JP2013064843A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of preventing any resonance frequency drop that is dependent on the duration of drive and a manufacturing method for the optical scanner.SOLUTION: An optical scanner comprises a planar structure having an oscillating part oscillable around a first axis, a pair of torsional beam parts linked to both sides of the oscillating part, and a main body part linked to other ends of the pair of torsional beam parts; a drive unit configured to be capable of oscillating the oscillating part; and a mirror part that has a reflective face formed separately from the structure and reflecting incident light and is fixed to one face of the oscillating part. The oscillating part includes a stress easing structure that is disposed in the connecting position between the oscillating part and the pair of torsional beam parts, extends from the oscillating part along the first axis, is configured to be greater in length in a second direction parallel to a face containing the structure and crossing a direction along the first axis than the pair of torsional beam parts, and eases any stress between the mirror part and the oscillating part.

Description

  The present invention relates to an optical scanner that scans light such as a laser.

  Currently, an optical scanner that scans light such as laser light with a swinging mirror is known. As an example of the optical scanner, a mirror that is swingably supported by a torsion beam portion is swung by a drive unit such as a piezoelectric element. When the mirror swings, dynamic distortion occurs in the mirror. In order to reduce this dynamic distortion, Patent Document 1 discloses a configuration in which a reinforcing portion having a reflecting surface is bonded to a base portion supported by a torsion beam portion. In Patent Document 1, the plan view shape of the reinforcing portion is formed the same as the plan view shape of the base portion.

JP2011-27881A

  When the reinforcing portion and the base portion are formed in the same planar view shape in the optical scanner driven by the inventors at the resonance frequency, the resonance frequency tends to decrease depending on the time for driving the optical scanner. Was discovered. When the resonance frequency is lowered depending on the driving time, the resonance frequency of the optical scanner is lowered after the optical scanner is manufactured and incorporated in the product. For example, when an optical scanner is used in a scanning image display device, intensity modulation of image light is performed in accordance with the resonance frequency of the optical scanner. In this case, a decrease in the resonance frequency after the optical scanner is incorporated into the product may cause a situation where an image is not displayed correctly. Also, when an optical scanner is used in a laser printer, laser intensity modulation for printing is performed in accordance with the resonance frequency of the optical scanner. Therefore, a decrease in the resonance frequency after being incorporated into the product may cause a decrease in the printed image quality.

  An object of the present invention is to provide an optical scanner that can prevent a resonance frequency from being lowered depending on a driving time in an optical scanner having a reinforcing portion, and a method for manufacturing the optical scanner.

  In order to solve the above-described problem, one aspect of the present invention is configured to be swingable about a first axis, and a swinging portion formed in line symmetry with respect to the first axis, and one end of the swinging portion is configured as described above. A pair of torsion beam portions connected to both sides of the swing portion and extending from the swing portion in a first direction parallel to the first axis, and connected to the other end of the pair of twist beam portions, A plate-like structure having a main body part spaced apart from the moving part and extending in a direction intersecting the first axis, and a force is applied periodically to the structure by applying a driving voltage. And a drive unit configured to be able to swing the swinging portion around the first axis, and a reflecting surface formed separately from the structure and reflecting incident light. A mirror portion fixed to one side of the swinging portion, and the swinging portion includes the swinging portion and the pair of A first length which is provided at a connection position with the beam portion, extends in the first direction from the swinging portion, is parallel to a plane including the structure and is perpendicular to the first direction. The optical scanner includes a stress relaxation structure that is configured to be larger than the pair of torsion beam portions and relaxes stress at a fixed position between the mirror portion and the swinging portion.

  As a result of analysis by the present inventors, it has been found that when the swinging portion swings, the stress is most concentrated at the connection position between the swinging portion and the pair of torsion beam portions. In the optical scanner according to one aspect of the present invention, the mirror portion is fixed to one surface of the swinging portion. Therefore, as in Patent Document 1, when the reinforcing portion and the swinging portion are formed in the same plane view shape, the mirror portion is fixed even at the connection position between the swinging portion and the pair of torsion beam portions. Has been. In other words, in the optical scanner disclosed in Patent Document 1, the fixed position between the mirror portion and the swinging portion matches the connection position between the swinging portion and the pair of torsion beam portions. Therefore, the stress concentrated at the connection position between the swinging portion and the pair of torsion beam portions when the optical scanner is driven also acts on the fixed position between the mirror portion and the swinging portion. If this stress continues to act on the fixed position between the mirror part and the swinging part, the fixed state between the mirror part and the swinging part may gradually change (for example, the mirror part peels off). The decrease in the resonance frequency depending on the driving time can be considered as one of the causes. The mirror portion corresponds to the reinforcing portion in Patent Document 1, and the swinging portion corresponds to the substrate portion in Patent Document 1.

  In the optical scanner according to one aspect of the present invention, the swinging portion includes a stress relaxation structure that relaxes stress at a fixed position between the mirror portion and the swinging portion. Specifically, the stress relaxation structure is provided at a connection position between the swinging portion and the pair of torsion beam portions. The stress relaxation structure extends from the swinging portion in a first direction parallel to the first axis that is the central axis of swinging. The stress relaxation structure has a first length that is wider than the pair of torsion beam portions in a second direction parallel to the plane including the structure and perpendicular to the first direction. With this stress relaxation structure, the fixing position of the mirror portion and the swinging portion is separated from the connection position between the swinging portion and the pair of torsion beam portions, where stress is concentrated. By separating, the stress acting on the fixed position between the mirror part and the swinging part is reduced, and the change of the fixed state between the mirror part and the swinging part is prevented. Accordingly, it is possible to prevent a decrease in the resonance frequency depending on the driving time of the optical scanner.

  The stress relaxation structure may be formed in a tapered shape that extends from an end portion of the swinging portion in the second direction and decreases in the first length as the swinging portion is separated from the swinging portion.

  The stress relaxation structure extends from the end portion in the second direction of the swinging portion. If the size of the swinging portion is determined in advance, only the length in the first direction may be set as a variable for determining the shape of the stress relaxation structure. Therefore, it is possible to determine an appropriate shape of the stress relaxation structure with a small number of trials and errors. In other words, it is easy to introduce in design.

  In addition, the stress relaxation structure is set to a value that saturates the fluctuation amount of the stress value at the fixed position with respect to the variation of the second length that is the length of the stress relaxation structure in the first direction. The second length may be included.

  Due to the stress relaxation structure, the stress at the fixed position between the mirror portion and the swinging portion is relaxed. At this time, if the stress relaxation structure is too small, there is a possibility that the stress acting on the fixed position between the mirror portion and the swinging portion cannot be sufficiently reduced. Therefore, the second length of the stress relaxation structure is set to a value at which the amount of change in the stress value at the fixed position is saturated with respect to the change in the second length. Accordingly, it is possible to sufficiently reduce the stress acting on the fixed position between the mirror portion and the swinging portion.

  The stress relaxation structure may be formed such that a ratio of the second length to a length of the swinging portion in the first direction is 0.2 or more and 0.4 or less.

  As shown in FIG. 13 to be described later, if the ratio of the second length to the length in the first direction of the oscillating portion is “0.2” or more, the fixed position with respect to the variation in the second length. The fluctuation of the stress acting on the surface becomes gradual, and the stress can be sufficiently reduced. On the other hand, as shown in FIG. 14, the second length is preferably as small as possible from the viewpoint of preventing a decrease in the resonance frequency. When the ratio of the second length to the length in the first direction of the oscillating portion is “0.4” or more, the stress hardly changes even if the second length is increased. Therefore, in order to achieve both the viewpoints of reducing stress and preventing the decrease in resonance frequency, the ratio of the second length to the length in the first direction of the swinging portion is “0.2” or more and “0.4”. It is desirable to be less than.

  The stress relaxation structure is connected to a first side extending along the first direction from the swinging portion, and an end of the first side opposite to the swinging portion, and the second side A second side extending along the direction toward the pair of torsion beams.

  The stress relaxation structure has a first side and a second side. That is, it is necessary to set two shapes of the first side and the second side as variables for determining the shape of the stress relaxation structure. Therefore, the degree of freedom of the shape that can be taken by the stress relaxation structure is increased, and the design can be made closer to the shape of the stress relaxation structure that is closer to the optimum.

  The stress relaxation structure may have the first length set to a value at which a variation amount of the stress value at the fixed position is saturated with respect to the variation of the first length.

  Due to the stress relaxation structure, the stress at the fixed position between the mirror portion and the swinging portion is relaxed. At this time, if the stress relaxation structure is too small, there is a possibility that the stress acting on the fixed position between the mirror portion and the swinging portion cannot be sufficiently reduced. Therefore, the first length of the stress relaxation structure is set to a value at which the amount of change in the stress value at the fixed position is saturated with respect to the change in the first length. Accordingly, it is possible to sufficiently reduce the stress acting on the fixed position between the mirror portion and the swinging portion.

  The stress relaxation structure may be formed such that a ratio of the first length to a length of the swinging portion in the second direction is 0.4 or more and 1 or less.

  When the first length of the stress relaxation structure changes, the stress acting on the fixed position between the mirror portion and the swinging portion changes. As shown in FIG. 5 to be described later, as the ratio of the first length to the length in the second direction of the oscillating portion increases from “0” (when there is no stress relaxation structure), the oscillating portion and the oscillating portion The stress acting on the fixed position with the part is reduced. When the ratio of the first length to the length in the second direction of the oscillating portion is “0.4” or more, the decrease in stress becomes gradual. Therefore, by forming the stress relaxation structure so that the ratio of the first length to the length in the second direction of the swinging portion is “0.4” or more and “1” or less, the mirror portion, the swinging portion, It is possible to sufficiently reduce the stress acting on the fixed position.

  Furthermore, the stress relaxation structure may have the first length set to a value at which a value of a resonance frequency of the optical scanner is saturated with respect to a variation in the first length.

  When the stress relaxation structure becomes large, the mass of the oscillating portion increases, so that the moment of inertia when the oscillating portion oscillates increases. An increase in the moment of inertia leads to a decrease in the resonance frequency. Therefore, the first length of the stress relaxation structure is set to a value at which the value of the resonance frequency in the oscillation of the oscillation portion is saturated with respect to the variation in the first length. Therefore, when the stress acting on the fixed position between the mirror portion and the swinging portion is reduced by the stress relaxation structure, it is possible to prevent the resonance frequency from being lowered.

  Furthermore, the stress relaxation structure may be formed such that a ratio of the first length to a length of the swinging portion in the second direction is 0.6 or less.

  When the first length of the stress relaxation structure changes, the value of the resonance frequency of the optical scanner changes. As shown in FIG. 6 to be described later, when the ratio of the first length to the length in the second direction of the swinging portion is from “0” (when no stress relaxation structure is present) to about “0.6”, The value of the resonance frequency is substantially constant. On the other hand, when the ratio of the first length to the length in the second direction of the swinging portion is larger than “0.6”, the ratio of the first length to the length in the second direction of the swinging portion increases. Along with this, the value of the resonance frequency decreases. Therefore, by forming the stress relaxation structure so that the ratio of the first length to the length in the second direction of the swinging portion is “0.6” or less, the mirror portion and the swinging portion are separated by the stress relaxation structure. When the stress acting on the fixed position is reduced, the resonance frequency can be prevented from lowering.

  Further, the mirror part is made of a material having a linear expansion coefficient different from that of the structure, and is fixed to one surface of the swinging part using a thermosetting adhesive having a durometer hardness of D65 or less. May be.

  According to this, a mirror part is comprised with the material from which the material of a structure differs from a linear expansion coefficient. When the mirror part and the swinging part are fixed with a thermosetting adhesive, heat is applied when the adhesive is cured. Because the linear expansion coefficients of the mirror and the structure are different, if they are fixed with an adhesive in a heated state, the difference in reduction amount between the two due to the difference in linear expansion coefficients when returning to room temperature. Occurs. Stress is generated in the mirror portion by the difference in the reduction amount. Due to this stress, static distortion occurs in the mirror portion. If the amount of static distortion of the mirror portion increases, the wavefront of the incident light is disturbed when the incident light is reflected, leading to a decrease in optical performance. Therefore, the smaller the amount of static distortion of the mirror part, the better. As shown in FIG. 7 to be described later, as the durometer hardness of the adhesive increases, the deformation amount (= static strain) of the mirror portion 130 increases. As apparent from FIG. 7, when the durometer hardness of the adhesive is larger than D65, the mirror portion is deformed. On the other hand, when the durometer hardness of the adhesive is D65 or less, the mirror portion hardly deforms. Therefore, it is possible to suppress static distortion of the mirror part by fixing the mirror part to one surface of the swinging part using a thermosetting adhesive having a durometer hardness of D65 or less.

  Further, a mass piece provided on at least one of the other surface of the oscillating portion and a position on one surface of the oscillating portion and spaced from the mirror portion, for adjusting the resonance frequency of the structure. Further, it may be provided.

  According to this, the mass piece for adjusting the resonance frequency of the optical scanner is provided on at least one of the other surface of the oscillating portion and a position on one surface of the oscillating portion spaced from the mirror portion. Therefore, the resonance frequency of the optical scanner can be adjusted without the mass piece blocking the incident light to the mirror portion.

  In order to solve the above-mentioned problem, another aspect of the present invention provides a preparation step for preparing any one of the optical scanners described above, a frequency determination step for determining a resonance frequency value of the optical scanner, and the determination step. A position determining step for determining a position on the swinging portion where the mass piece is provided based on the value of the resonance frequency determined in step 1 and the value of the target resonance frequency, and determination in the position determining step And an additional step of adding the mass piece to the position on the oscillating portion.

  Thereby, the resonance frequency of the prepared optical scanner can be adjusted to the target resonance frequency.

  ADVANTAGE OF THE INVENTION According to this invention, the optical scanner which can prevent that a resonant frequency falls according to the drive time of an optical scanner in an optical scanner which has a reinforcement part, and the manufacturing method of the optical scanner are provided.

1 is a perspective view of an optical scanner 100 according to a first embodiment. The perspective view of the optical scanner 500 which concerns on a comparative example. The figure explaining the change of the resonant frequency for every measurement frequency in the case where it has stress relaxation structure 111a (embodiment), and the case where it does not have (comparative example). 2 is a plan view of the optical scanner 100. FIG. The figure explaining the change of the stress in the fixed position of the mirror part 130 and the rocking | fluctuation part 111 when changing the width | variety of the left-right and the front-back direction of the stress relaxation structure 111a. The figure explaining the change of the resonant frequency of the optical scanner 100 when changing the width | variety of the left-right and front-back direction of the stress relaxation structure 111a. The figure explaining the change of the deformation amount of the mirror part 130 when changing the durometer hardness of the thermosetting adhesive which fixes the mirror part 130 and the rocking | fluctuation part 111. FIG. The figure explaining the process of adjusting the resonant frequency of the optical scanner. FIG. 6 is a diagram for explaining a manufacturing process of the optical scanner 100. (A) A table in which the addition amount and the addition position of the mass piece 140 are associated with the difference between the target resonance frequency and the resonance frequency of the optical scanner 100, and (B) the addition position of the mass piece 140 in the optical scanner 100 is described. To do. The perspective view of the optical scanner 200 which concerns on 2nd Embodiment. The top view of the optical scanner 200. FIG. The figure explaining the change of the stress in the fixed position of the mirror part 130 and the rocking | fluctuation part 211 when the width | variety of the front-back direction of the stress relaxation structure 211a is changed. The figure explaining the change of the resonant frequency of the optical scanner 200 when changing the width | variety of the front-back direction of the stress relaxation structure 211a.

<First Embodiment>
[Configuration of Optical Scanner 100]
A first embodiment reflecting one aspect of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the optical scanner 100 includes a structure 110 and a pedestal 120. The mirror unit 130 is swung around the first axis s by the piezoelectric element 114. By this swinging, the light incident on the mirror unit 130 is scanned.

  The structure 110 is a plate-like structure having a rectangular shape in plan view, which includes a pair of short sides parallel to the front-rear direction and a pair of long sides parallel to the left-right direction. Note that the front-rear direction is parallel to the first axis s. The structure 110 includes a swinging portion 111, a pair of torsion beam portions 112, and a main body portion 113. A piezoelectric element 114 is provided on one surface (for example, the upper surface) of the main body portion 113. In the present embodiment, the structure 110 is made of a metal material such as stainless steel or titanium. However, the structure 110 may be formed of a semiconductor material such as silicon. The structure 110 is parallel to the front, rear, left and right surfaces in FIG. Moreover, the size of the structure 110 in the front-rear direction, the left-right direction, and the up-down direction is, for example, about 20 mm, 30 mm, and 0.1 mm, respectively.

  A mirror portion 130 that reflects light such as a laser is fixed on the upper surface of the swinging portion 111. The mirror part 130 having a rectangular shape in plan view is made of a dielectric material such as sapphire or diamond. Therefore, the mirror part 130 has a linear expansion coefficient different from that of the swinging part 111. A metal thin film is formed on the upper surface or lower surface of the mirror unit 130 by a method such as sputtering or vapor deposition in order to reflect light such as laser. The swinging part 111 and the mirror part 130 are fixed with, for example, an epoxy-based, phenol-based, or silicon-based thermosetting adhesive. The swinging part 111 and the mirror part 130 are provided symmetrically with respect to the first axis s.

  The swing part 111 includes a stress relaxation structure 111 a that relaxes stress at a fixed position between the mirror part 130 and the swing part 111. The stress relaxation structure 111 a is provided at a connection position between the swinging portion 111 and the pair of torsion beam portions 112. In other words, the stress relaxation structure 111a extends from the swinging portion 111 in the front-rear direction, which is an example of the first direction. The width in the left-right direction of the stress relaxation structure 111a is larger than the width in the left-right direction of the pair of torsion beam portions 112. Since the stress relaxation structure 111a is configured to be wide in the left-right direction, paying attention to the area per unit length in the front-rear direction, the area per unit length in the front-rear direction of the stress relaxation structure 111a is equal to the pair of torsion beam portions 112. Larger than the area per unit length in the front-rear direction. Specifically, the stress relaxation structure 111a is formed in a rectangular shape in plan view having a first side and a second side. The first side is a side extending from the swinging portion 111 along the front-rear direction. The second side is a side that is connected to the end of the first side opposite to the swinging portion 111 and extends toward the pair of torsion beams 112 along the left and right sides. And the stress relaxation structure 111a connects the rocking | swiveling part 111 and a pair of torsion beam part 112 as a continuous body, without having gaps, such as a hole. The stress relaxation structure 111 a is formed in line symmetry so that the first axis s sufficiently matches the center line of the pair of torsion beam portions 112. The fixed position between the mirror part 130 and the swing part 111 is the position of the swing part 111 where the mirror part 130 does not rest on the upper surface and the swing part where the mirror part 130 rests on the upper surface in the front-rear direction. This corresponds to the boundary portion with the position 111. The connection position between the swinging portion 111 and the pair of torsion beam portions 112 is a portion where the width in the left-right direction of the pair of torsion beam portions 112 expands in the front-rear direction, that is, the swinging portion 111 and the pair of torsion beams. This corresponds to the boundary portion with the connection position with the portion 112.

  One end of the pair of torsion beam portions 112 is connected to both sides of the swinging portion 111 in the front-rear direction. The pair of torsion beam portions 112 extends from the swinging portion 111 in parallel to the front-rear direction. Here, the first axis s passes through the centers of the pair of torsion beam portions 112. The swinging portion 111 is elastically supported by the pair of torsion beam portions 112 so as to be swingable about the first axis s. That is, the pair of torsion beam portions 112 has a role as a torsion bar that supports the swinging portion 111 so as to be swingable about the first axis s.

  The main body portion 113 is connected to the other end of the pair of torsion beam portions 112, is separated from the swinging portion 111, and extends in a direction intersecting the first axis s. In the present embodiment, the main body portion 113 extends from the connecting portion with the pair of torsion beam portions 112 to both sides in the left-right direction. The main body portion 113 has a fixed portion 113a. A pair of fixed portions 113a is provided with a pair of torsion beam portions 112 and a swinging portion 111 interposed therebetween. In the present embodiment, a pair of rectangular through holes A are provided along the left-right direction at the ends of the main body portion 113 in the front-rear direction. A region of the main body portion that is located farther from the swinging portion 111 than the through hole A in the front-rear direction is the fixed portion 113a. In this fixed portion 113a, the structure 110 and the pedestal 120 are fixed.

  A piezoelectric element 114 as a driving unit is provided on the upper surface of the main body portion 113. A pair of piezoelectric elements 114 is provided at both ends in the left-right direction, which is an intermediate position in the front-rear direction of the main body portion 113. For example, the piezoelectric element 114 is formed by laminating 0.2 μm to 0.6 μm of gold, platinum, or the like as an electrode layer on both surfaces of a piezoelectric material such as lead zirconate titanate formed into a flat plate having a thickness of 30 μm to 100 μm. It is formed by doing. The piezoelectric element 114 and the main body portion 113 are bonded with a conductive adhesive. A thin metal wire (not shown) such as gold is connected to the upper surface of the piezoelectric element 114 by wire bonding or the like.

  A mass piece 140 is provided on the upper surface of the stress relaxation structure 111a. The mass piece 140 is provided at a position that is line-symmetric with respect to the first axis s. The mass piece 140 has a function of increasing the moment of inertia when the swinging portion 111 swings around the first axis s. The position where the mass piece 140 is provided is not limited to the upper surface of the stress relaxation structure 111a. By adjusting the moment of inertia, the position where the mass piece 140 is provided is appropriately changed so that the resonance frequency of the optical scanner 100 becomes a desired value. The mass piece 140 may be made of an acrylic, epoxy, or silicon adhesive. Additives may be added to these adhesives in order to increase the specific gravity of the mass piece 140 and improve adhesion. Further, the mass piece 140 is cured by applying ultraviolet rays, heating, humidity, or the like. In consideration of heat distortion of the swinging part 111 and optimization of the process, it is desirable to use an ultraviolet curable adhesive as the mass piece 140.

  The pedestal 120 is composed of a pair of columnar members extending in the left-right direction. The pedestal 120 is fixed to the lower surface of the fixed portion 113a of the structure 110. The width in the front-rear direction of the pedestal 120 is set equal to or less than the width in the front-rear direction of the fixed portion 113a. The vertical thickness of the pedestal 120 is sufficiently larger than the vertical thickness of the structure 110, for example, about 1 mm. Therefore, even if the structure 110 swings, the pedestal 120 hardly deforms. In other words, when the optical scanner 100 is driven, the fixed portion 113a is hardly deformed integrally with the pedestal 120, and the portion of the inner structure 110 in the front-rear direction of the pair of through holes A swings. The pedestal 120 is made of a metal material such as stainless steel, for example.

[Driving of optical scanner 100]
Since the structure 110 is made of metal, the piezoelectric element 114 can be deformed by applying a voltage between the structure 110 and a metal thin wire connected to the upper surface of the piezoelectric element 114. An AC voltage (drive signal) is applied to the piezoelectric element 114 provided on the right side and the piezoelectric element 114 provided on the left side so as to be in opposite phases. When the frequency of the AC voltage corresponds to the resonance frequency of the optical scanner 100, a plate wave is excited in the main body portion 114 as the piezoelectric element 114 is deformed. The plate wave is transmitted to the swinging portion 111 via the main body portion 113 and the pair of torsion beam portions 112, so that the swinging portion 111 swings around the first axis s at a predetermined resonance frequency. Here, the structure 110 is fixed to the pedestal 120 at the fixed portion 113a, and the main body portion 113 sandwiched between the fixed portions 113a is in a state of being suspended in the air by the pedestal 120. Therefore, when the optical scanner 100 is driven, the main body portion 113 is displaced in the vertical direction. However, since the torsion beam portion 112 is provided at a position that becomes a vibration node of the main body portion 113, even if the main body portion 113 is displaced in the vertical direction, the torsion beam portion 112 is suppressed from being displaced in the vertical direction. . Note that the frequency of the AC voltage may not exactly match the resonance frequency of the optical scanner 100. Depending on the Q value of the optical scanner 100, the frequency of the AC voltage may be offset from the resonance frequency of the optical scanner 100.

[Driving time dependence of resonance frequency]
In the present invention, in the optical scanner 100 having the mirror unit 130, the resonance frequency is prevented from being lowered depending on the driving time due to the stress relaxation structure 111a. In order to confirm the effect of the stress relaxation structure 111a, an optical scanner 500 having no stress relaxation structure 111a was created as a comparative example.

  The optical scanner 500 is different from the optical scanner 100 in the structure of the structure 510. More specifically, the optical scanner 500 is different from the optical scanner 100 in that the stress relaxation structure 111 a is not provided in the swinging portion 511. In other words, in the optical scanner 500, the swinging part 511 is formed in the same shape as the mirror part 130 in plan view. In the optical scanner 500, the same components as those in the optical scanner 100 are assigned the same numbers as those in the optical scanner 100, and the description thereof is omitted.

  The effect of the stress relaxation structure 111a will be described with reference to FIG. The horizontal axis in FIG. 3 represents the number of times the resonance frequency of the optical scanner has been measured. Each time the measurement is repeated, the cumulative driving time of the optical scanner increases. That is, the horizontal axis in FIG. 3 corresponds to the drive time from the completion of the manufacture of the optical scanner. The vertical axis in FIG. 3 indicates a ratio obtained by dividing the resonance frequency at each number of measurements by the initial resonance frequency. In FIG. 3, data indicated by a square and a solid line is actually measured data of the optical scanner 100. In FIG. 3, data indicated by diamonds and broken lines is actually measured data of the optical scanner 500.

  The resonance frequency of the optical scanner 100 hardly changes even if the number of measurements is repeated. On the other hand, the resonance frequency of the optical scanner 500 gradually decreases as the number of measurements is repeated. From this result, it can be seen that the resonance frequency is prevented from being lowered depending on the driving time in the optical scanner 100 by providing the stress relaxation structure 111a.

  The reason why the resonance frequency decreases depending on the driving time is not necessarily clear. However, as described above, when the oscillating portion oscillates, it is a fact that stress is concentrated most at the connection position between the oscillating portion and the pair of torsion beam portions. As a hypothesis, the fact that this stress acts on the fixed position between the oscillating part and the mirror part changes the fixed state between the oscillating part and the mirror part (for example, peeling of the adhesive) depending on the driving time. Therefore, it is considered as one of the causes that the resonance frequency is lowered.

  In the optical scanner 500, the fixed position of the swinging part 500 and the mirror part 130 matches the connection position of the swinging part 111 and the pair of torsion beam parts 112 in the front-rear direction. Therefore, in the optical scanner 500, the stress acting on the connection position between the swinging portion 511 and the pair of torsion beam portions 112 acts on the fixed portion between the mirror portion 130 and the swinging portion 111 as it is. On the other hand, in the optical scanner 100, by providing the stress relaxation structure 111a, the fixing position of the mirror part 130 and the swinging part 111 is separated from the connection position between the swinging part 111 and the pair of torsion beam parts 112. The Therefore, the stress acting on the fixed position between the mirror part 130 and the swinging part 111 is reduced, and a change in the fixed state between the mirror part 130 and the swinging part 111 is prevented. As a result, in the optical scanner 100 provided with the stress relaxation structure 111a, a decrease in the resonance frequency depending on the driving time is prevented.

[Examination of stress relaxation structure 111a]
In the optical scanner 100 provided with the stress relaxation structure 111a, a decrease in the resonance frequency depending on the driving time is prevented as compared with the optical scanner 500 not provided with the stress relaxation structure 111a. Here, the desirable form of the stress relaxation structure 111a is examined.

  The shape of the stress relaxation structure 111a will be described with reference to FIG. The length in the left-right direction of the swinging portion 111 and the length in the left-right direction of the stress relaxation structure 111a are denoted as Mx and X, respectively. Note that the length in the left-right direction of the swinging portion 111 is the length from the pair of torsion beam portions 112 to the end portion in the left-right direction of the swinging portion 111. Similarly, the length in the left-right direction of the stress relaxation structure 111a is the length from the pair of torsion beam portions 112 to the ends in the left-right direction of the stress relaxation structure 111a, in other words, the length in the left-right direction of the second side. That's it. The length of the oscillating portion 111 in the front-rear direction is denoted by My. In the front-rear direction, the length of the stress relaxation structure 111a from the connection position between the swinging portion 111 and the pair of torsion beam portions 112, in other words, the length in the front-rear direction of the first side is denoted as Y. Hereinafter, a desirable form of the stress relaxation structure 111a is examined by changing the values of X and Y by simulation under the same conditions (outer shape and material) of the structure 110 as the optical scanner 100.

  First, the stress acting on the fixed position between the mirror part 130 and the swinging part 111 will be focused on using FIG. The vertical axis in FIG. 5 indicates the magnitude of the stress acting on the fixed position between the mirror part 130 and the swing part 111. Specifically, the vertical axis in FIG. 5 represents the value of stress acting on the fixed position between the mirror portion 130 and the swinging portion 111 in the optical scanner 100 having the stress relaxation structure 111a having a certain shape. The ratio divided by the value of the stress acting on the fixed position between the mirror part 130 and the swinging part 511 is shown. The horizontal axis of FIG. 5 shows the ratio obtained by dividing the value of X by Mx. In FIG. 5, the case where Y / My is “0”, that is, the case of the optical scanner 500 in which the stress relaxation structure 111 a does not exist is shown by a rhombus plot. When Y / My is “0.21”, “0.42”, and “0.83”, they are indicated by a square and an alternate long and short dash line, a triangle and a broken line, and a circle and a solid line, respectively.

  As apparent from FIG. 5, as the value of X / Mx increases from “0”, the stress acting on the fixed position between the mirror portion 130 and the swinging portion 111 decreases. And when the value of X / Mx is a certain value or more, the decreasing tendency of the stress becomes moderate. Specifically, when Y / My is “0.21”, the stress value decreases as the value of X / Mx increases in the region where the value of X / Mx is less than “0.2”. And in the area | region where the value of X / Mx is "0.2" or more, the value of stress becomes substantially constant irrespective of X / Mx. When Y / My is “0.42,” the stress value decreases as the value of X / Mx increases in the region where the value of X / Mx is less than “0.4”. In the region where the value of X / Mx is “0.4” or more, the stress value is almost constant regardless of X / Mx. When Y / My is “0.83”, in the region where the value of X / Mx is less than “0.5”, the value of stress decreases as the value of X / Mx increases. And in the area | region where the value of X / Mx is "0.5" or more, the decreasing tendency of stress becomes loose. As the value of Y / My increases, the value of X / Mx, at which the stress decreasing tendency becomes gentle, tends to increase. However, when FIG. 5 is viewed generally, it can be said that, as an overall trend, when the value of X / Mx is “0.4” or more, the decreasing tendency of stress is saturated. That is, by setting the value of X / Mx to a value that saturates the amount of fluctuation of the stress value with respect to the fluctuation of the value of X / Mx, it acts on the fixed position between the mirror unit 130 and the swinging part 111. The stress can be sufficiently reduced. The value at which the fluctuation amount of the stress value is saturated is, for example, a range where the value of X / Mx is “0.4” or more and “1” or less.

  Next, the resonance frequency of the optical scanner 100 will be focused on using FIG. The vertical axis of FIG. 6 indicates the magnitude of the resonance frequency of the optical scanner 100. Specifically, the vertical axis in FIG. 6 indicates a ratio obtained by dividing the value of the resonance frequency in the optical scanner 100 including the stress relaxation structure 111 a having a certain shape by the value of the resonance frequency in the optical scanner 500. The horizontal axis of FIG. 6 shows the ratio obtained by dividing the value of X by Mx, as in the case of FIG. In FIG. 6, the symbols applied to the respective values of Y / My are the same as those in FIG.

  As apparent from FIG. 6, the resonance frequency of the optical scanner 100 decreases as the value of X / Mx increases from “0”. Specifically, when the value of X / Mx is a certain value or less, the resonance frequency behaves substantially constant. When the value of X / Mx exceeds a certain value, the resonance frequency starts to decrease as X / Mx increases. Specifically, when Y / My is “0.21”, in the region where the value of X / Mx is “0.6” or less, the value of the resonance frequency is almost constant regardless of X / Mx. In the region where the value of X / Mx exceeds “0.6”, the value of the resonance frequency slightly decreases as X / Mx increases. When Y / My is “0.42,” in the region where the value of X / Mx is “0.6” or less, the value of the resonance frequency is almost constant regardless of X / Mx. Then, in the region where the value of X / Mx exceeds “0.6”, the value of the resonance frequency decreases as X / Mx increases. When Y / My is “0.83”, in the region where the value of X / Mx is “0.6” or less, the value of the resonance frequency slightly decreases as X / Mx increases. Then, in the region where the value of X / Mx exceeds “0.6”, the value of the resonance frequency rapidly decreases as X / Mx increases. As the value of Y / My increases, the degree of decrease in the resonance frequency in the region where the value of X / Mx exceeds “0.6” increases. In other words, in the region where the value of X / Mx is “0.6” or less, regardless of the value of Y / My, the value of the resonance frequency is saturated with respect to the variation of the value of X / Mx. I can say that. Therefore, when the value of X / Mx is “0.6” or less, a decrease in the resonance frequency can be prevented.

  In this embodiment, the swinging part 111 and the mirror part 130 are fixed by a thermosetting adhesive. Since the linear expansion coefficients of the mirror unit 130 and the structure 110 are different, a difference in deformation due to thermal expansion is generated due to the difference between the temperature during curing and the normal temperature. The difference in the deformation amount becomes stress and causes static distortion of the mirror unit 130. When the amount of static distortion of the mirror unit 130 increases, the wavefront of the incident light is disturbed when the incident light is reflected, leading to a decrease in optical performance. In order to maintain the optical performance of the optical scanner 100, the type of adhesive will be considered here.

[Examination of fixing method of mirror unit 130]
With reference to FIG. 7, the measured deformation amount of the mirror part 130 will be described by paying attention to the hardness of the thermosetting adhesive. The vertical axis in FIG. 7 represents a ratio obtained by dividing the actual measurement value of the deformation amount of the mirror portion 130 deformed by the curing of the thermosetting adhesive by the temperature at the time of curing. Since the amount of deformation due to thermal expansion depends on temperature, the higher the temperature during curing, the larger the amount of deformation of the mirror portion 130 even if the same adhesive is used. This time, in order to investigate the influence of the hardness of the adhesive on the deformation amount of the mirror portion 130, the deformation amount of the mirror portion 130 caused by the difference in temperature at the time of curing is obtained by dividing the deformation amount of the mirror portion 130 by the temperature at the time of curing. The difference in deformation is eliminated. The horizontal axis in FIG. 7 is the durometer hardness of the cured thermosetting adhesive. A type D durometer was used for the measurement. In order to indicate that the value is of type D, the value on the horizontal axis in FIG. 7 is given “D” before the numerical value.

  Evidently from FIG. 7, in the area | region where the durometer hardness of a thermosetting adhesive is "D70" or more, the deformation amount of the mirror part 130 increases with the increase in the value of durometer hardness. On the other hand, when the durometer hardness of the thermosetting adhesive is “D60”, the mirror part 130 is not deformed. This tendency is that when the durometer hardness of the thermosetting adhesive is low, the cured adhesive serves as a buffer material, and the difference in deformation caused by the difference in linear expansion coefficient between the mirror part 130 and the structure 110 is reduced. It is thought to absorb. That is, when a thermosetting adhesive having a durometer hardness of “D65” or less is used, static distortion does not occur in the mirror portion 130 depending on the curing of the adhesive.

  From the viewpoint of preventing static distortion of the mirror, a thermosetting adhesive having a low durometer hardness at the time of curing, specifically, a thermosetting adhesive of “D65” or less is used to fix the mirror portion 130 and the swinging portion 111. Should be used. Here, the adhesive having low durometer hardness generally has low peel strength. In the case of the optical scanner 500 in which the stress relaxation structure 111a is not provided, the adhesive having a low peel strength cannot withstand the stress concentrated on the fixed position between the mirror portion 130 and the swinging portion 111, which increases the driving time. Accordingly, the resonance frequency is more likely to be lowered. However, in this embodiment, since the stress relaxation structure 111a is provided, stress is not concentrated at the fixed position between the mirror part 130 and the swinging part 111. Therefore, it is possible to use an adhesive having a low durometer hardness in order to prevent static distortion of the mirror without worrying about the peel strength of the adhesive.

[Resonance frequency adjustment method]
The optical scanner 100 described above can adjust the value of the resonance frequency by appropriately selecting the position where the mass piece 140 is provided. Hereinafter, this adjustment method will be described with reference to FIGS.

  In step S11, the optical scanner 100 is created. Details of step S11 will be described later with reference to FIG.

  In step S12, the resonance frequency of the created optical scanner 100 is acquired. The resonance frequency may be acquired by a method of actually measuring the optical scanner 100 by actually driving the optical scanner 100, or determining the resonance frequency by using a predetermined correspondence relationship based on the shape of the optical scanner 100. The actual measurement of the resonance frequency is performed by, for example, making light incident on the mirror unit 130 and detecting the reflected scanning light. As a specific example, an optical sensor is provided in a scanning region in which the scanning light moves, and the resonance frequency is determined based on timing at which an output corresponding to reception of the scanning light is obtained from the optical sensor. On the other hand, when based on the shape of the optical scanner 100, for example, for the design values of the oscillating portion 130 and the pair of torsion beam portions 112, the corresponding resonance frequency value is obtained by simulation or actual measurement. Then, the value of the change amount of the resonance frequency with respect to the change amount of the size of the swinging portion 130 or the pair of torsion beam portions 112 is obtained by simulation or actual measurement. The resonance frequency of the optical scanner 100 is determined from the actual measurement value of the size of the structure 110 using the correspondence between the change amount of the size and the change amount of the resonance frequency.

  In step S13, the range of the desired resonance frequency is compared with the value of the resonance frequency of the optical scanner 100 acquired in step S12. Here, the range of the desired resonance frequency is determined in advance based on the specifications of a product such as a printer or a laser display in which the optical scanner 100 is incorporated.

  In step S14, based on the result of the comparison in step S13, it is determined whether or not the acquired resonance frequency of the optical scanner 100 is included in a desired resonance frequency range. When the resonance frequency of the optical scanner 100 is included in the range of the desired resonance frequency (S14: Yes), the optical scanner 100 satisfies the specification, so an OK determination is made in step S15. The optical scanner 100 that has been determined to be OK is used as a product.

  If the resonance frequency of the optical scanner 100 is not included in the desired resonance frequency range (S14: No), it is determined in step S16 whether the resonance frequency of the optical scanner 100 is higher than the desired resonance frequency range. . When the resonance frequency of the optical scanner 100 is higher than the desired resonance frequency range (S16: Y), the mass piece 140 is added to the structure 110 and / or the mirror unit 130 in step S16. The additional position and additional amount of the mass piece 140 will be described later with reference to FIG. Thereafter, using the optical scanner 100 to which the mass piece 140 is added, step S12 and subsequent steps are executed again.

  By adding the mass piece 140, the moment of inertia of the swinging portion 111 increases. The increase in the moment of inertia decreases the resonance frequency of the optical scanner 100. Therefore, depending on the addition of the mass piece 140, only adjustment to lower the resonance frequency is possible. Therefore, when the resonance frequency of the optical scanner 100 is lower than the desired resonance frequency range (S16: N), an NG determination is made because adjustment is impossible (S18). The optical scanner 100 for which NG determination is made is not used as a product as a defective product.

[Create Optical Scanner 100]
The production process of the optical scanner 100 will be described with reference to FIG. Here, the case where the structure 110 is made of metal will be described as an example. First, in step S110, the structure 110 is formed. A metal plate (for example, stainless steel or titanium) constituting the structure 110 is divided into a size equal to the outer shape of the structure 110. In the divided metal plate, the swinging portion 111, the pair of torsion beam portions 112, and the main body portion 113 are formed by a predetermined removal process. The predetermined removal processing includes, for example, etching, press processing, electric discharge processing, laser processing, and the like. As an example, when wet etching is performed, a resist film for masking is formed at positions corresponding to the swinging portion 111, the pair of torsion beam portions 112, and the main body portion 113 of the divided metal plate. Thereafter, after the outer shape of the structure is formed by wet etching, the resist film is removed. It should be noted that, after the outer shapes of a plurality of structures are formed on a metal plate that is sufficiently larger than the outer shape of the structures, a large number of pieces can be divided into individual structures.

  Next, in step S <b> 111, a bulk piezoelectric element 114 having electrode layers on both sides of the piezoelectric material in advance is mounted on the structure 110. This mounting is performed using, for example, a conductive adhesive containing a conductive material such as a metal filler in a synthetic resin material such as epoxy, acrylic or silicon. Specifically, the piezoelectric element 114 is installed on the conductive adhesive applied to the main body portion 113 of the structure 110. After the piezoelectric element 114 is installed, the conductive adhesive is cured by placing the structure 110 in a heating furnace maintained in an atmosphere of 100 to 200 ° C. for 30 to 60 minutes. Thus, the mounting of the piezoelectric element 114 is completed.

  Next, in step S112, the pedestal 120 is created. The outer shape of the pedestal 120 is obtained by performing removal processing such as etching or pressing on the constituent material of the pedestal 120, as in the case of the structure 110.

  Next, in step S113, the base 120 and the structure 110 are fixed. This fixing is performed, for example, by welding the fixed portion of the structure and the pedestal by laser welding or the like. However, the structure 110 and the pedestal 120 may be fixed by other fixing methods such as bonding using a thermosetting adhesive or clamping using a predetermined fastener.

  In step S114, signal lines are connected to the piezoelectric element 114 and the structure 110 by wire bonding. This signal line is connected to an AC power source (not shown). Since the structure 110 and the piezoelectric element 114 are bonded by a conductive adhesive, when the optical scanner 100 is driven, an alternating voltage (drive signal) is generated between the piezoelectric element 114 and the structure 110 via the signal line. Is applied. Thus, the creation process of the optical scanner 100 is completed.

[Addition of mass piece 140]
The mass piece 140 is added to the difference between the target resonance frequency (for example, the center value of the desired resonance frequency range) and the resonance frequency of the optical scanner 100 acquired in step S12 (separation frequency df). This is performed based on a table (FIG. 10A) in which the addition amount and the addition position of the piece 140 are associated with each other. When the separation frequency df is less than 30 Hz, a mass piece of df × 65 μg is added so as to be symmetric with respect to the first axis s with respect to the position “C”. The position “C” corresponds to both the upper and lower surfaces of the stress relaxation structure 111a as shown in FIG. The position “C” is a relatively close distance from the first axis s. Since the frequency sensitivity is lower than when mass is applied to a distant distance, fine adjustment of the frequency is possible by applying mass to the position “C”. When the separation frequency df is 30 Hz or more and less than 100 Hz, a mass piece of df × 43 μg is added to the position “B” so as to be symmetric with respect to the first axis s. As shown in FIG. 10B, the position “B” is the center position in the front-rear direction of the swinging portion 111 and corresponds to the lower surface of the swinging portion 111 that is separated from the first axis s in the left-right direction. When the separation frequency df is 100 Hz or more, a mass piece of df × 28 μg is added to the position “A” so as to be symmetric with respect to the first axis s. As shown in FIG. 10B, the position “A” corresponds to the upper and lower surfaces farthest from the first axis s of the stress relaxation structure 111a, in other words, the four corners of the stress relaxation structure 111a. The position “A” is a distance relatively far from the first axis s. Since the frequency sensitivity is high when the mass is applied to a distant distance, the frequency can be largely adjusted by applying the mass to the position “A”. Thus, as the value of the separation frequency df increases, the amount of increase in the moment of inertia due to the addition of the mass piece 140 is set larger by adding mass to a position where the separation distance from the first axis s is greater.

Second Embodiment
[Configuration of Optical Scanner 200]
3 shows a second embodiment reflecting another aspect of the present invention. The optical scanner 200 according to the second embodiment is different from the optical scanner 100 according to the first embodiment in the shape of the swinging portion, specifically the stress relaxation structure. Therefore, in the optical scanner 200, the same structure as that of the optical scanner 100 is given the same number, and the description is omitted.

  As shown in FIG. 11, the optical scanner 200 includes a structure 210 and a pedestal 120. The structure 210 includes a swinging portion 211, a pair of torsion beam portions 112, and a main body portion 113. In the structure 210, the shapes of the pair of torsion beam portions 112 and the main body portion 113 are the same as those of the structure 110 shown in FIG.

  The swing part 211 includes a stress relaxation structure 211 a that relaxes stress at a fixed position between the mirror part 130 and the swing part 211. The stress relaxation structure 211 a is provided at a connection position between the swinging portion 211 and the pair of torsion beam portions 112. Specifically, the stress relaxation structure 211 a extends from the left and right ends of the swinging portion 211. In other words, the stress relaxation structure 211a is formed in a tapered shape so that the width in the left-right direction decreases as the distance from the swinging portion 211 increases. For example, the stress relaxation structure 211 a formed at the left rear portion with respect to the swing portion 211 extends from the left end of the swing portion 211 in the right rear direction and is connected to the pair of torsion beam portions 112. In other words, the stress relaxation structure 211a extends from the left and right ends of the oscillating portion 211 and a predetermined position of the pair of torsion beam portions 112, and the two extended positions are connected generally linearly. It is also expressed as a structure.

[Examination of stress relaxation structure 211a]
In the stress relaxation structure 111a according to the first embodiment, the stress acting on the fixed position between the mirror part 130 and the swinging part 111 and the fluctuation of the resonance frequency are adjusted by adjusting the lengths of the first side and the second side. Was investigated. In the first embodiment, since the two variables of the lengths of the first side and the second side can be adjusted, the design freedom increases, and the stress and the resonance frequency acting on the fixed position can be set more accurately. There is. On the other hand, since there are two variables in the stress relaxation structure 111a, many trials and errors are required to obtain a more optimal shape. The stress relaxation structure 211a in the second embodiment has a tapered shape extending from the left and right ends of the swinging portion 211. Therefore, the only variable that can be adjusted in the stress relaxation structure 211a is the length in the front-rear direction. Since there is only one variable, it is easy to introduce in design, and an appropriate shape of the stress relaxation structure can be determined with a small number of trials and errors.

  The shape of the stress relaxation structure 211a will be described in more detail with reference to FIG. The length in the front-rear direction of the oscillating portion 211 and the length in the front-rear direction of the stress relaxation structure 211a are labeled My and Y, respectively. Note that the length My in the front-rear direction of the swinging portion 111 is equal to the length of the mirror unit 130 in the front-rear direction. The length in the front-rear direction of the stress relaxation structure 211a is the length from the connection position of the swinging portion 211 and the pair of torsion beam portions 112 to the position where the stress relaxation structure 211a joins the pair of torsion beam portions 112. It is. Hereinafter, a desirable form of the stress relaxation structure 211a is examined by changing the value of Y by simulation under the conditions (outer shape and material) of the structure 210 similar to those of the optical scanner 200.

  First, the stress acting on the fixed position between the mirror part 130 and the swinging part 211 will be focused on using FIG. The vertical axis in FIG. 13 indicates the magnitude of the stress acting on the fixed position between the mirror part 130 and the swing part 211. Specifically, the vertical axis in FIG. 13 represents the value of the stress acting on the fixed position between the mirror part 130 and the swinging part 211 in the optical scanner 200 having the stress relaxation structure 211a having a certain shape. The ratio divided by the value of the stress acting on the fixed position between the mirror part 130 and the swinging part 511 is shown. The horizontal axis of FIG. 13 shows the ratio obtained by dividing the value of Y by Yx.

  As apparent from FIG. 13, as the value of Y / My increases from “0”, the stress acting on the fixed position between the mirror portion 130 and the swinging portion 211 decreases. And when the value of Y / My is a certain value or more, the decreasing tendency of the stress becomes moderate. Specifically, in a region where the Y / My value is less than “0.2”, the stress value decreases as the Y / My value increases. And in the area | region where the value of Y / My is "0.2" or more and less than "0.4", the decreasing tendency of stress becomes loose. In the region where the value of Y / My is “0.4” or more, the value of stress is substantially constant regardless of the value of Y / My. Therefore, by forming the stress relaxation structure 211a so that the value of Y / My becomes “0.2” or more, it is possible to sufficiently reduce the stress acting on the fixed position between the mirror portion 130 and the swinging portion 211. Become.

  Next, the resonance frequency of the optical scanner 200 will be focused on using FIG. The vertical axis in FIG. 14 indicates the magnitude of the resonance frequency of the optical scanner 200. Specifically, the vertical axis of FIG. 14 indicates a ratio obtained by dividing the resonance frequency value in the optical scanner 200 including the stress relaxation structure 211 a having a certain shape by the resonance frequency value in the optical scanner 500. The horizontal axis of FIG. 14 shows the ratio obtained by dividing the value of Y by My, as in the case of FIG.

  As apparent from FIG. 14, the resonance frequency of the optical scanner 200 decreases as the value of Y / My increases from “0”. And the decreasing trend is almost monotonously decreasing. Therefore, from the viewpoint of preventing a decrease in the resonance frequency, it is preferable that the Y / My value in the stress relaxation structure 211a is as small as possible. As described above, the value of Y / My is preferably “0.2” or more from the viewpoint of reducing the stress in FIG. In FIG. 13, when the value of Y / My is “0.4” or more, the stress hardly changes even if the value of Y / My increases. Therefore, in order to achieve both the viewpoints of reducing the stress and preventing the decrease in the resonance frequency, it is desirable that the value of Y / My is “0.2” or more and less than “0.4”.

  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 is described below.

  In the above-described embodiment, the structure 110 is made of metal. However, the present invention is characterized in that the resonance frequency can be prevented from decreasing depending on the driving time in the optical scanner 100 having the mirror unit 130 by providing the stress relaxation structure 111a. Therefore, even if the structure 110 is made of a nonmetal such as silicon, the structure is included in the scope of the present invention. Similarly, the shapes of the structure 110 and the pedestal 120 are not limited to the above-described embodiments. A flat plate-like structure 110 having a swinging part 111 including a stress relaxation structure 111a, a pair of torsion beam parts 112, a main body part 113, and a mirror part 130 fixed to the swinging part 111 is provided with respect to the base. All fixed types of optical scanners 100 are within the scope of the present invention. In the above-described embodiment, the piezoelectric element 114 is used as the drive unit. However, even an optical scanner that employs another driving method such as an electromagnetic driving method using a combination of a magnet and a coil pattern or an electrostatic driving method using an electrostatic force acting between electrode plates is included in the scope of the present invention. .

100, 200, 500 Optical scanner 110, 210 Structure 111, 211, 511 Oscillating part 111a, 211a Stress relaxation structure 112 Torsion beam part 113 Body part 113a Fixed part 114 Piezoelectric element 120 Base 130 Mirror part 140 Mass piece

Claims (12)

A swing portion configured to be swingable about a first axis, and formed symmetrically with respect to the first axis;
A pair of torsion beam portions, one end of which is connected to both sides of the swing portion, and extends from the swing portion in a first direction parallel to the first axis;
A plate-like structure having a body portion connected to the other end of the pair of torsion beam portions and extending in a direction that is separated from the swinging portion and intersects the first axis;
A driving unit configured to periodically apply a force to the structure by applying a driving voltage, and to swing the swinging portion around the first axis;
A mirror part that is formed separately from the structure and has a reflecting surface that reflects incident light, and is fixed to one surface of the rocking part,
The swing portion is provided at a connection position between the swing portion and the pair of torsion beam portions, extends from the swing portion in the first direction, is parallel to a plane including the structure, and the first A stress relaxation structure in which a first length, which is a length in a second direction orthogonal to the direction, is configured to be larger than the pair of torsion beam portions, and relieves stress at a fixed position between the mirror portion and the swing portion. Including,
An optical scanner characterized by that. The stress relaxation structure is
Extending from the end of the swinging portion in the second direction,
The first length decreases as the distance from the swinging portion decreases.
The optical scanner according to claim 1. The stress relaxation structure is set to a value at which a variation amount of a stress value at the fixed position is saturated with respect to a variation in a second length that is a length in the first direction of the stress relaxation structure. Has two lengths,
The optical scanner according to claim 2. The stress relaxation structure is
The ratio of the second length to the length in the first direction of the rocking portion is formed to be 0.2 or more and 0.4 or less.
The optical scanner according to claim 3. The stress relaxation structure is
A first side extending along the first direction from the swinging portion;
A second side connected to an end of the first side opposite to the swinging portion and extending toward the pair of torsion beams along the second direction;
The optical scanner according to claim 1. The stress relaxation structure has the first length set to a value at which a variation amount of the stress value at the fixed position is saturated with respect to the variation of the first length.
The optical scanner according to claim 5. The stress relaxation structure is formed such that a ratio of the first length to a length in the second direction of the swinging portion is 0.4 or more and 1 or less.
The optical scanner according to claim 6. The stress relaxation structure has the first length set to a value at which a value of a resonance frequency of the optical scanner is saturated with respect to a variation in the first length.
The optical scanner according to claim 5. The stress relaxation structure is formed such that a ratio of the first length to a length in the second direction of the swinging portion is 0.6 or less.
The optical scanner according to claim 8. The mirror part is
It is composed of a material having a different coefficient of linear expansion from that of the structure,
Using a thermosetting adhesive having a durometer hardness of D65 or less, it is fixed to one surface of the rocking part.
The optical scanner according to claim 1. A mass piece is provided on at least one of the other surface of the oscillating portion and one surface of the oscillating portion and spaced from the mirror portion, and adjusts the resonance frequency of the structure. ,
The optical scanner according to claim 1. It is a manufacturing method of the optical scanner according to claim 11, Comprising:
A preparation step of preparing the optical scanner according to any one of claims 5 to 10,
A frequency determining step for determining a value of a resonance frequency of the optical scanner;
A position determining step for determining a position on the rocking portion where the mass piece is provided, based on the value of the resonance frequency determined in the determining step and the value of the target resonance frequency;
An adding step of adding the mass piece to the position on the swinging portion determined in the position determining step;
An optical scanner manufacturing method comprising:

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