JP2015041051A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress sub-resonance of a mirror part of a light deflector in an optical scanner.SOLUTION: A light deflector 2 of an optical scanner 1 includes inside actuators 18a and 18b which turn a mirror part 10 forward and backward around a first axial line, and outside actuators 30a and 30b which turn the mirror part 10 forward and backward around a second axial line orthogonal to the first axial line and have a meander structure to have prescribed flexibility around the first axial line. A second driving voltage supplied from a second driving voltage generator 7 of a control unit 4 to the outside actuators 30a and 30b includes a sub-driving voltage Dc besides a main driving voltage Db. The frequency of the sub-driving voltage Dc is a frequency Fi of sub-resonance of the mirror part 10, and the phase of the sub-driving voltage is opposite to that of the sub-resonance.

Description

  The present invention relates to an optical scanner including an optical deflector and a control device that controls the optical deflector.

  An optical scanner including a MEMS (microelectro mechanical systems) optical deflector and a control device that controls the optical deflector is known (eg, Patent Document 1 / FIGS. 15 and 18).

  The optical deflector of the optical scanner of Patent Document 1 has a structure that scans scanning light two-dimensionally in the horizontal and vertical directions. That is, the optical deflector reciprocates around a horizontal scanning axis in order to scan in the horizontal direction a mirror portion that reflects light from a certain direction and scanning light as reflected light from the mirror portion. A horizontal scanning actuator that rotates, and a vertical scanning actuator that reciprocally rotates the mirror portion around the vertical scanning axis in order to scan the scanning light in the vertical direction (Patent Document 1 / 16 and 19).

  The optical deflector further utilizes the resonance of the mirror around the horizontal scanning axis to obtain a sufficiently high horizontal scanning frequency. In other words, the control device of the optical scanner controls the frequency of the main resonance so that the rotation frequency of the mirror around the horizontal scanning axis coincides with the frequency of the main resonance of the mirror around the horizontal scanning axis. The piezoelectric film of the horizontal scanning actuator is driven with a driving voltage of

JP 2008-40240 A

  The optical deflector has a sub-resonance with a frequency sufficiently close to the frequency of the main resonance, although the amplitude is smaller than that of the main resonance with respect to the rotation of the mirror around the horizontal scanning axis. There is. Therefore, when a drive voltage having a main resonance frequency is applied to the piezoelectric film of the horizontal scanning actuator, a sub-resonance frequency component may appear in the rotation of the mirror around the horizontal scanning axis. This hinders scanning control of scanning light in the horizontal direction.

  An object of the present invention is to provide an optical scanner capable of accurately suppressing sub-resonance when a mirror portion of an optical deflector is rotated using main resonance.

  The optical scanner of the present invention is an optical scanner including an optical deflector and a control device that controls the optical deflector, and the optical deflector includes a mirror unit that reflects light from a certain direction, and the mirror unit. A pair of torsion bars coupled to the mirror part from both sides of the first piezoelectric film, and a first driving voltage is supplied to the first piezoelectric film, whereby the thickness of the first piezoelectric film is increased. A first actuator that changes a degree of curvature in a direction and reciprocally rotates the mirror portion around a first axis as an axis of the torsion bar via the torsion bar; and the first actuator, A second piezoelectric film is provided, and the second drive voltage is supplied to change the degree of curvature in the thickness direction of the second piezoelectric film, and the mirror unit is moved via the first actuator and the torsion bar. The first And a second actuator for reciprocating rotation about the second axis perpendicular to the axis. The second actuator is configured as a meander structure having a predetermined softness around the first axis by connecting a plurality of cantilever portions formed with the second piezoelectric film in series by a folded portion. The control device includes: a first drive voltage generation unit that supplies a voltage of a main resonance frequency of the mirror unit around the first axis to the first actuator as the first drive voltage; and A voltage obtained by superimposing a sub-driving voltage whose frequency is lower than the frequency on the main driving voltage, the frequency of which is the same as the frequency of the sub-resonance of the mirror unit around the first axis and whose phase is opposite to the phase of the sub-resonance, A second drive voltage generation unit configured to supply the second actuator as the second drive voltage.

  According to the present invention, since the second actuator is configured as a meander structure having a predetermined softness around the first axis, the second actuator reciprocates around the first axis by supplying the second drive voltage to the second piezoelectric film. It also generates power. As a result, sub-reciprocating rotational power as reciprocating rotational power around the first axis due to the sub-driving voltage of the second driving voltage is generated as the acting force of the second actuator.

  The sub-reciprocating rotatory power is rotative power around the first axis, and the frequency is the same as the sub-resonant frequency of the mirror section, and the phase is opposite to the phase of the sub-resonant. The secondary reciprocating power around the first axis is transmitted from the second actuator via the first actuator and the torsion bar together with the main reciprocating power as the reciprocating power around the second axis by the main driving voltage of the second driving voltage. Then it is transmitted to the mirror part. As a result, the sub-resonance of the mirror part is accurately suppressed by the sub-reciprocating power.

  In the optical scanner of the present invention, the optical deflector is configured to be symmetrical on both sides of the mirror part in the direction of the second axis, and a pair of the first and second actuators are provided on both sides of the mirror part. Preferably they are present one by one.

  According to this configuration, the auxiliary reciprocating power exerts an acting force on the mirror portion symmetrically from both sides of the mirror portion. As a result, the force for suppressing the sub-resonance in the mirror part is stabilized, and the sub-resonance in the mirror part is further effectively suppressed.

  In the optical scanner of the present invention, the optical scanner includes a frame portion that surrounds the first actuator and is coupled to the first actuator at an inner peripheral edge, and each torsion bar has the end opposite to the coupling end to the mirror portion. Preferably, the frame portion is coupled to the inner peripheral edge of the frame portion, and the frame portion is coupled to the second actuator at the outer peripheral edge.

  According to this configuration, the sub-reciprocating power that suppresses the sub-resonance of the mirror part can be directly transmitted from the frame part to the torsion bar, so that the sub-resonance of the mirror part due to the sub-reciprocating power is further effectively suppressed. .

FIG. The figure which shows the bending state of each cantilever part in operation | movement of an outside actuator. Explanatory drawing about the frequency of the main resonance and subresonance of a mirror part. Explanatory drawing of the 2nd drive voltage which a 2nd drive voltage generation part produces | generates and supplies to the piezoelectric film of an outside actuator. The figure which shows that the secondary resonance was suppressed by supplying the 2nd drive voltage to the cantilever part of an outer side actuator. The perspective view of another optical deflector.

  The overall configuration of the optical scanner 1 will be described with reference to FIG. The optical scanner 1 includes an optical deflector 2, a laser light source 3, and a control device 4.

  The optical deflector 2 receives the output light La from the laser light source 3 from a certain forward direction and emits the scanning light Lb as reflected light forward. The control device 4 controls the laser light source 3 on (lit), off (dark) and luminance (light intensity), and the scanning direction of the scanning light Lb of the optical deflector 2. The control device 4 includes a light source control unit 5, a first drive voltage generation unit 6, and a second drive voltage generation unit 7. Details of the light source controller 5, the first drive voltage generator 6, and the second drive voltage generator 7 will be described later.

  The optical deflector 2 will be described. For convenience of explanation, the center o, the x-axis direction, the y-axis direction, and the z-axis direction are defined. The optical deflector 2 is used with the x-axis direction, the y-axis direction, and the z-axis direction set to, for example, a horizontal direction, a vertical direction, and a front-rear direction. Note that this use direction does not limit the use of the optical scanner 1 in directions other than these.

  Hereinafter, the relative positional relationship of each element of the optical deflector 2 will be described based on the relative positional relationship when the operation of the optical deflector 2 is stopped. When the optical deflector 2 is deactivated, the mirror surface of the mirror unit 10 exists on the xy plane.

  The optical deflector 2 of the present embodiment is manufactured using a well-known MEMS technology. That is, the optical deflector 2 uses a known MEMS technique to form a metal layer as an electrode layer or a wiring layer, a piezoelectric film layer as a piezoelectric film, an insulating layer, or the like on a silicon substrate layer. (For example, refer to Patent Document 1 for details).

  The optical deflector 2 includes a mirror part 10, an inner frame part 11, an outer frame part 12, torsion bars 15a and 15b, inner actuators 18a and 18b, and outer actuators 30a and 30b as main components. ing. The mirror unit 10 is positioned at the center of the optical deflector 2, and the optical deflector 2 has a symmetrical structure with respect to the yz plane.

  The inner frame portion 11 and the outer frame portion 12 are disposed in an internal / external relationship and surround the mirror portion 10. The inner frame portion 11 has a circular inner peripheral edge 22 and a square outer peripheral edge 23. The outer frame portion 12 has a peripheral frame shape with a rectangular outline having a long side in the x-axis direction.

  The torsion bars 15 a and 15 b are disposed on both sides in the y-axis direction with respect to the mirror unit 10, and protrude from the mirror unit 10 in the y-axis direction with an equal length. The torsion bars 15 a and 15 b are coupled to the inner peripheral edge 22 of the inner frame portion 11 at the end portion on the proximal end side, and are coupled to the peripheral edge of the mirror portion 10 at the end portion on the distal end side.

  The inner actuators 18a and 18b are formed in a semi-annular shape with a predetermined width, and are disposed on both sides in the x-axis direction with respect to the mirror unit 10 so that the mirror unit 10 is positioned in the ring formed by both. . The inner actuators 18a and 18b are coupled to the torsion bars 15a and 15b at both end portions as tip portions. The positions where the inner actuators 18a and 18b are coupled to the torsion bars 15a and 15b are closer to the inner peripheral edge 22 than the mirror part 10 relative to the midpoint of the torsion bars 15a and 15b in the y-axis direction, that is, closer to the base end part. Set to position.

  Portions 20a and 20b extending from the middle point of each inner actuator 18a and 18b to both sides in the x-axis direction connect the inner actuators 18a and 18b and the inner peripheral edge 22 of the inner frame portion 11 on the x-axis. The inner actuators 18a and 18b have a piezoelectric film layer parallel to the xy plane over almost the entire semicircular ring. The inner actuators 18a and 18b change the degree of curvature in the thickness direction of the piezoelectric film by applying a first drive voltage described later to the piezoelectric film.

  The outer actuators 30a and 30b have a meander structure in which a plurality of cantilever portions 31 (four in the example of FIG. 1) are coupled in series by a folded portion 32. The plurality of cantilever portions 31 are arranged in the x-axis direction with the longitudinal direction aligned in the y-axis direction.

  The outer actuators 30a and 30b are coupled to the lower end portion of the short side portion of the outer frame portion 12 at the base end portion 33 as the outer end in the x-axis direction, and are inner at the distal end portion 34 as the inner end in the x-axis direction. It is coupled to the lower end portion of the vertical side portion of the outer peripheral edge 23 of the frame portion 11. Each cantilever part 31 has a layer of a piezoelectric film parallel to the xy plane over almost the entire length. The cantilever portion 31 changes the degree of curvature in the thickness direction of the piezoelectric film by applying a second drive voltage described later to the piezoelectric film.

  The electrodes 35 a and 35 b are provided at the lower end portion of the short side portion of the outer frame portion 12. The left electrode 35a is provided for driving voltage supply to the left inner actuator 18a and the left outer actuator 30a. The right electrode 35b is provided for supplying a drive voltage to the right inner actuator 18b and the right outer actuator 30b. In the outer actuators 30a and 30b, different driving voltages are supplied to the piezoelectric film of the odd-numbered cantilever part 31 and the piezoelectric film of the even-numbered cantilever part 31 counted from the base end 33 side.

  Next, the operation of the optical scanner 1 will be described. While the operation of the optical scanner 1 is stopped, the laser light source 3 is off (light-off state), and the output light La is not emitted. The reflection surface of the mirror unit 10 of the optical deflector 2 is included in the xy plane.

  When the optical scanner 1 is in operation, the light source control unit 5 turns on (turns on) the laser light source 3. As a result, the output light La is emitted from the laser light source 3 toward the center o of the mirror unit 10. The light source control unit 5 typically maintains the current supplied to the laser light source 3 at an equal value during the operation period of the optical scanner 1 to keep the luminance of the output light La constant.

  When the light source control unit 5 generates a gray scale image at the irradiation destination of the scanning light Lb of the optical scanner 1, the light source control unit 5 changes the power supply current to the laser light source 3 during the operation period of the optical scanner 1 to output light La Change the brightness. The light source controller 5 can turn on the laser light source 3 only in the scanning forward path and turn off the laser light source 3 in the backward path in the horizontal and vertical scanning of the scanning light Lb.

  The first drive voltage generator 6 generates a first drive voltage to be applied to the piezoelectric films of the inner actuators 18a and 18b, and supplies the first drive voltage to the inner actuators 18a and 18b via the electrodes 35a and 35b. The first drive voltages to the left and right inner actuators 18a and 18b change in a sine waveform, and both the frequency and the pp voltage (peak-to-peak voltage) are set to be the same, and the phases are reversed. The frequency of the first drive voltage is made equal to the main resonance frequency Fh of the mirror unit 10 (described later in FIG. 3).

  As a result of the first drive voltage being applied to the piezoelectric films of the left and right inner actuators 18a and 18b in opposite phases, the increase and decrease in the bending degree of the piezoelectric film in the thickness direction of the left and right inner actuators 18a and 18b have an inverse relationship. Become. As a result, the torsion bars 15a and 15b are driven by the left and right inner actuators 18a and 18b at the joints with the left and right inner actuators 18a and 18b, and reciprocate around the axis. As a result, the mirror unit 10 reciprocates around the axes of the torsion bars 15a and 15b corresponding to the first axis in the present invention, and the scanning light Lb is reciprocated in the horizontal direction at a frequency Fh described later. .

  The axes of the torsion bars 15a and 15b are displaced on the yz plane by the reciprocal swing of the inner frame portion 11 around the x axis by the outer actuators 30a and 30b. When the normal line of the center of the mirror surface of the mirror unit 10 coincides with the z axis, the axis lines of the torsion bars 15a and 15b coincide with the y axis. Further, the center of the mirror surface of the mirror unit 10 maintains the position of the center o regardless of the operation of the inner actuators 18a and 18b and the outer actuators 30a and 30b.

  The second drive voltage generator 7 generates a second drive voltage to be applied to the piezoelectric film of the cantilever part 31 of the outer actuators 30a and 30b, and the piezoelectric of the cantilever part 31 of the outer actuators 30a and 30b via the electrodes 35a and 35b. Feed the membrane. Here, the cantilever portions 31 in the outer actuators 30a and 30b are numbered. Each of the outer actuators 30a and 30b includes four cantilever portions 31, and the cantilever portions 31 are sequentially arranged from the proximal end portion 33 side to the distal end portion 34 side, that is, in the y-axis direction in FIG. The numbers are 1 to 4 (see No. 1 to No. 4 in FIG. 2).

  The second drive voltage has the phase of the main drive voltage Db (FIG. 3 described later) supplied to the piezoelectric film of the odd-numbered cantilever part 31 and the phase of the main drive voltage Db supplied to the piezoelectric film of the even-numbered cantilever part 31 reversed. To. The frequency of the second drive voltage and the pp voltage are the same for the piezoelectric film of the odd-numbered cantilever part 31 and the piezoelectric film of the even-numbered cantilever part 31.

  FIG. 2 is an explanatory diagram of the operating state of the outer actuator 30a. The base end portion 33 of the outer actuator 30a is held at the z-axis coordinate = 0 position even during the operation of the outer actuator 30a, and only the tip end portion 34 is displaced in the z-axis direction. In FIG. 1-No. 4 denotes the number of the cantilever portion 31 in the outer actuator 30a.

  Although the operation state diagram of the outer actuator 30b is omitted, the outer actuators 30a and 30b operate symmetrically with respect to the yz plane.

  As described above, in the outer actuator 30a, the second drive voltage supplied to the piezoelectric film of the odd-numbered cantilever part 31 and the second drive voltage supplied to the piezoelectric film of the even-numbered cantilever part 31 have opposite phases. To be. Thereby, as shown in FIG. 2, the odd-numbered cantilever portion 31 and the even-numbered cantilever portion 31 have a reverse relationship in increase and decrease in the degree of curvature in the z-axis direction, and the distal end portion 34 is connected to the proximal end portion 33. On the other hand, the mirror unit 10 is reciprocally displaced in the z-axis direction, and the mirror unit 10 is reciprocally rotated around the x-axis corresponding to the second axis in the present invention. As a result, the scanning light Lb is reciprocated in the vertical direction.

  There is a gap between the cantilevers 31 of the outer actuators 30a and 30b, and the cantilevers 31 of the outer actuators 30a and 30b are curved and deformed in the z-axis direction. As a result, the outer actuators 30a and 30b have predetermined softness in all directions, particularly in the width direction (x-axis direction) and thickness direction (z-axis direction) of the gap between the cantilever portions 31.

  With reference to FIG. 3, the frequencies of the main resonance and the sub resonance of the mirror unit 10 will be described. FIG. 3 is a result of an experiment in which the relationship between the frequency of the first drive voltage applied to the piezoelectric films of the inner actuators 18a and 18b of the optical deflector 2 and the deflection angle of the mirror unit 10 is changed. Is shown. The first drive voltage is 13 Vpp, and the offset is 6.5 V.

  In the experiment of FIG. 3, only the main drive voltage Db of FIG. 4 to be described later is supplied from the second drive voltage generator 7 as the second drive voltage and applied to the piezoelectric films of the outer actuators 30a and 30b. Further, the pp voltage of the drive voltage supplied to the piezoelectric films of the inner actuators 18a and 18b in the experiment of FIG. 3 is constant regardless of the frequency. Db is set to 40 to 70 Vpp, the offset voltage is ½ of the pp voltage, and the frequency is 60 Hz.

  There are unipolar and bipolar driving methods for the piezoelectric film, and either of the driving methods for the piezoelectric films of the outer actuators 30a and 30b of the inner actuators 18a and 18b can be selected. In the experiment of FIG. 3, a predetermined offset voltage is set, and the outer actuators 30a and 30b of the inner actuators 18a and 18b are driven in a unipolar type. FIG. 2 described above shows a state in which the odd-numbered and even-numbered cantilever portions 31 are bent in opposite directions, which corresponds to bipolar driving. In the case of the unipolar drive, the cantilever portion 31 is bent only in one direction of positive and negative in the thickness direction of the piezoelectric film (substantially in the z-axis direction) and is not bent in the other direction. It will be switched between curving directions.

  In FIG. 3, the horizontal axis indicates the frequency, and the vertical axis indicates the deflection angle of the mirror unit 10. The mirror unit 10 reciprocates around the axis of the torsion bars 15a and 15b. The absolute values of the left and right maximum swing angles (maximum tilt angles) with respect to the yz plane are the same at each frequency. The shake angle on the vertical axis in FIG. 3 indicates the absolute value of the left and right maximum shake angles, and corresponds to ½ of the actual shake angle.

  As can be seen from FIG. 3, the deflection angle of the mirror portion 10 protrudes at the frequencies Fh and Fi, and is in the vicinity of 15 ° and 2 °, respectively. Fh is 25327 Hz as the resonance frequency in the main resonance mode of the mirror unit 10, and Fi is 25745 Hz as the resonance frequency in the sub resonance mode.

  The optical scanner 1 uses the main resonance mode of the mirror unit 10 to ensure a high scanning frequency in the horizontal direction of the output light La. That is, the first drive voltage generation unit 6 sets the frequency of the first drive voltage to Fh. However, in this case, since the sub-resonance mode Fi exists in the vicinity of Fh, the vibration component of Fi appears in the reciprocating oscillation of the mirror portion 10 around the axis of the torsion bars 15a and 15b, and the scanning light Lb Adversely affects horizontal scanning.

  In order to cope with this, in the optical scanner 1, the second drive voltage supplied from the second drive voltage generator 7 to the piezoelectric films of the outer actuators 30a and 30b is set to the main drive voltage as will be described with reference to FIG. The superimposed drive voltage Da is obtained by superimposing Db and the sub drive voltage Dc.

  FIG. 4 is an explanatory diagram of the second drive voltage generated by the second drive voltage generator 7 and supplied to the piezoelectric films of the outer actuators 30a and 30b. In FIG. 4, the horizontal axis represents time, and the vertical axis represents drive voltage.

  In FIG. 4, the dotted line is the main drive voltage Db, and the broken line is the sub drive voltage Dc (pp voltage of Dc <pp voltage of Db). Db and Dc are both sine waves. Db is set to 40 to 70 Vpp, the offset voltage is set to ½ of the pp voltage, and the frequency is set to 60 Hz. Dc is 8 Vpp, the offset is 4 V, and the frequency is Fi (= 25745 Hz). The superimposed drive voltage Da is obtained by superimposing Db and Dc (Da = Db + Dc). Da corresponds to the second drive voltage. The phase of Dc is set so as to be opposite to the phase of the secondary resonance in the secondary resonance mode of FIG.

  As described above, the main drive voltage Db is supplied to the piezoelectric film of the odd-numbered cantilever part 31 and supplied to the piezoelectric film of the even-numbered cantilever part 31 in each of the outer actuators 30a and 30b. The phase is reversed. On the other hand, the phase of the sub-drive voltage Dc supplied to the piezoelectric film of the odd-numbered cantilever part 31 is the same as that supplied to the piezoelectric film of the even-numbered cantilever part 31.

  However, the sub drive voltage Dc of the outer actuator 30a and the sub drive voltage Dc of the outer actuator 30b are in opposite phases. In order for the outer actuators 30a and 30b to apply to the torsion bars 15a and 15b a rotational force in the same direction around the axis of the torsion bars 15a and 15b, the tip portions of the left and right outer actuators 30a and 30b are opposite in the z-axis direction. It is because it is necessary to displace to.

  5 shows the frequency of the drive voltage applied to the inner actuators 18a and 18b of the optical deflector 2 while supplying the second drive voltage, that is, the superimposed drive voltage Da of FIG. 3, to the cantilever portions 31 of the outer actuators 30a and 30b. The result of the experiment which investigated the relationship between this frequency at the time of changing and the deflection angle of the mirror part 10 is shown.

  FIG. 5 shows that the sub-resonance mode is completely suppressed and disappears. The effect | action which the subresonance mode of the mirror part 10 is suppressed is demonstrated.

  The first drive voltage generator 6 supplies the first piezoelectric film to the inner actuators 18a and 18b. The first piezoelectric film is set to 13 Vpp, the offset is 6.5 V, and the frequency is Fh. The second drive voltage generator 7 supplies the second drive voltage to the outer actuators 30a and 30b. The second drive voltage is Da (= Db + Dc) defined in FIG. If it repeats, Db is set to 40-70Vpp, an offset voltage is 1/2 of pp voltage, and a frequency is set to 60 Hz. Dc is 8 Vpp, the offset is 4 V, and the frequency is Fi (= 25745 Hz). The phase of Dc is set so as to be opposite to the phase of the secondary resonance in the secondary resonance mode of FIG.

  The superimposed drive voltage Da supplied from the second drive voltage generator 7 is applied to the piezoelectric film of the cantilever part 31 of the outer actuators 30a and 30b. The outer actuators 30a and 30b apply main reciprocating power about the x axis to the mirror unit 10 via the tip 34 by driving with the main driving voltage Db included in the superimposed driving voltage Da. As a result, the mirror unit 10 reciprocates around the x axis at 60 Hz, and the scanning light Lb scans at 60 Hz in the vertical direction.

  On the other hand, as described above, the outer actuators 30a and 30b have a soft structure in the x-axis direction and the z-axis direction around the axes of the torsion bars 15a and 15b, that is, the outer actuators 30a and 30b are arranged in the x-axis direction and the z-axis direction. It is structured to be freely displaceable within the allowable range in the direction. As a result, the auxiliary driving voltage Dc is included in the superimposed driving voltage Da, so that the auxiliary reciprocating rotational power having the frequency Fi around the axis of the torsion bars 15a and 15b and the phase opposite to the phase of the auxiliary resonance mode is generated. The outer actuators 30a and 30b are generated at the tip 34.

  The auxiliary reciprocating power is transmitted from the tip 34 of the outer actuators 30a, 30b to the inner frame 11, and further from the inner frame 11 to the intermediate portions of the torsion bars 15a, 15b via the inner actuators 18a, 18b. As well as being transmitted, it is directly transmitted from the inner peripheral edge 22 of the inner frame portion 11 to the base end portions of the torsion bars 15a, 15b. The secondary reciprocating power is transmitted to the mirror unit 10 via the torsion bars 15a and 15b, and then canceled by the mirror unit 10 with the secondary resonance in the secondary resonance mode. As a result, sub-resonance is suppressed.

  Note that the application of the sub drive voltage Dc to the piezoelectric film of the cantilever part 31 of the outer actuators 30a and 30b has little influence on the reciprocating rotation around the x axis on the mirror part 10 by the driving force of the outer actuators 30a and 30b. . This is because the resonance frequency (e.g., 300 to 1000 Hz) of the mirror unit 10 around the x axis is sufficiently lower than Fi of the sub drive voltage Dc.

  In this optical scanner 1, the sub-reciprocating power for suppressing the sub-resonance of the mirror unit 10 is generated by the outer actuators 30 a and 30 b, so that the excitation unit that generates the sub-reciprocating power is used as the optical deflector 2. It is omitted to produce separately inside. As a result, the structure of the optical scanner 1 is simplified.

  Next, FIG. 6 is a perspective view of another optical deflector 42. In the optical scanner 1 of FIG. 1, when the optical deflector 42 of FIG. 6 is provided instead of the optical deflector 2, the sub-resonance mode around the axis of the torsion bars 15a and 15b can be similarly suppressed. .

  In the optical deflector 42 of FIG. 6, the same elements as those of the optical deflector 2 of FIG. 1 are designated by the same reference numerals as those of the optical deflector 2 and description thereof will be omitted, and only differences will be described. .

  In the optical deflector 42, the inner frame portion 11 and the inner actuators 18a and 18b of the optical deflector 2 described above are changed to the inner frame 44 and the inner actuators 45a, 45b, 47a and 47b.

  The inner frame 44 has a square outline shape surrounding the mirror portion 10 and has an inner peripheral edge 55 and an outer peripheral edge 51. The base end portions of the torsion bars 15 a and 15 b are coupled to the upper side portion and the lower side portion of the inner peripheral edge 55 of the inner frame 44. The distal end portions 34 of the outer actuators 30 a and 30 b are coupled to the lower end portions of the left and right side portions of the outer peripheral edge 51 of the inner frame 44.

  The inner actuators 45a, 45b, 47a, 47b are formed in a straight line parallel to the x-axis direction and are disposed on both sides of the torsion bars 15a, 15b, respectively, in the x-axis direction. The positions of the tip portions where the inner actuators 45a and 45b are coupled to the torsion bar 15a are the same as the positions where the upper tip portions of the inner actuators 18a and 18b are coupled to the torsion bar 15a in the optical deflector 2 of FIG. The position of the front end where the inner actuators 47a and 47b are coupled to the torsion bar 15b is the same as the position where the lower front end of the inner actuators 18a and 18b is coupled to the torsion bar 15b in the optical deflector 2 of FIG.

  Also in this optical deflector 42, the superimposed drive voltage Da supplied from the second drive voltage generator 7 is applied to the piezoelectric film of the cantilever part 31 of the outer actuators 30 a and 30 b. Along with this, the sub-reciprocal rotational power around the axis of the torsion bars 15a, 15b as the first axis is generated at the distal end portions 34 of the outer actuators 30a, 30b together with the main reciprocal rotational power around the x axis. Since the outer actuators 30a and 30b have a predetermined softness in the x-axis direction and the z-axis direction, the sub-reciprocation whose frequency is Fi and the phase is opposite to the phase of the sub-resonance mode around the axis of the torsion bars 15a and 15b. Rotational power is generated at the tip 34 of the outer actuators 30a, 30b.

  The auxiliary reciprocating power is transmitted from the tip 34 of the outer actuators 30a and 30b to the inner frame 44, and is further passed from the inner frame 44 to the middle of the torsion bars 15a and 15b via the inner actuators 45a, 45b, 47a and 47b. It is transmitted to the part and directly from the inner frame 44 to the base end portions of the torsion bars 15a and 15b. The sub-reciprocating power is transmitted to the mirror unit 10 via the torsion bars 15a and 15b, and is then canceled by the sub-resonance in the sub-resonance mode in the mirror unit 10, thereby suppressing the sub-resonance.

  In the present embodiment, the inner actuators 18a, 18b or the inner actuators 45a, 45b, 47a, 47b correspond to the first actuator of the present invention. The outer actuators 30a and 30b correspond to a second actuator that supports the first actuator in the present invention.

  The piezoelectric films of the inner actuators 18a, 18b or the inner actuators 45a, 45b, 47a, 47b correspond to the first piezoelectric film of the present invention. The piezoelectric film disposed on each cantilever part 31 of the outer actuators 30a and 30b corresponds to the second piezoelectric film of the present invention.

  The inner frame 11 corresponds to a frame that surrounds the first actuator and is coupled to the first actuator at the inner periphery.

  The axes of the torsion bars 15a and 15b are examples of the first axis. The x axis is an example of a second axis perpendicular to the first axis. Fh and Fi are examples of main resonance frequency and sub-resonance frequency, respectively.

  In the description of FIG. 4, the pp voltage of Dc <the pp voltage of Db, but is not limited to this. That is, it is assumed that the pp voltage of Dc ≧ the pp voltage of Db.

  In the illustrated embodiment, the torsion bars 15 a and 15 b are arranged at the inner end of the inner frame 22 (FIG. 1) or the inner frame 44 at the base end as the end opposite to the coupling end to the mirror unit 10. It is connected to the peripheral edge 55 (FIG. 6). However, the base ends of the torsion bars 15 a and 15 b can be separated from the inner peripheral edge 22 and the inner peripheral edge 55 without being coupled to the inner peripheral edge 22 and the inner peripheral edge 55. In that case, all of the secondary reciprocating power from the outer actuators 30a, 30b to the torsion bars 15a, 15b is transmitted to the torsion bars 15a, 15b via the inner actuators 18a, 18b, the inner actuators 45a, 45b or the inner actuators 47a, 47b. Is transmitted to. Then, the sub-resonance of the mirror unit 10 can be suppressed by the sub-reciprocating power transmitted to the mirror unit 10.

DESCRIPTION OF SYMBOLS 1 ... Optical scanner, 2, 42 ... Optical deflector, 4 ... Control apparatus, 6 ... 1st drive voltage generation part, 7 ... 2nd drive voltage generation part, 10 ... Mirror part, 11, 44 ... inner frame part (frame part), 15a, 15b ... torsion bar, 18a, 18b, 45a, 45b, 47a, 47b, 45, 47 ... inner actuator (first actuator) ), 22 ... inner peripheral edge, 23 ... outer peripheral edge, 30a, 30b ... outer actuator (second actuator), 31 ... cantilever part, 32 ... turn-up part, 33 ... proximal end Part, 34... Tip part.

Claims (3)

An optical scanner including an optical deflector and a control device that controls the optical deflector,
The optical deflector is
A mirror that reflects light from a certain direction;
A pair of torsion bars coupled to the mirror part from both sides of the mirror part;
A first piezoelectric film, and a first driving voltage is supplied to the first piezoelectric film to change a curvature of the first piezoelectric film in a thickness direction, and the mirror unit is interposed via the torsion bar. A first actuator that reciprocally rotates around a first axis as an axis of the torsion bar;
While supporting the first actuator and having a second piezoelectric film, the second drive voltage is supplied to change the curvature in the thickness direction of the second piezoelectric film, and the first actuator and the A second actuator that reciprocally rotates the mirror portion about a second axis perpendicular to the first axis via a torsion bar;
The second actuator is configured as a meander structure having a predetermined softness around the first axis by connecting a plurality of cantilever portions formed with the second piezoelectric film in series by a folded portion,
The controller is
A first drive voltage generation unit configured to supply a voltage having a frequency of main resonance of the mirror unit around the first axis to the first actuator as the first drive voltage;
A sub-drive voltage having a frequency lower than the frequency of the first drive voltage, the frequency being the same as the sub-resonance frequency of the mirror portion around the first axis, and the phase being opposite to the phase of the sub-resonance An optical scanner comprising: a second drive voltage generation unit that supplies a voltage obtained by superimposing a voltage to the second actuator as the second drive voltage. The optical scanner according to claim 1.
The optical deflector is configured to have a symmetrical structure on both sides of the mirror part in the direction of the second axis, and the pair of first and second actuators exist on both sides of the mirror part. Optical scanner. The optical scanner according to claim 2.
A frame portion surrounding the first actuator and coupled to the first actuator at an inner periphery;
Each torsion bar is coupled to the inner peripheral edge of the frame portion at the end opposite to the coupling end to the mirror portion,
The optical scanner according to claim 1, wherein the frame portion is coupled to the second actuator at an outer peripheral edge.