JP2011069954A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner in which a large amount of displacement of a mirror is obtained. <P>SOLUTION: The optical scanner 100 includes a mirror part 110, a supporting beam 120, a fixed part 140 and a piezoelectric driving part 130. The mirror part 110 rocks around a rocking axis line AR. The supporting beam 120 extends from the mirror part 110. The supporting beam 120 is connected to the fixed part 140. The piezoelectric driving part 130 is provided from the fixed part 140 to a part of the supporting beam 120. The supporting beam 120 has a pair of beam parts 123 disposed symmetrically with respect to the rocking axis line AR and connected to the fixed part 140. The pair of beam parts 123 have a first portion 123a and a bent portion 123b. The first portion 123a extends in a separating direction from the mirror part 110 along the rocking axis line AR. The bent portion 123b is connected to the first portion 123a and bent in the directions separating from the rocking axis line AR and along the rocking axis line 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 relating to the mechanical structure of an optical scanner using a MEMS mirror (hereinafter also simply referred to as an optical scanner) have been filed. As an example, the 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

  For example, when an optical scanner is used in an image display device, the angle of view of the display image depends on the amount of displacement of the mirror unit. Therefore, in order to display a large image or a detailed image, it is desirable that the amount of displacement of the mirror portion is larger.

  An object of the present invention is to provide an optical scanner capable of obtaining a large amount of displacement of a mirror portion.

  The first problem-solving means reflecting the present invention includes a mirror section that is swung around a swing axis and that scans incident light in a predetermined direction, a support beam that extends from the mirror section, and the support beam. And a piezoelectric drive unit provided to extend from the fixed part to a part of the support beam to drive the mirror part and the support beam to swing. The support beam includes the swinging part. A pair of beam portions arranged symmetrically with respect to the movement axis and connected to the fixed portion, the pair of beam portions extending along the swing axis in a direction away from the mirror portion A first portion that extends, is connected to the first portion, bends in a direction away from the swing axis and in a direction along the swing axis on a plane including the swing axis, and is connected to the fixed portion. It is characterized by having a bent portion.

  The second problem-solving means reflecting the present invention is characterized in that the bent portion has one end connected to the first portion and extending in a direction away from the swing axis, and one end of the bent portion. A third portion connected to the other end of the two portions, extending along the swing axis in a direction approaching the mirror portion, and having the other end connected to the fixed portion.

  According to a third problem solving means reflecting the present invention, the length of the third portion in the direction along the swing axis of the third portion is the length of the first portion in the direction along the swing axis. It is formed so that it may become longer than this.

  A fourth problem solving means reflecting the present invention is characterized in that the piezoelectric driving unit is provided from at least the fixing unit to the second part via the third part.

  The fifth problem-solving means reflecting the present invention is characterized in that the support beam is further connected at one end to the mirror portion and extends in a direction along the swing axis, and the other of the mirror connection portion. A beam connecting portion connected to an end and extending in a direction perpendicular to the swing axis on a plane including the swing axis, and one end of the first portion is connected to both ends of the beam connecting portion. And the other end is connected to one end of the second portion.

  In the first problem solving means reflecting the present invention, since the pair of beam portions have the bent portions, it is possible to obtain a large amount of displacement of the mirror portion as shown in an embodiment described later.

  In the second problem-solving means reflecting the present invention, the bent portion includes a second portion that extends in a direction away from the swing axis, and a third portion that extends along the swing axis in a direction approaching the mirror portion. Have In other words, the pair of beam portions are configured to be separated from the mirror portion by the first portion and to be folded once in the direction approaching the mirror portion by the second portion and the third portion. As shown in an embodiment described later, it is possible to obtain a large amount of displacement of the mirror portion when the bent portion is folded once.

  In the third problem solving means reflecting the present invention, the length of the third portion in the direction along the swing axis is longer than the length of the first portion in the direction along the swing axis. With this configuration, it is possible to obtain a large amount of displacement of the mirror portion as shown in an embodiment described later.

  In the fourth problem-solving means reflecting the present invention, the piezoelectric drive unit is provided from at least the fixed part to the second part. With this configuration, it is possible to efficiently transmit the power generated by the piezoelectric drive unit to the mirror. Accordingly, it is possible to obtain a large amount of displacement of the mirror portion.

  In the fifth problem solving means reflecting the present invention, the support beam includes a mirror connecting portion and a beam connecting portion. The pair of beam portions are bent and deformed by the power generated by the piezoelectric drive unit. This bending deformation is efficiently converted into the swing of the mirror portion through the beam connecting portion. Therefore, it becomes possible to obtain a larger amount of displacement of the mirror portion by having these configurations in addition to the bent portion.

1 is a plan view of an optical scanner 100 according to a first embodiment of the present invention. The top view of the optical scanner 100 of the periphery of the support beam 120 at the time of changing the frequency | count of folding of the bending part 123b based on 1st Embodiment. The figure which shows the relationship between the frequency | count of folding | turning of the bending part 123b, and an optical deflection angle based on 1st Embodiment. FIG. 3 is an enlarged plan view around a support beam 120 of the optical scanner 100 according to the first embodiment. The figure which shows the relationship between the length of the 3rd part 123b-2 and optical deflection angle based on 1st Embodiment. The top view of the optical scanner 200 which is a modification of 1st 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. The x direction is a direction parallel to the swing axis AR of the optical scanner 100. The y direction is a direction orthogonal to the thickness direction of the optical scanner 100 and the x direction, which is the direction perpendicular to the paper surface in FIG. The optical scanner 100 includes a mirror unit 110, a support beam 120, a piezoelectric drive unit 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 FIG.

  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 part 110 in plan view is substantially circular.

  The support beam 120 extends from the mirror unit 110 in a direction along the swing axis AR. A pair of support beams 120 are provided so as to be line symmetric with respect to a virtual axis parallel to the y direction passing through the center position of the mirror unit 110. The support beam 120 includes a mirror connection part 121, a beam connection part 122, and a beam part 123. One end of the mirror connection part 121 is connected to the mirror part 110. The mirror connection portion 121 extends in a direction along the swing axis AR. The mirror connecting portion 121 is disposed so as to include the swing axis AR. The beam connecting portion 122 is connected to the other end of the mirror connecting portion 121 and extends in the y direction.

  The beam portion 123 includes a first portion 123a and a bent portion 123b. A pair of beam portions 123 are provided so as to be line symmetric with respect to the swing axis AR. One end of the first portion 123a is connected to both ends of the beam connecting portion 122, respectively. The first portion 123a extends along the swing axis AR in a direction away from the mirror unit 110. One end of the bent portion 123b is connected to the other end of the first portion 123a. The bent portion 123b bends in a direction away from the swing axis AR and in a direction along the swing axis AR on a plane including the swing axis AR. The other end of the bent portion 123b is connected to the protruding portion 140a of the fixed portion 140.

  The bent portion 123b is a portion that extends in a direction away from the swing axis AR while the beam is folded back in a direction along the swing axis AR. The bent portion 123b includes a second portion 123b-1 and a third portion 123b-2. One end of the second portion 123b-1 is connected to the other end of the first portion 123a. The second portion 123b-1 extends in a direction away from the swing axis AR. Specifically, the second portion 123b-1 extends along the y direction so as to be separated from the swing axis AR. One end of the third portion 123b-2 is connected to the other end of the second portion 123b-1. The third portion 123b-2 extends along the swing axis AR in a direction approaching the mirror unit 110. The other end of the third portion 123b-2 is connected to the protruding portion 140a of the fixed portion 140.

  The fixed portion 140 is arranged in a square ring around the mirror portion 110 and the pair of support beams 120. In other words, the fixing portion 140 includes a pair of strip portions parallel to the y direction and a pair of strip portions parallel to the x direction. The fixing portion 140 has four projecting portions 140a for fixing the third portion 123b-2. The protruding portion 140 a protrudes from the vicinity of the pair of belt-shaped mirror portions 110 parallel to the y direction of the fixed portion 140 in a direction approaching the mirror portion 110. The fixed portion 140 serves as a fixed end when the mirror portion 110 and the support beam 120 are swung. That is, as long as it has a function of functioning as a fixed end, the fixed portion 140 may have any shape.

  The piezoelectric driving unit 130 swings and drives the mirror unit 110 and the support beam 120. The piezoelectric drive unit 130 is provided from at least the fixed portion 140a of the fixed portion 140 to the second portion 123b-1 via the third portion 123b-2. More specifically, as indicated by the black dot hatching in FIG. 1, the piezoelectric driving unit 130 is moved from the protruding portion 140a of the fixing unit 140 through the third portion 123b-2 and the second portion 123b-1. It is provided over a part of one part 123a. With this configuration, the power generated by the piezoelectric drive unit 130 can be efficiently transmitted to the mirror unit 110, and a large amount of displacement of the mirror unit 110 can be obtained. The piezoelectric drive 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 an alternating 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 driving unit 130 is fixed from the protruding portion 140a of the fixing unit 140 to a part of the first portion 123a, the expansion and contraction of the piezoelectric element in the x direction is in the thickness direction of the optical scanner 100 of the beam portion 123. It is converted into a bending deformation. 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 resist film for masking is formed on portions corresponding to the mirror portion 110, the support beam 120, and the fixing portion 140. Thereafter, the silicon substrate is etched. The portions where the resist film is formed on the silicon base material are formed as the mirror portion 110, the support beam 120, and the 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 of platinum (Pt) or gold (Au) from the fixing part 140 to a part of the first part 123a via the third part 123b-2 and the second part 123b-1. Etc. are deposited at a thickness of 0.2 μm to 0.6 μm. 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 with a thickness of 1 μm to 3 μm on the upper surface of the lower electrode. 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. In this embodiment, lead zirconate titanate (PZT) is used as the piezoelectric element.

  Finally, the upper electrode is formed on the piezoelectric element. Specifically, the upper electrode is formed by depositing platinum (Pt), gold (Au), or the like with a thickness of 0.2 μm to 0.6 μm on the upper surface of the piezoelectric element. For this deposition, a film forming method such as sputtering or vapor deposition is used as in the case of the lower electrode.

[Relationship between number of turns and optical deflection angle]
In the present embodiment, a large amount of displacement of the mirror portion 110 is obtained by providing the bent portion 123b. Here, the number of folding of the beam in the bent portion 123b is changed, and the relationship between the number of folding and the amount of displacement of the mirror is examined by simulation.

  FIG. 2 is a plan view of the periphery of the support beam 120 of the optical scanner 100 when the number of turns at the bent portion 123b is changed. The piezoelectric driving unit 130 is provided over the entire surface of the beam portion 123 existing on the positive side in the y direction. For simplification, the fixing part 140 is omitted in FIG.

  FIG. 2A is a plan view of the periphery of the support beam 120 when the bent portion 123b is folded once. In this case, the bent portion 123b corresponds to a state including the second portion 123b-1 and the third portion 123b-2.

  FIG. 2B is a plan view of the periphery of the support beam 120 when the bent portion 123b is folded twice. In this case, the bent portion 123b extends from the first portion 123a in a direction away from the swing axis AR, further extends along the swing axis AR so as to approach the mirror portion 110, and further from the swing axis AR. It is in a state where it extends in the direction of separating, further extends along the swing axis AR so as to be separated from the mirror unit 110, and then connected to the fixing unit 140.

  FIG. 2C is a plan view of the periphery of the support beam 120 when the bent portion 123b is folded three times. In this case, the bent portion 123b extends from the first portion 123a in a direction away from the swing axis AR, further extends along the swing axis AR so as to approach the mirror portion 110, and further from the swing axis AR. Extends in the direction of separating, further extends along the swing axis AR so as to be separated from the mirror portion 110, further extends in a direction away from the swing axis AR, and further swings toward the mirror portion 110. It is in a state of extending along the AR and then connecting to the fixing part 140.

  FIG. 2D is a plan view of the periphery of the support beam 120 when the bent portion 123b is folded back 0 times. This corresponds to a state where the bent portion 123b does not exist. The optical scanner 100 shown in FIG. 2D is not an embodiment of the present invention, but is shown for comparison with the case of FIGS. 2A to 2C in which the bent portion 123b exists.

  FIG. 3A is a diagram showing a result of examining a change in the optical deflection angle by simulation when the number of turns at the bent portion 123b is changed. FIG. 3B is a graph showing the result of FIG. In FIG. 3B, the horizontal axis corresponds to the number of mirror folding times, and the vertical axis corresponds to the optical deflection angle. The optical deflection angle is an angle at which light incident on the mirror unit 110 is scanned when the mirror unit 110 is swung. That is, the optical deflection angle has a one-to-one correspondence with the amount of displacement of the mirror portion. In all cases, an AC voltage of 40 V is applied to the piezoelectric drive unit 130.

  In FIG. 3, the optical deflection angle is larger in the case where the bent portion 123b exists than in the case where there is no folding (FIG. 2D). That is, it is confirmed that a large amount of displacement of the mirror portion 110 can be obtained by providing the bent portion 123b. Furthermore, the optical deflection angle becomes maximum when the number of times of folding is one. When the number of times of folding is two or more, the optical deflection angle decreases as the number of times of folding increases. In other words, the number of times of folding of the bent portion 123b is most effective.

[Relationship between the length of the bent portion 123b and the optical deflection angle]
As described above, it is most effective to turn the bent portion 123b once. Here, the relationship between the length of the bent portion 123b in the x direction and the optical deflection angle is examined when the number of turns of the bent portion 123b is one. FIG. 4 is an enlarged plan view around the support beam 120 of the optical scanner 100. The length of the first portion 123a in the x direction is a length L1. The length of the third portion 123b-2 in the x direction is a length L2. The piezoelectric drive unit 130 is provided over the entire surface of the beam portion 123. For simplification, the fixing part 140 is omitted in FIG. Hereinafter, the relationship between the folding ratio L2 / L1, which is a value obtained by dividing the length L2 by the length L1, and the optical deflection angle is shown.

  FIG. 5A is a diagram showing a result of examining a change in the optical deflection angle by simulation when the folding ratio L2 / L1 is changed. For comparison, a result in the case where the folding ratio L2 / L1 is 0% is also shown. When the folding ratio L2 / L1 is 0%, as in the case shown in FIG. 2D, this corresponds to a state in which the bent portion 123b does not exist. FIG. 5B is a graph showing the result of FIG. In FIG. 5B, the horizontal axis corresponds to the folding ratio L2 / L1, and the vertical axis corresponds to the optical deflection angle. In all cases, an AC voltage of 40 V is applied to the piezoelectric drive unit 130.

  In FIG. 5, the optical deflection angle is minimum in the state where the bent portion 123b does not exist (L2 / L1 = 0%). When the folding ratio L2 / L1 is 25% to 50%, the optical deflection angle increases as the folding ratio L2 / L1 increases. When the folding ratio L2 / L1 is 75%, the optical deflection angle is smaller than when the folding ratio L2 / L1 is 50%. In the region where the folding ratio L2 / L1 is 100% or more, the optical deflection angle increases again as the folding ratio L2 / L1 increases. The value of the optical deflection angle in the region where the folding ratio L2 / L1 is 100% or more is larger than the value of the optical deflection angle in the region where the folding ratio L2 / L1 is 100% or less. Therefore, in the case where the folding ratio L2 / L1 is 100% or more, in other words, the length of the third portion 123b-2 in the x direction is longer than the length of the first portion 123a in the x direction. In this case, a large optical deflection angle, that is, a large amount of displacement of the mirror portion can be obtained.

<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 optical scanner 100 has a shape in which the mirror unit 110 is supported by a pair of support beams 120 as shown in FIG. However, for example, the mirror unit 110 may be cantilevered by the single support beam 120. In short, as long as the beam portion 123 has a bent portion 123b, it can be either cantilevered or cantilevered.

  In the above-described embodiment, as shown in FIG. 1, in the optical scanner 100, the mirror connecting portion 121 extending from the mirror portion 110 is connected to the beam connecting portion 122, and the beam connecting portion 122 has a pair of beam portions 123. Connected. However, the mirror connecting part 121 and the beam connecting part 122 may be omitted. FIG. 6 is a plan view of an optical scanner 200 that is a modification of the first embodiment. The same configuration as that of the optical scanner 100 is assigned the same drawing number and the description thereof is omitted. A pair of support beams 220 are provided so as to be line symmetric with respect to a virtual axis parallel to the y direction passing through the center position of the mirror part 110. The support beam 220 does not have a mirror connection portion and a beam connection portion, and has only a pair of beam portions 223. The beam portion 223 includes a first portion 223a and a bent portion 223b. A pair of beam portions 223 are provided so as to be line symmetric with respect to the swing axis AR. One end of the first portion 223 a is connected to the mirror unit 110. The first portion 223a extends along the swing axis AR in a direction away from the mirror unit 110. One end of the bent portion 223b is connected to the other end of the first portion 223a. The bent portion 223b bends in a direction away from the swing axis AR and in a direction along the swing axis AR on a plane including the swing axis AR. The other end of the bent portion 223b is connected to the protruding portion 140a of the fixed portion 140. The bent portion 223b includes a second portion 223b-1 and a third portion 223b-2. One end of the second portion 223b-1 is connected to the other end of the first portion 223a. The second portion 223b-1 extends in a direction away from the swing axis AR. Specifically, the second portion 223b-1 extends along the y direction so as to be separated from the swing axis AR. One end of the third portion 223b-2 is connected to the other end of the second portion 223b-1. The third portion 223b-2 extends in a direction approaching the mirror unit 110 along the swing axis AR. The other end of the third portion 223b-2 is connected to the protruding portion 140a of the fixing portion 140. This optical scanner 200 is naturally included in the intended scope of the present invention.

100, 200, 500 Optical scanner 110, 511 Mirror part 120, 220 Support beam 121 Mirror connection part 122 Beam connection part 123, 223 Beam part 123a, 223a First part 123b, 223b Bending part 123b-1, 223b-1 Second Portions 123b-2 and 223b-2 Third portions 130 and 530 Piezoelectric driving portions 140 and 514 Fixed portion 140a Protruding portion 510 Base 512 First elastic beam 513 Second elastic beam 520 Base 521 Base joint AR Swing axis L1 First Length L2 in the x direction of the portion 123a Length in the x direction of the bent portion 123b

Claims (5)

A mirror that is swung around a swing axis and scans incident light in a predetermined direction;
A support beam extending from the mirror portion;
A fixing part to which the support beam is coupled;
A piezoelectric drive unit that is provided over a part of the support beam from the fixed unit, and that swings and drives the mirror unit and the support beam;
The support beam is
It is arranged so as to be symmetric with respect to the swing axis, and has a pair of beam parts connected to the fixed part,
The pair of beam portions is
A first portion extending along the swing axis in a direction away from the mirror portion;
A bent portion connected to the first portion, bent in a direction away from the swing axis and in a direction along the swing axis on a plane including the swing axis, and connected to the fixed portion;
An optical scanner characterized by that. The bent portion is
A second portion having one end connected to the first portion and extending away from the swing axis;
One end of the second portion is connected to the other end of the second portion, the third portion extends along the swing axis in a direction approaching the mirror portion, and the other end is connected to the fixed portion.
The optical scanner according to claim 1. The third part is
The length of the third portion in the direction along the swing axis is formed to be longer than the length of the first portion in the direction along the swing axis.
The optical scanner according to claim 2. The piezoelectric driving unit is provided from at least the fixed part to the second part via the third part,
The optical scanner according to claim 2, wherein the optical scanner is an optical scanner. The support beam further includes
One end of the mirror is connected to the mirror portion, and a mirror connecting portion extending in a direction along the swing axis,
A beam connecting portion connected to the other end of the mirror connecting portion and extending in a direction perpendicular to the swing axis on a plane including the swing axis;
The first part is
One end thereof is connected to each of both ends of the beam connecting portion,
The other end is connected to one end of the second part.
The optical scanner according to claim 2, wherein the optical scanner is an optical scanner.