JP2011053570A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner capable of reducing a driving voltage at the time of swing driving, and capable of reducing a mirror distortion. <P>SOLUTION: This optical scanner 100 includes a mirror part 110, a set of the first beams 111, a frame part 112, a set of the second beams 120, a fixing part 140, and a piezoelectric driving part 130. The set of the first beams 111 is extended from a mirror part along a direction separated from the mirror part 110, on a plane including a swinging axis AR. The frame part 112 is arranged to surround the mirror part 110, and is connected with the set of the first beams 111. The set of the second beams 120 is extended from the frame part 112 in a direction along the swinging axis AR. The set of the second beams 120 is connected to the fixing part 140. A gravity center CM of the mirror part 110 is separated in a direction orthogonal to the swinging axis AR, with respect to a second beam extension line EL2 of connecting the set of the first beams 111 in the direction along the swinging axis AR. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical scanner used in a laser printer or an image display device, and more particularly to an optical scanner having a MEMS mirror.

  Conventionally, optical scanners have been used in laser printers and image display devices that display light by scanning light. In general, there are optical scanners using a polygon mirror, galvanometer mirrors, and MEMS (Micro-Electro-Mechanical Systems) mirrors. In particular, the optical scanner using the MEMS mirror needs only one light reflecting surface, and the mirror, the torsion bar, and the support frame can be integrally processed. Therefore, the optical scanner using the polygon mirror and the galvanometer mirror can be downsized. Weight reduction is possible.

  Many inventions related to the mechanical structure of an optical scanner using a MEMS mirror (hereinafter simply referred to as an optical scanner) have been filed. As an example, an optical scanner described in Patent Document 1 is shown in FIG. The optical scanner 500 is divided into a base 510 and a pedestal 520. A mirror portion 511 is located at the center of the base 510. The mirror unit 511 is supported at both ends by a pair of first elastic beams 512. The pair of first elastic beams 512 is connected to a second elastic beam 513 divided into two branches. The second elastic beam 513 is connected to the fixed part 514. A piezoelectric driving unit 530 for swinging the mirror unit 511, the first elastic beam 512, and the second elastic beam 513 is formed from the upper surface of the second elastic beam 513 to the fixing unit 514. The pedestal 520 is provided under the base 510 so that the fixed portion 514 and the pedestal joint 521 are joined.

  The operation of the optical scanner 500 will be described. The piezoelectric element included in the piezoelectric driving unit 530 is polarized by applying a voltage. The piezoelectric driving unit 530 extends or contracts in the longitudinal direction of the second elastic beam 513 due to the polarization of the piezoelectric element. Since the piezoelectric driving unit 530 is fixed to the second elastic beam 513 and the fixing unit 514, the expansion and contraction of the piezoelectric driving unit 530 is converted into a bending deformation in which the second elastic beam 513 is deformed in the thickness direction of the base 510. That is, the piezoelectric drive unit 530 functions as a unimorph. The bending deformation of the second elastic beam 513 is for swinging the first elastic beam 512, the second elastic beam 513, and the mirror part 511 through the connection position of the first elastic beam 512 and the second elastic beam 513. Converted to rotational torque.

JP 2003-57586 A

  An optical scanner using a MEMS mirror can be made smaller and lighter than an optical scanner using a polygon mirror and a galvanometer mirror. Therefore, it is preferable to use it for a light and small device. In this case, the power supply is reduced in weight, so the voltage (drive voltage) for driving the optical scanner is preferably as low as possible.

  When the optical scanner is oscillated, the mirror portion of the optical scanner accelerates and decelerates in the rotation direction about the oscillation axis, and changes the light reflection direction. This acceleration and deceleration exerts a force on the mirror part. The force exerted on the mirror part temporarily distorts the shape of the mirror part itself. When the mirror section is distorted, optical characteristics such as a reflection direction and a wavefront shape of light reflected by the mirror section are deteriorated. Therefore, it is desirable that the amount of distortion of the mirror portion during the swing drive is reduced.

  An object of the present invention is to provide an optical scanner capable of reducing a driving voltage and a mirror distortion at the time of swing driving.

  A first problem-solving means reflecting the present invention includes a mirror unit that is oscillated around an oscillation axis and scans incident light in a predetermined direction, and a plane including the oscillation axis from the mirror unit. A pair of first beams extending from the mirror portion in a direction away from the mirror portion, a frame portion disposed so as to surround the mirror portion and connected to the pair of first beams, and a direction along the swing axis A pair of opposing second beams extending from the frame portion; a fixed portion to which the second beam is connected; and a drive portion for swinging the mirror portion; The center of gravity is arranged so as to be separated in a direction perpendicular to the swing axis with respect to a second beam extension line connecting the pair of second beams in the direction along the swing axis. Features.

  The second problem-solving means reflecting the present invention is the first problem-solving means, wherein the set of first beams includes a first beam extension line connecting the set of first beams. It extends relative to the mirror so as to be orthogonal to the line.

  A third problem-solving means reflecting the present invention is the second problem-solving means, wherein the pair of first beams is viewed from a direction orthogonal to the first beam extension line and the second beam extension line. The shape of the mirror part extends relative to the mirror part so as to be symmetrical with respect to the first beam extension line.

  According to a fourth problem solving means reflecting the present invention, in any one of the first to third problem solving means, the frame portion has a center of gravity of the mirror portion with respect to the second beam extension line. The first distance that is the distance in the direction perpendicular to the swing axis between the mirror part and the frame part on the side opposite to the side is the center of gravity of the mirror part with respect to the second beam extension line The mirror portion and the frame portion on the side are arranged so as to surround the mirror portion so as to be larger than a second interval that is an interval in a direction orthogonal to the swing axis. .

  According to a fifth problem-solving means reflecting the present invention, in the fourth problem-solving means, the first interval and the second interval are determined so that the swing axis coincides with the center of gravity of the mirror portion. It is characterized by that.

  A sixth problem-solving means reflecting the present invention is the fifth problem-solving means, wherein the mirror portion has a third interval that is an interval between the second beam extension line and the center of gravity of the mirror portion. It is configured to be 20% to 40% of the width of the mirror portion in the direction orthogonal to the two beam extension lines.

  The seventh problem-solving means reflecting the present invention is any one of the first to sixth problem-solving means, wherein the mirror portion is in a direction orthogonal to the first beam extension line and the second beam extension line. It is characterized in that the shape seen from the above is formed in a circular shape. In addition, it should be understood that a circle includes a polygon (hexagon, octagon, etc.) having more vertices than a rectangle in addition to the circle itself.

  An eighth problem-solving means reflecting the present invention is the problem-solving means of any one of the first to seventh aspects, wherein the second beam is connected to the frame portion and extends in a direction along the swing axis. A frame connecting portion, a beam connecting portion connected to the frame connecting portion and extending in a direction perpendicular to the swing axis on a plane including the swing axis, and connected to both ends of the beam connect portion, A pair of opposing fixed portion connecting portions extending in a direction along the swing axis, and the driving portion includes a piezoelectric element provided from the fixed portion to the fixed portion connecting portion. Features.

  In the first problem solving means reflecting the present invention, the distortion of the mirror portion is reduced by providing the frame portion. In addition, since the center of gravity of the mirror portion is separated in the direction perpendicular to the swing axis with respect to the second beam extension line, it is possible to reduce the driving voltage necessary for obtaining a predetermined deflection angle. Therefore, both reduction of mirror distortion and lowering of the drive voltage are possible.

  The mirror unit is swung around the swing axis. For this reason, the further the distance from the swing axis, the greater the distortion of the mirror portion. In the second problem-solving means reflecting the present invention, the mirror section is configured such that the first beam extension line connecting the first beam set is orthogonal to the second beam extension line. Extends relative to each other. In other words, in the second problem solving means reflecting the present invention, the first beam extends from a portion where the distortion of the mirror portion increases. Therefore, the distortion of the mirror portion is further reduced while maintaining the drive voltage low.

  In the third problem solving means reflecting the present invention, the shape of the mirror portion viewed from the direction orthogonal to the first beam extension line and the second beam extension line is symmetrical with respect to the first beam extension line. The first beam extends relative to the mirror portion. Due to the line-symmetrical shape of the mirror part, distortion of the mirror part in a direction parallel to the second beam extension line occurs line-symmetrically with respect to the first beam extension line. As a result, the uneven distortion of the mirror part is alleviated, so that the distortion of the mirror part is further reduced while maintaining a low drive voltage.

  Since the center of gravity of the mirror portion is separated from the second beam extension line in a direction perpendicular to the swing axis, the swing axis does not coincide with the second beam extension line. The swing axis is separated from the second beam extension line on the same side as the center of gravity of the mirror portion. At this time, the swing axis is further away from the second beam extension line than the center of gravity of the mirror portion. In the fourth problem solving means reflecting the present invention, the frame portion is disposed so as to surround the mirror portion so that the first interval is longer than the second interval. Therefore, when the swing axis approaches the center of gravity of the mirror portion, the distortion distribution of the mirror portion in the direction orthogonal to the swing axis approaches a state of line symmetry with respect to the swing axis. As a result, the uneven distortion of the mirror part is alleviated, so that the distortion of the mirror part is further reduced while maintaining a low drive voltage.

  In the fifth problem solving means reflecting the present invention, the center of gravity of the mirror portion coincides with the swing axis. Due to this coincidence, the distribution of distortion of the mirror portion in the direction orthogonal to the swing axis is axisymmetric with respect to the swing axis. As a result, the uneven distortion of the mirror part is alleviated, so that the distortion of the mirror part is further reduced while maintaining a low drive voltage.

  In the sixth problem-solving means reflecting the present invention, the distance between the second beam extension line and the center of gravity of the mirror part is 20% to 40% of the width of the mirror part in the direction orthogonal to the second beam extension line. Thus, a mirror unit is configured. With this configuration, as shown in an embodiment described later, distortion of the mirror portion is further reduced while maintaining a low drive voltage.

  In the seventh problem-solving means reflecting the present invention, the mirror portion is formed so that the shape seen from the direction orthogonal to the first beam extension line and the second beam extension line is circular. Therefore, for example, the mass of the mirror portion becomes smaller than in the case of a rectangle or the like, and the moment of inertia around the swing axis is reduced. As a result, the distortion of the mirror portion is further reduced while maintaining a low drive voltage.

  In the eighth problem-solving means reflecting the present invention, the drive unit includes a piezoelectric element. Accordingly, it is possible to provide an optical scanner that has high responsiveness to an input drive signal and can reduce the voltage by using high drive force. In addition, the pair of fixed portion connecting portions included in the second beam has a so-called bifurcated structure that is connected to both ends of the beam connecting portion and extends in a direction along the swing axis. The fixed portion connecting portion bends and deforms as the mirror portion swings. This bending deformation is efficiently converted into the swing of the mirror portion through the beam connecting portion. Therefore, an optical scanner capable of lowering the voltage is provided. Then, since the piezoelectric element is provided from the fixed portion to the fixed portion connecting portion, an optical scanner capable of directly applying a driving force to the fixed portion connecting portion that performs the bending motion and capable of reducing the voltage is provided. .

1 is a plan view of an optical scanner 100 according to a first embodiment of the present invention. FIG. 4 is a partially enlarged plan view of the periphery of a mirror unit 110 of the optical scanner 100 according to the first embodiment. The figure which shows the result of having calculated | required the mirror distortion and the drive voltage by simulation in the case of changing the value of the space | interval W1, W2, and W3 in the said 1st Embodiment. The partial enlarged plan view which shows the two comparative examples which concern on the said 1st Embodiment. The figure explaining the change of a drive voltage and a mirror distortion in the case of changing the value of the space | interval W1 and W2 in the said 1st Embodiment. The figure explaining the change of a drive voltage and a mirror distortion in the case of changing the value of the space | interval W3 in the said 1st Embodiment. The partial enlarged plan view of the mirror part 210 periphery of the optical scanner 200 based on the 2nd Embodiment of this invention. The figure explaining the change of a drive voltage and mirror distortion when the shape of a mirror part differs in the said 2nd Embodiment. FIG. 10 is a diagram showing an example of a conventional optical scanner in Patent Document 1.

<First Embodiment>
[Configuration of Optical Scanner 100]
FIG. 1 is a plan view of an optical scanner 100 according to the first embodiment of the present invention. FIG. 2 is a partially enlarged plan view of the periphery of the mirror unit 110 of the optical scanner 100. The x direction is a direction parallel to the swing axis AR of the optical scanner 100. The y direction is a direction perpendicular to the thickness direction of the optical scanner 100 and the x direction, which is the direction perpendicular to the paper surface in FIGS. The optical scanner 100 includes a mirror unit 110, a set of first beams 111, a frame unit 112, a set of second beams 120, a set of piezoelectric drive units 130 and a fixed unit 140. The optical scanner 100 is bonded to a base (not shown). Hereinafter, individual components of the optical scanner 100 will be described with reference to FIGS. 1 and 2.

  The mirror unit 110 is configured to be swingable about the swing axis AR in order to scan incident light in a predetermined direction. The shape of the mirror 110 in plan view is substantially rectangular. The center-of-gravity position CM of the mirror unit 110 is located on the positive side in the y direction with respect to the swing axis AR.

  The pair of opposed first beams 111 extend from the mirror unit 110 in a direction away from the mirror unit 110 on a plane including the swing axis AR. Specifically, the pair of first beams 111 extends from the mirror unit 110 in the y direction. At this time, the first beam extension line EL <b> 1 (see FIG. 2) connecting the pair of first beams 111 is disposed on the center of gravity CM of the mirror unit 110. That is, the planar view shape of the mirror part 110 is line-symmetric with respect to the first beam extension line EL1. The first beam extension line EL1 is along the y direction. In other words, the pair of first beams 111 extends in the y direction from the central part of the side parallel to the x direction of the mirror part 110.

  The frame part 112 is disposed so as to surround the mirror part 110. The shape of the frame part 112 in plan view is substantially rectangular, like the mirror part 110. A set of first beams 111 is connected to the frame portion 112.

  The pair of opposing second beams 120 extend from the frame portion 112 in a direction along the swing axis AR. More specifically, the second beam 120 includes a frame connecting part 121, a beam connecting part 122, and a fixed part connecting part 123. The frame connecting portion 121 is connected to the frame portion 112 and extends in a direction along the swing axis AR. The beam connecting portion 122 is connected to the frame connecting portion 121 and extends in the y direction. The set of fixed portion connecting portions 123 is connected to both ends of the beam connecting portion 122 and extends in a direction along the swing axis AR. The frame connecting portion 121, the beam connecting portion 122, and the fixed portion connecting portion 123 are arranged with respect to a second beam extension line EL2 (see FIG. 2) that connects the pair of second beams 120 in the direction along the swing axis AR. Arranged so as to be symmetrical. Here, the second beam extension line EL2 is orthogonal to the first beam extension game EL1. Further, the second beam extension line EL2 is located on the positive side in the y direction with respect to the swing axis AR and the center of gravity CM of the mirror unit 110. In other words, the mirror unit 110 is arranged such that the center of gravity CM is spaced away from the second beam extension line EL2 on the negative side in the y direction. Here, the center of gravity CM of the mirror unit 110 means the center of mass of the mirror unit 110.

  The fixing portion 140 is an outer frame that surrounds the mirror portion 110, the set of first beams 111, the frame portion 112, and the set of second beams 120 as disclosed in Patent Document 1. However, for the sake of simplicity, only the vicinity of the connecting portion between the pair of second beams 120 and the fixing portion 140 is shown in FIG. A fixed part connecting portion 123 is connected to the fixed part 140.

  The piezoelectric drive unit 130 swings and drives the mirror unit 110. Specifically, the piezoelectric drive unit 130 is formed from a part of the fixed part 140 to the fixed part connecting part 123. The piezoelectric driving unit 130 includes a lower electrode, a piezoelectric element, and an upper electrode (not shown).

  The operation of the optical scanner 100 will be described. First, when a voltage is periodically applied between the lower electrode and the upper electrode, the polarized piezoelectric element expands or contracts in the x direction. Since the piezoelectric drive part 130 is fixed to the fixed part connecting part 123 and the fixed part 140, the expansion and contraction of the piezoelectric element in the x direction is converted into a bending deformation of the fixed part connecting part 123 in the thickness direction of the optical scanner 100. . This bending deformation is converted into a rotational torque for swinging the mirror part 110 via the beam connecting portion 122. When the mirror unit 110 is swung, the optical scanner 100 can scan the light incident on the mirror unit 110 in a predetermined direction.

[Method for Manufacturing Optical Scanner 100]
A method for manufacturing the optical scanner 100 will be described. First, on a thin rectangular silicon substrate having a thickness of about 30 μm to 200 μm, a portion corresponding to the mirror part 110, the pair of first beams 111, the frame part 112, the pair of second beams 120, and the fixing part 140 In addition, a resist film for masking is formed. Thereafter, the silicon substrate is etched. The portions of the silicon base material where the resist film is formed are formed as a mirror portion 110, a set of first beams 111, a frame portion 112, a set of second beams 120, and a fixing portion 140 by etching. Finally, the outer shape of the optical scanner 100 is formed by removing the resist film.

  Next, a lower electrode is formed on the cut silicon substrate. Specifically, the lower electrode is formed by depositing platinum (Pt), gold (Au), or the like with a thickness of 0.2 μm to 0.6 μm from a part of the fixed part 140 to the fixed part connecting part 123. Formed with. For this deposition, for example, a film forming method such as sputtering or vapor deposition is used.

  Next, a piezoelectric element is formed on the aforementioned lower electrode. Specifically, the piezoelectric element is formed by depositing a piezoelectric material such as PZT with a thickness of 1 μm to 3 μm from a part of the fixed part 140 to the fixed part connecting part 123. For this deposition, for example, a film forming method such as an aerosol deposition method (for example, see Japanese Patent Application Laid-Open No. 2007-31737) in which film formation is performed by spraying nano-sized fine particles is used.

  Finally, the upper electrode is formed on the piezoelectric element. Specifically, the upper electrode has a thickness of 0.2 μm to 0.6 μm of platinum (Pt), gold (Au), etc. on the piezoelectric element from a part of the fixed part 140 to the fixed part connecting part 123. It is formed by depositing. For this deposition, a film forming method such as sputtering or vapor deposition is used as in the case of the lower electrode.

[Explanation of simulation data]
In this embodiment, (1) the frame portion 112 is provided, and (2) the center of gravity CM of the mirror portion 110 is separated to the y-direction negative side with respect to the second beam extension line EL2, thereby swinging driving. It is possible to reduce driving voltage and mirror distortion at the time. As shown in FIG. 2, the distance in the y direction between the mirror part 110 and the frame part 112 on the side opposite to the side where the center of gravity CM of the mirror part is present with respect to the second beam extension line EL2, that is, the mirror part 110. An interval on the positive side in the y direction between the frame portion 112 and the frame portion 112 is an interval W1. The distance in the y direction between the mirror part 110 and the frame part 112 on the side where the center of gravity CM of the mirror part exists with respect to the second beam extension line EL2, that is, the distance between the mirror part 110 and the frame part 112 on the negative side in the y direction. Is the interval W2. An interval in the y direction between the center of gravity CM of the mirror unit 110 and the second beam extension line EL2 is defined as an interval W3. The width in the y direction of the mirror part 110 is 1000 μm in this embodiment. Here, the relationship between the values of the intervals W1, W2, and W3 and the reduction of the drive voltage and the reduction of the mirror distortion is examined by simulation.

  FIG. 3 is a diagram illustrating a result of obtaining the mirror distortion and the driving voltage by simulation when the values of the intervals W1, W2, and W3 are changed. The mirror distortion is a thickness direction in a plane including the mirror part 110 when the mirror part 110 is tilted with respect to a stationary state when the mirror part 110 is driven to swing at a predetermined drive frequency. It is the difference between the maximum and minimum values of displacement. In the present embodiment, the predetermined drive frequency is 32 KHz and the predetermined angle is 6.25 °. The drive voltage is a voltage value necessary for the deflection angle of the mirror unit 110 to be a predetermined angle of 6.25 °. The first to fifth embodiments in FIG. 3 have the same configuration as that of the optical scanner 100, and differ in the arrangement of the configuration, that is, the values of the intervals W1, W2, and W3. The arrangement of the configuration in the first embodiment is the same as that of the optical scanner 100.

  As shown in FIG. 3 as Comparative Example 1 and Comparative Example 2, simulations were also performed for two comparative examples in order to explain the effects of the present embodiment. 4A is a partially enlarged plan view of the periphery of the mirror unit 110 of the optical scanner 300 that is the first comparative example. As shown in FIG. 4A, the optical scanner 300 has a structure in which the frame portion 112 is removed from the optical scanner 100. In the optical scanner 300, the same number is assigned to the configuration common to the optical scanner 100. 4B is a partially enlarged plan view of the periphery of the mirror unit 110 of the optical scanner 400 that is the second comparative example. As shown in FIG. 4B, in the optical scanner 400, the center of gravity CM of the mirror unit 110 is located on the swing axis AR. In this case, the swing axis AR coincides with the second beam extension line EL2. In the optical scanner 400, the same number is assigned to the configuration common to the optical scanner 100.

  A change in drive voltage and mirror distortion when the values of the intervals W1 and W2 are changed will be described with reference to FIG. In FIG. 5, three data points correspond to Example 2, Example 1, and Example 3 in order from the left. In FIG. 5, the vertical axis represents mirror distortion and driving voltage. In FIG. 5, the drive voltage does not change greatly between the first embodiment, the second embodiment, and the third embodiment. On the other hand, the mirror distortion is minimum in the second embodiment and is maximum in the third embodiment. As shown in FIG. 3, the value of the interval W3 is the same between the first embodiment, the second embodiment, and the third embodiment (W3 = 300 μm). On the other hand, the relationship between the interval W1 and the interval W2 differs between these embodiments. Specifically, in Example 2, the interval W1 is larger than the interval W2 (W1 = 270 μm, W2 = 135 μm). In the first embodiment, the interval W1 is equal to the interval W2 (W1 = 135 μm, W2 = 135 μm). In the third embodiment, the interval W1 is smaller than the interval W2 (W1 = 135 μm, W2 = 270 μm). That is, when the interval W1 is larger than the interval W2, distortion of the mirror portion is further reduced while maintaining a low drive voltage.

  Here, the reason why the distortion of the mirror part is further reduced when the interval W1 is larger than the interval W2 will be considered. As shown in FIG. 2, in the optical scanner 100, the center of gravity CM of the mirror portion 110 is separated from the second beam extension line EL2 in the y direction negative side, so that the swing axis AR coincides with the second beam extension line EL2. do not do. The swing axis AR is separated from the second beam extension line EL2 on the same side as the center of gravity CM of the mirror unit 110. At this time, the swing axis AR is further away from the second beam extension line EL2 than the center of gravity CM of the mirror unit 110. If the interval W1 is larger than the interval W2, in other words, the frame portion 112 is extended to the positive side in the y direction without changing the relative position between the mirror portion 110 and the second beam 120. The center of gravity approaches the second beam extension line EL2. When the mirror part 110 is swung, the frame part 112 and the first beam 111 are also swung together with the mirror part 110. That is, the fact that the center of gravity of the frame part 112 approaches the second beam extension line EL2 means that the center of gravity of the entire system including the mirror part 110, the first beam 111, and the frame part 112, that is, the swing axis AR, is the second beam extension line. Equivalent to approaching EL2. Therefore, making the interval W1 larger than the interval W2 exhibits the effect of bringing the swing axis AR closer to the center of gravity CM of the mirror unit 110. As the swing axis AR approaches the center of gravity CM of the mirror unit 110, the distortion distribution of the mirror unit 110 in the y direction approaches a line-symmetric state with respect to the swing axis AR. As a result, the deviation in distortion of the mirror portion is alleviated. In other words, if the interval W1 and the interval W2 are determined so that the swing axis AR coincides with the center of gravity CM of the mirror unit 110, the distortion of the mirror unit is further reduced.

  Next, changes in drive voltage and mirror distortion when the value of the interval W3 is changed will be described with reference to FIG. In FIG. 6, the horizontal axis represents the value of the interval W3. The three data points correspond to Example 4, Example 2, and Example 5 in FIG. 3 in order from the left. As shown in FIG. 3, the values of the intervals W1 and W2 are the same between the second embodiment, the fourth embodiment, and the fifth embodiment (W1 = 270 μm, W2 = 135 μm). In FIG. 6, the vertical axis represents mirror distortion and driving voltage. The drive voltage decreases as the interval W3 increases. Therefore, from the viewpoint of reducing the driving voltage, the interval W3 is preferably 200 μm or more. On the other hand, the mirror distortion decreases as the interval W3 increases when the interval W3 ranges from 200 μm to 300 μm, and increases as the interval W3 increases when the interval W3 ranges from 300 μm to 400 μm. The mirror distortion is minimum in Example 2 (W3 = 300 μm). Therefore, from the viewpoint of reducing mirror distortion, the interval W3 is desirably 400 μm or less. Considering both viewpoints of reduction of driving voltage and reduction of mirror distortion at the time of swing driving, it is desirable that the interval W3 is within a range of 200 μm or more and 400 μm or less. Here, since the width of the mirror unit 110 in the y direction is 1000 μm, the range of the interval W3 corresponds to 20% to 40% of the width of the mirror unit 110 in the y direction. More preferably, the interval W3 is 300 μm. The value of the interval W3 corresponds to 30% of the width of the mirror unit 110 in the y direction.

<Second Embodiment>
[Configuration of Optical Scanner 200]
FIG. 7 is a partially enlarged plan view of the periphery of the mirror unit 110 of the optical scanner 200 according to the second embodiment of the present invention. The optical scanner 200 is different from the optical scanner 100 in the first embodiment in the shape of the mirror unit 210. Specifically, the shape of the mirror unit 210 in plan view is substantially circular. The center-of-gravity position CM of the mirror unit 210 is located on the positive side in the y direction with respect to the swing axis AR, similarly to the mirror unit 110. In the optical scanner 200, the same number is assigned to the configuration common to the optical scanner 100.

[Explanation of simulation results]
FIG. 8 is a diagram for explaining changes in driving voltage and mirror distortion when the shape of the mirror portion is different. Note that Example 1 in FIG. 8 is the same as Example 1 (see FIG. 3) in the first embodiment. An optical scanner 200 is shown in FIG. In FIG. 8, the values of the intervals W1, W2, and W3 are the same between the first embodiment and the sixth embodiment, while the shape of the mirror portion is rectangular in the first embodiment, while the first embodiment is different from the first embodiment. 6 is circular. The driving voltage hardly changes between Example 1 and Example 6. On the other hand, with respect to mirror distortion, Example 6 is reduced by about 10% compared to Example 1. This is considered to be because the mass of the mirror unit 210 is smaller than that of the rectangular shape because the shape of the mirror unit 210 is circular, and as a result, the moment of inertia around the swing axis AR is reduced. That is, it can be said that the mirror part 210 having a substantially circular shape in plan view is more desirable than the mirror part 110 having a substantially rectangular shape in plan view (see the first embodiment) from the viewpoint of reducing mirror distortion.

<Modification>
The present invention is not limited to the embodiments described so far, and various modifications and changes can be made without departing from the spirit of the present invention. An example of the modification will be described below.

  In the above-described embodiment, the mirror unit 110 is driven to swing by the piezoelectric drive unit 130. However, the mirror unit 110 may be driven to swing by a drive mechanism other than this. For example, an electrostatic drive method may be employed in which a pair of electrodes are provided on the back surface of the mirror unit 110 and a pedestal (not shown), and the reflection mirror is driven to swing using Coulomb force. Alternatively, an electromagnetic drive system may be employed in which a coil is provided on the back surface of the mirror unit 110 and a permanent magnet is provided on the pedestal, and the reflection mirror is driven to swing using a magnetic force.

  In the above-described embodiment, the set of first beams 111 extends from the mirror unit 110 in the y direction. However, the pair of first beams 111 may extend in other directions such as the x direction. Further, the first beam 111 may extend in the y direction, and the other first beam 111 may extend in the x direction. In short, the pair of first beams 111 may extend from the mirror unit 110 in a direction away from the mirror unit 110 on a plane including the swing axis AR.

  In the above-described embodiment, the planar view shape of the frame portion 112 is a rectangle like the mirror portion 110. However, as long as the frame part 112 can surround the mirror part 110, the frame part 112 may have another plan view shape such as a circular shape. However, from the viewpoint of ease of processing, the shape of the frame portion 112 in plan view is preferably a rectangle.

  In the above-described embodiment, the second beam 120 includes the frame connection part 121, the beam connection part 122, and the fixed part connection part 123. However, the second beam 120 may have other configurations. For example, the frame portion 112 and the fixed portion 140 may be directly connected by a single beam.

  In the embodiment described above, the mirror part 110 is arranged on the y direction negative side with respect to the second extension line EL2, so that the center of gravity CM of the mirror part 110 is on the y direction negative side with respect to the second extension line EL2. To position. However, the center of gravity CM of the mirror part 110 is positioned on the negative side in the y direction with respect to the second extension line EL2 by other methods, for example, adding a weight to the back surface of the mirror part 110, or providing a concave groove. It may be adjusted.

100, 200, 300, 400, 500 Optical scanner 110, 210, 511 Mirror part 111 First beam 112 Frame part 120 Second beam 121 Frame connecting part 122 Beam connecting part 123 Fixed part connecting part 1
140, 514 Fixed portion 130, 530 Piezoelectric drive portion 510 Base 512 First elastic beam 513 Second elastic beam 520 Base 521 Base joint AR AR Oscillation axis CM Center of gravity EL1 of mirror portion 110 First beam extension line EL2 Second beam Extension line W1 Y-direction positive side gap W2 between the mirror part 110 and the frame part 112 Y2 negative side gap W3 between the mirror part 110 and the frame part 112 The center of gravity CM of the mirror part 110 and the second beam extension line EL2 spacing in the y direction

Claims (8)

A mirror that is swung around a swing axis and scans incident light in a predetermined direction;
A set of first beams extending from the mirror portion in a direction away from the mirror portion on a plane including the swing axis;
A frame portion arranged so as to surround the mirror portion and connected to the pair of first beams;
A pair of opposing second beams extending from the frame in a direction along the swing axis;
A fixing portion to which the second beam is connected;
A drive unit for swinging and driving the mirror unit,
The mirror portion is arranged such that the center of gravity thereof is separated in a direction orthogonal to the swing axis with respect to a second beam extension line that connects the pair of second beams in a direction along the swing axis. The
An optical scanner characterized by that. The set of first beams extends relative to the mirror portion such that a first beam extension line connecting the set of first beams is orthogonal to the second beam extension line.
The optical scanner according to claim 1. The pair of first beams has a mirror symmetrical shape with respect to the first beam extension line when viewed from a direction orthogonal to the first beam extension line and the second beam extension line. And extending relative to the mirror part,
The optical scanner according to claim 2. The frame is
A first interval which is an interval in a direction perpendicular to the swing axis between the mirror portion and the frame portion on the side opposite to the side where the center of gravity of the mirror portion exists with respect to the second beam extension line, To be larger than a second interval which is an interval in a direction perpendicular to the swing axis between the mirror portion and the frame portion on the side where the center of gravity of the mirror portion exists with respect to the second beam extension line. , Arranged to surround the mirror part,
The optical scanner according to any one of claims 1 to 3. The first interval and the second interval are determined so that the swing axis coincides with the center of gravity of the mirror part.
The optical scanner according to claim 4. The mirror part is
The third interval, which is the interval between the second beam extension line and the center of gravity of the mirror part, is 20% to 40% of the width of the mirror part in the direction orthogonal to the second beam extension line, Composed,
The optical scanner according to claim 5. The mirror portion is formed so that a shape seen from a direction orthogonal to the first beam extension line and the second beam extension line is circular.
The optical scanner according to claim 1, wherein the optical scanner is an optical scanner. The second beam is
A frame connecting portion connected to the frame portion and extending in a direction along the swing axis;
A beam connecting portion connected to the frame connecting portion and extending in a direction perpendicular to the swing axis on a plane including the swing axis;
A pair of opposing fixed portion connecting portions connected to both ends of the beam connecting portion and extending in a direction along the swing axis,
The drive unit is
Including a piezoelectric element provided from the fixed portion to the fixed portion connecting portion,
The optical scanner according to claim 1, wherein the optical scanner is an optical scanner.

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