JP6310786B2 - Optical deflector - Google Patents

Description

  The present invention relates to an optical deflector manufactured as a MEMS (Micro Electro Mechanical Systems) device.

  2. Description of the Related Art In recent years, research institutes have actively developed optical deflectors as a kind of MEMS devices manufactured using micromachining technology and the like. The optical deflector includes a mirror portion that reflects incident light and an actuator that reciprocally rotates the mirror portion around a rotation axis, and emits reflected light by reciprocating rotation of the mirror portion around the rotation axis. is there. The optical deflector can be applied to various optical devices such as a laser projector, a laser beam printer, a laser radar, a barcode reader, and an area sensor, and contributes to miniaturization of these optical devices.

  As an actuator for an optical deflector, a piezoelectric actuator that uses expansion and contraction of a piezoelectric film is used. In particular, a piezoelectric actuator in which a plurality of piezoelectric cantilevers are connected in a meander pattern arrangement via a folded portion (hereinafter referred to as a “meander-structured piezoelectric actuator”) can obtain a large driving force and displacement. It is suitable when driving at a frequency other than (see, for example, Patent Document 1).

JP 2008-40240 A

  In an optical deflector having a meander structure piezoelectric actuator, a mirror line is set so that a symmetry line of a mirror part having a geometric shape such as a circle or rectangle is set as a rotation axis, and the mirror part reciprocates around the symmetry line. The operating end of the meander-structure piezoelectric actuator connected to is displaced. Then, adjacent piezoelectric cantilevers move with the folded portion as a base point.

  Since the folded portion has a predetermined rigidity and connects adjacent piezoelectric cantilevers, when the adjacent piezoelectric cantilevers move around the folded portion, the piezoelectric cantilevers tend to move toward the folded portion. When the position of the working end of the meander-structure piezoelectric actuator deviates from a desired position, there arises a disadvantage that the rotation axis of the mirror part deviates from the symmetry line of the mirror part set as the rotation axis.

  4 to 6, when the optical deflector is applied to an optical device, the position of the rotational axis of the mirror 101 that reciprocally rotates is the position of the symmetry line (the set rotational axis) of the mirror 101. The problem that the irradiation position of light deviates from a predetermined position due to deviation from the above will be described.

  4 to 6, the mirror unit 101 reflects the incident light 102 incident on the mirror unit 101 from a predetermined direction and emits the reflected light as the scanning light 103 by the reciprocating rotation around the rotation axis of the mirror unit 101. FIG. 10 is a diagram illustrating generation of an irradiation pattern on the screen 104 by the scanning light 103. The mirror unit 101 is a member that is axisymmetric with respect to the axis, for example, a member such as a circle or a rectangle, and the symmetry line is set as a rotation axis so as to reciprocate around the axis of the mirror unit 101. It shall be.

4 to 6, the symmetry line position M ₀ indicates the position of the symmetry line of the mirror unit 101 set as the rotation axis of the mirror unit 101. The rotation axis position R ₀ indicates the position of the rotation axis where the mirror unit 101 reciprocally rotates by the action of the meander structure piezoelectric actuator.

4A, FIG. 5A, and FIG. 6A show the set paths of the scanning light 103 when the symmetry line position M ₀ and the rotation axis position R ₀ coincide, and FIGS. 4B, 5B, and 6B show the rotation axis position. The path of the scanning light 103 when R ₀ deviates from the symmetrical line position M ₀ is shown. 4B, FIG. 5B, and FIG. 6B, since the rotation axis position _R0 is located at the end of the mirror unit 101, the rotation angle range A of the mirror unit 101 is as shown in FIG. 5A, which is almost twice the rotation angle range A of FIG. 6A.

FIGS. 4A, 5A, 6A, the incident light 102 from a laser light source (not shown), enters the symmetry line position M ₀ when the symmetry line position M ₀ and the axis of rotation position R ₀ is matched. 4A, FIG. 5A, and FIG. 6A, the screen 104 is fixedly disposed at a position where the irradiation region B by the scanning light 103 is generated, allows the incident light 102 to pass therethrough, and changes the irradiation pattern by the scanning light 103. It is a virtual screen formed to generate.

  4 to 6, the incident angle of the incident light 102 with respect to the mirror unit 101 is set to two rotation positions (solid line) of the mirror unit 101 having the maximum rotation angle around the rotation axis in FIGS. 4A, 5A, and 6A. With respect to the normal line of the mirror unit 101 at the reference rotation position (position indicated by the two-dot chain line leader line) located between the position indicated by the leader line and the position indicated by the dashed leader line) It is defined as the angle formed by incident light.

FIG. 4 is a diagram illustrating a state where the incident angle of the incident light 102 with respect to the mirror unit 101 at the reference rotation position is 0 °, and the surface of the screen 104 has an emission angle of 0 ° from the mirror unit 101 at the reference rotation position. It is set to be perpendicular to the scanning light emitted at. It can be seen that the irradiation region B in FIG. 4B in which the rotational axis position R ₀ is shifted from the symmetry line position M ₀ is shifted from the predetermined position shown in FIG. 4A with respect to the irradiation region B in FIG. 4A.

FIG. 5 is a diagram illustrating a state where the incident angle of the incident light 102 with respect to the mirror unit 101 at the reference rotation position is 45 ° to the left, and the surface of the screen 104 is 45 ° to the right from the mirror unit 101 at the reference rotation position. It is set perpendicular to the scanning light emitted at the emission angle. It can be seen that the irradiation area B of FIG. 5B in which the rotational axis position R ₀ is shifted from the symmetry line position M ₀ is enlarged and an extended image is generated with respect to the irradiation area B of FIG. 5A.

FIG. 6 is a diagram illustrating a state where the incident angle of the incident light 102 with respect to the mirror portion 101 at the reference rotation position is 45 ° to the right, and the surface of the screen 104 is 45 ° to the left from the mirror portion 101 at the reference rotation position. It is set perpendicular to the scanning light emitted at the emission angle. It can be seen that the irradiation area B in FIG. 6B in which the rotational axis position R ₀ is shifted from the symmetry line position M ₀ is reduced with respect to the irradiation area B in FIG. 6A, and a contracted image is generated.

  In the present invention, when the mirror portion is reciprocally rotated by a meander-structure piezoelectric actuator, the optical deflection that suppresses the position of the rotational axis from deviating from the position of the symmetry line of the mirror set as the rotational axis of the mirror. The purpose is to provide a vessel.

  An optical deflector according to a first aspect of the present invention is a plurality of piezoelectric cantilevers having a line-symmetric shape, a mirror part that reflects light, a frame part that surrounds and supports the mirror part, and a series connection in a meander pattern arrangement And a plurality of piezoelectric actuators interposed between the mirror portion and the frame portion and reciprocally rotating the mirror portion about a symmetry line of the mirror portion as a rotation axis. A first piezoelectric cantilever adjacent to the mirror portion of the cantilever is composed of a first half and a second half, and the first half is formed from the symmetry line with respect to the first piezoelectric cantilever and the first piezoelectric cantilever. Extending to the folded portion connecting the second piezoelectric cantilevers adjacent to each other, the second half extending from the symmetry line to the opposite side of the folded portion, and the second half being the first half. To be heavier than Made is characterized in that is.

  Piezoelectric cantilevers connected by means of a meander pattern array bend and move with a folded portion connected to an adjacent piezoelectric cantilever as a base point, so that the piezoelectric cantilever tends to move toward the folded portion side that is a base point. Further, when there are a plurality of folded portions, the influence on the position of the operating end of the piezoelectric actuator connected to the mirror portion becomes stronger as the folded portion is closer to the working end.

  According to the present invention, the second half extending from the symmetry line to the opposite side with respect to the folded portion between the first piezoelectric cantilever and the second piezoelectric cantilever adjacent to the mirror portion is based on the weight of the first half. It is formed to be heavy. Therefore, the center-of-gravity movement of the piezoelectric actuator accompanying reciprocal rotation around the rotation axis is suppressed. Therefore, it can suppress that the rotation axis of a mirror part shifts from the symmetrical line of a mirror part.

  In the first invention, the second half is formed to be heavier than the first half by adding a weight to the second half or by providing a notch in the first half. It is preferable.

  As described above, by providing the weight or the notch in the half of the first piezoelectric cantilever, a configuration in which the second half is formed to be heavier than the weight of the first half can be easily realized.

  An optical deflector according to a second aspect of the invention has a mirror part that reflects light, an inner frame part that has a line-symmetric shape and surrounds and supports the mirror part, and an outer part that surrounds and supports the inner frame part A pair of torsion bars having one end connected to the mirror and the other end connected to the inner frame on the first rotation axis of the mirror, and the mirror and inner frame An inner piezoelectric actuator that reciprocally rotates the torsion bar about the first rotation axis, and a plurality of piezoelectric cantilevers connected in series in a meander pattern arrangement, and the inner frame portion, An outer piezoelectric actuator that is interposed between the outer frame portion and that reciprocally rotates the inner frame portion around a symmetric line of the inner frame portion orthogonal to the first rotation axis as a second rotation axis. , Adjacent to the inner frame portion of the plurality of piezoelectric cantilevers The first piezoelectric cantilever includes a first half and a second half, and the first half connects the first piezoelectric cantilever and the second piezoelectric cantilever adjacent to the first piezoelectric cantilever from the symmetry line. The second half is formed to extend from the symmetry line to the opposite side of the folding part, and the second half is heavier than the first half. It is characterized by that.

  According to the present invention, the second half extending from the symmetry line of the mirror portion to the opposite side with respect to the folded portion between the first piezoelectric cantilever and the second piezoelectric cantilever adjacent to the inner frame portion is the first half. It is formed to be heavier than the weight of the part. Therefore, the center-of-gravity movement of the piezoelectric actuator accompanying the reciprocating rotation around the second rotation axis is suppressed, and the second rotation axis is prevented from deviating from the symmetry line of the inner frame portion.

  Therefore, even if the mirror unit is a biaxial optical deflector that reciprocally rotates around the first rotation axis and the second rotation axis, the second rotation axis is prevented from deviating from the symmetry line, and the mirror unit It is possible to suppress the intersection of the first rotation axis and the second rotation axis from deviating from a predetermined position.

  In the second invention, the second half is formed to be heavier than the first half by adding a weight to the second half or by providing a notch in the first half. It is preferable.

  As described above, by providing the weight or the notch in the half of the first piezoelectric cantilever, a configuration in which the second half is formed to be heavier than the weight of the first half can be easily realized.

The perspective view which shows the optical deflector of 1st Embodiment. The figure which showed the simulation result. The perspective view which shows the optical deflector of 2nd Embodiment. The figure which the incident angle of the incident light 102 with respect to the mirror part 101 of a reference | standard rotation position is 0 degree. The figure which the incident angle of the incident light 102 with respect to the mirror part 101 of a reference | standard rotation position is 45 degrees on the left. The figure which the incident angle of the incident light 102 with respect to the mirror part 101 of a reference | standard rotation position is right 45 degrees.

[First Embodiment]
FIG. 1 is a perspective view showing a uniaxial optical deflector 1. The optical deflector 1 includes a rectangular mirror portion 2 and a rectangular frame 3 surrounding the mirror portion 2 with the same center.

  As shown in FIG. 1, in order to describe the structure of the optical deflector 1, an xyz three-axis orthogonal coordinate system is defined. In the three-axis orthogonal coordinate system, the origin O is defined as the center of the mirror surface on the front surface of the rectangular mirror unit 2. The x axis and the y axis are defined as directions parallel to the long side and the short side of the rectangular frame 3 that is a stationary member. In the z-axis, as shown in FIG. 1, the direction from the rear side to the front side in the thickness direction of the optical deflector 1 is defined as positive.

  The mirror part 2 is a rectangular plate-shaped member, and has two symmetrical lines in front view (viewed in the z-axis direction). One symmetry line passes through the center O and is a straight line (symmetry line X) parallel to the x axis, and the other symmetry line passes through the center point O and is a straight line parallel to the y axis. In addition, the shape of the mirror part 2 is not limited to a rectangular plate shape, and may be another shape as long as the shape is axisymmetric with respect to a symmetric line X passing through the center O of a disk or the like. The symmetry line X is set as the rotation axis of the mirror unit 2.

  The mirror unit 2 has a mirror surface on the front surface, and laser light emitted from a laser light source (not shown) is incident on the center O, and the mirror surface of the mirror unit 2 reflects the laser light at a reflection angle corresponding to the incident angle. Then, it is emitted as scanning light. FIG. 1 shows a state in which the operation of the optical deflector 1 is stopped, and the normal line of the center O on the mirror surface of the mirror unit 2 coincides with the z axis. The optical deflector 1 is formed in a line-symmetric structure with respect to the yz plane.

  The rectangular frame 3 is an annular rectangular member that surrounds the mirror portion 2 and is formed symmetrically with respect to the x-axis and the y-axis passing through the center O.

  The piezoelectric actuator 4 is interposed between the mirror unit 2 and the rectangular frame 3. Specifically, the piezoelectric actuator 4 is disposed on the inner peripheral side of the rectangular frame 3 and on both sides of the mirror part 2 in the x-axis direction, and is connected to the mirror part 2 by a symmetric line X by a connecting part 8. The portion 9 is connected to the rectangular frame 3 by a symmetry line X.

  The end portion of the piezoelectric actuator 4 on the connecting portion 8 side functions as an operating end (front end) of the actuator, and the end portion of the piezoelectric actuator 4 on the connecting portion 9 side functions as a support end (base end). The piezoelectric actuator 4 has a meander structure in which a plurality of piezoelectric cantilevers are arranged in a meander pattern and connected in series.

  The piezoelectric actuator 4 includes piezoelectric cantilevers 5a to 5e arranged in a meander pattern and connected in series by folded portions 6a to 6d as piezoelectric actuators having a meander structure. The piezoelectric cantilevers 5a to 5e and the folding portions 6a to 6d are numbered in order from the closest to the mirror portion 2 in alphabetical order at the end of the reference numerals. Hereinafter, when the piezoelectric cantilevers 5a to 5e and the folded portions 6a to 6d are collectively referred to as “piezoelectric cantilever 5” and “folded portion 6”, respectively.

  The piezoelectric cantilever 5 has a laminated structure including a piezoelectric film and two electrodes sandwiching the piezoelectric film from both sides in the thickness direction. Specifically, the piezoelectric cantilever 5 has a lower electrode adhesion film, a lower electrode, and a piezoelectric element for improving the adhesion between the substrate, the thermal oxide film, and the thin film in contact with the electrode in order from the lower layer in front view (z-axis direction view). Consists of interlayer film, piezoelectric film, upper electrode, upper electrode adhesion film, interlayer insulating film, wiring part, outer layer film that has a function to protect wiring and circuit elements from moisture and metal ions, which controls the orientation of the film A laminated structure composed of a laminated body.

Si etc. are mentioned as a material of a board | substrate. In addition, as a material of the laminate formed on the substrate, a thermal oxide film such as SiO ₂ , a lower electrode adhesion film such as TiO _X , a lower electrode and an upper electrode such as Pt, an interlayer film that controls the orientation of the piezoelectric film Is SRO (strontium ruthenate), the piezoelectric film is PZT (lead zirconate titanate), the upper electrode adhesion film is Ti, the interlayer insulating film is SiO ₂ , SiN, etc., and the wiring part is Al.

  The laminate is formed on the substrate by sequentially forming a film from the lower layer using a known method such as a sputtering method, an electron beam evaporation method, or an ion plating method using reactive arc discharge. . In addition, the mirror part 2, the rectangular frame 3, and the piezoelectric actuator 4 of this embodiment have the said board | substrate in common.

Examples of the material for the outer layer film include SiN, SiON, TEOS, SiO ₂ , and Al ₂ O _3. However, the outer layer film is hydrophobic to protect the laminate from moisture in the external environment, and has a film quality with respect to the atmospheric environment. SiN that is difficult to change with time (stress change) and has low impurity transmittance and easy film stress control is preferable.

  As shown in FIG. 1, the piezoelectric cantilever 5a adjacent to the mirror part 2 is composed of a first half part 10a and a second half part 10b. The first half 10a extends from the symmetry line X to the folded portion 6a that connects the piezoelectric cantilever 5a and the piezoelectric cantilever 5b adjacent to the piezoelectric cantilever 5a, and the second half 10b extends from the symmetry line X to the folded portion 6a. And on the opposite side. The first half 10a is a member having the above laminated body on a substrate, and the second half 10b is a member formed by a substrate on which the above laminated body is not formed.

  The piezoelectric cantilever 5a is connected to the mirror part 2 near the symmetry line X by the connecting part 8, and the mirror part 2 other than the part connected to the connecting part 8 (the part of the mirror part 2 facing the piezoelectric cantilever 5a). ).

  As shown in FIG. 1, the piezoelectric cantilever 5a has a weight 11 on the back surface of the second half 10b in front view (viewed in the z-axis direction), and the second half 10b is the weight of the first half 10a. It is formed to be heavier. The weight 11 may be formed in a disk shape, a conical shape, a rectangular plate shape, or the like.

  Further, if the second half 10b is formed to be heavier than the weight of the first half 10a, the second half 10b can be made thicker without providing the weight 11, thereby increasing the thickness of the first half 10b. You may form so that it may become heavier than the weight of the part 10a. Further, the weight of the second half 10b may be increased by extending the length of the second half 10b from the symmetry line X. When the extended second half 10b contacts the rectangular frame 3, a part of the extended second half 10b may be bent, and the first half 10a is notched. May be provided.

  The rectangular frame 3 is an annular rectangular member that surrounds and supports the mirror portion 2 and is formed in line symmetry with respect to the x-axis and the y-axis passing through the center O. The rectangular frame 3 is connected to the piezoelectric actuator 4 on the symmetry line X by the connecting portion 9. In addition, an electrode pad 7 is disposed on the front surface of the rectangular frame 3 and is electrically connected to the electrode of the piezoelectric cantilever 5 via a wiring (not shown).

  Next, the operation of the uniaxial optical deflector 1 of the first embodiment will be described. A drive voltage that increases or decreases at the same drive frequency Fa is supplied to the piezoelectric film of each piezoelectric cantilever 5 through the electrode pad 7. However, the drive voltage applied to the piezoelectric cantilevers 5a, 5c and 5e and the drive voltage applied to the piezoelectric cantilevers 5b and 5d are voltages having opposite phases.

  Then, the piezoelectric film of each piezoelectric cantilever 5 expands and contracts in the longitudinal direction of the piezoelectric cantilever 5 according to the applied drive voltage and drive frequency Fa, and each piezoelectric cantilever 5 is curved and deformed in the thickness direction. Is applied to the mirror unit 2 at the drive frequency Fa. Accordingly, the mirror unit 2 reciprocates around the rotation axis at the drive frequency Fa.

  The lengths of the piezoelectric cantilevers 5a and 5e at both ends of the meander pattern array are half of the lengths of the intermediate piezoelectric cantilevers 5b to 5d. Therefore, when the drive voltage is applied to the piezoelectric film, the deformation amount of the piezoelectric cantilevers 5a and 5e is about half of the deformation amount of the piezoelectric cantilevers 5b to 5d.

  Then, incident light in which laser light is incident on the position of the center (origin) O of the mirror unit 2 from a laser light source (not shown) is reflected from the mirror unit 2 at a reflection angle corresponding to the rotation angle around the rotation axis, The light is emitted from the deflector 1. The reflected light of the mirror unit 2 is emitted from the optical deflector 1 as scanning light whose emission direction changes in the yz plane.

  A simulation was conducted to examine the operational effect of the piezoelectric cantilever 5a formed so that the second half 10b is heavier than the weight of the first half 10a. The simulation result will be described with reference to FIGS. 2A and 2B. 2A and 2B, the xyz three-axis orthogonal coordinate system corresponds to the xyz three-axis orthogonal coordinate system in FIG.

  In this simulation, the second half 10b made of the substrate having no piezoelectric laminate is not provided with the weight 11 on the back surface of the second half 10b, and the length from the symmetry line X is set to the length of the first half. By setting it longer than 10a, it set so that it might become heavier than the weight of the 1st half part 10a. 2A shows a case where the second half 10b is formed longer than the first half 10a without being bent, and FIG. 2B shows a case where the second half 10b is bent toward the back side and formed longer than the first half 10a. The simulation result of the amount of displacement in the z-axis direction of the optical deflectors 31, 31 ′ is shown.

  For the simulation of the displacement amount in the z-axis direction, mode analysis of the MEMS structure was performed by FEM (finite element method). In the mode analysis, an operation (transition) at each unique resonance point is calculated. As the simulation software, “Oofelie (registered trademark)” manufactured by Open-Engineering was used.

  2A and 2B, the darker color region has a larger displacement amount in the z-axis direction, and the lighter color region has a smaller displacement amount in the z-axis direction. The white region indicates that the displacement was not displaced in the z-axis direction in the simulation result. Further, in FIGS. 2A and 2B, reference numeral 33 indicates a rotation axis of the mirror unit 32.

  2A and 2B, the region where the amount of displacement in the z-axis direction is zero includes the symmetry line X, and the rotation axis 33 of the mirror portion 32 coincides with the symmetry line X. Therefore, in the optical deflectors 31 and 31 ′, even when the mirror unit 32 is reciprocally rotated, the actual rotation axis 33 of the mirror unit 2 is prevented from being displaced from the position of the symmetry line X of the mirror unit 2. It could be confirmed.

[Second Embodiment]
FIG. 3 is a perspective view of the biaxial optical deflector 51 when the operation is stopped. The optical deflector 51 includes a disk-shaped mirror part 52, an inner frame part 55 that surrounds and supports the mirror part 52, and an outer frame part 60 that surrounds and supports the inner frame part 55 at the center point. Aligned and provided.

  As shown in FIG. 3, in order to describe the structure of the optical deflector 51, an xyz three-axis orthogonal coordinate system is defined. In the three-axis orthogonal coordinate system, the origin O is placed at the center of the mirror surface on the front surface of the disk-shaped mirror unit 52. Further, the x axis and the y axis are defined as directions parallel to the long side and the short side of the outer frame portion 60 that is a stationary member, respectively. As shown in FIG. 3, the z-axis defines the direction from the rear side to the front side as positive in the thickness direction of the optical deflector 51.

  As shown in FIG. 3, the mirror part 52 is a disk-shaped member. Further, in the mirror unit 52, a straight line passing through the center O and parallel to the x axis in the front view (viewing in the z-axis direction) is defined as a symmetric line X, and a straight line passing through the center O and parallel to the y axis is defined as a symmetric line Y. .

  The mirror unit 52 has a mirror surface on the front surface, and laser light emitted from a laser light source (not shown) is incident on the center point O. The mirror surface of the mirror unit 52 emits laser light at a reflection angle corresponding to the incident angle. Reflected and emitted as scanning light. FIG. 3 shows a state in which the operation of the optical deflector 51 is stopped, and the normal line of the center point O on the mirror surface of the mirror unit 52 coincides with the z axis. The optical deflector 51 is formed in a symmetric structure with respect to the yz plane.

  The shape of the mirror part 52 is not limited to a disk shape, but may be any shape as long as it is symmetric with respect to the symmetric line X and the symmetric line Y passing through the center O such as a flat plate shape such as a rectangle, a square, or a regular hexagon. The shape may be acceptable.

  When the optical deflector 51 operates, the symmetry line X of the mirror unit 52 does not stay on the x-axis line passing through the center O, but is a straight line (first rotation axis) parallel to the y-axis in the xz plane. Reciprocally rotate around. On the other hand, the symmetry line Y of the mirror part 52 coincides with the symmetry line of the inner frame part 55 and does not stay on the y-axis line passing through the center O, but is a straight line (second rotation) in the yz plane. Reciprocally rotate around the axis).

  As shown in FIG. 3, the torsion bar 54 is disposed on both outer sides in the y-axis direction of the mirror part 52, extends from the mirror part 52 to the inner frame part 55 along the y-axis, Both end portions are connected to the mirror portion 52 and the inner frame portion 55. The axis of the torsion bar 54 is formed so as to coincide with the symmetry line Y of the mirror portion 52.

  As shown in FIG. 3, the inner piezoelectric actuator 53 has a semicircular shape with a predetermined width, and is disposed on both outer sides in the x-axis direction of the mirror portion 52 and inside the inner frame portion 55. Are connected to each torsion bar 54 at both ends thereof. The inner piezoelectric actuator 53 connects the semi-annular central portion of the inner piezoelectric actuator 53 and the inner periphery of the inner frame portion 55 on the symmetry line X by a connecting portion 56.

  The inner frame portion 55 is a ring-shaped rectangular member having a symmetry line Y and surrounding the mirror portion 2 as shown in FIG. 3, and is symmetrical with respect to the x axis and the y axis passing through the center O. Is formed. Further, the inner frame portion 55 is connected to the outer piezoelectric actuator 61 on the symmetry line X by a connecting portion 66.

  The outer piezoelectric actuator 61 is disposed on the inner peripheral side of the outer frame portion 60 and on both outer sides of the inner frame portion 55 in the x-axis direction, and is connected to the inner frame portion by connecting portions 66 and 67 disposed on the symmetry line X. 55 and the outer frame part 60. The outer piezoelectric actuator 61 includes piezoelectric cantilevers 62a to 62e arranged in a meander pattern and connected in series by folded portions 63a to 63d as a piezoelectric actuator having a meander structure. The piezoelectric cantilevers 62a to 62e and the folding portions 63a to 63d are numbered in the order from the closer to the mirror portion 2 in alphabetical order at the end of the reference numerals. Hereinafter, the piezoelectric cantilevers 62a to 62e and the folded portions 63a to 63d are collectively referred to as “piezoelectric cantilevers 62” and “folded portions 63”, respectively.

  Similar to the piezoelectric cantilever 5 of the first embodiment, the piezoelectric cantilever 62 has a laminated structure including a piezoelectric film and two electrodes that sandwich the piezoelectric film from both sides in the thickness direction. Specifically, the piezoelectric cantilever 62 has a laminated structure including a substrate, a laminated body including a lower electrode, a piezoelectric film, and an upper electrode in order from the lower layer in front view (viewed in the z-axis direction). The piezoelectric cantilever 62 of the inner piezoelectric actuator 53 and the outer piezoelectric actuator 61 of the second embodiment is formed so as to include the same laminated structure, and the mirror portion 52, the inner frame portion 55, the inner piezoelectric actuator 53, and the outer piezoelectric actuator 61. And the outer frame part 60 has the said board | substrate in common.

  As shown in FIG. 3, the piezoelectric cantilever 62a adjacent to the inner frame portion 55 has a first half 80a extending from the symmetry line X to the folded portion 63a connected to the piezoelectric cantilever 62b adjacent to the piezoelectric cantilever 62a; It has the 2nd half part 80b extended from the symmetry line X on the opposite side to the folding | turning part 63a. The first half 80a is a member having the above laminated body on the substrate, and the second half 80b is a member formed of a substrate on which the above laminated body is not formed.

  The piezoelectric cantilever 62a is connected to the inner frame portion 55 in the vicinity of the symmetry line X by the connecting portion 66, and the inner frame portion 55 other than the portion connected to the connecting portion 66 (the inner frame portion facing the piezoelectric cantilever 62a). 55 portion).

  As shown in FIG. 3, the piezoelectric cantilever 62a has a weight 81 on the back surface of the second half 80b in front view (viewed in the z-axis direction), and the second half 80b is the weight of the first half 80a. It is formed to be heavier. The weight 81 may be formed in a disk shape, a conical shape, a rectangular plate shape, or the like.

  In addition, if the second half 80b is formed so as to be heavier than the weight of the first half 80a, the first half 80b can be formed by increasing the thickness of the second half 80b without providing the weight 81. You may form so that it may become heavier than the weight of the part 80a. Further, the weight of the second half 80b may be increased by extending the length of the second half 80b from the symmetry line X. When the extended second half 80b comes into contact with the outer frame portion 60, a part of the extended second half 80b may be bent or cut into the first half 80a. A notch may be provided.

  The outer frame portion 60 is an annular rectangular member that surrounds and supports the inner frame portion 55, and is formed in line symmetry with respect to the x axis and the y axis that pass through the center O. Further, the outer frame portion 60 is connected to the outer piezoelectric actuator 61 on the symmetry line X by a connecting portion 67. In addition, an electrode pad 70 is disposed on the front surface of the outer frame portion 60 and is electrically connected to the inner piezoelectric actuator 53 and the electrode layer of the piezoelectric cantilever 62 via a wiring (not shown).

  Next, the operation of the biaxial optical deflector 51 of the second embodiment will be described. In the optical deflector 51, the drive voltage applied to the inner piezoelectric actuator 53 that reciprocally rotates the mirror unit 52 about the y-axis passing through the center O of the mirror unit 52, and the x-axis about the center O of the mirror unit 52. The driving voltages applied to the outer piezoelectric actuator 61 that reciprocally rotates the inner frame portion 55 are applied independently to the inner piezoelectric actuator 53 and the outer piezoelectric actuator 61, respectively.

  The reciprocating rotation of the inner frame portion 55 around the x axis by the outer piezoelectric actuator 61 is performed by applying a driving voltage to the outer piezoelectric actuator 61 which is a meander structure piezoelectric actuator, as in the optical deflector 1 of the first embodiment. Is called.

  Next, reciprocal rotation around the y-axis line of the mirror unit 52 by the inner piezoelectric actuator 53 will be described. When a first voltage is applied to one of the pair of inner piezoelectric actuators 53, 53 and a second voltage having a phase opposite to the first voltage is applied to the other, the inner piezoelectric actuators 53, 53 are bent and deformed, respectively. . These bending deformations cause torsional displacement in the torsion bar 54, and rotational torque about the torsion bar 54 acts on the mirror portion 52.

  Then, the mirror unit 52 reciprocates around the y-axis passing through the center O of the mirror unit 52 with the torsion bars 54 and 54 as the rotation axis, thereby reciprocatingly rotating the mirror unit 52 to perform optical scanning in the x-axis direction. I do.

  According to the optical deflector 51 of the second embodiment, similarly to the optical deflector 1 of the first embodiment, even when the mirror unit 52 is reciprocally rotated around the x-axis and the y-axis, respectively. The actual rotation axis of the rotating mirror unit 52 is prevented from shifting from the position of the symmetry line X. Since the mirror part 52 is supported by the torsion bars 54, 54 on the first rotation axis, it is possible to prevent the mirror part 52 from being shifted from the center O which is the intersection of the first rotation axis and the second rotation axis of the mirror part 52.

  The optical deflector 1 of the first embodiment and the optical deflector 51 of the second embodiment can be used for, for example, a laser projector, a laser beam printer, a laser radar, a barcode reader, an area sensor, and the like.

DESCRIPTION OF SYMBOLS 1, 31, 32 ', 51 ... Optical deflector, 2, 32, 52 ... Mirror part, 3 ... Rectangular frame (frame part), 4 ... Piezoelectric actuator, 5, 5a-5e, 35a-35e, 35a', 62 , 62a to 62e ... piezoelectric cantilevers, 6, 6a to 6d, 63, 63a to 63d ... folded portion, 10a, 10a ', 80a ... first half, 10b, 10b', 80b ... second half, 11, 81 ... weight, 53 ... inner piezoelectric actuator, 55 ... inner frame part, 60 ... outer frame part, 61 ... outer piezoelectric actuator.

Claims (4)

A mirror part having a line-symmetric shape and reflecting light;
A frame portion surrounding and supporting the mirror portion;
It has a plurality of piezoelectric cantilevers connected in series in a meander pattern arrangement, and is interposed between the mirror part and the frame part, and reciprocally rotates the mirror part around the axis of symmetry about the symmetry line of the mirror part. A piezoelectric actuator to be moved,
A first piezoelectric cantilever adjacent to the mirror portion of the plurality of piezoelectric cantilevers is composed of a first half and a second half.
The first half extends from the symmetry line to a folded portion that connects the first piezoelectric cantilever and a second piezoelectric cantilever adjacent to the first piezoelectric cantilever,
The second half extends from the line of symmetry to the opposite side of the folded portion;
The optical deflector, wherein the second half is formed to be heavier than the first half. The optical deflector according to claim 1,
The second half is formed to be heavier than the first half by adding a weight to the second half or by providing a notch in the first half. An optical deflector. A mirror that reflects light;
An inner frame portion having a line-symmetric shape and surrounding and supporting the mirror portion;
An outer frame part surrounding and supporting the inner frame part;
On the first rotation axis of the mirror part, a pair of torsion bars having one end connected to the mirror part and the other end connected to the inner frame part;
An inner piezoelectric actuator interposed between the mirror part and the inner frame part to reciprocately rotate the torsion bar around the first rotation axis;
A plurality of piezoelectric cantilevers connected in series in a meander pattern arrangement, interposed between the inner frame portion and the outer frame portion, and a second symmetry line of the inner frame portion orthogonal to the first rotation axis; An outer piezoelectric actuator that reciprocally rotates the inner frame portion around the rotation axis,
The first piezoelectric cantilever adjacent to the inner frame portion of the plurality of piezoelectric cantilevers is composed of a first half and a second half.
The first half extends from the symmetry line to the folded portion connecting the first piezoelectric cantilever and the second piezoelectric cantilever adjacent to the first piezoelectric cantilever;
The second half extends from the line of symmetry to the opposite side of the folded portion;
The optical deflector, wherein the second half is formed to be heavier than the first half. The optical deflector according to claim 3, wherein
The second half is formed to be heavier than the first half by adding a weight to the second half or by providing a notch in the first half. An optical deflector.