800 μm × 800 μm) is formed on the contact parts 116, 117 (300 μm × 300 μm) and the movable member 101, and the first The uniaxial deflection optical scanning device 100 of the embodiment was completed.

  FIG. 8 is a diagram showing a configuration of an optical scanning device according to the second embodiment of the present invention. FIG. 8A is a plan view, and FIG. 8B is a diagram of FIG. It is AA 'line sectional drawing. In the optical scanning device 800 of the present embodiment shown in FIG. 6A, the movable member 801 is supported at its central portion by two beam members 802 and 803 provided on the same straight line. The two beam members 802 and 803 have cross-sectional dimensions, shapes, and lengths set so as to be rigid enough to obtain the deflection angle required by the movable member 801, and are provided on the outside of the movable member 801. It is fixed to the member 804. Comb-like shapes are formed on the end surfaces 813 and 815 on both sides of the movable member 801 that are not supported by the beam members 802 and 803, and are formed in close proximity to the holding member 804, and are formed on the holding member 804. It is formed so as to engage with the electrodes 812 and 814. On the movable member 801, a mirror 811 having a sufficient reflectance with respect to the light to be used is formed. The holding member 804 is supported at its central portion by two beam members 819 and 820 provided on the same straight line perpendicular to the beam members 802 and 803. The two beam members 819 and 820 are set in cross-sectional dimensions, shapes, and lengths so as to have rigidity enough to obtain a deflection angle required by the holding member 804 including the movable member 801, and the outside of the holding member 804. It is fixed to the holding member 818 provided in the. Comb-like shapes are formed on the end surfaces 822 and 828 on both sides of the holding member 804 that are not supported by the beam members 819 and 820, close to and opposed to the holding member 818, and are formed in the holding member 818. It is formed so as to engage with the electrodes 821 and 827. As shown in FIG. 8B, the holding member 804 and the holding member 818 have a two-layer structure integrated with the holding member 833 through an insulating material 834. The holding member 818 has a current path 806 and a contact portion 816 for applying a voltage to the comb-like electrode 812, a current path 805 and a contact portion 817 for applying a voltage to the comb-like electrode 814, and a comb-like shape. A current path 823 and a contact part 824 for applying a voltage to the electrode 821 and a current path 831 and a contact part 832 for applying a voltage to the comb-like electrode 827 are formed, and the four contact parts 816 and 817 are formed. , 824, 832 are insulated from each other by insulating slits 807, 808, 809, 810, 825, 826, 829, 830.

  Next, a method of manufacturing the optical scanning device in the second embodiment will be described with reference to manufacturing process diagrams of FIGS. 9 to 12, the same reference numerals as those in FIG. 8 denote the same components. 9 (a), FIG. 10 (a), FIG. 11 (a), and FIG. 12 (a) are plan views, FIG. 9 (b), FIG. 10 (b), and FIG. FIGS. 12B and 12B are cross-sectional views taken along lines AA ′ in FIGS. 9A, 10A, 11A, and 12A, respectively. . The basic manufacturing process of the optical scanning device of the second embodiment is the same as the manufacturing process of the optical scanning device of the first embodiment shown in FIGS.

  First, for the formation of the movable member 801, the beam members 802, 803, 819, and 820 and the holding members 804 and 818, an SOI substrate made of low-resistance single crystal silicon that can be easily used as a conductive material with high precision fine processing is used. Using. Two silicon substrates 901 and 902 having a double-side polished surface having a thickness of 50 μm were bonded together via a silicon oxide film 903 having a thickness of 5 μm to form an SOI substrate. Using this photolithography and dry etching technique, which is known as a silicon microfabrication technology from this SOI substrate, holding member 804 (2 mm × 1.5 mm), beam members 802 and 803 (width 20 μm, length 60 μm), movable Member 801 (1 mm × 1 mm), comb-like shapes 812, 813, 814, 815 (length 100 μm, interval 5 μm, pitch 50 μm), same comb-teeth shapes 821, 822, 827, 828 (length 100 μm, interval 5 μm) Insulating slits 807, 808, 809, 810, 825, 826, 829, and 830 (width 5 μm) were formed.

  Next, as shown in FIG. 10B, a central portion (portion surrounded by a dotted line in the drawing) of one silicon substrate 902 is removed from the SOI substrate, and a space in which the movable member 801 and the holding member 804 are rotationally displaced is formed. Form. Then, as shown in FIG. 11B, the insulating slit portions 807, 808, 809, 810, 825, 826, 829, and 830 are removed from the portion where the silicon is removed and the silicon oxide film 903 appears on the surface. The part of the silicon oxide film except the part (the part surrounded by the dotted line in the figure) was removed by dry etching. Finally, as shown in FIGS. 12A and 12B, a mirror part 811 (800 μm × 800 μm) is formed on the contact parts 816, 817, 824, 832 (300 μm × 300 μm) and the movable member 801. The biaxial deflection optical scanning device 800 of the second embodiment is completed.

  FIG. 13 is a plan view showing a driving state of the biaxially deflected optical scanning device according to the second embodiment. The optical scanning device 800 according to the second embodiment shown in the figure has a static electricity caused by the difference between the floating potential induced in the movable member 801 and the holding members 804 and 818 installed between the electrodes and the electrode potential. Displacement due to attractive force. Therefore, the voltages applied to the two sets of electrodes are adjusted so that the floating potential is always zero. In FIG. 14, which is a time chart showing the potential change of each electrode, Va and Vb are voltages that generate an electrostatic attractive force that displaces the movable member. Therefore, as can be seen from FIG. 14B, when a voltage having the same absolute value but different polarity is applied to the opposing electrodes, the floating potential induced in the movable member 801 is always zero. Similarly, when the electrostatic attractive force for displacing the holding member 804 is set such that the combination of the voltage Vc and the voltage Vd has the same absolute value and different polarities, the floating potential induced in the holding member 804 becomes zero and is movable. It becomes equipotential with the member 801. By adopting such a method of applying pressure, it is possible to independently change the displacement amount and the period of displacement (vibration frequency) of the movable member 801 and the holding members 804 and 818. At this time, the applied frequency of Va and Vb is equal to the resonance frequency determined by the first beam member and the movable portion held by the first beam member, and the applied frequency of Vc and Vd is the second beam member. And if it is set equal to the resonance frequency determined by the movable part held by the second beam member, a large deflection angle can be obtained with a small applied voltage. Furthermore, the same applies when each applied frequency is set equal to twice the corresponding resonant frequency.

  As in each of the embodiments described above, the electrostatic actuator and the optical scanning device are not subjected to viscous resistance due to air when the movable part held in a reduced pressure environment is moved by appropriate packaging. Can be further reduced.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described within the scope of the claims.

It is a figure which shows the structure of the optical scanning device based on the 1st Example of this invention. It is a top view which shows the mode of each drive of the conventional optical scanning device and the optical scanning device concerning a 1st embodiment. It is a circuit diagram which shows the equivalent circuit which a floating potential generate | occur | produces. It is a manufacturing process figure of the optical scanning device in a 1st example of an embodiment. It is a manufacturing process figure of the optical scanning device in a 1st example of an embodiment. It is a manufacturing process figure of the optical scanning device in a 1st example of an embodiment. It is a manufacturing process figure of the optical scanning device in a 1st example of an embodiment. It is a figure which shows the structure of the optical scanning device based on the 2nd Example of this invention. It is a manufacturing process figure of the optical scanning device in the 2nd example of an embodiment. It is a manufacturing process figure of the optical scanning device in the 2nd example of an embodiment. It is a manufacturing process figure of the optical scanning device in the 2nd example of an embodiment. It is a manufacturing process figure of the optical scanning device in the 2nd example of an embodiment. It is a top view which shows the mode of a drive of the optical scanning apparatus of 2 axis | shaft deflection | deviation of the example of 2nd Embodiment. It is a time chart which shows the electric potential change of each electrode in the optical scanning apparatus of the biaxial deflection | deviation of the 2nd Example.

Explanation of symbols

100, 800; optical scanning device,
101, 801; a movable member;
102, 103, 802, 803, 819, 820; beam members;
104, 804, 818, 833; holding member,
105, 106, 805, 806, 823, 831; current path;
107-110, 807-810, 825, 826, 829, 830; insulating slit,
111,811; mirror,
112, 114, 812, 814, 821, 827; comb-like electrodes;
113, 115, 813, 815, 822, 828; end face,
116, 117, 816, 817, 824, 832; contact part,
118,834; insulating material,
401, 402, 901, 902; silicon substrate,
403, 903; silicon oxide film.

Claims (13)

  A movable member supported by a beam member on the holding member and capable of swinging in a direction perpendicular to a plane direction of the holding member; and a holding member facing the movable member not provided with the beam member, And a movable member and an electrode portion insulated from the beam member. A drive voltage is applied between the electrode portions, and a floating potential corresponding to a potential difference half of the drive voltage generated on the plane of the movable member. An electrostatic actuator characterized in that the movable member is swung by electrostatic attraction.   The end of the movable member not provided with the beam member and the end of the holding member facing the end of the movable member are each formed in a comb shape, and are formed so that the comb shapes are engaged with each other. 1. The electrostatic actuator according to 1.   The electrostatic actuator according to claim 1, wherein the movable member, the beam member, and the holding member are processed and formed from the same substrate.   The frequency of the drive signal of the electrostatic actuator according to any one of claims 1 to 3 is determined by a spring constant of the beam member and an inertia of the movable member held by the beam member. Or an electrostatic actuator that is set equal to twice the resonance frequency.   A movable member that is supported on the first holding member by the first beam member and that can swing in a direction perpendicular to the planar direction of the first holding member, and the first holding member is the second beam member. A second holding member that supports the second holding member provided with the first beam member and the second beam member; and the movable member and the first and second beam members provided on the second holding member. Provided to the second holding member that is opposed to the movable member that is not provided with the first beam member. The movable member is swung by an electrostatic attractive force corresponding to a potential difference between the drive voltages applied to the electrode portions, and is opposed to the first holding member not provided with the second beam member. Each drive voltage applied to the electrode portion provided on the second holding member An electrostatic actuator, characterized in that oscillating the first holding member by electrostatic attraction by the floating potential corresponding to the potential difference.   The end of the movable member not provided with the first beam member and the end of the first holding member facing the end of the movable member are each formed in a comb shape, and the comb shapes are engaged with each other. The end portion of the first holding member and the end portion of the second holding member that are opposed to the end portion of the first member are formed in a comb shape. The electrostatic actuator according to claim 5, wherein the electrostatic actuators are formed so as to mesh with each other.   The electrostatic actuator according to claim 5 or 6, wherein the movable member, the first and second beam members, and the first and second holding members are processed and formed from the same substrate.   The electrostatic actuator according to claim 3, wherein the substrate is a substrate formed using single crystal silicon as a material.   The frequency of the drive signal of the electrostatic actuator according to any one of claims 5 to 8 is determined by a spring constant of the first beam member and an inertia of the movable member held by the first beam member. An electrostatic actuator that is set equal to a resonance frequency of the movable member or equal to twice the resonance frequency.   The electrostatic actuator according to claim 1, wherein the electrostatic actuator operates in a reduced pressure atmosphere.   A mirror member is formed on the surface of the movable member of the electrostatic actuator according to any one of claims 1 to 4, and the light beam incident on the mirror member is deflected and scanned in a rotation direction about the beam member. An optical scanning device.   A mirror member is formed on the surface of the movable member of the electrostatic actuator according to any one of claims 5 to 9, and a light beam incident on the mirror member is used with the first and second beam members as axes. An optical scanning device characterized by performing biaxial deflection scanning in the rotational direction. 13. The optical scanning device according to claim 11, wherein the optical scanning device operates in a reduced pressure atmosphere.

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