JP2018005001A - Drive device, optical deflection system, optical scanning system, image projection device, object recognition device and drive method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformity of movable speed of a reflection surface.SOLUTION: A drive device of an optical deflector moving a reflection surface by deformation generated when voltage is applied to a first piezoelectric part and a second piezoelectric part, which are adjacent to each other, comprises: first application means for applying first drive voltage having a predetermined wave form to the first piezoelectric part; second application means for applying second drive voltage having a different wave form from that of the first drive voltage to the second piezoelectric part; and control means for controlling drive of the first application means and the second application means. The control means performs control to make first start time at which the first application means starts applying the first drive voltage different from second start time at which the second application means starts applying the second drive voltage.SELECTED DRAWING: Figure 20

Description

  The present invention relates to a driving device, an optical deflection system, an optical scanning system, an image projection device, an object recognition device, and a driving method.

  In recent years, as a means for deflecting a light beam and performing optical scanning, a reflecting surface can be moved by applying a driving voltage having a different waveform to adjacent piezoelectric parts to deform the piezoelectric part. There is an optical deflector that rotates around. For this optical deflector, there is known a driving device having a control means for controlling the waveform of the driving voltage applied to the adjacent piezoelectric portion (see, for example, Patent Document 1).

  In such a drive device, application of a drive voltage to the piezoelectric parts is usually started simultaneously with adjacent piezoelectric parts.

  However, when the application start times of drive voltages having different waveforms applied to adjacent piezoelectric parts are the same, at least one of the piezoelectric parts is applied with a drive voltage whose voltage value changes abruptly. Become. For example, when the timing at which the minimum value of each drive voltage is applied is different, at least one of the drive voltages changes rapidly from zero to a value greater than the minimum value. At this time, the mechanical resonance of the optical deflector is excited by harmonics included in the drive voltage that changes rapidly, and the uniformity of the movable speed of the reflecting surface cannot be stably increased.

  The present invention has been made in view of the above, and an object thereof is to improve the uniformity of the movable speed of the reflecting surface.

  The present invention provides a drive device for an optical deflector that moves a reflecting surface around a predetermined axis by deformation caused by applying voltages to adjacent first and second piezoelectric portions, wherein the first piezoelectric portion First application means for applying a first drive voltage having a predetermined waveform to the second piezoelectric element, second application means for applying a second drive voltage having a waveform different from the first drive voltage to the second piezoelectric portion, and the first Control means for controlling driving of the application means and the second application means, wherein the control means includes a first start time at which the first application means starts applying the first drive voltage, and the second It is a drive device which controls so that application means may differ from the 2nd start time which starts application of the 2nd drive voltage.

  According to the present invention, the uniformity of the moving speed of the reflecting surface can be improved.

It is the schematic of an example of an optical scanning system. It is a hardware block diagram of an example of an optical scanning system. It is a functional block diagram of an example of a drive device. It is a flowchart of an example of the process which concerns on an optical scanning system. It is the schematic of an example of the motor vehicle carrying a head up display apparatus. It is a schematic diagram of an example of a head up display device. It is the schematic of an example of the image forming apparatus carrying an optical writing device. It is the schematic of an example of an optical writing device. It is the schematic of an example of the motor vehicle carrying a laser radar apparatus. It is the schematic of an example of a laser radar apparatus. It is the schematic of an example of the packaged optical deflector. It is a top view when an example of an optical deflector is seen from + Z direction. It is P-P 'sectional drawing of the optical deflector shown in FIG. It is Q-Q 'sectional drawing of the optical deflector shown in FIG. It is the schematic diagram which represented typically the deformation | transformation of the 2nd drive part of an optical deflector. (A) is a graph which shows an example of the waveform of the drive voltage A applied to the piezoelectric drive part group A of an optical deflector, (b) is applied to the piezoelectric drive part group B of an optical deflector. It is a graph which shows an example of the waveform of the drive voltage B, (c) is a graph which shows an example which superimposed the waveform of the drive voltage of (a), and the waveform of the drive voltage of (b). It is a graph which shows the time change of the deflection | deviation angle around the 2nd axis | shaft of a reflective surface when the movable speed around the 2nd axis | shaft of a reflective surface is constant (uniform). It is a graph which shows the time change of the deflection angle around the 2nd axis of the reflective surface when the movable speed around the 2nd axis of the reflective surface is not constant (uniform). (A) It is an image figure of an example of the projection image in case the movable speed around the 2nd axis of a reflective surface is uniform, (b) The projection image in case the movable speed around the 2nd axis of a reflective surface is non-uniform | heterogenous. It is an image figure of an example. It is an example of the waveform of 1 drive voltage and the waveform of 2nd drive voltage. It is a figure for demonstrating a resonant frequency and a frequency reduction area | region. It is an example of the waveform of the 1st drive voltage of the modification 1 of control, and the waveform of the 2nd drive voltage. It is an example of the waveform of the 1st drive voltage of the modification 2 of control, and the waveform of the 2nd drive voltage. It is an example of the waveform of the 1st drive voltage of the modification 3 of control, and the waveform of the 2nd drive voltage. It is an example of the waveform of the 1st drive voltage of the modification 4 of control, and the waveform of the 2nd drive voltage. It is a top view when the 1st modification of an optical deflector is seen from + Z direction. It is a top view when the 2nd modification of an optical deflector is seen from + Z direction. It is a figure for demonstrating a resonant frequency and a harmonic component. It is an example of the waveform which started applying a 1st drive voltage and a 2nd drive voltage simultaneously.

  Hereinafter, embodiments of the present invention will be described in detail.

[Optical scanning system]
First, an optical scanning system to which a driving apparatus according to an embodiment of the present invention is applied will be described in detail with reference to FIGS.

  FIG. 1 shows a schematic diagram of an example of an optical scanning system. As shown in FIG. 1, the optical scanning system 10 optically scans the surface to be scanned 15 by deflecting the light emitted from the light source device 12 according to the control of the driving device 11 by the reflecting surface 14 of the optical deflector 13. It is.

  The optical scanning system 10 includes a driving device 11, a light source device 12, and an optical deflector 13 having a reflecting surface 14.

  The drive device 11 is an electronic circuit unit including, for example, a CPU (Central Processing Unit) and an FPGA (Field-Programmable Gate Array). The optical deflector 13 is, for example, a MEMS (Micro Electromechanical Systems) device having a reflective surface 14 and capable of moving the reflective surface 14. The light source device 12 is, for example, a laser device that irradiates a laser. The scanned surface 15 is, for example, a screen.

  The drive device 11 generates a control command for the light source device 12 and the optical deflector 13 based on the acquired optical scanning information, and outputs a drive signal to the light source device 12 and the optical deflector 13 based on the control command.

  The light source device 12 irradiates the light source based on the input drive signal. The optical deflector 13 moves the reflecting surface 14 in at least one of the uniaxial direction and the biaxial direction based on the input drive signal.

Thus, for example, the control of the driving device 11 based on the image information which is an example of the optical scanning information causes the reflecting surface 14 of the optical deflector 13 to reciprocate in a biaxial direction within a predetermined range and enter the reflecting surface 14. An arbitrary image can be projected on the scanned surface 15 by deflecting the light emitted from the light source device 12 and performing optical scanning. Details of the optical deflector and details of control by the driving device of the present embodiment will be described later.

  Next, an exemplary hardware configuration of the optical scanning system 10 will be described with reference to FIG. FIG. 2 is a hardware configuration diagram of an example of the optical scanning system 10. As shown in FIG. 2, the optical scanning system 10 includes a driving device 11, a light source device 12, and an optical deflector 13, and each is electrically connected.

[Driver]
Among these, the drive device 11 includes a CPU 20, a RAM 21 (Random Access Memory), a ROM 22 (Read Only Memory), an FPGA 23, an external I / F 24, a light source device driver 25, and an optical deflector driver 26.

  The CPU 20 is an arithmetic device that reads out programs and data from a storage device such as the ROM 22 onto the RAM 21 and executes processing to realize the overall control and functions of the drive device 11.

  The RAM 21 is a volatile storage device that temporarily stores programs and data.

  The ROM 22 is a nonvolatile storage device that can retain programs and data even when the power is turned off, and stores processing programs and data that the CPU 20 executes to control each function of the optical scanning system 10. Yes.

  The FPGA 23 is a circuit that outputs control signals suitable for the light source device driver 25 and the optical deflector driver 26 in accordance with the processing of the CPU 20.

  The external I / F 24 is an interface with, for example, an external device or a network. The external device includes, for example, a host device such as a PC (Personal Computer), a storage device such as a USB memory, an SD card, a CD, a DVD, an HDD, and an SSD. The network is, for example, a car CAN (Controller Area Network), a LAN (Local Area Network), the Internet, or the like. The external I / F 24 may be configured to enable connection or communication with an external device, and the external I / F 24 may be prepared for each external device.

  The light source device driver 25 is an electric circuit that outputs a drive signal such as a drive voltage to the light source device 12 in accordance with the input control signal.

  The optical deflector driver 26 is an electric circuit that outputs a drive signal such as a drive voltage to the optical deflector 13 in accordance with the input control signal.

  In the driving device 11, the CPU 20 acquires optical scanning information from an external device or a network via the external I / F 24. The CPU 20 may be configured so that the optical scanning information can be acquired. The optical scanning information may be stored in the ROM 22 or the FPGA 23 in the driving device 11, or a new SSD or the like may be included in the driving device 11. A storage device may be provided, and the optical scanning information may be stored in the storage device.

Here, the optical scanning information is information indicating how the scanned surface 15 is optically scanned. For example, when an image is displayed by optical scanning, the optical scanning information is image data. For example, when optical writing is performed by optical scanning, the optical scanning information is writing data indicating the writing order and writing location. In addition, for example, when object recognition is performed by optical scanning, the optical scanning information is irradiation data indicating the timing and irradiation range for irradiating light for object recognition.

  The drive device 11 according to the present embodiment can realize the functional configuration described below by the instruction of the CPU 20 and the hardware configuration shown in FIG.

[Functional configuration of drive unit]
Next, a functional configuration of the driving device 11 of the optical scanning system 10 will be described with reference to FIG. FIG. 3 is a functional block diagram of an example of a driving device of the optical scanning system. As shown in FIG. 3, the drive device 11 includes a control unit 30 and a drive signal output unit 31 as functions.

  The control unit 30 is realized by, for example, the CPU 20, the FPGA 23, and the like, acquires optical scanning information from an external device, converts the optical scanning information into a control signal, and outputs the control signal to the drive signal output unit 31. For example, the control unit 30 constitutes a control unit, acquires image data as optical scanning information from an external device or the like, generates a control signal from the image data by a predetermined process, and outputs the control signal to the drive signal output unit 31.

  The drive signal output unit 31 constitutes application means, and is realized by the light source device driver 25, the optical deflector driver 26, and the like, and outputs a drive signal to the light source device 12 or the optical deflector 13 based on the input control signal. . The drive signal output unit 31 (applying unit) may be provided for each target that outputs a drive signal, for example.

  The drive signal is a signal for controlling driving of the light source device 12 or the optical deflector 13. For example, in the light source device 12, the driving voltage is used to control the irradiation timing and irradiation intensity of the light source. Further, for example, in the optical deflector 13, the driving voltage is used to control the timing and movable range for moving the reflecting surface 14 of the optical deflector 13. The driving device may acquire the irradiation timing and the light receiving timing of the light source from an external device such as the light source device 12 and the light receiving device, and synchronize these with the driving of the optical deflector 13.

[Optical scanning processing]
Next, a process in which the optical scanning system 10 optically scans the scanned surface 15 will be described with reference to FIG. FIG. 4 is a flowchart of an example of processing according to the optical scanning system.

  In step S11, the control unit 30 acquires optical scanning information from an external device or the like. In step S <b> 12, the control unit 30 generates a control signal from the acquired optical scanning information, and outputs the control signal to the drive signal output unit 31. In step S <b> 13, the drive signal output unit 31 outputs a drive signal to the light source device 12 and the optical deflector 13 based on the input control signal. In step S <b> 14, the light source device 12 performs light irradiation based on the input drive signal. The optical deflector 13 moves the reflecting surface 14 based on the input drive signal. By driving the light source device 12 and the optical deflector 13, light is deflected in an arbitrary direction and optically scanned.

  In the optical scanning system 10, one driving device 11 has a device and a function for controlling the light source device 12 and the optical deflector 13, but the driving device for the light source device and the driving device for the optical deflector Alternatively, it may be provided separately.

  In the optical scanning system 10, the function of the control unit 30 and the function of the drive signal output unit 31 of the light source device 12 and the optical deflector 13 are provided in one drive device 11, but these functions are separately provided. For example, a drive signal output device having a drive signal output unit 31 may be provided in addition to the drive device 11 having the control unit 30. In the optical scanning system 10, an optical deflection system that performs optical deflection may be configured by the optical deflector 13 having the reflecting surface 14 and the driving device 11.

[Image projection device]
Next, with reference to FIG. 5 and FIG. 6, an image projection apparatus to which the drive device of this embodiment is applied will be described in detail.

  FIG. 5 is a schematic diagram according to an embodiment of an automobile 400 equipped with a head-up display device 500 which is an example of an image projection device. FIG. 6 is a schematic diagram of an example of the head-up display device 500.

  The image projection device is a device that projects an image by optical scanning, for example, a head-up display device.

  As shown in FIG. 5, the head-up display device 500 is installed, for example, in the vicinity of a windshield (a windshield 401 or the like) of the automobile 400. The projection light L emitted from the head-up display device 500 is reflected by the windshield 401 and travels toward the observer (driver 402) who is the user.

  Accordingly, the driver 402 can visually recognize an image or the like projected by the head-up display device 500 as a virtual image. In addition, you may make it the structure which installs a combiner in the inner wall face of a windshield, and makes a user visually recognize a virtual image with the projection light reflected by a combiner.

  As shown in FIG. 6, the head-up display device 500 emits laser light from red, green, and blue laser light sources 501R, 501G, and 501B. The emitted laser light passes through an incident optical system composed of collimator lenses 502, 503, and 504 provided for each laser light source, two dichroic mirrors 505 and 506, and a light amount adjusting unit 507. The light is deflected by an optical deflector 13 having a reflecting surface 14.

  The deflected laser light is projected onto a screen through a projection optical system including a free-form surface mirror 509, an intermediate screen 510, and a projection mirror 511.

  In the head-up display device 500, the laser light sources 501R, 501G, and 501B, the collimator lenses 502, 503, and 504 and the dichroic mirrors 505 and 506 are unitized as an optical housing by an optical housing.

  The head-up display device 500 projects the intermediate image displayed on the intermediate screen 510 onto the windshield 401 of the automobile 400 so that the driver 402 can visually recognize the intermediate image as a virtual image.

  The respective color laser beams emitted from the laser light sources 501R, 501G, and 501B are substantially collimated by the collimator lenses 502, 503, and 504, and are combined by the two dichroic mirrors 505 and 506. The combined laser light is two-dimensionally scanned by the optical deflector 13 having the reflecting surface 14 after the light amount is adjusted by the light amount adjusting unit 507. The projection light L that has been two-dimensionally scanned by the optical deflector 13 is reflected by the free-form surface mirror 509, corrected for distortion, and then condensed on the intermediate screen 510 to display an intermediate image. The intermediate screen 510 includes a microlens array in which microlenses are two-dimensionally arranged, and enlarges the projection light L incident on the intermediate screen 510 in units of microlenses.

  The optical deflector 13 reciprocally moves the reflecting surface 14 in the biaxial direction, and two-dimensionally scans the projection light L incident on the reflecting surface 14. The drive control of the optical deflector 13 is performed in synchronization with the light emission timings of the laser light sources 501R, 501G, and 501B.

  The head-up display device 500 as an example of the image projection device has been described above. However, the image projection device is any device that projects an image by performing optical scanning with the optical deflector 13 having the reflective surface 14. Good.

  For example, it is mounted on a projector that is placed on a desk or the like and projects an image on a display screen, or a mounting member that is mounted on an observer's head or the like, and is projected on a reflective transmission screen that the mounting member has, or an eyeball as a screen The present invention can be similarly applied to a head-mounted display device that projects an image.

  The image projection apparatus is not only a vehicle or a mounting member, but also, for example, a moving body such as an aircraft, a ship, or a mobile robot, or a work robot that operates a driving target such as a manipulator without moving from the spot. It may be mounted on a non-moving body.

[Optical writing device]
Next, with reference to FIG. 7 and FIG. 8, an optical writing device to which the driving device 11 of this embodiment is applied will be described in detail.

  FIG. 7 is an example of an image forming apparatus incorporating the optical writing device 600. FIG. 8 is a schematic diagram of an example of an optical writing device.

  As shown in FIG. 7, the optical writing device 600 is used as a constituent member of an image forming apparatus represented by a laser printer 650 having a printer function using laser light. In the image forming apparatus, the optical writing device 600 performs optical writing on the photosensitive drum by optically scanning the photosensitive drum which is the surface to be scanned 15 with one or a plurality of laser beams.

  As shown in FIG. 8, in the optical writing device 600, the laser light from the light source device 12 such as a laser element passes through an imaging optical system 601 such as a collimator lens, and is then transmitted by the optical deflector 13 having the reflecting surface 14. Deflection is performed in one or two axial directions.

  Then, the laser beam deflected by the optical deflector 13 passes through a scanning optical system 602 including a first lens 602a, a second lens 602b, and a reflection mirror unit 602c, and then the surface to be scanned 15 (for example, a photosensitive drum or a photosensitive drum). (Paper) and write optically. The scanning optical system 602 forms a light beam in a spot shape on the scanned surface 15.

  The light deflector 13 having the light source device 12 and the reflecting surface 14 is driven based on the control of the driving device 11.

  As described above, the optical writing device 600 can be used as a constituent member of an image forming apparatus having a printer function using laser light.

  Also, by making the scanning optical system different so that optical scanning is possible not only in one axis direction but also in two axis directions, a laser label device that performs printing by deflecting laser light to a thermal medium, optical scanning, and heating. It can be used as a component of the image forming apparatus.

  The optical deflector 13 having the reflecting surface 14 applied to the optical writing device consumes less power for driving than a rotating polygonal mirror using a polygon mirror or the like, so that power saving of the optical writing device is achieved. Is advantageous.

  Further, since the wind noise during vibration of the optical deflector 13 is smaller than that of the rotary polygon mirror, it is advantageous for improving the quietness of the optical writing device. The optical writing device requires much less installation space than the rotary polygon mirror, and the optical deflector 13 generates only a small amount of heat. Therefore, the optical writing device can be easily downsized, and thus is advantageous for downsizing the image forming apparatus. Is

[Object recognition device]
Next, with reference to FIG. 9 and FIG. 10, an object recognition device to which the driving device of the present embodiment is applied will be described in detail.

  FIG. 9 is a schematic diagram of an automobile equipped with a laser radar device which is an example of an object recognition device. FIG. 10 is a schematic diagram of an example of a laser radar device.

  The object recognition device is a device that recognizes an object in a target direction, for example, a laser radar device.

  As shown in FIG. 9, a laser radar device 700 is mounted on, for example, an automobile 701, optically scans the target direction, and receives reflected light from the target object 702 existing in the target direction, thereby receiving the target object. 702 is recognized.

  As shown in FIG. 10, the laser light emitted from the light source device 12 is reflected through an incident optical system including a collimating lens 703 that is an optical system that makes diverging light substantially parallel light, and a plane mirror 704. Scanning is performed in one or two axial directions by an optical deflector 13 having a surface 14.

  Then, the object 702 in front of the apparatus is irradiated through a projection lens 705 or the like that is a projection optical system. Driving of the light source device 12 and the optical deflector 13 is controlled by the driving device 11. The reflected light reflected by the object 702 is detected by the photodetector 709.

  That is, the reflected light is received by the image sensor 707 via the condenser lens 706 that is a light receiving optical system, and the image sensor 707 outputs a detection signal to the signal processing circuit 708. The signal processing circuit 708 performs predetermined processing such as binarization and noise processing on the input detection signal, and outputs the result to the distance measurement circuit 710.

  The distance measuring circuit 710 determines whether the light source device 12 emits the laser beam and the timing at which the photodetector 709 receives the laser beam, or the phase difference for each pixel of the received image sensor 707. The presence / absence of 702 is recognized, and further distance information with respect to the object 702 is calculated.

  Since the optical deflector 13 having the reflecting surface 14 is less likely to be damaged than a polygonal mirror and is small in size, it is possible to provide a small and highly durable radar device. Such a radar radar apparatus is attached to, for example, a vehicle, an aircraft, a ship, a robot, and the like, and can optically scan a predetermined range to recognize the presence or absence of an obstacle and the distance to the obstacle.

  In the object recognition apparatus, the laser radar apparatus 700 as an example has been described. However, the object recognition apparatus performs optical scanning by controlling the optical deflector 13 having the reflecting surface 14 with the driving device 11 to detect light. Any device that recognizes the object 702 by receiving reflected light with a vessel may be used, and is not limited to the above-described embodiment.

  For example, object information such as shape is calculated from distance information obtained by optically scanning the hand or face, and biometric authentication that recognizes the target object by referring to the record, or recognizes an intruder by optical scanning of the target range The present invention can be similarly applied to a security sensor, a three-dimensional scanner component that calculates and recognizes object information such as a shape from distance information obtained by optical scanning, and outputs it as three-dimensional data.

[Packaging]
Next, with reference to FIG. 11, the packaging of the optical deflector controlled by the drive device of this embodiment will be described. FIG. 11 is a schematic diagram of an example of a packaged optical deflector.

  As shown in FIG. 11, the optical deflector 13 is attached to an attachment member 802 disposed inside the package member 801, and a part of the package member is covered with a transmission member 803 and sealed to achieve packaging. Is done. Further, an inert gas such as nitrogen is sealed in the package. As a result, deterioration of the optical deflector 13 due to oxidation is suppressed, and durability against changes in the environment such as temperature is improved.

  Next, details of the optical deflector used in the optical deflection system, optical scanning system, image projection apparatus, optical writing apparatus, and object recognition apparatus described above and details of control by the driving apparatus of the present embodiment will be described. .

[Details of optical deflector]
First, the optical deflector will be described in detail with reference to FIGS.

  FIG. 12 is a plan view of a double-sided type optical deflector that can deflect light in two axial directions. 13 is a cross-sectional view taken along the line P-P ′ of FIG. 14 is a cross-sectional view taken along the line Q-Q 'of FIG.

  As shown in FIG. 12, the optical deflector 13 includes a mirror unit 101 that reflects incident light, and a first drive unit 110a that is connected to the mirror unit and drives the mirror unit around a first axis parallel to the Y axis. 110b, a first support 120 that supports the mirror unit and the first drive unit, and a first support unit that is connected to the first support unit and drives the mirror unit and the first support unit about a second axis parallel to the X axis. Two drive units 130a and 130b, a second support unit 140 that supports the second drive unit, and an electrode connection unit 150 that is electrically connected to the first drive unit, the second drive unit, and the drive device.

  The optical deflector 13 is formed, for example, by forming a single SOI (Silicon On Insulator) substrate by etching or the like, and on the formed substrate, the reflecting surface 14, the first piezoelectric drive units 112a and 112b, and the second piezoelectric drive unit 131a. Each component is integrally formed by forming ~ 131f, 132a to 132f, electrode connecting part 150, and the like. Note that each of the above-described components may be formed after the SOI substrate is formed or during the formation of the SOI substrate.

  In the SOI substrate, a silicon oxide layer 162 is provided on a first silicon layer made of single crystal silicon (Si), and a second silicon layer made of single crystal silicon is further provided on the silicon oxide layer. It is a substrate. Hereinafter, the first silicon layer is referred to as a silicon support layer 161, and the second silicon layer is referred to as a silicon active layer 163.

  Since the silicon active layer 163 has a smaller thickness in the Z-axis direction with respect to the X-axis direction or the Y-axis direction, a member formed only of the silicon active layer 163 has a function as an elastic part having elasticity.

  Note that the SOI substrate is not necessarily flat and may have a curvature or the like. In addition, the member used for forming the optical deflector 13 is not limited to the SOI substrate as long as it is a substrate that can be integrally formed by etching or the like and can be partially elastic.

  The mirror unit 101 includes, for example, a circular mirror unit base 102 and a reflection surface 14 formed on the + Z side surface of the mirror unit base. The mirror part base | substrate 102 is comprised from the silicon | silicone active layer 163, for example.

  The reflecting surface 14 is made of a metal thin film containing, for example, aluminum, gold, silver or the like. Further, the mirror portion 101 may have a mirror portion reinforcing rib formed on the surface of the mirror portion base 102 on the −Z side. The rib is composed of, for example, a silicon support layer 161 and a silicon oxide layer 162, and can suppress distortion of the reflecting surface 14 caused by movement.

  The first drive units 110a and 110b are connected at one end to the mirror unit base 102, extend in the first axial direction, and movably support the mirror unit 101, and one end to the torsion bar. The first piezoelectric drive units 112a and 112b are connected to each other and connected to the inner peripheral portion of the first support unit at the other end.

  As shown in FIG. 13, the torsion bars 111 a and 111 b are composed of a silicon active layer 163. The first piezoelectric driving units 112a and 112b are configured by forming a lower electrode 201, a piezoelectric unit 202, and an upper electrode 203 in this order on the surface of the silicon active layer 163 that is an elastic part on the + Z side.

  The upper electrode 203 and the lower electrode 201 are made of, for example, gold (Au) or platinum (Pt). The piezoelectric portion 202 is made of, for example, PZT (lead zirconate titanate) that is a piezoelectric material.

  Returning to FIG. 12, the first support part 120 is a rectangular support body that is formed of, for example, a silicon support layer 161, a silicon oxide layer 162, and a silicon active layer 163 and is formed so as to surround the mirror part 101.

  For example, the second driving units 130a and 130b include a plurality of second piezoelectric driving units 131a to 131f and 132a to 132f connected so as to be folded back, and one end of each of the second driving units 130a and 130b is a first support. The other end is connected to the outer peripheral part of the part 120, and the other end is connected to the inner peripheral part of the second support part 140.

  At this time, the connection location between the second drive unit 130a and the first support unit 120, the connection site between the second drive unit 130b and the first support unit 120, the connection site between the second drive unit 130a and the second support unit 140, and the The connection part of the 2 drive part 130b and the 2nd support part 140 is point-symmetric with respect to the center of the reflective surface 14. FIG.

  As shown in FIG. 14, the second driving units 130 a and 130 b are formed by sequentially forming a lower electrode 201, a piezoelectric unit 202, and an upper electrode 203 on the + Z side surface of the silicon active layer 163 that is an elastic unit. . The upper electrode 203 and the lower electrode 201 are made of, for example, gold (Au) or platinum (Pt). The piezoelectric portion 202 is made of, for example, PZT (lead zirconate titanate) that is a piezoelectric material.

  Returning to FIG. 12, the second support unit 140 includes, for example, a silicon support layer 161, a silicon oxide layer 162, and a silicon active layer 163, and includes a mirror unit 101, first drive units 110 a and 110 b, a first support unit 120, and This is a rectangular support formed so as to surround the second drive units 130a and 130b.

  The electrode connection unit 150 is formed, for example, on the surface of the second support unit 140 on the + Z side, and the upper electrodes 203 and the lower electrodes 201 of the first piezoelectric driving units 112a and 112b and the second piezoelectric driving units 131a to 131f. , And the drive device 11 via an electrode wiring such as aluminum (Al).

  Each of the upper electrode 203 and the lower electrode 201 may be directly connected to the electrode connecting portion, or may be indirectly connected by connecting the electrodes to each other.

  In the present embodiment, the case where the piezoelectric portion 202 is formed only on one surface (the surface on the + Z side) of the silicon active layer 163 that is an elastic portion has been described as an example. May be provided on both the one side and the other side of the elastic portion.

  In addition, as long as the mirror unit 101 can be driven around the first axis or the second axis, the shape of each component is not limited to the shape of the embodiment. For example, the torsion bars 111a and 111b and the first piezoelectric drive units 112a and 112b may have a curved shape.

  Further, on the + Z side surface of the upper electrode 203 of the first drive units 110a and 110b, on the + Z side surface of the first support unit, on the + Z side surface of the upper electrode 203 of the second drive units 130a and 130b, 2 An insulating layer made of a silicon oxide film may be formed on at least one of the surfaces on the + Z side of the support portion.

  At this time, an electrode wiring is provided on the insulating layer, and the insulating layer is not partially removed or formed as an opening at a connection spot where the upper electrode 203 or the lower electrode 201 and the electrode wiring are connected. This increases the degree of freedom in designing the first drive units 110a and 110b, the second drive units 130a and 130b, and the electrode wiring, and can further suppress a short circuit due to contact between the electrodes. The insulating layer may be any member having an insulating property, and may have a function as an antireflection material.

[Details of control of drive unit]
Next, details of the control of the driving device that drives the first driving unit and the second driving unit of the optical deflector will be described.

  The piezoelectric unit 202 included in the first driving unit 110a, 110b and the second driving unit 130a, 130b undergoes deformation (for example, expansion and contraction) proportional to the potential of the applied voltage when a positive or negative voltage is applied in the polarization direction. The so-called reverse piezoelectric effect is exhibited. The first driving units 110a and 110b and the second driving units 130a and 130b move the mirror unit 101 using the above-described inverse piezoelectric effect.

  At this time, the angle at which the light beam incident on the reflecting surface 14 of the mirror unit 101 is deflected is called a deflection angle. When the voltage is not applied to the piezoelectric portion, the deflection angle is set to zero. When the deflection angle is larger than the angle, the deflection angle is positive. When the deflection angle is smaller, the deflection angle is negative.

  First, control of the drive device that drives the first drive unit will be described. In the first driving units 110a and 110b, when a driving voltage is applied in parallel to the piezoelectric units 202 included in the first piezoelectric driving units 112a and 112b via the upper electrode 203 and the lower electrode 201, the respective piezoelectric units 202 are connected. Deform. Due to the action of the deformation of the piezoelectric portion 202, the first piezoelectric driving portions 112a and 112b are bent and deformed.

  As a result, the driving force around the first axis acts on the mirror portion 101 via the twist of the two torsion bars 111a and 111b, and the mirror portion 101 moves around the first axis. The driving voltage applied to the first driving units 110 a and 110 b is controlled by the driving device 11.

  Therefore, the drive unit 11 applies the drive voltage having a predetermined sine waveform in parallel to the first piezoelectric drive units 112a and 112b included in the first drive units 110a and 110b, so that the mirror unit 101 is moved around the first axis. Can be moved at a period of a drive voltage having a predetermined sine waveform.

  In particular, for example, when the frequency of the sinusoidal waveform voltage is set to about 20 kHz, which is about the same as the resonance frequency of the torsion bars 111a and 111b, utilizing the mechanical resonance caused by the torsion of the torsion bars 111a and 111b, The mirror unit 101 can be resonantly oscillated at about 20 kHz.

  Next, with reference to FIGS. 15-21, control of the drive device which drives a 2nd drive part is demonstrated.

  FIG. 15 is a schematic diagram schematically illustrating driving of the second drive unit 130b of the optical deflector. A region represented by diagonal lines is the mirror unit 101 or the like.

  Among the plurality of second piezoelectric drive units 131a to 131f included in the second drive unit 130a, the even-numbered second piezoelectric drive unit counted from the second piezoelectric drive unit (131a) closest to the mirror unit, that is, the second piezoelectric drive unit. The piezoelectric drive units 131b, 131d, and 131f are referred to as a piezoelectric drive unit group A.

  Further, among the plurality of second piezoelectric drive units 132a to 132f included in the second drive unit 130b, odd-numbered second piezoelectric drive units counted from the second piezoelectric drive unit (132a) closest to the mirror unit, That is, the second piezoelectric drive units 132a, 132c, and 132e are similarly referred to as a piezoelectric drive unit group A.

  When the drive voltage is applied in parallel, the piezoelectric drive unit group A is bent so that the piezoelectric drive unit group A is bent and deformed in the same direction as shown in FIG. 101 moves around the second axis.

  Of the plurality of second piezoelectric drive units 131a to 131f of the second drive unit 130a, the odd-numbered second piezoelectric drive units counted from the second piezoelectric drive unit (131a) closest to the mirror unit, that is, The second piezoelectric drive units 131a, 131c, and 131e are referred to as a piezoelectric drive unit group B.

  Further, among the plurality of second piezoelectric driving units 132a to 132f included in the second driving unit 130b, the even-numbered second piezoelectric driving unit counted from the second piezoelectric driving unit (132a) closest to the mirror unit, That is, 132b, 132d, and 132f are similarly set as the piezoelectric drive unit group B.

  When the drive voltage is applied in parallel, the piezoelectric drive unit group B is bent and deformed in the same direction as shown in FIG. 15 (iii) so that the mirror unit has a negative deflection angle. 101 Moves around the second axis.

  As shown in FIGS. 15 (i) and (iii), in the second drive unit 130a or 130b, the plurality of piezoelectric units 202 included in the piezoelectric drive unit group A or the plurality of piezoelectric units 202 included in the piezoelectric drive unit group B are bent. By deforming, the movable amount due to the bending deformation can be accumulated, and the deflection angle around the second axis of the mirror unit 101 can be increased.

  For example, as shown in FIG. 12, the second drive units 130a and 130b are connected to the first support unit in a point-symmetric manner with respect to the center point of the first support unit. Therefore, when a driving voltage is applied to the piezoelectric driving unit group A, the second driving unit 130a generates a driving force that moves in the + Z direction at the connecting portion between the first support unit and the second driving unit 130a, and the second driving unit 130b has the second driving unit 130b. A driving force that moves in the −Z direction is generated at the connection portion between the first support portion and the second driving portion 130b, and the amount of movement can be accumulated to increase the deflection angle of the mirror portion 101 around the second axis.

  Further, as shown in FIG. 15 (ii), no voltage is applied, or the movable amount of the mirror unit 101 by the piezoelectric drive unit group A by the voltage application and the movement of the mirror unit 101 by the piezoelectric drive group B by the voltage application. When the amount is balanced, the deflection angle is zero.

  The mirror part can be driven around the second axis by applying a driving voltage to the second piezoelectric driving part so as to continuously repeat FIGS. 15 (i) to 15 (iii).

[Drive voltage]
The drive voltage applied to the second drive unit is controlled by the drive device. With reference to FIG. 16, the drive voltage applied to the piezoelectric drive unit group A (hereinafter referred to as drive voltage A) and the drive voltage applied to the piezoelectric drive unit group B (hereinafter referred to as drive voltage B) will be described. In addition, an application unit that applies the drive voltage A (first drive voltage) is a first application unit, and an application unit that applies the drive voltage B (second drive voltage) is a second application unit.

  FIG. 16A shows an example of the waveform of the drive voltage A applied to the piezoelectric drive unit group A of the optical deflector. FIG. 16B is an example of a waveform of the drive voltage B applied to the piezoelectric drive unit group B of the optical deflector. FIG. 16C is a diagram in which the waveform of the drive voltage A and the waveform of the drive voltage B are superimposed.

  As shown in FIG. 16A, the waveform of the drive voltage A applied to the piezoelectric drive unit group A is, for example, a sawtooth waveform, and the frequency is, for example, 60 Hz. Further, the waveform of the drive voltage A has a rising time period TrA in which the voltage value increases from the minimum value to the next maximum value, and a falling period in which the voltage value decreases from the maximum value to the next minimum value. For example, a ratio of TrA: TfA = 9: 1 is set in advance. At this time, the ratio of TrA to one cycle is referred to as symmetry of drive voltage A.

  As shown in FIG. 16B, the waveform of the drive voltage B applied to the piezoelectric drive unit group B is, for example, a sawtooth waveform, and the frequency is, for example, 60 Hz. In addition, the waveform of the drive voltage B indicates that the time width of the rising period in which the voltage value increases from the minimum value to the next maximum value is TrB, and the falling period in which the voltage value decreases from the maximum value to the next minimum value. For example, a ratio of TfB: TrB = 9: 1 is set in advance. At this time, the ratio of TfB to one cycle is referred to as symmetry of the drive voltage B. Also, as shown in FIG. 16C, for example, the period TA of the waveform of the drive voltage A and the period TB of the waveform of the drive voltage B are set to be the same.

  The sawtooth waveform of the drive voltage A and the drive voltage B is generated, for example, by superimposing sine waves.

  In the present embodiment, the drive voltages A and B use a sawtooth waveform drive voltage. However, the present invention is not limited to this, and a drive voltage having a sawtooth waveform with a rounded apex or a sawtooth waveform. It is also possible to change the waveform according to the device characteristics of the optical deflector, such as a drive voltage having a waveform with the straight line region as a curve. In this case, the symmetry is the ratio of the rise time to one cycle or the ratio of the fall time to one cycle. At this time, it may be arbitrarily set whether the rise time or the fall time is used as a reference.

  Next, with reference to FIG. 17 to FIG. 19, a description will be given of a temporal change in the moving speed around the second axis of the reflecting surface of the optical deflector, that is, the deflection angle around the second axis of the reflecting surface.

  FIG. 17 is a diagram illustrating a temporal change in a deflection angle (light scanning angle) of the reflecting surface around the second axis when the movable speed of the reflecting surface around the second axis is constant (uniform). FIG. 18 is a diagram illustrating a temporal change in the deflection angle (optical scanning angle) of the reflecting surface around the second axis when the movable speed of the reflecting surface around the second axis is not constant (uniform). FIG. 19A is an image diagram of a projected image when the movable speed of the mirror unit 101 around the second axis is uniform. FIG. 19B is an image diagram of a projected image when the movable speed of the mirror unit 101 around the second axis is nonuniform.

  It is desirable that the time change of the deflection angle around the second axis of the reflecting surface 14, that is, the movable speed of the reflecting surface 14 around the second axis is linear as shown in FIG. That is, it is desirable that the movable speed around the second axis of the mirror unit 101 does not vary. If fluctuation occurs in the movable speed around the second axis of the mirror unit 101, linear optical scanning is hindered, and for example, unevenness in brightness, distortion, etc. occur in the image formed on the scanned surface 15 and image quality deteriorates. Because it invites.

  However, in practice, the optical deflector 13 has a resonance frequency. When a drive voltage is applied to the optical deflector 13, if the overlap between the harmonic component of the drive voltage and the resonance frequency is large, the optical deflector 13 Will be excited. As a result, as shown in FIG. 18, the movable speed around the two axes of the reflecting surface 14 fluctuates, and the uniformity of the movable speed cannot be maintained.

[Harmonic component and resonance frequency]
The harmonic components and the resonance frequency will be described with reference to FIG. FIG. 28 is an example of a graph showing the relationship between the harmonic component and the resonance frequency of the optical deflector 13. There are a plurality of resonance frequencies of the optical deflector 13, and the resonance frequencies (resonance modes) of the 0th order (lowest order, f0), 1st order (f1),. At this time, when the harmonic component of the drive voltage overlaps with the resonance frequency of the optical deflector 13, especially when the overlap between the harmonic component signal intensity and the 0th-order resonance frequency where the resonance mode drive sensitivity is high is large. The resonance of the optical deflector 13 is excited, and abnormal vibration occurs in the optical deflector 13. Due to this abnormal vibration, the moving speed of the reflecting surface 14 fluctuates, and the uniformity of the moving speed cannot be maintained.

[Projected image]
When image projection is performed using an optical deflector that performs optical scanning at a nonuniform moving speed as shown in FIG. 18, the projection image originally displayed as shown in FIG. As described above, luminance unevenness and distortion occur in the entire image.

  The harmonic component of the drive voltage is included in the waveform when a sudden change occurs in the drive voltage. This is because a sine wave with a short period is superimposed in order to cause a rapid change in the drive voltage, and harmonics are generated at short intervals.

  A sudden change in the drive voltage occurs in the following cases. For example, a certain piezoelectric unit belonging to the piezoelectric drive unit group A is a first piezoelectric unit, and a piezoelectric unit belonging to the piezoelectric drive unit group B adjacent to the first piezoelectric unit is a second piezoelectric unit. At this time, the waveform of the drive voltage applied to the first piezoelectric unit is different from the waveform of the drive voltage applied to the second piezoelectric unit. In such a case, the time when the voltage value applied to the piezoelectric part becomes the minimum value does not match between the first piezoelectric part and the second piezoelectric part.

  At this time, when application of the drive voltage is started simultaneously to the first piezoelectric unit and the second piezoelectric unit from a stopped state where no drive voltage is applied, that is, first output of the drive voltage to the first piezoelectric unit is started. The output start time is the same as the second output start time for starting output of the drive voltage to the second piezoelectric unit. At this time, for example, the waveform of the drive voltage is as shown in FIG. 29, and both the first drive voltage and the second drive voltage instantaneously change suddenly immediately after the output start time.

  In this way, when a sudden change in the drive voltage occurs immediately after the output start time, the resonance of the optical deflector is excited by the harmonic component of the drive voltage. There was a problem that it could not be made uniform.

  Therefore, in the present embodiment, when the drive device 11 applies a drive voltage having a predetermined waveform to adjacent piezoelectric units, the start time when the first application unit starts applying the drive voltage A (first drive voltage). Control is performed such that the (first start time) is different from the start time (second start time) at which the second application unit starts applying the drive voltage B (second drive voltage).

  As a result, an abrupt change immediately after the start of output of the drive voltage is suppressed, fluctuation of the moving speed in the moving operation around the second axis of the reflecting surface 14 is suppressed, and uniformity of the moving speed of the reflecting surface 14 is improved. Can do.

  Hereinafter, the reason why the uniformity of the movable speed of the mirror unit 101 is improved by the above control will be described in detail with reference to FIGS.

  FIG. 20 is a diagram illustrating drive signal waveforms in which the application start time of the first drive voltage and the application start time of the second drive voltage are different. At this time, a period in which the drive voltage is not applied to both the first piezoelectric part and the second piezoelectric part is a stop period, a period in which the waveforms of the first drive voltage and the second drive voltage are constant, a normal operation period, and a stop period The period during which the transition to the normal operation period is made the transition period. In FIG. 20, the stop period is from the application start time of the second drive voltage, the transition period is from the application start time of the second drive voltage to the end of the period T11, and the normal operation period is from the start of the period T12.

  As shown in FIG. 20, the start time (first start time) for applying the second drive voltage to the first piezoelectric portion, and the start time (second start time) for applying the second drive voltage to the second piezoelectric portion, Is different.

  As a result, since the first drive voltage and the second drive voltage are not applied at the same time, both the applied first drive voltage and the second drive voltage are restrained from abruptly changing the drive voltage, thereby suppressing abnormal vibration. be able to.

  A time difference between the first start time and the second start time is defined as a start time difference ΔT. At this time, for example, ΔT is preferably set to a time that coincides with the fall time of the first drive voltage or the rise time of the second drive voltage. Thus, output is started at the timing when the minimum voltage value of the waveform of the first drive voltage and the minimum voltage value of the waveform of the second drive voltage match without changing the waveform of the drive voltage between the transition period and the normal operation period. Therefore, the difference from the stop period (0 V) disappears or becomes the smallest, and a rapid change in voltage is suppressed, so that abnormal vibration can be suppressed. Further, by not changing the waveform between the transition period and the normal operation period, it is possible to limit the high-frequency component included in the drive signal (drive voltage).

  At this time, the abnormal vibration can be further suppressed by adjusting the symmetry of the waveform of the first drive voltage or the waveform of the second drive voltage. The reason will be described below with reference to FIG.

  FIG. 21 is a diagram for explaining suppression of abnormal vibration by symmetry adjustment. FIG. 21 shows the relationship between the frequency component (harmonic component) of the drive voltage having a sawtooth waveform and the frequency characteristics of the resonance mode of the optical deflector 13 in the drive method of this embodiment. The frequency component of the sawtooth waveform driving voltage is obtained by Fourier transforming an ideal sawtooth waveform and decomposing the applied signal into frequency components. The applied voltage component generated from the direct current (0 Hz) at the driving frequency interval. Represented by superposition.

  FIG. 21 also shows the spectral characteristics of the lowest-order resonance mode that the optical deflector 13 has. FIG. 21 illustrates the case where the drive frequency (repetition frequency) of the drive signal is set to 1 / half integer of the lowest-order resonance frequency of the optical deflector. With this setting, it is possible to reduce the overlap between the harmonic component, which is a signal component generated periodically, and the resonance frequency of the optical deflector.

  When an optical deflector is driven by a predetermined drive signal, depending on the waveform of the drive signal, a “valley (theoretically the signal intensity is zero) in a frequency spectrum (the drive signal is Fourier-transformed and decomposed into frequency components). Is reduced to a point) ”. Further, the signal intensity is reduced in the frequency region near the “valley”. This “valley” is called the null frequency, and the frequency region around the “valley” is called the frequency reduction region. The frequency region in the vicinity of the “valley” is, for example, a frequency region whose frequency is about ± 10% from the null frequency.

The null frequency fn is given by the following equation when the drive voltage symmetry is S and the drive frequency is fs. The frequency reduction region is obtained as follows.

  The order N is an integer, and the null frequency appears periodically. That is, when the null frequency with the lowest frequency is the first null frequency, the second and third null frequencies appear periodically. As is clear from the above equation (1), the null frequency fn and the frequency reduction region can be adjusted to desired values using the drive frequency fs of the drive voltage or the symmetry S of the drive voltage as a parameter.

  Therefore, by adjusting the drive voltage symmetry so that the resonance frequency of the optical deflector (especially the zeroth-order resonance frequency) is included in the frequency reduction region, the overlap between the resonance frequency of the optical deflector and the harmonic component is reduced. It becomes possible to do. Thereby, it is possible to suppress excitation of resonance of the optical deflector by harmonics, and to further improve the uniformity of the movable speed of the reflecting surface 14.

  Note that the symmetry may be different between the first drive voltage and the second drive voltage. For example, the symmetry of the first drive voltage and the second drive voltage may be adjusted so that the resonance frequency is sandwiched between the null frequency of the first drive voltage and the null frequency of the second drive voltage. This is due to the following reason. In the vicinity of the symmetry in the case where the zeroth-order resonance frequency and the null frequency are substantially matched, there is a region where the phase of the high-frequency vibration caused by the high-frequency component changes abruptly (hereinafter, a phase change abrupt region). At this time, for example, the first drive voltage is outside (symmetry is adjusted so that the null frequency is larger than the resonance frequency) than the phase change sudden region, and the second drive voltage is inside (null with respect to the resonance frequency). By adjusting the symmetry so that the frequency of the frequency becomes small), the phase of the high-frequency vibration generated by the high-frequency component of the first drive voltage and the phase of the high-frequency vibration generated by the high-frequency component of the second drive voltage are reversed. It is possible to reduce the change of the phase difference with respect to the change with time of the symmetry (time change of the null frequency) and improve the robustness.

  As described above, in the drive device 11 of the present embodiment, the first start time for starting application of the first drive voltage having the predetermined waveform and the second start for applying the second drive voltage having a waveform different from the first drive voltage. The uniformity of the movable speed of the reflecting surface 14 can be improved by controlling the two start times to be different.

  More specifically, as shown in FIG. 20, the drive device 11 makes the first start time and the second start time different so that the timing at which the minimum value of the voltage value is applied differs from the first drive voltage. When the application of the two drive voltages is started, a sudden change in the instantaneous drive voltage as shown in FIG. 28 is suppressed. For example, by changing the first start time and the second start time so that the voltage application can be started at the timing when the minimum value of the normal operation period of each drive voltage is applied, the voltage value is not changed suddenly, The voltage application of each drive voltage can be started.

  As a result, an increase in the harmonic component due to a sudden change is suppressed, and excitation of resonance of the optical deflector 13 due to the harmonic component that is one of the causes of the non-uniformity of the movable speed of the reflecting surface 14 is suppressed. Therefore, the movable swing shown in FIG. 18 can be brought close to the ideal movable shown in FIG. That is, the uniformity of the moving speed of the reflecting surface can be improved. By improving the uniformity as described above, for example, luminance unevenness and distortion of the projected image shown in FIG. 19B can be suppressed, and the projected image shown in FIG. 19A can be displayed.

  In the above embodiment, as shown in FIG. 20, the waveform of the drive voltage during the transition period and the waveform of the drive voltage during the normal operation period are the same, but they may be different. That is, the waveform of the drive voltage may be different before a predetermined time when the transition period shifts to the normal operation period and after the predetermined time. Below, the modification of control of the drive device 11 is demonstrated.

[Modification 1]
Modification 1 of the above embodiment will be described with reference to FIG. Modification 1 is the same as the above embodiment except for the waveform of the drive voltage. FIG. 22 is an example of the first drive voltage and the second drive voltage in the first modification. The waveform of the drive voltage differs before and after the time when the waveform of the first drive voltage and the waveform of the second drive voltage shift from the transition period to the normal operation period.

  In FIG. 22, the drive device 11 gradually changes the symmetry of the first drive voltage and the second drive voltage from the period T21 to T24, and after the period T25 after a predetermined time, the first drive voltage and the second drive. The voltage symmetry is controlled so as not to change. Further, control is performed so that the waveform gradually approaches T25 from T21. At this time, the second drive voltage is controlled so that the ratio of the rise time to one cycle is gradually increased. In other words, control is performed so that the symmetry of the second drive voltage is gradually reduced, and control is performed so as to gradually increase the voltage change at the rise of the second drive voltage. This is due to the following reason.

  Immediately after voltage application, the voltage value may not be stable depending on the element. For example, even if the voltage is applied by adjusting the symmetry so that the resonance frequency is included in the frequency reduction region, if the voltage change is abruptly changed and the sensitivity of the element cannot follow the voltage change, the symmetry Adjustment effects and unexpected generation of harmonic components occur. Therefore, as described above, immediately after the start of application, the drive voltage symmetry is set so that the change in voltage at the rising edge becomes gentle compared to the waveform after a predetermined time, so that the device adapts to adapt. The voltage change rate (rise time slope) is gradually increased.

  Thereby, since the change in voltage immediately after the start of application becomes gentle, it is possible to suppress the harmonic component from exciting resonance and to improve the uniformity of the movable speed of the reflecting surface 14.

  At this time, it is preferable to adjust the symmetry of the drive voltage so that the resonance frequency is included in the frequency reduction region in all cycles. For example, in FIG. 22, the drive device 11 adjusts the symmetry so that the resonance frequency is included in the frequency reduction region near the third null frequency in the period T21. Further, in the period T23, the symmetry is adjusted so that the resonance frequency is included in the frequency reduction region near the second null frequency. Further, after the period T25, the symmetry is adjusted so that the resonance frequency is included in the frequency reduction region near the first null frequency.

  As described above, the resonance frequency is included in the frequency reduction region in all cycles, so that the overlap between the harmonic component and the resonance frequency can be reduced.

Further, as shown in FIG. 22, the driving device 11 changes the waveforms of the first driving voltage and the second driving voltage so that the shape gradually approaches the periods T21, T22, T23 and the frequency after the period T25. You are in control. This stepwise change can further suppress a sudden change.

  Furthermore, when the applied voltage minimum value during the normal operation period is greater than zero, the drive device 11 is within a range in which the resonance frequency of the optical deflector 13 does not deviate from the above-described frequency reduction region in the period immediately after the start of application of the drive voltage. The symmetry of the drive voltage may be changed. Thereby, it is not necessary to cause a sudden voltage change corresponding to the applied voltage minimum value during the normal operation period, and abnormal vibration can be suppressed. For example, if the applied voltage minimum value is ΔE and the rise time is Tr, the symmetry is adjusted so that the slope increases by ΔE / Tr.

  As described above, in the first modification, the drive device 11 changes the waveform of the drive voltage before and after the predetermined time, thereby further suppressing the rapid change in the drive voltage and suppressing abnormal vibration. The uniformity of the movable speed can be improved. In addition, by controlling the waveform of the drive voltage in the transition period step by step so that the waveform approximates the waveform of the drive voltage during the normal operation period, the sudden change in the drive voltage is suppressed to suppress abnormal vibration and reflection. The uniformity of the moving speed of the surface can be improved.

  In addition, as in Modification 2 described below, the driving device 11 controls only the second driving voltage whose rising voltage changes suddenly so that the waveform of the driving voltage is different before and after the predetermined time. May be.

[Modification 2]
Modification 2 will be described with reference to FIG. The modification 2 is the same as that of the said embodiment except the waveform of a drive voltage. FIG. 23 is an example of the first drive voltage and the second drive voltage in Modification 2.

  As shown in FIG. 23, in the second modification, the drive device 11 causes the drive voltage symmetry to change before and after a predetermined time only for the second drive voltage, where the change in the rise of the drive voltage is relatively steep. The first drive voltage is controlled so that the symmetry of the drive voltage does not change before and after the predetermined time. Thus, by controlling so that only the waveform of one drive voltage changes gradually, the complexity of control of the drive voltage can be suppressed.

  In other words, the drive device 11 has a rise time for one cycle of the drive voltage after a predetermined time with respect to a drive voltage having a smaller ratio of the rise time in one cycle of the first drive voltage and the second drive voltage. Control is performed such that the ratio of the rise time to one cycle of the drive voltage before a predetermined time is larger than the ratio.

  In FIG. 23, the drive device 11 starts voltage application for the first drive voltage one cycle before a predetermined time. However, if it is before the predetermined time, the timing for starting voltage application can be arbitrarily set. At this time, the time difference ΔT between the first start time and the second start time is preferably “arbitrary integer m × period T + rise time of the second drive voltage”. Thus, output is started at the timing when the minimum voltage value of the waveform of the first drive voltage and the minimum voltage value of the waveform of the second drive voltage match without changing the cycle of the first drive voltage and the second drive voltage. Therefore, the difference from the stop period (0 V) disappears or becomes the smallest, and a rapid change in voltage is suppressed, so that abnormal vibration can be suppressed.

  As described above, in the second modification, the drive device 11 rises with respect to one cycle of the drive voltage after a predetermined time after the transition period shifts to the normal operation period with respect to the drive voltage with the smaller ratio of the rise time with respect to one cycle. Control is performed such that the ratio of the rise time to one cycle of the drive voltage before a predetermined time is larger than the ratio of time. As a result, the step-by-step control of the drive voltage in the transition period is limited to the waveform of one drive voltage, so that control complexity can be suppressed. At this time, the symmetry of the drive voltage may be adjusted so that the resonance frequency of the optical deflector is included in the frequency reduction region.

[Modification 3]
Next, Modification 3 will be described with reference to FIG. The third modification is the same as the above embodiment except for the waveform of the drive voltage. FIG. 24 is an example of the first drive voltage and the second drive voltage in Modification 3.

  In the third modification, the driving device 11 performs control so that the period T is different between the transition period and the normal operation period. For example, as shown in FIG. 24, the period of the drive voltage waveform (for example, period T41) before the predetermined time when the transition period transitions to the normal operation period is changed to the period of the drive voltage waveform after the predetermined time (for example, T45). ). Thereby, since the rapid change of a voltage is suppressed when the period T becomes long, abnormal vibration can be suppressed.

  Further, as shown in FIG. 24, the driving device 11 changes the first drive voltage and the second drive voltage so as to be gradually reduced from the period T41, the period T42, and the period T43, and gradually the period T45. You may control so that a shape may approach the subsequent waveform. By this stepwise change, it is possible to suppress an abrupt change in the voltage value due to a sudden change in the cycle, and to suppress abnormal vibration.

  At this time, the cycle may be changed around the predetermined time only for the drive voltage having the smaller ratio of the rise time in one cycle of the first drive voltage and the second drive voltage. Thereby, complication of control can be suppressed by controlling only in one side in a transition period.

  As described above, in the third modification, control is performed so that one cycle of the drive voltage before the predetermined time is different from one cycle of the drive voltage after the predetermined time. Furthermore, a sudden change in the drive voltage can be suppressed by making one cycle of the drive voltage before the predetermined time longer than one cycle of the drive voltage after the predetermined time. Thereby, abnormal vibration is suppressed and the uniformity of the movable speed of the reflecting surface can be improved.

[Modification 4]
Next, Modification 4 will be described with reference to FIG. The modification 4 is the same as that of the said embodiment except the waveform of a drive voltage. FIG. 25 is an example of the waveform of the first drive voltage and the waveform of the second drive voltage in Modification 4.

  In the fourth modification, the driving device 11 controls the applied voltage maximum value to be different between the transition period and the normal operation period. For example, as shown in FIG. 25, the applied voltage maximum value (for example, the applied voltage maximum value in the cycle T51) of the drive voltage waveform before the predetermined time when the transition period shifts to the normal operation period is set as the drive voltage after the predetermined time. The applied voltage maximum value (for example, the applied voltage maximum value in the period T55) of the waveform is made smaller.

  Thus, when the drive voltage immediately after the start of application includes a harmonic component that overlaps with the resonance frequency of the optical deflector 13, the drive voltage is small, so that resonance is not greatly excited. Therefore, resonance excitation due to harmonic components can be suppressed, and the uniformity of the movable speed of the reflecting surface 14 can be improved.

  Also, as shown in FIG. 25, the drive device 11 changes the first drive voltage and the second drive voltage so that the applied voltage maximum value increases stepwise as the cycle T51, the cycle T52, and the cycle T53, Control may be performed so that the shape gradually approaches the waveform after the period T55. By this stepwise change, it is possible to suppress an abrupt change in the voltage value due to a sudden change in the cycle, and to suppress abnormal vibration.

  As described above, in the fourth modification, the drive device 11 controls the waveform of the drive voltage before the predetermined time so that the maximum voltage value becomes smaller than the waveform of the drive voltage after the predetermined time. Excitation of resonance of the optical deflector can be suppressed. Thereby, abnormal vibration is suppressed and the uniformity of the movable speed of the reflecting surface 14 can be improved.

  As mentioned above, although embodiment of this invention and its modification were demonstrated, embodiment mentioned above and its modification show one example of application of this invention. The present invention is not limited to the above-described embodiment and its modifications, and can be embodied by adding various modifications and changes without departing from the scope of the invention.

  For example, in the above-described embodiment and its modification, the drive device 11 always applies a drive voltage having a waveform having a positive voltage value to the piezoelectric part. However, the drive voltage is applied to the piezoelectric part and the piezoelectric part is deformed. If it is the structure which arises, it will not be restricted to this. As an example, the driving device 11 may apply a driving voltage having a waveform having a negative voltage value to the piezoelectric unit, or may apply a positive voltage value and a negative voltage value alternately.

  Further, in the above-described embodiment and its modification, the driving device 11 finally changes the waveform of the driving voltage in a normal operation period within a range in which a sudden voltage change does not occur when the waveform of the driving voltage is changed step by step. It should be close to the shape of the waveform. For example, if it is in a range that does not cause abnormal vibration due to a sudden voltage change, during the change, the same waveform or a waveform that does not resemble the waveform of the operating period than the waveform of the previous cycle The drive voltage may be applied.

  In the above embodiment and its modification, as shown in FIG. 12, the optical deflector 13 is a cantilever type optical deflector in which the first piezoelectric drive units 112a and 112b extend from the torsion bars 111a and 111b in the + X direction. Although it is used, the present invention is not limited to this as long as the reflecting surface 14 is movable by a piezoelectric part to which a voltage is applied.

  For example, as shown in FIG. 26, the two-sided type includes first piezoelectric drive units 212a and 212b extending from the torsion bars 211a and 211b in the + X direction and first piezoelectric drive units 212c and 212d extending in the −X direction. The optical deflector may be used. Further, when the reflecting surface is movable only in one axial direction, the reflecting surface 14 may be provided on the movable portion 220 as shown in FIG. At this time, the reflection surface 14 may be provided on the entire movable portion 220.

  DESCRIPTION OF SYMBOLS 10 ... Optical scanning system, 11 ... Drive apparatus, 12 ... Light source device, 13 ... Optical deflector, 14 ... Reflecting surface, 15 ... Scanned surface, 30 ... Control part (an example of control means), 31 ... Drive signal output part (Example of applying means), 101... Mirror section, 102... Mirror base, 110 a, 100 b... First driving section a, b, 111 a, b ... Torsion bars a, b, 112 a, 112 b. ... 1st support part, 130a, 130b ... 2nd drive part, 131a-131f ... 2nd piezoelectric drive part a, 132a-132f ... 2nd piezoelectric drive part b, 140 ... 2nd support part, 150 ... Electrode connection part, 161 ... Silicon support layer, 162 ... Silicon oxide layer, 163 ... Silicon active layer, 201 ... Lower electrode, 202 ... Piezoelectric part, 203 ... Upper electrode, 400 ... Car, 500 ... Head-up display device ( The image projection apparatus), 600 ... optical writing device, 650 ... laser printer (image forming apparatus), 700 ... laser radar device (object recognition device)

JP 2006-80978 A

Claims (18)

A driving device for an optical deflector that moves a reflecting surface by deformation caused by voltage application between adjacent first and second piezoelectric portions,
First application means for applying a first drive voltage having a predetermined waveform to the first piezoelectric portion;
Second application means for applying a second drive voltage different from the waveform of the first drive voltage to the second piezoelectric portion;
Control means for controlling driving of the first application means and the second application means;
With
The control means has a first start time when the first application means starts applying the first drive voltage and a second start time when the second application means starts applying the second drive voltage. Drive device to control. The drive device according to claim 1,
The first drive voltage is a drive voltage having a waveform including a first rise time and a first fall time;
The drive device, wherein the second drive voltage is a drive voltage having a waveform including a second rise time and a second fall time. The drive device according to claim 2,
The control means controls the driving of the second application means so that the first start time and the second start time are different from each other by the first rise time, or the first start time and the second start time. Is a driving device for controlling the driving of the first applying means so as to be different from the second rising time. The drive device according to claim 2 or 3,
The control unit controls the first application unit or the second application unit so that a waveform of a drive voltage before a predetermined time is different from a waveform of a drive voltage after the predetermined time. The drive device according to claim 4,
The control unit is configured to control the first application unit or the second application unit so that the waveform of the drive voltage before the predetermined time gradually approaches the waveform of the drive voltage after the predetermined time. A drive device that controls the waveform of the previous drive voltage to change stepwise. The drive device according to claim 4 or 5, wherein
The control means has a ratio of a rising time with respect to one cycle of the driving voltage before the predetermined time and a rising time with respect to one cycle of the driving voltage after the predetermined time with respect to the first applying means or the second applying means. A drive device that controls the ratio of the two to be different. The drive device according to claim 4 or 5, wherein
The control unit applies one of the drive voltages after the predetermined time to the application unit that applies a drive voltage having a waveform having a small ratio of the rise time to one cycle among the first application unit and the second application unit. A drive device that controls the ratio of the rise time to one period of the drive voltage before the predetermined time to be larger than the ratio of the rise time to the period. The drive device according to claim 4 or 5, wherein
The control means controls the first application means or the second application means so that one cycle of the drive voltage before the predetermined time is different from one cycle of the drive voltage after the predetermined time. apparatus. The drive device according to claim 4 or 5, wherein
The control means controls the driving voltage waveform before the predetermined time so that the maximum voltage value is smaller than the driving voltage waveform after the predetermined time with respect to the first applying means or the second applying means. To drive. The drive device according to any one of claims 4 to 9,
The drive device in which the predetermined time is a time at which a waveform of an applied drive voltage becomes constant. The drive device according to claim 2,
The control means is such that the resonance frequency of the optical deflector is included in at least one of the frequency regions where the harmonic component of the drive voltage is reduced with respect to the first application means or the second application means. A drive device that controls a ratio of the first rise time or the second fall time to one cycle of the drive voltage. The drive device according to claim 11,
The control means controls the first application means or the second application means so that a drive voltage waveform symmetry before the predetermined time is different from a drive voltage waveform symmetry after the predetermined time. Drive device. The drive device according to claim 11,
The control means is configured such that, with respect to the first application means or the second application means, the waveform of the first drive voltage or the second drive from the first start time or the second start time to the predetermined time. A driving device that changes a waveform of a voltage stepwise and controls the resonance frequency to be included in the frequency reduction region that is different in each step. A drive device according to any one of claims 1 to 13,
A mirror portion having the reflecting surface;
A piezoelectric drive unit that includes the piezoelectric unit and moves the mirror unit around one axis when the piezoelectric unit is deformed;
An optical deflection system comprising: An optical deflection system according to claim 14,
A light source unit that emits light toward the reflecting surface of the light deflection system;
An optical scanning system comprising: An image projection apparatus for projecting an image by scanning a surface to be scanned with light modulated based on image information,
An optical scanning system according to claim 15,
A projection optical system that projects the light emitted from the optical scanning system toward the surface to be scanned;
An image projection apparatus comprising: An object recognition device that optically scans a scanning direction and recognizes an object by reflected light from an object existing in the scanning direction,
An optical scanning system according to claim 15,
A light receiving unit for receiving reflected light from the object;
An object recognition unit for recognizing an object based on information of the light source unit and the light receiving unit;
An object recognition apparatus comprising: A driving method of a driving device for an optical deflector that moves a reflecting surface by deformation caused by applying voltages to adjacent first and second piezoelectric portions,
A control step of controlling voltage application to the first piezoelectric unit and the second piezoelectric unit;
Applying a first drive voltage to the first piezoelectric portion according to the control step, and applying a second drive voltage to the second piezoelectric portion;
Have
In the application step, the first start time for starting the application of the first drive voltage is different from the second start time for the second application means to start applying the second drive voltage in the application step. To control the driving method.