JP5105526B2 - Optical deflector - Google Patents

Description

  The present invention relates to an optical deflector that deflects and scans a light beam such as a laser beam.

  In recent years, as an MEMS (micro electro mechanical systems) device using a semiconductor process or micromachine technology, an optical deflector in which mechanical parts such as a mirror (reflector) and a movable part for rotating the mirror are integrally formed on a semiconductor substrate. Has been proposed. In such an optical deflector, in order to further improve the deflection / scanning performance, it is desired to control the driving state (for example, deflection angle and deflection speed) of the mirror more quickly and accurately. For this reason, it is necessary to detect the drive state (for example, the rotation angle) of the mirror and perform feedback control.

  Therefore, as a method for detecting the rotation angle of the mirror, for example, there is a method in which the laser beam deflected and scanned by the optical deflector is detected by a separate sensor. However, with this method, the system itself becomes large. For this reason, a method has been proposed in which the optical deflector itself has a detection mechanism (see, for example, Patent Documents 1 to 3).

In the optical deflector of Patent Document 1, one end of a movable frame portion is connected to and supported by a fixed portion, and torque generated at the movable frame portion is transmitted to a torsion bar (elastic beam) joined to the other end. The mirror part provided at the tip of the mirror is driven to rotate. A piezoresistive element is incorporated in the base end of the elastic beam supporting the mirror on the frame side, and the torsion angle of the elastic beam is detected. Detect the rotation angle. The optical deflector of Patent Document 2 is an electromagnetic drive system, and incorporates a sensor that detects a change in a magnetic field to detect the angle of a mirror having a hard magnetic thin film. Further, the optical deflector of Patent Document 3 is an electrostatic drive system, and angle detection is performed by measuring the capacitance between the mirror and the counter electrode.
JP 2004-226548 A JP 2000-235152 A JP 2006-184603 A JP 2005-127147 A

  On the other hand, an optical deflector using a piezoelectric drive system using a piezoelectric actuator as a mirror drive source has been proposed (see, for example, Patent Document 4). In this optical deflector, one end of the piezoelectric actuator is connected to and supported by a frame portion (support portion), and the torque generated by the piezoelectric actuator is transmitted to a torsion bar (elastic beam) joined to the other end. The mirror unit previously provided is rotationally driven. This optical deflector is advantageous in that it has a small and simple structure and can provide a large driving force, is easy to manufacture, and is easily mass-produced.

  In the optical deflector using this piezoelectric actuator, in order to detect the rotation angle of the mirror part, as in Patent Document 1, a piezoresistive element or a strain gauge is provided at the base end part on the support part side of the torsion bar that supports the mirror. It can be considered that the rotation angle of the mirror is detected by detecting the twist angle of the elastic beam. However, since a piezoresistive element and a strain gauge are incorporated, the structure becomes complicated.

  On the other hand, instead of a piezoresistive element, etc., a separate piezoelectric sensor is provided to detect angular displacement by piezoelectric electromotive force, or a piezoelectric actuator that drives a mirror can be used as a sensor separately from the wiring as an actuator. It is conceivable to provide wiring. In this case, the detection mechanism can be formed by using a step of forming a piezoelectric actuator for driving the mirror.

  However, because the torsional displacement of the torsion bar is very small, it is difficult to measure the torsional displacement as a piezoelectric electromotive force with a good S / N ratio. Further, since the position of the piezoelectric sensor for detection is close to the piezoelectric actuator of the optical deflector, crosstalk with the drive signal of the piezoelectric actuator becomes a problem.

  The present invention has been made in view of the above background, and an object of the present invention is to provide an optical deflector that can detect and control a mirror driving state quickly and accurately in an optical deflector using a piezoelectric actuator. .

  The present invention includes a mirror portion having a reflecting surface, a torsion bar extending outward from an end portion of the mirror portion, a support portion provided so as to surround the mirror portion, and one end connected to the torsion bar. A first piezoelectric actuator having an end connected to and supported by the support portion, the first piezoelectric actuator having a support and a piezoelectric body formed on the support, the piezoelectric body Including one or more piezoelectric cantilevers that bend and deform by piezoelectric driving by applying a driving voltage to the first piezoelectric actuator, and rotating the mirror portion via the torsion bar by applying the driving voltage to the first piezoelectric actuator An optical deflector to be driven includes a second piezoelectric actuator having one end connected to the torsion bar and the other end connected to the mirror portion, and the second piezoelectric actuator is supported. Characterized in that it consists of one or more piezoelectric cantilevers which performs bending deformation by the piezoelectric drive when a driving voltage is applied to the piezoelectric body formed on (first invention).

  According to the optical deflector of the first invention, since the second piezoelectric actuator is provided between the mirror portion and the torsion bar, the mirror portion is rotationally driven via the torsion bar by driving the first piezoelectric actuator. When this is done, a force that deforms the second piezoelectric actuator is applied, and a piezoelectric electromotive force is generated in the piezoelectric cantilever. Since this piezoelectric electromotive force reflects the rotational driving state of the mirror part, the driving state of the mirror part can be detected quickly and accurately based on the piezoelectric electromotive force of the second piezoelectric actuator, It is possible to control the driving state of the unit. Further, when the driving voltage is applied to the second piezoelectric actuator and the second piezoelectric actuator is bent and deformed, the bending deformation is immediately reflected in the rotational driving state of the mirror portion. Based on this bending deformation, it becomes possible to control the drive state of the mirror portion. Thus, by providing the second piezoelectric actuator, it is possible to quickly detect and control the driving state of the mirror with high accuracy.

  In the optical deflector according to the first aspect of the present invention, a piezoelectric electromotive force generated according to bending deformation of the piezoelectric cantilever of the second actuator due to the rotational drive of the mirror portion is detected, and the mirror portion is based on the piezoelectric electromotive force. It is preferable to include a rotation angle detecting means for detecting the rotation angle of the first (second invention).

  According to the optical deflector of the second invention, since the second piezoelectric actuator bending deformation immediately reflects the rotational driving state of the mirror section, the mirror section is based on the piezoelectric electromotive force generated by the bending deformation. By detecting this rotation angle, the rotation angle of the mirror part can be detected quickly and accurately.

  In the optical deflector according to the first or second invention, the first piezoelectric actuator may be configured such that a rotation driving parameter of the mirror portion is a predetermined value using the rotation angle detected by the rotation angle detecting means. It is preferable to include a control means for controlling the drive voltage applied to the (third invention).

  According to the optical deflector of the third aspect of the invention, since the rotation angle of the mirror unit is detected quickly and accurately by the rotation angle detection means, the rotation angle of the mirror unit is used to determine the rotation drive parameters (for example, By performing feedback control of the driving of the first actuator so that the deflection angle and the deflection speed are set to predetermined values, desired deflection / scanning can be performed quickly and accurately.

  In the optical deflector according to any one of the first to third inventions, the first piezoelectric actuator is opposed to sandwich the mirror portion and a pair of torsion bars extending outward from both ends of the mirror portion. It is preferable that one or two pairs are arranged, and the mirror portion is rotationally oscillated by the one or two pairs of first piezoelectric actuators (fourth invention).

  According to the optical deflector of the fourth invention, one pair or two pairs of the first piezoelectric actuators are arranged to face each other with the mirror part and the torsion bar interposed therebetween, and the mirror part is driven by driving the first piezoelectric actuator. It can be rotated around one axis. As a result, the mirror unit can be rotated about one axis, and desired deflection and scanning can be efficiently performed stably in one direction with a small optical deflector.

  In the optical deflector according to the fourth aspect of the present invention, the second piezoelectric actuator is disposed in one or two pairs so as to face each other with the mirror portion interposed therebetween, and is based on the one or two pairs of first piezoelectric actuators. It is preferable that a piezoelectric electromotive force is generated according to bending deformation caused by rotational vibration of the mirror portion, and the rotation angle detecting means detects the rotation angle of the mirror portion based on the piezoelectric electromotive force (fifth invention). .

  According to the optical deflector of the fifth invention, one pair or two pairs of second piezoelectric actuators are arranged to face each other with the mirror portion interposed therebetween, and the piezoelectric electromotive force generated by each of these second piezoelectric actuators is used. The rotation angle of the mirror portion can be detected stably during the rotational vibration of the mirror portion by the first piezoelectric actuator.

  In the optical deflector according to any one of the first to fifth inventions, the drive voltage applied to the one or two pairs of first piezoelectric actuators is preferably an alternating voltage (sixth invention).

  According to the optical deflector of the sixth aspect of the invention, the mirror unit can be oscillated and oscillated about one axis for optical scanning by driving each pair of the first piezoelectric actuators opposed across the torsion bar. During this optical scanning, the scanning angle of the mirror portion can be detected quickly and accurately by the rotation angle detecting means.

  In the optical deflector according to the sixth aspect of the invention, the first AC voltage applied to the piezoelectric actuator on one side of the torsion bar of the one or two pairs of first piezoelectric actuators, and the torsion It is preferable that the second AC voltage applied to the piezoelectric actuator on the other side of the bar is 180 degrees out of phase with each other (seventh invention).

  According to the optical deflector of the seventh invention, the mirror portion is centered on the torsion bar by bending and deforming the piezoelectric cantilevers of each pair of the first and second piezoelectric actuators facing each other across the torsion bar in opposite phases. Thus, it is possible to efficiently rotate and vibrate and perform optical scanning. Also during this optical scanning, the rotation angle detecting means can detect the scanning angle of the mirror portion quickly and accurately.

  In the optical deflector according to any one of the first to seventh inventions, the mirror part, the torsion bar, the support part, and the support body of the piezoelectric cantilever may be integrally formed by processing a semiconductor substrate. Preferred (8th invention).

  According to the optical deflector of the eighth invention, the mirror part, the torsion bar, the support part, and the support body of the piezoelectric cantilever are integrally formed by shape processing. Compared to the case of forming using a method, a bonding member, an adhesive, or the like is unnecessary, and the alignment accuracy can be improved, and the formation can be easily performed with high accuracy. In addition, since the entire optical deflector is mechanically connected by being formed integrally, stress is not concentrated on the connecting portion as compared with the case of forming and connecting separately. The strength of the deflector can be improved. Furthermore, since it is formed from a semiconductor substrate (for example, a silicon substrate such as a single crystal silicon substrate or an SOI substrate), a part of the semiconductor substrate can be easily removed and integrated by using a semiconductor planar process and a MEMS process. Can be formed.

  In the optical deflector of the eighth invention, the piezoelectric body of the piezoelectric cantilever is preferably formed by shaping a single-layer piezoelectric film directly formed on the semiconductor substrate (ninth invention). .

  According to the optical deflector of the ninth invention, since the piezoelectric body of the piezoelectric cantilever is formed by shaping a single-layer piezoelectric film directly formed on the semiconductor substrate, the structure is simple, and the semiconductor planar It can be easily formed using a process. Moreover, the support body and the piezoelectric body can be formed integrally, and no adhesive is required compared to the case where the support body and the piezoelectric body are formed and bonded separately, and the alignment accuracy is improved. It is possible to improve the strength of the piezoelectric actuator without stress concentration on the bonded portion.

  In the optical deflector according to the ninth aspect of the invention, the reflecting surface of the mirror part and the electrode of the piezoelectric cantilever are formed of a metal thin film directly formed on the semiconductor substrate and a metal formed directly on the piezoelectric film. Preferably, the thin film is formed by shape processing (the tenth invention).

  According to the optical deflector of the tenth invention, the reflecting surface of the mirror part and the electrode of the piezoelectric cantilever are formed by shaping the metal thin film directly formed, so that the structure is simple and the semiconductor planar process is performed. And can be easily formed.

  According to the optical deflector of the present invention, since the entire optical deflector can be integrally formed using a semiconductor planar process and a MEMS process, the optical deflector can be easily manufactured, and mass production and yield can be improved. Improvement is possible. Furthermore, when this optical deflector is incorporated into a device, the entire device can be integrally formed using a semiconductor planar process and a MEMS process, so that it can be easily incorporated into other devices, and can be reduced in size and size. Mass production is possible.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of an optical deflector according to the present embodiment, FIG. 2 is an explanatory diagram illustrating the operation of a first piezoelectric actuator in the optical deflector of FIG. 1, and FIG. 3 is a first diagram of the optical deflector of FIG. FIG. 4 is a graph showing detection of the rotation angle of the mirror unit in the optical deflector of FIG. 1 (drive voltage of the first piezoelectric actuator and output voltage of the second piezoelectric actuator). FIG. 5 is an explanatory diagram showing a manufacturing process of the optical deflector of FIG. 1.

  As shown in FIG. 1, the optical deflector A of the present embodiment includes a mirror unit 1 that reflects incident light, torsion bars 2 a and 2 b connected to the mirror unit 1, and the mirror unit 1 as a torsion bar. 2 pairs of 1st piezoelectric actuators 8a-8d driven via 2a, 2b, a support part 10 which supports the 1st piezoelectric actuators 8a-8d, and 2 pairs for detecting the rotation angle of mirror part 1 Second piezoelectric actuators 9a to 9d.

  The mirror portion 1 has a rectangular shape, and the pair of torsion bars 2a and 2b extend outward from the center positions of the pair of opposite sides. One torsion bar 2 a has a base end portion connected to the support portion 10 and a tip end portion connected to the mirror portion 1. The torsion bar 2a is connected to the respective distal end portions of the pair of first piezoelectric actuators 8a and 8c facing each other with the base end portion interposed therebetween, while the pair of second piezoelectric members facing each other with the distal end portion sandwiched therebetween. The actuators 9a and 9c are connected to respective tip portions.

  Also, the other torsion bar 2 b has a base end portion connected to the support portion 10 and a tip end portion connected to the mirror portion 1. The torsion bar 2b is connected to the respective distal end portions of the pair of first piezoelectric actuators 8b and 8d opposed to each other with the base end portion interposed therebetween, while the pair of second second electrodes opposed to each other across the distal end portion. The piezoelectric actuators 9b and 9d are connected to the respective leading ends.

  Each of the first piezoelectric actuators 8a to 8d is supported with a base end portion connected to the support portion 10. The support portion 10 is provided so as to surround the mirror portion 1, the torsion bars 2a and 2b, the first piezoelectric actuators 8a to 8d, and the second piezoelectric actuators 9a to 9d. Each of the first piezoelectric actuators 8a to 8d is composed of one piezoelectric cantilever. Each piezoelectric cantilever includes support bodies 4a to 4d, lower electrodes 5a to 5d, piezoelectric bodies 6a to 6d, and upper electrodes 7a to 7d.

  Further, the second piezoelectric actuators 9a to 9d are supported with their base ends connected to the mirror unit 1, respectively. Each of these second piezoelectric actuators 9a to 9d is composed of one piezoelectric cantilever. Each piezoelectric cantilever includes support bodies 4e to 4h, lower electrodes 5e to 5h, piezoelectric bodies 6e to 6h, and upper electrodes 7e to 7h, respectively.

  The optical deflector A includes upper electrode pads 11a to 11d and lower electrode pads for applying a driving voltage between the upper electrodes 7a to 7d and the lower electrodes 5a to 5d of the first piezoelectric actuators 8a to 8d. 12a to 12d and upper electrode pads 14a to 14d and lower electrode pads 15a to 15d for outputting piezoelectric electromotive force between the upper electrodes 7e to 7h and the lower electrodes 5e to 5h of the second piezoelectric actuators 9a to 9d. Are provided on the support portion 10.

  The lower electrode pads 12a to 12d, 15a to 15d and the lower electrodes 5a to 5h are formed of a metal thin film on a silicon substrate (in this embodiment, two metal thin films, hereinafter also referred to as a lower electrode layer) and a semiconductor planar process. It is formed by using and shape processing. As a material of this metal thin film, for example, titanium (Ti) is used for the first layer (lower layer), and platinum (Pt) is used for the second layer (upper layer). Specifically, the lower electrodes 5a to 5h are formed on almost the entire surface of the supports 4a to 4h. The lower electrode pads 12a to 12d are electrically connected to the lower electrodes 5a to 5d, and the lower electrode pads 15a to 15d are electrically connected to the lower electrodes 5e to 5h via the support 10 and the lower electrode layers on the torsion bars 2a and 2b. Is done.

  The piezoelectric bodies 6a to 6h are separated from each other on the lower electrodes 5a to 5h, respectively, by processing a single piezoelectric film (hereinafter also referred to as a piezoelectric layer) on the lower electrode layer using a semiconductor planar process. Is formed. As a material of this piezoelectric film, for example, lead zirconate titanate (PZT) which is a piezoelectric material is used. Specifically, the piezoelectric bodies 6a to 6h are formed on almost the entire surface of the support bodies 4a to 4h.

  The upper electrode pads 11a to 11d, 14a to 14d, the upper electrode wirings 13a to 13d, and the upper electrodes 7a to 7h are a metal thin film on the piezoelectric layer (in this embodiment, one metal thin film, hereinafter referred to as the upper electrode layer). Is formed by shape processing using a semiconductor planar process. For example, platinum or gold (Au) is used as the material of the metal thin film. Specifically, the upper electrodes 7a to 7h are formed on almost the entire surface of the piezoelectric bodies 6a to 6h. The upper electrode pads 11a to 11d are electrically connected to the upper electrodes 7a to 7d, and the upper electrode pads 14a to 14d are connected to the support portion 10 and the upper electrode wirings 13a to 13d formed on the torsion bars 2a and 2b. Conduction is made to the upper electrodes 7e to 7h. The upper electrode wirings 13a to 13d are provided so as to be separated from each other in a plan view, and are insulated from the lower electrode pads 12a to 12d, 15a to 15d and the lower electrodes 5a to 5h.

  The mirror unit 1 includes a mirror unit support 1a and a mirror surface reflection film (reflection surface) 1b formed on the mirror unit support 1a. The mirror surface reflecting film 1b is formed by processing a metal thin film (one metal thin film in this embodiment) on the mirror support 1a using a semiconductor planar process. As the material for the metal thin film, for example, Au, Pt, silver (Ag), aluminum (Al), or the like is used.

  Further, the mirror part support 1a, the torsion bars 2a and 2b, the supports 4a to 4d of the first piezoelectric actuators 8a to 8d, the supports 4e to 4h of the second piezoelectric actuators 9a to 9d, and the support 10 is integrally formed by processing the shape of the silicon substrate. As a technique for processing the shape of the silicon substrate, a semiconductor planar process and a MEMS process using a photolithography technique, a dry etching technique, or the like are used.

  A gap 10 ′ is provided between the mirror unit 1 and the support unit 10 so that the mirror unit 1 can be rotated to a predetermined angle. The mirror unit 1 is integrally formed, so that it is mechanically connected to the first piezoelectric actuators 8a to 8d via the torsion bars 2a and 2b, and the mirror is driven according to the driving of the first piezoelectric actuators 8a to 8d. Part 1 rotates. In addition, the mirror unit 1 is integrally formed so as to be mechanically connected to the second piezoelectric actuators 9a to 9d, and the second piezoelectric actuators 9a to 9d are bent and deformed according to the rotation of the mirror unit 1. To do.

  Further, the optical deflector A is connected to a control circuit 20 that controls the deflection / scanning of the mirror unit 1. As a function, the control circuit 20 controls the phase, frequency, amplitude, waveform, etc. of the driving voltage of the first piezoelectric actuators 8a to 8d, so that the deflection / scanning phase, frequency, deflection angle, etc. of the mirror unit 1 are controlled. The control means 22 which controls this is provided. Furthermore, the control circuit 20 includes a rotation angle detection unit 21 that detects the rotation angle of the mirror unit 1 based on the piezoelectric electromotive force generated by the second piezoelectric actuators 9a to 9d. And the control means 22 feedback-controls the 1st piezoelectric actuators 8a-8d based on the rotation angle detected by the rotation angle detection means 21. FIG. Note that the adjustment means 23 in FIG. 1 is provided only in a second embodiment described later, and will be described later.

  Next, the operation of the optical deflector A of this embodiment will be described. First, in the optical deflector A, the control means 22 applies a voltage to the two pairs of first piezoelectric actuators 8a to 8d. As a result, the two pairs of first piezoelectric actuators 8a to 8d are driven to generate angular displacements at the tip portions, respectively. Due to these angular displacements, the mirror unit 1 rotates about a single axis x1 coaxial with the pair of torsion bars 2a and 2b.

  Here, FIG. 2 is a diagram illustrating a driving state of the first piezoelectric actuators 8a to 8d of the optical deflector A of the present embodiment when the mirror unit 1 is rotationally driven. 2 schematically shows an end surface taken along line II (end surface viewed from the direction of the arrow) shown in FIG. As shown in FIG. 2, with respect to one pair of first piezoelectric actuators 8a and 8c, voltages ± V1 having opposite polarities are applied between the upper electrodes 7a and 7c and the lower electrodes 5a and 5c, respectively. And then bend and deform in opposite directions.

  Due to these bending deformations, the base end portions of the first piezoelectric actuators 8a and 8c are connected to and supported by the support portion 10, so that the tip portion is the thickness of the support portion 10 (substrate) as shown in FIG. Rotate up and down in the direction. Since voltages ± V1 having opposite polarities are applied to the first piezoelectric actuators 8a and 8c, the tips of the first piezoelectric actuators 8a and 8c move in opposite directions. As a result, torsional displacement occurs in the torsion bar 2a, and rotational torque about the torsion bar 2a acts on the mirror portion 1.

  Similarly, when the other pair of first piezoelectric actuators 8b and 8d are driven by applying voltages ± V1 having opposite polarities to each other, a torsional displacement occurs in the same direction in the torsion bar 2b, and the torsion in the mirror section 1 occurs. A rotational torque about the bar 2b acts.

  Therefore, by the driving of the first piezoelectric actuators 8a to 8d, as shown by the arrows in FIG. 2, the rotational torque α about the torsion bars 2a and 2b acts on the mirror unit 1. Thereby, as shown by the arrow of FIG. 1, the mirror part 1 rotates around 1 axis | shaft x1 centering | focusing on the torsion bars 2a and 2b.

  At this time, a first AC voltage having the same phase is applied to one of the pair of first piezoelectric actuators 8a and 8b. A second AC voltage having the same phase is also applied to the other first piezoelectric actuator 8c, 8d of each pair. At this time, the first AC voltage and the second AC voltage are AC voltages (for example, sine waves) that are opposite in phase or out of phase. As a result, the mirror unit 1 can be rotated to perform optical scanning with a predetermined deflection angle at a predetermined frequency in one direction. At this time, in these first piezoelectric actuators 8a to 8d, an alternating voltage having a frequency near the mechanical resonance frequency (primary resonance point) of the mirror unit 1 including the torsion bars 2a and 2b is applied as a drive voltage. By performing resonance driving, optical scanning can be performed with a larger deflection angle. The driving of the first piezoelectric actuators 8a to 8d may be non-resonant driving, and the applied voltage may be a DC voltage.

  At the same time, in the optical deflector A, the rotation angle detection means 21 detects the piezoelectric electromotive force generated in the second piezoelectric actuators 9a to 9d, and the rotation angle of the mirror unit 1 based on the detected piezoelectric electromotive force. Is detected.

  Here, FIG. 3 is a diagram illustrating a driving state of the second piezoelectric actuators 9a to 9d when the mirror unit 1 of the optical deflector of the present embodiment is rotationally driven. FIG. 3 schematically illustrates an end surface taken along the line II-II shown in FIG. 1 (an end surface viewed from the arrow direction). In FIG. 3, the first piezoelectric actuators 8a and 8c are indicated by broken lines. As shown in FIG. 3, when the torsion bar 2a is rotated by the rotation angle θ1 by driving the first piezoelectric actuators 8a and 8c, the mirror portion 1 is rotated at the rotation angle θ2 by the moment of inertia, The second piezoelectric actuators 9a and 9c are bent and deformed in opposite directions. That is, when the mirror unit 1 is swinging, a difference Δθ is generated between the twist angle θ1 of the torsion bar 2a and the deflection angle θ2 of the mirror unit 1 due to the moment of inertia of the mirror unit 1. Since one of the second piezoelectric actuators 9a and 9c is fixed to the mirror portion 1 and the other is fixed to the torsion bar 2a, stress is generated in the piezoelectric actuators 9a and 9c due to this Δθ, and the piezoelectric actuators 9a and 9c become distortion. 9c is deformed as shown in FIG. The piezoelectric bodies 6e and 6g provided in the piezoelectric actuators 9a and 9c generate polarization due to this distortion, and generate a voltage between the upper and lower electrodes. The piezoelectric electromotive force generated by these bending deformations is output to the rotation angle detection means 21. Similarly, when the torsion bar 2b is rotated by the rotation angle θ1 by driving the first piezoelectric actuators 8b and 8d, the mirror unit 1 is rotated at the rotation angle θ2, and one pair of the second piezoelectric actuators 9b and 9d is It bends and deforms in opposite directions to generate a piezoelectric electromotive force according to the force. Based on these piezoelectric electromotive forces, the rotation angle of the mirror unit 1 is detected.

  FIG. 4A shows the drive voltages of the first piezoelectric actuators 8a to 8d and the output voltages of the second piezoelectric actuators 9a to 9d. In FIG. 4A, the horizontal axis indicates time, and the vertical axis indicates voltage. Note that the output voltages of the piezoelectric actuators 9a to 9d are shown by a factor of 100. The output voltages of the piezoelectric actuators 9a to 9d have waveforms delayed by the time Δλ with respect to the driving voltages of the piezoelectric actuators 8a to 8d. At this time, the amplitude of the mirror unit 1 is as shown in FIG. In FIG. 4B, the horizontal axis indicates time, and the vertical axis indicates amplitude. Thus, since the time change of the output voltage of the second piezoelectric actuators 9a to 9d has the same timing as the time change of the amplitude of the mirror unit 1, the piezoelectric electromotive force (output voltage) of the second piezoelectric actuators 9a to 9d. ), The rotation angle of the mirror unit 1 can be detected in real time. Then, based on the detected rotation angle, the control means 22 performs feedback control of the drive voltages of the first piezoelectric actuators 8a to 8d, whereby the deflection / scanning performance can be improved.

Therefore, according to the optical deflector A of the present embodiment, by providing the second piezoelectric actuators 9a to 9d, the driving state of the mirror unit 1 can be detected quickly and accurately, and the detected driving state is obtained. By performing feedback control based on this, the deflection / scanning performance can be improved.
[Manufacturing process]
In FIG. 5, the manufacturing process of the optical deflector A in this embodiment is shown. 5A to 5H schematically show a cross section of the optical deflector A. FIG.

  As shown in FIG. 5A, an SOI substrate 31 is used as a substrate on which the mirror support 1a, the torsion bars 2a and 2b, the supports 4a to 4h, and the support 10 are formed. The SOI substrate 31 is a bonded substrate of single crystal silicon (also referred to as an active layer 31a or SOI layer) / silicon oxide (intermediate oxide film layer 31b) / single crystal silicon (handling layer 31c). As for the thickness of each layer of the SOI substrate, for example, the thickness of the active layer 31a is 5 to 100 [μm], the thickness of the intermediate oxide film layer 31b is 0.5 to 2 [μm], and the thickness of the handling layer 31c is 100 to 600 [μm]. It is. The surface of the active layer 31a is subjected to an optical polishing process.

  First, as shown in FIG. 5B, the front surface (active layer 31a side) and the back surface (handling layer 31c side) of the SOI substrate 31 are oxidized by a thermal oxidation furnace (diffusion furnace), and the thermal silicon oxide films 32a and 32b are obtained. (Thermal oxide film forming step). The thickness of the thermally oxidized silicon films 32a and 32b is, for example, 0.1 to 1 [μm].

  Next, as shown in FIG. 5C, a lower electrode layer 33, a piezoelectric layer 34, and an upper electrode layer 35 are sequentially formed on the surface of the SOI substrate 31 (active layer 31a side).

  First, in the lower electrode layer forming step, a lower electrode layer 33 made of a two-layer metal thin film is formed on the thermally oxidized silicon film 32a on the active layer 31a side of the SOI substrate 31. As the material of the lower electrode layer 33, Ti is used for the first (lower) metal thin film, and Pt is used for the second (upper) metal thin film. Each metal thin film is formed by, for example, sputtering or electron beam evaporation. The thickness of each metal thin film is, for example, about 30 to 100 [nm] for the first layer Ti and about 100 to 300 [nm] for the second layer Pt.

  Next, in the piezoelectric layer forming step, a piezoelectric layer 34 made of a single piezoelectric film is formed on the lower electrode layer 33. As a material of the piezoelectric layer 34, lead zirconate titanate (PZT) which is a piezoelectric material is used. The thickness of the piezoelectric film is, for example, about 1 to 10 [μm]. The piezoelectric film is formed by, for example, an ion plating method using reactive arc discharge. The ion plating method using reactive arc discharge is specifically described in Japanese Patent Application Laid-Open Nos. 2001-234331, 2002-177765, and 2003-81694 by the applicant of the present application. Use the technique.

  In this reactive ion plating method using arc discharge plasma, a source metal is heated and evaporated in a high-density oxygen plasma generated in a vacuum vessel by a plasma gun, and each metal vapor and in a vacuum vessel or on a semiconductor substrate are heated. By reacting with oxygen, a piezoelectric film is formed on the semiconductor substrate. By using this method, a piezoelectric film can be formed at high speed even at a relatively low film formation temperature. In particular, when a piezoelectric film is formed by an arc discharge reactive ion plating method, a seed layer is formed as a foundation by, for example, a chemical solution deposition method (CSD (Chemical Solution Deposition) method). A piezoelectric film having characteristics can be formed.

  The piezoelectric film may be formed by, for example, a sputtering method or a sol-gel method. However, by using an ion plating method using reactive arc discharge, a thick film having excellent piezoelectric characteristics (piezoelectric characteristics equivalent to a bulk piezoelectric body) can be formed.

  Next, in the upper electrode layer forming step, an upper electrode layer 35 made of a single metal thin film is formed on the piezoelectric layer 34. As a material of the upper electrode layer 35, Pt or Au is used. The upper electrode layer 35 is formed by, for example, sputtering or electron beam evaporation. The thickness of the upper electrode layer 35 is, for example, about 10 to 200 [nm].

  Next, as shown in FIG. 5D, in the shape processing step, the shapes of the upper electrode layer 35, the piezoelectric layer 34, and the lower electrode layer 33 are processed, and the first and second piezoelectric actuators 8a to 8d are processed. , 9a to 9d of piezoelectric cantilevers, upper electrodes 7a to 7h, piezoelectric bodies 6a to 6h, and lower electrodes 5a to 5h are formed.

  Specifically, first, a resist material is patterned on the upper electrode layer 35 by using a photolithography technique. Next, using the patterned resist material as a mask, the upper electrode layer 35 and the piezoelectric layer 34 are dry-etched using a RIE (Reactive Ion Etching) apparatus. Thereby, the upper electrode pads 11a to 11d, 14a to 14d, the upper electrodes 7a to 7h, and the piezoelectric bodies 6a to 6h are formed. At this time, upper electrode wirings 13a to 13d (electrode wiring patterns) for connecting these electrode pads for the upper electrodes and upper electrodes of predetermined piezoelectric cantilevers are also formed.

  Similarly, a resist material is patterned on the lower electrode layer 33 by using a photolithography technique. Next, using the patterned resist material as a mask, dry etching is performed on the lower electrode layer 33 using an RIE apparatus. Thereby, lower electrode pads 12a to 12d, 15a to 15d, and lower electrodes 5a to 5h are formed.

  At this time, as shown in FIG. 5D, the shape processing step of the lower electrode layer is also used as a reflecting surface forming step, and the lower electrode layer corresponding to the position of the mirror portion 1 is masked with a resist material and dry etching is performed. The mirror surface reflection film 1b of the mirror part 1 is formed by leaving the film as a reflection film.

  In addition, when it is desired to increase the light reflection efficiency of the mirror unit 1, a reflection surface forming step may be performed again after the shape processing step. In this case, first, a single metal thin film (reflective film) is formed on the entire surface of the SOI substrate 31 on the SOI layer 31a side. As the material of the reflective film, for example, Au, Pt, Ag, Al or the like is used. The reflective film is formed by using, for example, a sputtering method or a vapor deposition method. The thickness of the reflective film is, for example, about 100 to 500 [nm].

  Next, the shape of the reflective film is processed. Specifically, first, a resist material is patterned on the reflective film using a photolithography technique. Next, using the patterned resist material as a mask, the reflective film is dry-etched using an RIE apparatus. As a result, the mirror surface reflection film 1b is formed on the thermal silicon oxide film 32a on the active layer 31a side of the SOI substrate 31.

  Next, as shown in FIGS. 5E to 5H, in the support forming step, the mirror support 1a, the torsion bars 2a and 2b, the first and second piezoelectric actuators 8a to 8d, and 9a to 9d. The piezoelectric cantilever supports 4a to 4h and the support portion 10 are formed.

  First, as shown in FIG. 5E, the thermal oxide film 32b is removed to form a hard mask. Specifically, the entire surface of the SOI substrate 31 is protected with a thick film resist, and the thermally oxidized silicon film 32b on the rear surface handling layer 31c side is removed with buffered hydrofluoric acid (BHF). Then, a single Al thin film 37 is formed on the entire surface of the handling layer 31c on the back side of the SOI substrate 31. The Al thin film 37 is formed by using, for example, a sputtering method or a vapor deposition method. Then, a resist material is patterned on the Al thin film 37 using a photolithography technique. Next, wet etching is performed on the Al thin film 37 using the patterned resist material as a mask. Thereby, a hard mask used for dry etching by an ICP (Inductively Coupled Plasma) -RIE apparatus shown in FIG.

  Next, as shown in FIG. 5F, the shape of the active layer 31a (single crystal silicon) is processed. First, a resist material is patterned using a photolithography technique, and using the patterned resist material as a mask, the silicon shapes of the thermal oxide film 32a and the active layer 31a are processed using an ICP-RIE apparatus. The ICP-RIE apparatus is a dry etching apparatus used in micromachining technology, and is an apparatus capable of deeply digging silicon vertically.

  Next, as shown in FIG. 5G, the shape of the handling layer 31c is processed. Using the hard mask formed in FIG. 5E, the silicon of the handling layer 31c is processed using an ICP-RIE apparatus. Thereby, the back sides of the torsion bars 2a and 2b and the supports 4a to 4h are deeply dug into a hollow state.

  Next, as shown in FIG. 5H, the intermediate oxide film layer 31b of the SOI substrate 31 is removed by wet etching using buffered hydrofluoric acid (BHF). Accordingly, the mirror portion 1, the torsion bars 2a and 2b, the first piezoelectric actuators 8a to 8d, and the second piezoelectric actuators 9a to 9d are partially separated from the SOI substrate 31 to form a gap. The rotation of the torsion bars 2a and 2b, the driving of the first piezoelectric actuators 8a to 8d, and the deformation of the second piezoelectric actuators 9a to 9d are enabled.

  The optical deflector is manufactured through the above steps. In addition, after performing the above-mentioned process, each device is isolate | separated as a piece (chip) from the SOI substrate 31 by a dicing process. The chip of each device is mounted on a TO (Transister Outline) type CAN package by die bonding and wire bonding.

Thus, since the optical deflector A can be integrally formed using a semiconductor planar process and a MEMS process, it can be easily manufactured and can be downsized, mass-produced, and improved in yield. Moreover, the second piezoelectric actuators 9a to 9d can be formed by using the process of forming the first piezoelectric actuators 8a to 8d, and the number of processes is not increased and the process is not complicated. Furthermore, when the optical deflector A is incorporated into a device, the entire device can be integrally formed using a semiconductor planar process and a MEMS process, so that the optical deflector A can be easily incorporated into another device. It becomes.
[Example 1-1]
As Example 1-1, a test of drive characteristics (rotation angle detection / maximum deflection angle feedback control) of the optical deflector A of the present embodiment will be described. In this example, the above-described optical deflector A was designed so that the resonance frequency was 5 [kHz], and was manufactured using the above-described manufacturing process. At this time, the thickness of each layer of the SOI substrate was an active layer 50 [μm], an intermediate oxide film layer 2 [μm], and a handling layer 525 [μm], and the thickness of the thermally oxidized silicon film was 500 [nm]. The thickness of the lower electrode layer (Ti / Pt) is 50 nm for Ti, 150 nm for Pt, the thickness of the piezoelectric layer is 3 [μm], and the thickness of the upper electrode layer (Pt) is 150 [nm].

For this optical deflector, an AC voltage having a peak-to-peak voltage Vpp = 20 [V] and a frequency of 5 [kHz] was applied to the first piezoelectric actuators 8a to 8d as a drive signal. At this time, an angular displacement signal with a slight phase lag was obtained from the drive signals of the first piezoelectric actuators 8a to 8d as output signals of the second piezoelectric actuators 9a to 9d by the rotation angle detection means 21. Based on this angular displacement signal, the rotation angle detection means 21 detects that the maximum deflection angle (deflection angle) of the optical deflector is ± 5 °. At the same time, it was detected that the deflection angle of the optical deflector was accompanied by a fluctuation of ± 0.05 ° when it was rotationally driven at the maximum deflection angle ± 5 °. Also, when this optical deflector is rotationally driven at a maximum deflection angle of ± 5 ° with the mechanical resonance frequency of the mirror portion shifted from the initial operation due to a change in the temperature of the external environment, It was detected that the deflection angle was accompanied by fluctuation of ± 2 °. With respect to these deflection angle fluctuations (fluctuations), the control means 22 performs feedback control of the strength, phase and frequency of the drive signals of the first actuators 8a to 8d based on the detected rotation angle of the mirror unit 1. Thus, it was possible to absorb the fluctuation of the deflection angle and to maintain stable oscillation of the mirror unit 1 with a certain maximum deflection angle.
[Example 1-2]
As Example 1-2, a test of drive characteristics (rotation angle detection / maximum deflection angle feedback control) of the optical deflector A of the present embodiment will be described. In this example, a plurality of optical deflectors designed to have a resonance frequency of 5 [kHz] similar to Example 1-1 were produced.

When the resonance frequencies of these optical deflectors were measured, the resonance frequencies were distributed in the range of 5.997 to 5.003 [kHz]. At this time, an AC voltage having a peak-to-peak voltage Vpp of 20 [V] and a frequency of 5 [kHz] is applied to the first piezoelectric actuators 8a to 8d with respect to the optical deflectors having resonance frequencies of 5.997 [kHz] and 5.003 [kHz]. When applied as a drive signal, the rotation angle detector 21 was able to detect the maximum deflection angle of the optical deflector as ± 4 °. Further, the control means 22 feedback-controls the intensity, phase, and frequency of the drive signals of the first actuators 8a to 8d based on the detected rotation angle of the mirror unit 1 so that the maximum of all manufactured optical deflectors can be maximized. The deflection angle can be adjusted to ± 5 ° with high accuracy.
[Example 1-3]
As Example 1-3, a test of driving characteristics of the optical deflector A of the present embodiment (detection of rotation angle and suppression of abnormal vibration by feedback control) will be described. In this example, an optical deflector designed to have a resonance frequency of 5 [kHz], similar to Example 1-1, was produced.

With respect to this optical deflector, an alternating voltage having a peak-to-peak voltage Vpp = 20 [V] and a frequency of 5 [kHz] was applied to the first piezoelectric actuators 8a to 8d as a drive signal. From the rotation angle of the mirror unit 1, the maximum deflection angle of the optical deflector was detected as ± 5 °. Furthermore, external vibration with a frequency of 5 [kHz] and an acceleration of 500 [G] was added during operation of the optical deflector. At this time, the intensity, phase and frequency of the drive signals of the first piezoelectric actuators 8a to 8d are feedback-controlled by the control means 22 based on the detected rotation angle of the mirror unit 1 to attenuate external vibration. Thus, it was possible to control the instantaneous increase (abnormal amplitude increase) of the rotation angle of the mirror portion 1 due to external vibration.
[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS. 6 is an explanatory view showing the operation of the second piezoelectric actuator in the optical deflector according to the second embodiment of the present invention, and FIG. 7 is a graph showing adjustment of the rotation angle of the mirror portion in the optical deflector of FIG. is there. The optical deflector A ′ of the present embodiment has the same configuration as the optical deflector of the first embodiment, and only the operation is different.

  In the optical deflector A 'of the present embodiment, the second piezoelectric actuators 9a to 9d are used for assisting / adjusting the rotational drive of the mirror unit 1 by driving the first piezoelectric actuator 8a. The control circuit 20 connected to the optical deflector A ′ functions as a mirror part by controlling the drive voltage applied to the second piezoelectric actuators 9a to 9d, thereby driving the first piezoelectric actuators 8a to 8d. 1 is provided with an adjusting means 23 for adjusting the rotational drive of 1. In the present embodiment, the control circuit 20 does not include the rotation angle detection unit 21.

  Next, the operation of the optical deflector A 'according to this embodiment will be described. First, in the optical deflector A ′, a voltage is applied to the two pairs of first piezoelectric actuators 8a to 8d by the control means 22 as in the first embodiment. As a result, the two pairs of first piezoelectric actuators 8a to 8d are driven to generate angular displacements at the tip portions, respectively. These angular displacements cause torsional displacements in the torsion bars 2a and 2b, and a rotational torque α about the torsion bars 2a and 2b acts on the mirror portion 1.

  At the same time, in the optical deflector A ′ of the present embodiment, the adjusting means 23 applies a voltage to the second piezoelectric actuators 9 a to 9 d.

  Here, FIG. 6 is a diagram illustrating a driving state of the second piezoelectric actuators 9a to 9d when the mirror unit 1 of the optical deflector A ′ of the present embodiment is rotationally driven. FIG. 6 schematically shows the end surface taken along the line II-II (the end surface viewed from the direction of the arrow) shown in FIG. In FIG. 6, the first piezoelectric actuators 8a and 8c are indicated by broken lines. As shown in FIG. 6, voltages ± V2 having opposite polarities are applied between the upper electrodes 7e, 7g and the lower electrodes 5e, 5g of the piezoelectric cantilevers of the second piezoelectric actuators 9a, 9c in one pair. When driven, it bends and deforms in opposite directions.

  Due to these bending deformations, the base end portions of the second piezoelectric actuators 9a and 9c are connected to and supported by the mirror portion 1, so that the tip portion is the thickness of the mirror portion 1 (substrate) as shown in FIG. Rotate up and down in the direction. Since voltages ± V2 having opposite polarities are applied to the second piezoelectric actuators 9a and 9c, the tips of the second piezoelectric actuators 9a and 9c move in opposite directions. As a result, torsional displacement occurs in the torsion bar 2a, and rotational torque about the torsion bar 2a acts on the mirror portion 1.

  Similarly, when the other pair of second piezoelectric actuators 9b and 9d are driven by applying voltages ± V2 having opposite polarities to each other, a torsional displacement occurs in the same direction in the torsion bar 2b, and the torsion is caused in the mirror section 1. A rotational torque about the bar 2b acts.

  Therefore, torsional displacement occurs in the torsion bars 2a and 2b due to the angular displacement generated by the second piezoelectric actuators 9a to 9d, and the rotational torque β about the torsion bars 2a and 2b acts on the mirror portion 1.

  Therefore, the mirror unit 1 has the torsion bars 2a and 2b as the central axis according to the torsional displacement (rotation) of the torsion bars 2a and 2b caused by driving the first and second piezoelectric actuators 8a to 8d and 9a to 9d. As 1 axis x1. At this time, since the second piezoelectric actuators 9a and 9c are connected to the mirror unit 1 instead of the support unit 10, the second piezoelectric actuators 9a and 9c can be additionally provided without reducing the rotational torque α generated by the first piezoelectric actuators 8a and 8c. Rotational torque β can be generated.

  For this reason, the rotational torque applied to the torsion bars 2a and 2b becomes the sum α + β of the rotational torque generated by the first piezoelectric actuators 8a to 8d and the second piezoelectric actuators 9a to 9d, and the maximum deflection angle of the mirror unit 1 is increased. be able to. Furthermore, the first piezoelectric actuators 8a to 8d and the second piezoelectric actuators 9a to 9d can be independently controlled by applying drive voltages separately. Therefore, the rotational torque α + β can be controlled to a predetermined value. Therefore, the rotational drive of the mirror unit 1 can be adjusted so that the rotational drive parameter of the mirror unit 1 and the rotational drive parameters of the torsion bars 2a and 2b are set to a predetermined value or limited to a predetermined range.

  At this time, in the driving of the first piezoelectric actuators 8a to 8d, the phase of the resonance driving of the mirror unit 1 by this driving is delayed by Δλ due to the moment of inertia. Therefore, the frequency of the drive signals of the second piezoelectric actuators 9a to 9d can be matched with the resonance frequency of the mirror unit 1 by the first piezoelectric actuators 8a to 8d. As a result, it is possible to increase the maximum deflection angle by suppressing the buffering of the rotational torques α and β generated respectively. Further, by adjusting the phase and frequency of the drive signals of the second piezoelectric actuators 9a to 9d, it is possible to adjust the rotational drive parameters of the mirror unit 1.

  FIG. 7A shows the drive voltages of the first piezoelectric actuators 8a to 8d and the drive voltages of the second piezoelectric actuators 9a to 9d. In FIG. 7A, the horizontal axis indicates time, and the vertical axis indicates voltage. The driving voltages of the second piezoelectric actuators 9a to 9d have a delayed waveform whose phase is delayed by Δλ with respect to the driving voltages of the first piezoelectric actuators 8a to 8d. At this time, the amplitude of the mirror unit 1 is as shown in FIG. In FIG.7 (b), a horizontal axis shows time and a vertical axis | shaft shows an amplitude. As described above, by adding the rotational drive by the second piezoelectric actuators 9a to 9d to the rotational drive by the first piezoelectric actuators 8a to 8d, the amplitude (maximum deflection angle) of the mirror unit 1 can be increased. .

Therefore, according to the optical deflector A ′ of the present embodiment, by providing the second piezoelectric actuators 9a to 9d, it is possible to quickly and accurately control the driving state of the mirror unit 1 and increase the maximum deflection angle. In addition, the deflection / scanning performance can be improved by quick and accurate control of the deflection angle and the deflection speed.
[Example 2-1]
As Example 2-1, a test of the drive characteristics (increase in the maximum deflection angle) of the optical deflector A ′ of the present embodiment will be described. In this example, the above-described optical deflector was designed so that the resonance frequency was 5 [kHz], and manufactured by the above-described manufacturing process. At this time, the thickness of each layer of the SOI substrate was an active layer 50 [μm], an intermediate oxide film layer 2 μm, and a handling layer 525 [μm], and the thickness of the thermally oxidized silicon film was 500 [nm]. The thickness of the lower electrode layer (Ti / Pt) is 50 nm for Ti, 150 nm for Pt, the thickness of the piezoelectric layer is 3 [μm], and the thickness of the upper electrode layer (Pt) is 150 [nm].

In this optical deflector, when an AC voltage having a peak-to-peak voltage Vpp = 20 [V] and a frequency of 5 [kHz] is applied as a first drive signal to the first piezoelectric actuators 8a to 8d, the maximum deflection of the optical deflector is obtained. An angle of ± 5 ° was obtained. At this time, in addition to the first drive signal, the second piezoelectric actuators 9a to 9d are supplied with a peak-to-peak voltage Vpp = 20 [V], a frequency of 5 [kHz], and a phase difference Δλ = π / from the first drive signal. When an AC voltage of 4 was applied as the second drive signal, ± 8 ° was obtained as the maximum deflection angle of the optical deflector, and the maximum deflection angle increased 1.6 times.
[Example 2-2]
As Example 2-2, a test of drive characteristics (resonance frequency adjustment) of the optical deflector A ′ of the present embodiment will be described. In this example, a plurality of optical deflectors designed to have a resonance frequency of 5 [kHz], similar to Example 2-1, were produced.

  When the resonance frequencies of these optical deflectors were measured, the resonance frequencies were distributed in the range of 5.997 to 5.003 [kHz]. A peak-to-peak voltage Vpp = 20 [V] and an AC voltage with a frequency of 5 [kHz] were applied as a first drive signal to the first piezoelectric actuators 8a to 8d with respect to the optical deflector having a resonance frequency of 5 [kHz]. However, ± 5 ° was obtained as the maximum deflection angle of the optical deflector. On the other hand, with respect to the optical deflectors having resonance frequencies of 4.997 [kHz] and 5.003 [kHz], the first piezoelectric actuators 8a to 8d are supplied with the peak-to-peak voltage Vpp = 20 [V] and the AC voltage of frequency 5 [kHz]. When applied as a driving signal of 1, the maximum deflection angle of the optical deflector decreased to ± 4 ° due to the influence of the deviation of the driving frequency of the first piezoelectric actuators 8a to 8d and the resonance frequency of the mirror unit 1.

At this time, for the optical deflectors having resonance frequencies of 5.997 [kHz] and 5.003 [kHz], in addition to the first drive signal, the peak-to-peak voltage Vpp = 20 [ V], frequencies 5.997 [kHz] and 5.003 [kHz], and an AC voltage having a phase difference Δλ = π / 4 with respect to the first drive signal is applied as the second drive signal, the maximum deflection angle of the optical deflector is ± 5 ° was obtained.
[Example 2-3]
As Example 2-3, a test of drive characteristics (suppression of abnormal vibration) of the optical deflector A ′ of the present embodiment will be described. In this example, an optical deflector designed to have a resonance frequency of 5 [kHz], similar to Example 2-1, was produced.

  With respect to this optical deflector, when an AC voltage having a peak-to-peak voltage Vpp = 20 [V] and a frequency of 5 [kHz] is applied to the first piezoelectric actuators 8a to 8d as the first drive signal, the maximum deflection of the optical deflector is obtained. An angle of ± 5 ° was obtained.

  During the operation of this optical deflector, external vibration with frequency 5 [kHz] and acceleration 500 [G] was added. At this time, a second drive signal having a phase delayed by π / 2 from the first drive signal is applied to the second piezoelectric actuators 9a to 9d with respect to external vibration, and the first piezoelectric actuators 8a to 8d By adding the rotational torque β that decreases the rotational torque α, it was possible to suppress an instantaneous increase (abnormal amplitude increase) of the rotational angle of the mirror portion 1 due to external vibration.

  The optical deflectors of the first and second embodiments include, for example, an image display device such as a projection display, an optical scanning device for image formation such as an electrophotographic copying machine and a laser printer, a laser radar, a bar It can be used for sensing optical scanning devices such as code readers and area sensors.

The perspective view which shows the structure of the optical deflector in 1st Embodiment of this invention. Explanatory drawing which shows the action | operation of the 1st piezoelectric actuator in the optical deflector of FIG. Explanatory drawing which shows the action | operation of the 2nd piezoelectric actuator in the optical deflector of FIG. The graph which shows the detection of the rotation angle of the mirror part in the optical deflector shown in FIG. Explanatory drawing which shows the manufacturing process of the optical deflector shown in FIG. Explanatory drawing which shows the action | operation of the 2nd piezoelectric actuator in the optical deflector of 2nd Embodiment of this invention. The graph which shows adjustment of the rotation angle of the mirror part in the optical deflector of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mirror part, 2a, 2b ... Torsion bar, 4a-4h ... Support body, 5a-5h ... Lower electrode, 6a-6d ... Piezoelectric body, 7a-7d ... Upper electrode, 8a-8d ... 1st piezoelectric actuator, 9a to 9d ... second piezoelectric actuator, 10 ... support, 11a to 11d, 14a to 14d ... upper electrode pad, 12a to 12d, 15a to 15d ... lower electrode pad, 13a to 13d ... upper electrode wiring, 20 ... control Circuit, 21 ... Rotation angle detection means, 22 ... Control means, 23 ... Adjustment means,
31 ... SOI substrate, 31a ... active layer, 31b ... intermediate oxide film layer, 31c ... handling layer, 32a, 32b ... thermally oxidized silicon film, 33 ... lower electrode layer, 34 ... piezoelectric layer, 35 ... upper electrode layer, 37 ... Al thin film.

Claims (10)

A mirror part having a reflective surface; a torsion bar extending outward from the end of the mirror part; a support part provided so as to surround the mirror part; one end connected to the torsion bar and the other end being the support A first piezoelectric actuator connected to and supported by the unit, and the first piezoelectric actuator is one that performs bending deformation by piezoelectric driving when a driving voltage is applied to the piezoelectric body formed on the supporting body. In the optical deflector comprising the above piezoelectric cantilever and rotating the mirror portion via the torsion bar by the piezoelectric drive of the first piezoelectric actuator,
A second piezoelectric actuator having one end connected to the torsion bar and the other end connected to the mirror portion is supported, and the second piezoelectric actuator applies a drive voltage to the piezoelectric body formed on the support. An optical deflector comprising one or more piezoelectric cantilevers that bend and deform by piezoelectric driving when applied.   2. The optical deflector according to claim 1, wherein a piezoelectric electromotive force generated according to bending deformation of a piezoelectric cantilever of the second actuator by rotation driving of the mirror portion is detected, and based on the piezoelectric electromotive force, An optical deflector comprising rotation angle detection means for detecting a rotation angle.   3. The optical deflector according to claim 1, wherein the rotation angle detected by the rotation angle detecting means is applied to the first piezoelectric actuator so that a parameter for rotational driving of the mirror portion becomes a predetermined value. An optical deflector comprising control means for controlling a driving voltage to be applied.   4. The optical deflector according to claim 1, wherein the first piezoelectric actuator is opposed to sandwich the mirror portion and a pair of torsion bars extending outward from both ends of the mirror portion. 5. One or two pairs are arranged, and the mirror section is rotationally oscillated by the one or two pairs of first piezoelectric actuators.   5. The optical deflector according to claim 4, wherein the second piezoelectric actuator is disposed in one or two pairs so as to face each other with the mirror portion interposed therebetween, and the one or two pairs of first piezoelectric actuators are used. An optical deflector characterized in that a piezoelectric electromotive force is generated according to bending deformation caused by rotational vibration of a mirror portion, and the rotation angle detecting means detects a rotation angle of the mirror portion based on the piezoelectric electromotive force.   6. The optical deflector according to claim 1, wherein the drive voltage applied to the one or two pairs of first piezoelectric actuators is an AC voltage.   7. The optical deflector according to claim 6, wherein a first AC voltage applied to a piezoelectric actuator on one side of the one or two pairs of first piezoelectric actuators and the torsion bar. An optical deflector having a phase difference of 180 degrees from the second AC voltage applied to the piezoelectric actuator on the other side.   8. The optical deflector according to claim 1, wherein the mirror part, the torsion bar, the support part, and the support body of the piezoelectric cantilever are integrally formed by processing a semiconductor substrate. Light deflector.   9. The optical deflector according to claim 8, wherein the piezoelectric body of the piezoelectric cantilever is formed by shaping a single-layer piezoelectric film directly formed on the semiconductor substrate.   10. The optical deflector according to claim 9, wherein the reflecting surface of the mirror portion and the electrode of the piezoelectric cantilever are a metal thin film directly formed on the semiconductor substrate and a metal thin film directly formed on the piezoelectric film. An optical deflector characterized by being formed by processing the shape.

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