JP2011064964A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical scanner equipped with a movable part capable of preventing the transmission of vibration to ambient members as much as possible. <P>SOLUTION: A square pyramid recessed part 203 is formed by an anisotropic etching. A square grill masking is applied on a wafer, and the anisotropic etching is performed by using KOH or tetramethyl ammonium hydroxide. The masked portion form a summit in the cross section of an isosceles trapezium in first and second projections 240, 250. The anisotropic etching corrodes the wafer in a diagonal direction from the masked portion. The inclined face of the isosceles trapezium recessed part 203 is formed by the corrosion. The angle between the long side of the isosceles trapezium and the inclined face of the square pyramid is approximately 54.7 degrees. In the square grill masking, the distance between the grills is so decided that the distance between a light reflection face 201 and a back face 202 becomes approximately 2 to 5 μm. Thus, a plurality of square pyramid recessed parts 203 line up as a grill on the back face 202. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical scanner that is rotated by an electrostatic force generated between electrodes and reflects light in a desired direction.

  There is known an optical scanner that includes a movable portion and a fixed portion, and includes comb-like electrodes that alternately protrude from the movable portion and the fixed portion. When a voltage is applied to the electrodes, a potential difference is generated between the movable portion electrode and the fixed portion electrode, and the potential difference generates an electrostatic force between the electrodes. Thereby, the movable part is rotated with respect to the fixed part. Various means for reducing the weight of the movable part in order to adjust the characteristics of the optical scanner are known (Patent Document 1).

JP 2006-18250 A

  A movable support part is further provided between the movable part and the fixed part, the movable support part supports the movable part, and the fixed part supports the movable support part. Accordingly, when the movable part is rotatable about two axes with respect to the fixed part, the rotation of the movable part may be transmitted to peripheral members such as the movable support part simply by reducing the weight of the movable part. At this time, the peripheral member vibrates so as to wave with the rotation of the movable portion, and the driving efficiency of the optical scanner decreases.

  The present invention has been made in view of this problem, and an object of the present invention is to obtain an optical scanner including a movable part capable of preventing vibrations from being transmitted to peripheral members as much as possible.

  An optical scanner according to a first invention of the present application has a light reflecting surface and a back surface which are flat surfaces, a movable portion that rotates around a first rotation axis, and protrudes from the back surface with a certain length, and the longitudinal direction is the back surface. A first protrusion that extends on a straight line parallel to the first protrusion, and a second protrusion that protrudes from the back surface with a certain length and that extends in a straight line whose longitudinal direction is perpendicular to the first protrusion and parallel to the back surface. The first protrusion has an isosceles trapezoidal cross section in a plane perpendicular to the longitudinal direction and the back surface of the first protrusion, and the second protrusion corresponds to the longitudinal direction and the back surface of the second protrusion. A cross section in a plane perpendicular to each other forms an isosceles trapezoid, a plurality of first protrusions protrude from the back surface at equal intervals and in parallel, and a plurality of second protrusions protrude from the back surface at equal intervals and in parallel. Features.

  It is preferable that the distance between the first protrusions and the distance between the second protrusions are the same length.

  An optical scanner according to a second invention of the present application has a light reflecting surface and a back surface that are flat surfaces, and includes a movable portion that rotates around a first rotation axis, and the movable portion is masked in a square lattice pattern on the back surface. And a plurality of concave portions having a regular quadrangular pyramid shape formed by anisotropic etching, and the plurality of concave portions are arranged on the back surface in a lattice shape.

  A movable support portion provided around the movable portion, a first support portion that supports the movable portion so as to be rotatable around the first rotation axis with respect to the movable support portion, and a periphery of the movable support portion And a second support portion that supports the movable support portion with respect to the fixed portion so as to be rotatable around a second rotation axis that is not parallel to the first rotation axis. It is preferable to provide.

  The movable portion is a plate-shaped octagon, and has two side surfaces perpendicular to the first rotation axis and two side surfaces parallel to the first rotation axis. A plurality of first comb-teeth electrodes projecting at right angles from two side surfaces parallel to the rotation axis of the first, and the first support portion has two side surfaces perpendicular to the first rotation axis It is preferable that the movable support part has a 2nd comb-tooth electrode which protrudes toward a movable part alternately and in parallel with respect to several 1st comb-tooth electrode.

  The movable support portion is a plate-shaped octagon, and has an octagonal hole portion larger than the movable portion, and the hole portion includes two inner surfaces perpendicular to the first rotation axis, And the second comb electrode protrudes at right angles from the two inner surfaces parallel to the first rotation axis, and the first comb electrode has the first inner surface parallel to the first rotation axis. The support part is connected to the center of two inner side surfaces perpendicular to the first rotation axis, and the outer side surface of the movable support part includes two outer side surfaces perpendicular to the first rotation axis; Two outer surfaces parallel to the first rotation axis, and the second support portion projects perpendicularly from the center of the two outer surfaces parallel to the first rotation axis, and The third comb electrode protrudes perpendicularly to the second rotation axis from the two support portions, and the fixing portion is arranged in parallel and alternately with the plurality of third comb electrodes. 4th projecting toward the support It is preferred to have teeth electrodes.

  According to the present invention, an optical scanner including a movable part capable of preventing vibrations from being transmitted to peripheral members as much as possible is obtained.

It is a rear perspective view of an optical scanner. It is a partial front view of a movable part. It is a partial cross section figure of the movable part in the III-III line of FIG. It is a partially expanded sectional view of the back surface of a movable part. It is the graph which showed the relationship between the distance from a movable part center, and the displacement of a movable support part.

  Hereinafter, an optical scanner 100 according to the present invention will be described with reference to the drawings.

  First, the configuration of the optical scanner 100 in a stationary state will be described with reference to FIGS. In addition, the partial cross-sectional shape of the movable part in the IV-IV line of FIG. 2 is the same as the shape shown in FIG.

  The optical scanner 100 includes a movable part 200 that is an octagonal plate and a gimbal part 300 provided so as to surround the periphery of the movable part 200.

  The movable part 200 is a regular octagonal prism having a thickness, and the thickness is extremely smaller than the length of one side of the regular octagon. The top surface of the regular octagonal prism forms a light reflecting surface 201 that is a mirror surface, and the bottom surface forms a back surface 202. The length between the light reflecting surface 201 and the back surface 202 is about 2 to 5 μm. A plurality of regular quadrangular pyramid-shaped recesses 203 are formed on the back surface 202.

  The gimbal part 300 is a square tube having the same thickness as the movable part 200. The square tube has an opening 310 that penetrates in the thickness direction. The outer edge 301 and the opening 310 of the rectangular tube form an octagon. The movable part 200 is placed in the opening 310.

  The movable unit 200 is connected to the opening 310 by the first X-direction support shaft 211 and the second X-direction support shaft 212. The first X-direction support shaft 211 and the second X-direction support shaft 212 are provided on the first rotation axis L, and are connected to the center of the side surface of the movable unit 200 and the center of the side surface of the opening 310. Is done. A side surface of the movable portion and the opening 310 to which the first X-direction support shaft 211 is connected and a side surface of the movable portion and the opening 310 to which the second X-direction support shaft 212 is connected are parallel to each other. The movable portion to which the first and second X-direction support shafts 211 and 212 are connected and the side surface of the opening 310 are perpendicular to the first rotation axis L.

  From the side surface of the movable part 200 that is parallel to the first rotation axis L, the first and second movable part side comb electrodes 221 and 222 protrude at right angles. The 1st and 2nd movable part side comb-tooth electrodes 221 and 222 consist of a plurality of rectangular parallelepipeds, and are arranged at regular intervals.

  The first and second gimbal side comb electrodes 321 and 322 protrude from the side surface of the opening 310 parallel to the first rotation axis L at a right angle. The first and second gimbal side comb-teeth electrodes 321 and 322 are composed of a plurality of rectangular parallelepipeds, and are spaced apart from each other so as to alternate with the first and second movable part side comb-teeth electrodes 221 and 222. Are lined up.

  The gimbal part 300 is connected to a fixed part (not shown) by the first Y direction support shaft 311 and the second Y direction support shaft 312. The first Y-direction support shaft 311 and the second Y-direction support shaft 312 are provided on a second rotation axis M that is perpendicular to the first rotation axis L. The first Y-direction support shaft 311 is connected to the center of one outer surface of the gimbal portion 300, and the second Y-direction support shaft 312 is connected to the center of the other outer surface of the gimbal portion 300. The outer surface to which the first Y-direction support shaft 311 is connected is parallel to the outer surface to which the second Y-direction support shaft 312 is connected and is parallel to the first rotation axis L. The first Y-direction support shaft 311 and the second Y-direction support shaft 312 are connected to the fixed portion via first and second hinge portions 331 and 332 having elasticity.

  In the following, description will be made using right-handed coordinates where the direction in which the first rotation axis L extends is the X axis, the direction in which the second rotation axis M extends is the Y axis, and the thickness direction of the movable part 200 is the Z axis. .

  From the first Y-direction support shaft 311 and the second Y-direction support shaft 312, the first to eighth support shaft-side comb electrodes 321 to 328 protrude perpendicularly to the second rotation axis M. To do. The first to fourth support shaft side comb-teeth electrodes 321 to 328 are composed of a plurality of rectangular parallelepipeds, and are arranged at regular intervals.

  The first to eighth fixed portion side comb-teeth electrodes (not shown) project at right angles from the fixed portion toward the first Y-direction support shaft 311 and the second Y-direction support shaft 312. The first to eighth fixed portion side comb-teeth electrodes are composed of a plurality of rectangular parallelepipeds, and are arranged at regular intervals so as to alternate with the first to eighth support shaft side comb-teeth electrodes 321 to 328. .

  Next, the shape of the back surface 202 will be described.

  First and second protrusions 240 and 250 are provided on the back surface 202. The first and second protrusions 240 and 250 protrude from the back surface 202 with a certain length to form a lattice.

  The first protrusion 240 is a prism having a top surface 241 and a bottom surface that form an isosceles trapezoidal shape. A side surface having a base of an isosceles trapezoid is connected to the back surface 202. The height direction of the prism, that is, the longitudinal direction of the first protrusion 240 is parallel to the back surface and the first rotation axis L. There are a plurality of first protrusions 240 that are equidistant and parallel to each other.

  The second protrusion 250 is a prism having the same shape as the first protrusion 240. The side surface forming the bottom of the isosceles trapezoid is connected to the back surface 202. The height direction of the prism, that is, the longitudinal direction of the second protrusion 250 is parallel to the back surface and the second rotation axis M. That is, the longitudinal direction of the second protrusion 250 intersects with the longitudinal direction of the first protrusion 240 at a right angle. There are a plurality of second protrusions 250 that are equidistant and parallel to each other. In addition, the interval between the first protrusions 240 and the interval between the second protrusions 250 are the same.

  The first and second protrusions 240 and 250 form convex portions arranged in a lattice shape on the back surface 202, and a regular pyramid-shaped concave portion 203 is formed between the first protrusion 240 and the second protrusion 250. Is done.

  The regular quadrangular pyramid-shaped recess 203 is formed by anisotropic etching. A square lattice masking is performed on the wafer, and anisotropic etching, which is one of wet etching, is performed using KOH or tetramethylammonium hydroxide. The masked portion forms the top side in the isosceles trapezoidal cross section of the first and second protrusions 240 and 250. Anisotropic etching corrodes the wafer in an oblique direction from the masked portion. Due to the corrosion, a slope of the concave portion 203 having a regular quadrangular pyramid shape is formed. The angle between the long side of the isosceles trapezoid and the slope of the regular quadrangular pyramid is about 54.7 degrees. In the square lattice masking, the distance between the lattices is determined so that the length between the light reflecting surface 201 and the back surface 202 is about 2 to 5 μm. Accordingly, a plurality of regular quadrangular pyramid-shaped recesses 203 are arranged on the back surface 202 in a lattice pattern.

  On the other hand, although it is conceivable to adopt a method of forming the concave portion 203 by Deep RIE, the concave portion is formed in a rectangular parallelepiped shape by Deep RIE. At this time, since it is difficult to form the bottom of the concave portion smoothly, uniform weight distribution and strength distribution cannot be obtained in the entire movable portion 200. Therefore, individual differences may occur in the resonance frequency of the movable part 200. However, according to this embodiment, since the entire movable part 200 can obtain a uniform weight distribution and intensity distribution as compared with the etching means using Deep RIE, individual differences in the resonance frequency of the movable part 200 can be suppressed.

  Next, the operation of the optical scanner 100 will be described.

  First, the rotation of the movable part 200 will be described.

  When a potential difference is applied between the first and second movable part side comb electrodes 221 and 222 and the first and second gimbal side comb electrodes 321 and 322 by a power supply device (not shown), the first and second Between the two movable part side comb-teeth electrodes 221 and 222 and the first and second gimbal side comb-teeth electrodes 321 and 322, an attractive force, that is, an electrostatic attractive force is generated by electrostatic force. Here, the driving torque T that causes electrostatic attraction between the first and second movable part side comb electrodes 221 and 222 and the first and second gimbal side comb electrodes 321 and 322 is the first torque Further, it increases or decreases according to the potential difference between the second movable part side comb-tooth electrodes 221 and 222 and the first and second gimbal side comb-tooth electrodes 321 and 322, that is, the driving voltage of the optical scanner 100. The drive voltage is adjusted so that the movable part 200 rotates at the resonance frequency fr due to the resonance phenomenon.

  Then, the first and second X-direction support shafts 211 and 212 are twisted by electrostatic attraction, and the first and second movable part side comb-teeth electrodes 221 and 222 become the first and second gimbal side comb-teeth electrodes. It moves in the direction that overlaps 321 and 322. As a result, the movable portion 200 rotates around the first and second X-direction support shafts 211 and 212, that is, around the first rotation shaft. When the movable part 200 rotates, the angle of the light reflecting surface 201 with respect to the gimbal part 300 changes, and the emission direction of the reflected light from the light reflecting surface 201 changes.

The resonance frequency fr of the movable portion 200 that rotates about the first and second X-direction support shafts 211 and 212 is obtained by the following equation.
fr = (1 / 2π) √ (k / I) (1)
Here, k is a torsion spring constant, and I is a moment of inertia. Referring to this equation, it can be seen that the resonance frequency fr is determined by the torsion spring constant k and the moment of inertia I.

On the other hand, the driving torque T of the optical scanner 100 is based on the following equation.
T = kθ (2)
Here, k is a torsion spring constant, and θ is a swing angle of the movable part 200. From this equation, it can be seen that when the driving torque T is constant, the deflection angle θ increases as the torsion spring constant k is decreased. Note that when the driving voltage of the optical scanner 100 is constant, the driving torque T is constant.

  From Equation (1), when the resonance frequency fr is to be kept constant, the torsion spring constant k can be reduced by reducing the moment of inertia I. If the torsion spring constant k can be reduced, the deflection angle θ can be increased from the equation (2).

Here, the inertia moment I of the movable part 200 is generally obtained by the following equation.
I = (a2 + b2) · M / 12 (3)
Here, M is the mass of the movable part 200, a is the length of the long side direction of the movable part 200 with respect to the direction perpendicular to the rotational axis of the movable part 200, and b is the movable part 200 with respect to the direction perpendicular to the rotational axis. The length in the short side direction. That is, the moment of inertia I is represented by the product of the distance from the rotation axis and the mass. Therefore, if the mass of the rotating part can be reduced, the inertia moment I can be reduced.

  In the present embodiment, the mass of the movable portion 200 is smaller than when the concave portion 203 is not formed on the back surface 202 of the movable portion 200. Therefore, the inertia moment I of the movable part 200 is reduced, and the resonance frequency fr and the swing angle θ can be increased as compared with the conventional case under the condition where the drive voltage is equal. That is, the resonance frequency fr of the movable portion 200 is 5.74 kHz when the concave portion 203 is not formed on the back surface 202, but according to the present embodiment, it is 6.53 kHz, and the resonance frequency can be increased by about 1 kHz. .

  Next, rotation of the gimbal unit 300 will be described.

  When a potential difference is applied between the first to eighth support shaft side comb electrodes 321 to 328 and the first to eighth fixed portion side comb electrodes by a power supply device (not shown), the first to eighth An attractive force, that is, an electrostatic attractive force that is attracted to each other by an electrostatic force is generated between the support shaft side comb-tooth electrodes 321 to 328 and the first to eighth fixed portion side comb-tooth electrodes. Due to the electrostatic attractive force, the gimbal portion 300 rotates with respect to the fixed portion. Here, the gimbal portion 300 is configured so that only the potential difference generated between the first to eighth support shaft side comb electrodes 321 to 328 and the first to eighth fixed portion side comb electrodes without using the resonance phenomenon. , That is, DC driven.

  When the movable part 200 rotates at a high frequency, vibration generated by the inertial mass of the movable part 200 may be transmitted to the gimbal part 300. Thereby, the gimbal part 300 undulates, that is, the gimbal part 300 vibrates in the Z-axis direction. Since this vibration is due to the inertial mass of the movable part 200, it can be reduced if the inertial mass of the movable part 200 decreases.

  The amount of vibration of the gimbal portion 300 when the concave portion 203 is formed on the back surface 202 and when the concave portion 203 is not formed, that is, the displacement in the Z-axis positive direction will be described with reference to FIG. FIG. 5 shows the displacement of the gimbal part 300 in the positive Z-axis direction when the movable part 200 is rotated with the maximum displacement in the Z-axis direction being 1 μm.

  In FIG. 5, the position away from the center of the light reflecting surface 201 by 750 μm in the positive Y-axis direction is the joining position of the movable part 200 and the second movable part side comb-teeth electrode 222. Further, the position 1600 μm away from the center of the light reflecting surface 201 in the Y-axis positive direction is a joint position between the gimbal portion 300 and the first Y-direction support shaft 311. The position 2300 μm away from the center of the light reflecting surface 201 in the Y-axis positive direction is the forefront of the first Y-direction support shaft 311, that is, the second Y-direction support shaft 312 and the second hinge portion 332. It is a junction.

  The displacement of the second Y-direction support shaft 312 with respect to the positive Z-axis direction is 0.065 μm when the concave portion 203 is not formed on the back surface 202 at the joint position with the gimbal portion 300. On the other hand, according to this embodiment, the displacement is 0.047 μm.

  The displacement of the second Y-direction support shaft 312 with respect to the positive direction of the Z-axis is 0.050 μm when the concave portion 203 is not formed on the back surface 202 at the joint position with the second hinge portion 332. On the other hand, according to the present embodiment, the displacement is 0.028 μm.

  That is, when the concave portion 203 is formed on the back surface 202, the vibration amount in the peripheral member of the movable portion 200, that is, the displacement in the Z-axis positive direction is reduced as compared with the case where the concave portion 203 is not formed.

  According to the present embodiment, it is possible to prevent the vibration of the movable part 200 from being transmitted to peripheral members such as the gimbal part 300 as much as possible, and thereby light can be accurately reflected. Further, since the first and second protrusions 240 and 250 are arranged in a lattice shape, the strength of the movable part 200 can be sufficiently ensured. Thereby, distortion of the rotation part by rotation can be suppressed to the minimum, and light can be accurately reflected in a desired direction.

  Although the optical scanner 100 having two rotation axes has been described, the rotation axis is not limited to two axes.

  Moreover, the chemical | medical agent used for anisotropic etching is not limited to KOH or tetramethylammonium hydroxide.

DESCRIPTION OF SYMBOLS 100 Optical scanner 200 Movable part 201 Light reflection surface 202 Back surface 203 Concave part 211 1st X direction support shaft 212 2nd X direction support shaft 221 2nd movable part side comb-tooth electrode 240 1st protrusion 250 2nd protrusion 300 Gimbal part 310 Opening part 311 1st Y direction support shaft 312 2nd Y direction support axis L 1st rotation axis M 2nd rotation axis

Claims (6)

A movable portion that has a light reflecting surface and a back surface that are flat surfaces and rotates about a first rotation axis;
A first protrusion that protrudes from the back surface with a certain length, and whose longitudinal direction extends on a straight line parallel to the back surface;
A second protrusion that protrudes from the back surface with a certain length and that extends in a straight line whose longitudinal direction is perpendicular to the first protrusion and parallel to the back surface;
The first protrusion has an isosceles trapezoidal cross section in a plane perpendicular to the longitudinal direction and the back surface of the first protrusion,
The second protrusion has an isosceles trapezoidal cross section in a plane perpendicular to the longitudinal direction and the back surface of the second protrusion.
A plurality of the first protrusions protrude from the back surface at equal intervals and in parallel,
An optical scanner in which a plurality of the second protrusions protrude from the back surface at equal intervals and in parallel.   The optical scanner according to claim 1, wherein an interval between the first protrusions and an interval between the second protrusions are the same length. It has a light reflecting surface and a back surface that are flat surfaces, and includes a movable portion that rotates around a first rotation axis,
The movable part has a plurality of square quadrangular pyramid recesses formed by anisotropic etching after providing a square lattice masking on the back surface,
The plurality of recesses are optical scanners arranged on the back surface in a grid pattern. A movable support provided around the movable part;
A first support portion that supports the movable portion so as to be rotatable around the first rotation axis with respect to the movable support portion;
A fixed portion provided around the movable support portion;
2. A second support portion that supports the movable support portion with respect to the fixed portion so as to be rotatable around a second rotation shaft that is not parallel to the first rotation shaft. Or the optical scanner of 3. The movable part is a plate-like octagon, and has two side surfaces perpendicular to the first rotation axis and two side surfaces parallel to the first rotation axis. A plurality of first comb electrodes protruding perpendicularly from two side surfaces parallel to the first rotation axis,
The first support portion is connected to the center of two side surfaces perpendicular to the first rotation axis,
5. The optical scanner according to claim 4, wherein the movable support portion includes second comb-shaped electrodes that protrude toward the movable portion alternately and in parallel with the plurality of first comb-shaped electrodes. The movable support part is a plate-shaped octagon, and has an octagonal hole larger than the movable part,
The hole has two inner surfaces perpendicular to the first rotation axis, and two inner surfaces parallel to the first rotation axis, and the second comb teeth The electrode protrudes perpendicularly from two inner surfaces parallel to the first rotation axis,
The first support portion is connected to the center of two inner surfaces perpendicular to the first rotation axis,
The outer surface of the movable support portion has two outer surfaces perpendicular to the first rotation axis, and two outer surfaces parallel to the first rotation axis,
The second support part protrudes at a right angle from the center of two outer surfaces parallel to the first rotation axis, and is perpendicular to the second rotation axis from the second support part. A protruding third comb electrode;
The optical scanner according to claim 5, wherein the fixing portion includes fourth comb electrodes protruding toward the second support portion alternately and in parallel with the plurality of third comb electrodes.

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