JP2010002637A - Optical scanning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanning apparatus which utilizes plate wave oscillations, which can eliminate the discrepancy in the oscillation characteristics due to manufacturing errors. <P>SOLUTION: The optical scanning apparatus includes: a substrate; a driving means exciting plate wave oscillation in the substrate; a torsion spring member connected to the substrate; a swinging member connected to the torsion spring member and swinging about the torsion spring member as a swinging center axis by the torsion oscillation of the torsion spring member excited by the plate wave oscillation of the substrate; and a light-reflecting surface formed on the swinging member, wherein at least one of the substrate and the swinging member has a protruding piece for trimming. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical scanning device.

  In recent years, devices using MEMS (Micro Electro Mechanical System) technology have been put into practical use in a wide range of fields including displays and printers. Devices that apply MEMS technology are expected to meet the demand for higher functionality such as downsizing and cost reduction of electronic equipment. The MEMS technology has been developed as a technology for integrating micro structures such as sensors and actuators together with electric circuits on a substrate by a semiconductor process. Various materials that can be formed in a semiconductor device manufacturing process are generated on the substrate, and these are generated. This technology enables high-precision processing.

  Along with the development of this MEMS technology, various devices are being improved in function and size. For example, in an optical scanning device that performs optical scanning, an image display device such as a laser beam printer or a head-mounted display, an optical input device such as a bar code reader, etc., has been improved in function and size, and more There is a demand for further miniaturization. As an optical scanning device that satisfies these requirements, for example, an optical scanning device that scans light with a configuration in which a micromirror is torsionally vibrated using a micromachining technique has been proposed. Such a device having an optical function of transmitting, reflecting, or absorbing light is called an optical MEMS. Among optical MEMS, for example, a MEMS mirror manufactured as a reflection mirror having a drawing function such as a scanner is called a micromirror device.

  As an apparatus using such a micromirror device, for example, there is an optical scanning apparatus as disclosed in Patent Document 1. The optical scanning device disclosed in Patent Document 1 excites plate wave vibration on a substrate by a driving source such as a piezoelectric body and swings a mirror unit connected to the substrate by a torsion spring using the plate wave vibration. Is. If these resonances are utilized, a large deflection angle can be obtained even with a relatively small driving force, and high-speed and high-displacement driving is possible with a small amount of driving energy. In addition, the overall configuration is simple, and the substrate, the torsion spring, and the mirror portion can be integrally formed from a thin plate, which is advantageous in terms of cost.

JP 2006-293116 A

  However, when such an optical scanning device is mass-produced, manufacturing variations may occur in each optical scanning device. For this reason, the vibration characteristics may be different between the optical scanning devices, and if the driving conditions are made common, the intended operation may not be obtained. For example, when driving at a resonance frequency, the resonance frequency differs between optical scanning devices due to manufacturing errors, and if the drive conditions are common, resonance may not occur.

  An object of the present invention is to provide an optical scanning device using plate wave vibration that can eliminate the difference in vibration characteristics due to manufacturing errors.

  According to the present invention, the substrate, the driving means for exciting the plate wave vibration to the substrate, the torsion spring member connected to the substrate, the torsion spring member, and excited by the plate wave vibration of the substrate. A swing member that swings about the torsion spring member as a swing center axis by a torsional vibration of the torsion spring member, and a light reflecting surface formed on the swing member, the substrate or the swing At least one of the members has a projecting piece for trimming, and an optical scanning device is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the optical scanning device using a plate wave vibration which can eliminate the difference in the vibration characteristic by a manufacturing error can be provided.

<First Embodiment>
FIG. 1A is a perspective view of the optical scanning device 100 according to the first embodiment of the present invention, and FIG. The optical scanning device 100 includes a substrate 10, a swing member 20, a torsion spring member 30, a drive element 40, and a support member 50. One end of the substrate 10 in the longitudinal direction is a free end, and the other end is a fixed end fixed to the support member 50 and is cantilevered by the support member 50. A pair of arm portions 11 are formed on the free end side of the substrate 10 so as to be separated in a direction orthogonal to the longitudinal direction of the substrate 10. The arm part 11 is provided with a protruding piece part 11a. Details thereof will be described later.

  The oscillating member 20 has a rectangular outer shape in plan view, and a light reflecting surface 21 is formed on the upper surface thereof to constitute a mirror portion. The outer shape of the swing member 20 may be, for example, a circle or an ellipse. The light reflecting surface 21 may be formed by applying a mirror finish to the surface of the swing member 20 or may be formed by attaching a light reflecting material to the swing member 20. An example of the light reflecting material is a single crystal Si wafer piece. In addition, when the rocking | swiveling member 20 is comprised from a single crystal Si wafer, the process which forms such a mirror surface is unnecessary. The light reflecting surface 21 can be formed on these members by, for example, forming a reflecting film by a vacuum deposition method. The swing member 20 is provided with a protruding piece 20a. Details will be described later.

  One torsion spring member 30 is provided on each side of the rocking member 20 and extends in a direction perpendicular to the longitudinal direction of the substrate 10. One end of the torsion spring member 30 is connected to the arm portion 11 of the substrate 10 and the other end is connected to the swing member 20 to form a beam connecting the swing member 20 and the arm portion 11.

  In the case of this embodiment, the board | substrate 10, the rocking | swiveling member 20, and the torsion spring member 30 are integrally formed from one board | plate material. Examples of the plate material include a metal thin plate, for example, a stainless thin plate (SUS304) having a thickness of several tens to several hundreds μm. SUS304 is one of the preferred materials because of its excellent mechanical rigidity and relatively high yield stress. In addition, when a metal thin plate is used, a member including the substrate 10, the swing member 20, and the torsion spring member 30 as a single unit is easily obtained by punching the metal thin plate into a square shape by pressing and punching the openings 12 and 12. Can be formed. At this time, if a mirror surface is formed on the surface of the thin metal plate to form a reflection film, the light reflection surface 21 can be formed in advance. The substrate 10, the rocking member 20, and the torsion spring member 30 can also be integrally formed by a so-called photolithography process using a Si wafer and performing fine processing by resist coating and etching, but it is more preferable to press a metal thin plate. It is simple.

  The drive element 40 is provided on the substrate 10 and excites plate wave vibration in the substrate 10 by the vibration. In the present embodiment, the drive element 40 is a piezoelectric body. As the piezoelectric body, a piezoelectric film may be directly formed on the substrate 10, or a separate piezoelectric body may be bonded and fixed on the substrate 10. The drive element 40 can employ a magnetic material in addition to the piezoelectric material.

  Next, the swinging operation of the swinging member 20 will be described with reference to FIG. When an AC voltage is applied to the drive element 40 that is a piezoelectric body, the drive element 40 repeatedly contracts, thereby exciting plate wave vibration in the substrate 10. The plate wave vibration of the substrate 10 can apply a force that gives a rotational moment to the swinging member 20 connected to the torsion spring member 30, and the torsion spring member 30 is elastically twisted. As a result, torsional vibration is excited in the torsion spring member 30, and the swing member 20 swings about the torsion spring member 30 as the swing center axis. If the resonance of these systems is used, a large swing angle of the swinging member 20 can be obtained even with a relatively small driving force, and high-speed and high-displacement driving can be performed with less power.

  Thus, by projecting laser light from a light source (not shown) onto the light reflecting surface 21 and reflecting it onto the scanning object, scanning of the laser light on the scanning object can be performed.

Next, vibration characteristics of the optical scanning device 100 will be described. The vibration characteristics of the substrate 10, the swing member 20, and the torsion spring member 30 are greatly affected by their shapes. For example, if the inertia moment of the swing member 20 is I and the spring constant of the torsion spring member 30 is k, the resonance frequency f of the vibration model composed of the swing member 20 and the torsion spring member 30 is
f = 2π√ (k / I)
It is represented by The resonance frequency greatly depends on the moment of inertia I of the oscillating member 20 and the spring constant k of the torsion spring member 30, and these greatly depend not only on the physical properties of the member but also on the shape.

  On the other hand, when the optical scanning device 100 is mass-produced, there are manufacturing errors in the shapes of the substrate 10, the swing member 20, and the torsion spring member 30. For this reason, vibration characteristics may differ between the optical scanning devices 100, and if the driving conditions are made common, the intended operation may not be obtained. For example, when driving at the resonance frequency, the resonance frequency differs between the optical scanning devices 100 due to manufacturing errors, and if the drive conditions are common, resonance may not occur.

  In order to eliminate such a difference in vibration characteristics due to manufacturing errors, in this embodiment, projecting pieces 11a and 20a for trimming are provided. The manufacturing error is calibrated by trimming the protruding pieces 11a and 20a. The protruding pieces 11 a and 20 a are formed integrally with the substrate 10 and the swing member 20. In the present embodiment, the protruding piece portions are provided on both the substrate 10 and the swing member 20, but either one may be provided.

  In the case of this embodiment, the protruding piece portion 11 a is provided at the free end of the substrate 10 and is formed so as to protrude from the tip of the arm portion 11. The protruding piece 20 a is provided so as to protrude from both ends in the longitudinal direction of the swing member 20, which is farthest from the torsion spring member 30. The light reflecting surface 20a is not formed on the protruding piece 20a. This prevents the light reflecting surface 20a from being damaged when the protruding piece 20a is trimmed.

  The protruding pieces 11a and 20a are trimmed by, for example, being locally broken or evaporated by a laser. FIG. 1B is a perspective view of the optical scanning device 100 after trimming, and the projecting pieces 11a ′ and 20a ′ are trimmed. Moreover, when performing such trimming, it is preferable to process each protrusion piece part 20a equally as much as possible so that the balance of rocking | fluctuation, such as rotation, may not be lost after trimming. The same applies to each protruding piece 11a.

  Such trimming can be performed for the purpose of adjusting the resonance frequency of the optical scanning device 100 or the like. That is, the resonance frequency may be different for each optical scanning device 100 due to a manufacturing error. Therefore, the resonance frequency is made uniform so that the drive conditions of the drive element 40 are made as common as possible. For the purpose of adjusting the resonance frequency, it is desirable to provide the protruding piece portion 11a on the free end side and the protruding piece portion 20a at a position farthest from the torsion spring member 30 as in this embodiment. This is because the resonance frequency can be easily adjusted with a small amount of trimming. For example, if the protruding piece 20a is provided at a position farthest from the torsion spring member 30, the influence on the moment of inertia of the swinging member 20 becomes large, so that the resonance frequency can be easily adjusted with a small amount of trimming.

  Trimming can be performed directly on, for example, the substrate 10 and the swinging member 20 having been enlarged. However, this causes problems such as an increase in the size of the optical scanning device 100 as a whole. As in this embodiment, by partially protruding the substrate 10 and the swing member 20 and using them for trimming, the manufacturing error can be calibrated without increasing the overall size.

  Then, by using the optical scanning device 100 of the present embodiment as the optical scanning device 100 of the first and second embodiments, the manufacturing error is calibrated before shipping, and calibration at the time of use after shipping. Can be dealt with by the control of the first and second embodiments.

  In the present embodiment, the outer shape of the protruding piece portions 11a and 20a is a rectangular parallelepiped shape, but other outer shapes such as a hemispherical shape or a comb-like shape may be employed. Moreover, the position of the protrusion piece parts 11a and 20a can also be selected arbitrarily.

Second Embodiment
The swing member 20 is required to have high speed swing and high rigidity. If the rocking member 20 has insufficient rigidity, there is a case where bending (hereinafter referred to as dynamic bending) occurs due to inertial force during rocking. When dynamic deflection occurs, the light reflecting surface 21 also bends, so that the reflected light reflected by the light reflecting surface 21 is distorted, and the optical characteristics of the light reflecting surface 21 are deteriorated.

  The amount of deflection due to dynamic deflection is determined by the size, displacement angle, drive frequency of the rocking member 20, and the density and Young's modulus, which are physical properties of the rocking member 20. Normally, the size, displacement angle, drive frequency, and the like of the oscillating member 20 are determined by the specification values required by the application of the optical scanning device 100. Therefore, there is a limit in reducing dynamic deflection by adjusting these. is there.

  On the other hand, in the present embodiment, the swinging member 20 is provided with the projecting piece 20a for trimming, and it is desirable to provide it at the position farthest from the torsion spring member 30 as described above in terms of adjusting the resonance frequency. However, as a result, the moment of inertia of the oscillating member 20 increases, and dynamic deflection is likely to occur.

  In the present embodiment, the torsion spring member 30 is branched to increase the support rigidity of the swing member 20. FIG. 3 is a perspective view of an optical scanning device 100 according to the second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and only different components are described.

  The torsion spring member 30 of the present embodiment has a branching source portion 31 connected to the substrate 10 and a plurality of branching portions 32 branched from the branching source portion 31 and connected to the swing member 20. . FIG. 4A is a plan view of the torsion spring member 30 (viewed from the normal direction of the substrate 10 when stationary).

  The branching source portion 31 extends linearly in a direction orthogonal to the longitudinal direction of the substrate 10 and serves as a swing center axis of the swing member 20. The branch portions 32 are linearly extended in a direction intersecting with the branch source portion 31, and one each on one side and the other side of the center line CL in the longitudinal direction of the branch source portion 31, respectively. A total of two are arranged. The two branch portions 32 branch from the branch source portion 31 in a direction orthogonal to the longitudinal direction of the branch source portion 31, and the connection end of each branch portion 32 with the swing member 20 is orthogonal to the center line CL. Thus, they are separated from each other in the surface direction of the swing member 20. In the case of this embodiment, the branch part 32 is arrange | positioned symmetrically with respect to the centerline CL, and the torsion spring member 30 has comprised the Y shape by planar view. Further, the center line CL (center line in a design shape without trimming of the protruding piece portion 20a; hereinafter the same) is a half position (projecting) when the longitudinal length of the swinging member 20 is L. It passes through a half position in the design shape without trimming of the piece 20a, and therefore passes through the center (center of gravity) of the rocking member 20 in plan view. The shape of the swing member 20 is symmetrical with respect to the center line CL in plan view. Further, in the case of the example in the figure, since the light reflecting surface 21 is formed over the entire longitudinal direction of the swinging member 20, the center line CL passes through the center of the light reflecting surface 21 in plan view. By branching the torsion spring member 30 in this way, the support rigidity of the swing member 20 can be increased, and dynamic deflection can be made difficult to occur.

  The torsion spring member 30 can employ various shapes other than the shapes shown in FIGS. 3 and 4A. 4 (B) to 4 (E) and FIGS. 5 (A) and 5 (B) are plan views showing other shape examples of the torsion spring member 30. FIG.

  FIG. 4B is obtained by rounding the radius R at the bent portion (branch point) of the branch source portion 31 and the branch portion 32 in the example of FIG. In the case of the configuration in which the torsion spring member 30 is branched as in the present embodiment, there is a possibility that stress concentrates on the bent portion. In the example of FIG. 4B, stress concentration is avoided by rounding the bent portion. In the example of FIG. 4B, the radius R is also rounded at the connecting portion between the branch portion 32 and the swing member 20. This also avoids stress concentration at the connection site. Although not shown in the drawing, it is desirable to form a roundness at the connecting portion between the branching source portion 31 and the substrate 10 (arm portion 11).

  In the example of FIGS. 4C and 4D, the branch portion 32 is arcuate. In this way, the branch portion 32 may be curved.

  In the example of FIGS. 4A to 4D, one branch portion 32 is arranged on each side of the center line CL in the longitudinal direction of the branch source portion 31 and one on the other side. However, two or more may be arranged. The example of FIG. 4E is an example in which two branch portions 32 are arranged on each of one side and the other side of the center line CL in the longitudinal direction of the branch source portion 31 for a total of four. is there. In the example of FIG. 4E, the branch portion 32 is arranged symmetrically with respect to the center line CL. When the number of the branch portions 32 is increased, the support rigidity of the swing member 20 can be further increased.

  4A to 4E, the same number of branch portions 32 are arranged on one side and the other side of the center line CL in the longitudinal direction of the branch source portion 31, but they are different. Alternatively, at least one branch portion 32 may be provided on each side of the center line CL in the longitudinal direction of the branch source portion 31 and on the other side. In particular, when the center line CL passes through a position shifted from the center of the swinging member 20 in a plan view, the number of the branch portions 32 may be varied.

  The example of FIG. 5A is an example in which the center line CL passes through a position shifted from the center of the swing member 20 in plan view. The center line CLG is a line passing through a position that is half the length of the swing member 20 in the longitudinal direction, and the center line CL is deviated from the center line CLG. In this case, the swing center axis of the swing member 20 is shifted from the center of gravity of the swing member 20.

  The torsion spring member 30 includes a branching source portion 31, two branching portions 32a, and one branching portion 32b. One branch portion 32a (the left side in the figure) and the branch portion 32b are disposed on the center side (center line CLG side) of the swing member 20 with respect to the center line CL in the longitudinal direction of the branch source portion 31. The branch portion 32a (right side in the figure) is arranged on the opposite side to the center line CL.

  The distance D1 from the connection point between the branch portion 32b and the swing member 20 to the center line CL is longer than the distance D2 from the connection point between the other branch portion 32a and the swing member 20 to the center line CL. Yes. The two branch portions 32a are symmetric with respect to the center line CL.

  In the example of FIG. 5A, if only the branch portion 32a is configured, the center line CL is shifted from the center line CLG, and therefore the dynamic deflection of the swing member 20 is on the center line CLG side, that is, on the center of gravity side. May occur significantly. In the example of FIG. 5A, the support rigidity on the center of gravity side of the swing member 20 can be increased by providing the branch portion 32b.

  The improvement in support rigidity by branching the torsion spring member 30 is to prevent distortion of the light reflecting surface 21. Therefore, when the light reflecting surface 21 is formed on a part of the swing member 20, it is sufficient if the support rigidity of the part can be improved.

  5B, the light reflecting surface 21 is not formed over the entire longitudinal direction of the swinging member 20, and is formed to be shifted to the right in the same figure from the center line CLG of the swinging member 20. . If the length in the longitudinal direction of the light reflecting surface 21 is L ′, the center line CL in the longitudinal direction of the branching source portion 31 passes through the center of the light reflecting surface 21 in plan view, while FIG. In the same manner as in the example, it is an example of passing through a position shifted from the center of the swing member 20.

  The pair of branch portions 32 are arranged symmetrically with respect to the center line CL in plan view. In the case of the example of FIG. 5B, the dynamic deflection of the swinging member 20 may occur remarkably on the center line CLG side, that is, on the center of gravity side. The support rigidity is increased and distortion of the light reflecting surface 21 can be prevented. In the example of FIG. 5B as well, it is of course possible to add a branch portion such as the branch portion 32b of FIG. 5A, and the center line CL is centered on the light reflecting surface 21 in plan view. It is only necessary to include at least a pair of branch portions that pass through and are symmetrical with respect to the center line CL.

<Third Embodiment>
The optical scanning device of the present invention can be applied to various devices such as an image forming device such as a laser beam printer, an image display device such as a head mounted display, and an input device such as a barcode reader. Further, the present invention can be applied to a flat panel display in which a two-dimensional scanner is configured by the optical scanning device of the present invention and an original scanning optical scanner for a reading sensor.

  In addition, when the optical scanning device of the present invention is applied to various devices as described above, there is no restriction on the arrangement direction of the optical scanning device, but in consideration of the static deflection of the substrate (10), the longitudinal direction of the substrate It is more preferable to arrange them so as to be in the direction of gravity.

(A) is a perspective view of the optical scanning device 100 according to the first embodiment of the present invention, and (B) is a perspective view of the optical scanning device 100 after trimming. FIG. 5 is an operation explanatory diagram of the optical scanning device 100. It is a perspective view of the optical scanning device 100 concerning 2nd Embodiment of this invention. (A) thru | or (E) is a top view which shows the example of a shape of the torsion spring member 30. FIG. (A) And (B) is a top view which shows the example of a shape of the torsion spring member 30. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical scanning device 10 Board | substrate 11a, 20a Projection piece part 20 Oscillation member 30 Torsion spring member

Claims (10)

A substrate,
Driving means for exciting plate wave vibration on the substrate;
A torsion spring member coupled to the substrate;
An oscillating member coupled to the torsion spring member and oscillating about the torsion spring member as an oscillation center axis by torsional vibration of the torsion spring member excited by plate wave oscillation of the substrate;
A light reflecting surface formed on the rocking member,
At least one of the substrate and the swing member has a trimming protruding piece. The swing member has the protruding piece;
The optical scanning device according to claim 1, wherein the light reflecting surface is not formed on the protruding piece portion. The torsion spring member is
A branching source connected to the substrate;
A plurality of branch portions branched from the branch source portion and connected to the swing member;
The optical scanning device according to claim 1, wherein:   4. The optical scanning device according to claim 3, wherein a bent portion between the branching source part and the branching part is rounded. The branching source portion is linear,
The branch portion is
Branching in a direction perpendicular to the longitudinal direction of the branching source portion, and at least one each is arranged on one side and the other side of the center line in the longitudinal direction of the branching source portion. The optical scanning device according to claim 3 or 4. A plurality of the branched portions are
The optical scanning device according to claim 5, further comprising at least a pair of the branch portions arranged symmetrically with respect to a longitudinal center line of the branch source portion. The torsion spring member and the swing member are integrally formed from a single plate material,
In plan view, the center line in the longitudinal direction of the branching source portion passes through the center of the light reflecting surface,
6. The optical scanning according to claim 5, wherein the plurality of branch portions include at least a pair of the branch portions arranged symmetrically with respect to a center line in a longitudinal direction of the branch source portion in a plan view. apparatus.   The optical scanning device according to claim 7, wherein a center line in a longitudinal direction of the branching source portion passes through a position shifted from a center of the swinging member in a plan view. The torsion spring member and the swing member are integrally formed from a single plate material,
In plan view, the center line in the longitudinal direction of the branching source portion passes through a position shifted from the center of the swinging member,
A plurality of the branched portions are
A first branch portion disposed closer to the center of the swing member than a center line in the longitudinal direction of the branch source portion; and the first branch portion with respect to a center line in the longitudinal direction of the branch source portion; A second branch portion disposed on the opposite side,
The distance from the connection point between the first branch portion and the swing member to the center line is longer than the distance from the connection point between the second branch portion and the swing member to the center line. The optical scanning device according to claim 5.   8. The optical scanning device according to claim 1, wherein the substrate, the torsion spring member, and the swing member are integrally formed from a single plate material.

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