JP2012212022A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of reducing temperature dependency of a resonant frequency and to provide a manufacturing method of the optical scanner.SOLUTION: The optical scanner includes a tabular structure constituted of a first material, and a pedestal. The structure includes: a mirror part; a pair of twisted beam parts whose one ends are connected to both sides of the mirror part; and a body part connected to the other ends of the twisted beam parts. The structure further includes a drive part capable of swinging the mirror part at a predetermined resonant frequency. The structure is fixed to at least the pedestal at a pair of fixed parts that face each other in the both sides of the pair of twisted beam parts and the mirror part that are parts of the body part. A coefficient of linear expansion of a second material constituting the pedestal is larger than the coefficient of linear expansion of the first material, and an absolute value of the temperature dependency of the resonant frequency is set to become smaller than an absolute value of temperature dependency of a resonant frequency when the pedestal is constituted of the first material.

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 vibrating mirror is known. For example, the optical scanner described in Patent Document 1 scans light incident on a mirror by a mirror supported so as to be swingable by a torsion beam swinging in a resonance state by a driving unit such as a piezoelectric element. To do. And the structure (main-body part) containing a mirror is being fixed to the base (base).

JP 2009-186652 A

  The resonant frequency of the optical scanner varies depending on various factors. For example, the resonance frequency of the optical scanner varies depending on the Young's modulus of the structure including the mirror. As an explanation thereof, the behavior of the resonance frequency of the optical scanner 100 when the structure 110 is formed of a material having a different Young's modulus (= rigidity) in the shape of the optical scanner 100 shown in FIG. Shown in In FIG. 10, the horizontal axis indicates the relative value of Young's modulus, and the vertical axis indicates the amount of fluctuation of the resonance frequency. The horizontal axis in FIG. 10 is shown as a relative value based on the Young's modulus of the middle data point on the horizontal axis among the three data points. The vertical axis in FIG. 10 shows the ratio of the amount of variation from the three data points with the resonance frequency of the middle data point on the vertical axis as a reference (100%). As apparent from FIG. 10, the Young's modulus and the resonance frequency are directly proportional. The Young's modulus of the structure 110 is basically determined by the type of material constituting the structure 110. However, the Young's modulus of the material generally has temperature dependence. Specifically, even for the same type of material, the Young's modulus decreases as the temperature increases, and the Young's modulus increases as the temperature decreases. Since the resonance frequency depends on the Young's modulus, the resonance frequency also has temperature dependency. Therefore, a change in the ambient temperature in which the optical scanner is placed changes the resonance frequency of the optical scanner.

  As an apparatus using the optical scanner, for example, a laser printer, a scanning image display apparatus, or the like can be considered. In these apparatuses, since the change in the scanning speed results in output distortion, it is desirable that the scanning speed be constant. That is, when an optical scanner that is swung in a resonance state is used, the resonance frequency of the optical scanner is required to be maintained at a predetermined value. However, as described above, when the ambient temperature in which the optical scanner is placed changes, the resonance frequency changes even in the same optical scanner. Therefore, in order to obtain an optical scanner that can be driven stably, the temperature dependence of the resonance frequency needs to be reduced. Therefore, an object of the present invention is to provide an optical scanner capable of reducing the temperature dependence of the resonance frequency, and a method for manufacturing the optical scanner.

  In order to solve the above-described problem, one aspect of the present invention includes a mirror portion that includes a reflecting surface that reflects light and is configured to be swingable about a first axis, and one end of the mirror portion on both sides of the mirror portion. A pair of torsion beam portions extending from the mirror portion parallel to the first axis and connected to the other end of the pair of torsion beam portions, spaced apart from the mirror portion and intersecting the first axis A flat plate-like structure that is formed of a first material and is provided at least in the structure, and the mirror portion is configured to have the first axis at a predetermined resonance frequency. A drive unit configured to be swingable around, and a pedestal to which the structure is fixed. The structure is a part of the main body part, and includes the pair of torsion beam parts and the mirror part. A pair of fixed parts facing each other The pedestal is constituted by a second material having a linear expansion coefficient different from that of the first material, and the linear expansion coefficient of the second material is larger than the linear expansion coefficient of the first material. The absolute value of the temperature dependence of the resonance frequency is set to a value that is larger and smaller than the absolute value of the temperature dependence of the resonance frequency when the pedestal is made of the first material. This is an optical scanner.

  According to this, the structure is fixed to at least the pedestal in the pair of fixed portions. The pair of fixed parts is a part of the main body part that faces the pair of torsion beam parts and the mirror part. In other words, the structure and the base are fixed on both sides of the main body portion with the pair of torsion beam portions and the mirror portion interposed therebetween. And the value of the linear expansion coefficient of the 2nd material which comprises a base is set so that the following 2 conditions may be satisfy | filled. (1) A value larger than the linear expansion coefficient of the first material constituting the structure, and (2) the absolute value of the temperature dependence of the resonance frequency is smaller than the absolute value when the pedestal is made of the first material. Value. Here, since the linear expansion coefficient of the pedestal is larger than that of the structure, thermal stress is generated in the structure due to temperature change. Specifically, when the temperature rises, the pedestal expands more than the structure. This difference in the amount of expansion applies tension in the longitudinal direction of the torsion beam to the torsion beam part and the mirror part sandwiched between the fixed parts of the base and the structure. When tension is applied to the torsion beam, the rigidity of the torsion beam is apparently increased. The higher the rigidity of the torsion beam, the higher the resonance frequency of the optical scanner. On the other hand, the Young's modulus decreases as the temperature increases. That is, the change in Young's modulus of the first material due to the temperature rise works in the direction of lowering the resonance frequency. However, since the linear expansion coefficient of the second material is larger than the linear expansion coefficient of the first material, the thermal stress generated in the structure acts in the direction of increasing the resonance frequency as the temperature rises. Therefore, the temperature dependence of the resonance frequency is reduced. When the temperature decreases, the pedestal contracts more than the structure, and thus a force that compresses the torsion beam in the longitudinal direction works. That is, the apparent rigidity of the torsion beam is lowered, and the resonance frequency is lowered. Therefore, even when the temperature is lowered, similarly, the change in the resonance frequency due to the change in the Young's modulus of the structure (which works in the direction of increasing) is caused by the difference in the expansion amount between the pedestal and the structure. It is reduced by a change in frequency (which works in the direction of lowering).

  Further, the pedestal is provided by a first material constituted by the second material, and a third material having a linear expansion coefficient different from that of the second material provided between the first layer and the structure. A second layer configured, and the second layer may be fixed to the fixed portion of the structure, and the first layer may be fixed to the second layer.

  According to this, the pedestal has the first layer and the second layer. Since the first layer and the second layer are made of materials having different linear expansion coefficients, the selection range of the pedestal that can further reduce the temperature dependence of the resonance frequency is expanded depending on the combination of materials.

  Furthermore, the second layer may be configured to be thinner than the first layer.

  According to this, the second layer in contact with the structure is thinner than the first layer. Therefore. The linear expansion coefficient of the entire pedestal is roughly determined by the first layer, and fine adjustment is possible by selecting the material of the second layer.

  Further, the first material and the second material may be a metal.

  According to this, both a structure and a base are comprised from the metal which is a ductile material. If the structure or pedestal is made of a brittle material such as silicon, for example, depending on the combination of materials, the structure or pedestal may be damaged due to thermal stress. Therefore, the structure and the pedestal are made of metal, thereby increasing the degree of freedom in combining materials. Further, since it can be manufactured by machining such as a press, an optical scanner can be provided at low cost.

  Further, the drive unit is provided in the main body portion, and excites plate waves in the main body portion, thereby swinging the mirror portion around the first axis via the main body portion and the pair of torsion beam portions. It may be a piezoelectric element that can be moved.

  As a result, a so-called external excitation type optical scanner in which the plate wave excited by the piezoelectric element swings the mirror can be obtained. Therefore, a large deflection angle can be obtained.

  In order to solve the above-mentioned problem, another aspect of the present invention is a method for manufacturing the above-described optical scanner, which is a value larger than the linear expansion coefficient of the first material constituting the structure, and A candidate determining step of determining a second material candidate that is a candidate material for the second material constituting the pedestal from a population including a plurality of materials having different values of linear expansion coefficient; and the second material. In a case where a candidate is used as the second material, a dependency determining step for determining temperature dependency of a resonance frequency of the optical scanner, and two or more of the temperature dependencies determined by the dependency determining step Among the second material candidates, the second material candidate having the absolute value of the temperature dependency having the minimum value is determined by the second material determining step and the second material determining step. Said first Using the materials, the generation step of generating said optical scanner, a method for manufacturing an optical scanner and having.

  According to this, the pedestal is constituted by the second material that minimizes the temperature dependency of the resonance frequency of the optical scanner. Therefore, an optical scanner in which the temperature dependence of the resonance frequency is reduced can be obtained.

  Furthermore, the acquisition step of acquiring the linear expansion coefficient of the two or more second material candidates, the value of the linear expansion coefficient of the two or more second material candidates, and the dependency determining step are determined. A relationship determining step of determining a correlation with the temperature dependence in the two or more second material candidates, the second material determining step based on the correlation determined by the relationship determining step; In addition to the two or more second material candidates, a material having a linear expansion coefficient corresponding to a value whose absolute value of temperature dependency is close to a minimum is determined as the second material from the population. May be.

  According to this, based on the correlation between the linear expansion coefficient and the temperature dependence of the resonance frequency, the second material having the minimum temperature dependence is determined. Therefore, it is possible to determine the second material based on the value of the linear expansion coefficient without determining the temperature dependence of the resonance frequency for all the second material candidates.

  Further, a determination step for determining whether or not the temperature dependency of the second material determined by the second material determination step is within a predetermined range, and the temperature dependency is predetermined in the determination step. A third material determining step of determining a material to be used as the third material constituting the second layer of the pedestal from the population when it is determined that it does not fall within a range; In the third material determination step, when the temperature dependency is a negative value, a material having a larger linear expansion coefficient than the second material is determined as the third material, and the temperature dependency is a positive value. A material having a smaller linear expansion coefficient than the second material is determined as the third material, and the creation step is determined in the determination step that the temperature dependence does not fall within a predetermined range. The above The material and the first layer of the pedestal, with the pedestal of the third material and the second layer may be produced the optical scanner.

  According to this, when the temperature dependency of the resonance frequency does not fall within a predetermined range, a pedestal having a laminated structure including the first layer and the second layer is created. When the temperature dependency of the resonance frequency of the pedestal made of only the second material is a positive value, in other words, when the resonance frequency also increases as the temperature rises, the linear expansion coefficient is smaller than that of the second material. The material having is determined as the third material constituting the second layer. Thereby, the linear expansion coefficient when it sees with the whole base can be made small, and the temperature dependence of a resonant frequency can be reduced. On the other hand, when the temperature dependence of the resonance frequency of the pedestal made of only the second material is negative, in other words, when the resonance frequency decreases with increasing temperature, a linear expansion coefficient larger than that of the second material is obtained. The material having is determined as the third material constituting the second layer. Thereby, the linear expansion coefficient when it sees with the whole base can be enlarged, and the temperature dependence of a resonant frequency can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the optical scanner which can reduce the temperature dependence of a resonant frequency, and the manufacturing method of the optical scanner are provided.

1A is a perspective view of an optical scanner 100, and FIG. 1B is a plan view of the optical scanner 100 and an AA cross-sectional view according to the first embodiment. The figure which shows the result of having calculated | required the temperature dependence of the resonance frequency with the linear expansion coefficient of the constituent material of the base 120 by (A) simulation, (B) The result calculated | required by measurement. The figure which plots the result of FIG. 2 on a graph, and shows the correlation with the temperature dependence of the resonant frequency of the optical scanner 100, and the linear expansion coefficient of a base. (A) The perspective view of the optical scanner 200 based on 2nd Embodiment, (B) The top view of the optical scanner 200, and AA sectional drawing. The figure which shows the relationship between the linear expansion coefficient of the constituent material of the 1st layer 221 and the 2nd layer 222, and the temperature dependence of the resonant frequency in the combination when the base 220 is made into 2 layer structure. 12 is a flowchart for explaining a manufacturing process of the optical scanners 100 and 200 according to the third embodiment. The flowchart explaining the examination process of a base lamination in the flowchart of FIG. The flowchart explaining the manufacturing process of the optical scanner in the flowchart of FIG. The figure explaining the change of the temperature dependence of the resonant frequency when the thickness of the 2nd layer 222 of the base 220 changes. FIG. 6 is a diagram for explaining the correlation between the Young's modulus of the structure 110 and the resonance frequency of the optical scanner 100.

<First Embodiment>
Embodiments according to one aspect of the present invention will be described below with reference to the drawings. Note that one aspect of the present invention is not limited to the configuration described below, and various configurations can be employed in the same technical idea. For example, in each configuration described below, a predetermined configuration may be omitted or replaced with another configuration. Moreover, you may make it include another structure.

[Configuration of Optical Scanner 100]
As shown in FIG. 1, the optical scanner 100 includes a structure 110 and a pedestal 120. The mirror portion 111 of the structure 110 is swung around the first axis a by the piezoelectric element 114. By this oscillation, the light incident on the mirror portion 111 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 first axis a and a pair of long sides orthogonal to the first axis a. The structure 110 includes a mirror 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. The structure 110 is made of, for example, a first material that is a metal. Hereinafter, the structure 110 will be described.

  The mirror portion 111 includes a reflection surface that reflects light such as a laser. In the present embodiment, the shape of the mirror portion 111 is rectangular in plan view. However, the shape of the mirror portion 111 is not limited to this, and may be any shape such as a circle, an ellipse, or a polygon in plan view. The reflecting surface is provided by, for example, a method in which the surface of the mirror portion 111 is mirror-polished, or a dielectric such as sapphire or a diamond on which a metal thin film such as aluminum or silver is formed is attached to the mirror portion 111.

  One end of the pair of torsion beam portions 112 is connected to both sides of the mirror portion 111. The pair of torsion beam portions 112 each extend in a direction away from the mirror portion 111. In the present embodiment, the extending direction of the pair of torsion beam portions 112 is parallel to the first axis a. Specifically, the first axis a passes through the centers of the pair of torsion beam portions 112. By the pair of torsion beam portions 112, both sides of the mirror portion 111 are elastically supported so as to be swingable around the first axis a. That is, the pair of torsion beam portions 112 serves as a torsion bar that supports the mirror portion 111 so as to be swingable about the first axis a.

  The main body portion 113 is connected to the other end of the pair of torsion beam portions 112, is separated from the mirror portion 111, and extends in a direction intersecting the first axis a. 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 direction orthogonal to the first axis a. The main body portion 113 includes a fixed portion 113a and a node coupling portion 113b. A pair of fixed portions 113a is provided with a pair of torsion beam portions 112 and a mirror portion 111 interposed therebetween. In the present embodiment, a rectangular through hole is provided at the end of the main body portion 113 in the first axis a direction along a long side orthogonal to the first axis a. In the first axis a direction, the region of the main body portion that is located farther from the mirror portion 111 than the through hole is the fixed portion 113a. In this fixed portion 113a, the structure 110 and the pedestal 120 are fixed. The node fixing portion 113b is provided at a central portion in a direction orthogonal to the first axis a of the rectangular through hole. The node fixing portion 113b extends in the first axis a direction, and connects the body portion 113 closer to the mirror portion 113 than the rectangular through hole and the fixed portion 113a. More specifically, the node fixing portion 113b is positioned in the same straight line as the pair of torsion beam portions 112. Thereby, the thermal stress due to the difference in linear expansion coefficient between the structure 110 and the pedestal 120 is efficiently converted into tension / contraction of the pair of torsion beam portions 112 via the node fixing portion 113b.

  A piezoelectric element 114 as a driving unit is provided on the upper surface of the main body portion 113. A pair of the piezoelectric elements 114 is provided at both ends of the main body portion 113 in the first axis a direction and in the direction orthogonal to the first axis a. The piezoelectric element 114 is, for example, laminated with 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 in a flat plate shape with 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.

  The pedestal 120 has a rectangular shape in plan view. The pedestal 120 has a rectangular hole that is hollowed out in a rectangular shape at the center. Along the longitudinal direction of the rectangular hole, the fixed portion 113 a of the structure 110 is fixed to an adjacent portion of the rectangular hole of the pedestal 120. The thickness of the pedestal 120 is sufficiently larger than the thickness of the structure 110. Therefore, even if the structure 110 swings, the pedestal 120 hardly deforms. The pedestal 120 has a single layer structure including only the first layer 121. The second material constituting the first layer 121 is, for example, a metal having a linear expansion coefficient different from that of the first material constituting the structure 110. More specifically, the value of the linear expansion coefficient of the second material is set so as to satisfy the following two conditions. (1) A value greater than the linear expansion coefficient of the first material, (2) the temperature of the resonance frequency when the pedestal 120 is made of the same first material as the structure 110, and the absolute value of the temperature dependence of the resonance frequency. A value that is smaller than the absolute value of the dependency.

  Since the structure 110 is made of metal, the piezoelectric element 114 can be deformed by applying a voltage between the structure 110 and the electrode layer on the upper surface of the piezoelectric element 114. An AC voltage is applied to the piezoelectric element 114 provided on one side with respect to the first axis a and the piezoelectric element 114 provided on the other 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 mirror portion 111 through the main body portion 113 and the pair of torsion beam portions 112, so that the mirror portion 111 swings around the first axis a 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 up and down, the torsion beam portion 112 is not displaced up and down. Further, a node fixing portion 113 b provided on the same straight line as the torsion beam portion 112 connects the fixed portion 113 a and the torsion beam portion 112. Therefore, the torsion beam portion 112 is further suppressed from being displaced in the vertical direction. Therefore, when the mirror portion 111 is swung around the first axis a, the vertical displacement is suppressed. Accordingly, the light incident on the mirror portion 111 is always incident on the same position on the mirror portion 111, so that stable light scanning is possible.

[Examination of constituent materials of pedestal 120]
As shown in FIG. 2, the temperature dependence of the resonance frequency of the optical scanner 100 is changed by using materials having different linear expansion coefficients for the pedestal 120. In the present embodiment, SUS430 is used as the material of the structure 110. The linear expansion coefficient α of SUS430 is 10.4 × 10 ⁻⁶ [/ ° C.]. Against the structure 110 of SUS430, the material of the base ^{120, SUS420 (α = 10.3 × 10} -6 [/℃]),SECC(α=11.7×10 -6 [/ ℃]), ^{SUS309 (α = 14.5 × 10 -6} [/℃]),SUS316(α=16.5×10 -6 [/℃]),SUS304(α=17.3×10 -6 [/ ℃]) It is selected from the population including five kinds of metals. In FIG. 2, the temperature dependence of the resonance frequency is shown in units of the amount of change in the resonance frequency (Hz / ° C.) with respect to a temperature increase of 1 ° C.

2A shows the temperature dependence of the resonance frequency when the structure 110 is formed of SUS430 in the optical scanner 100 shown in FIG. 1 and the material of the pedestal 120 (= linear expansion coefficient) is changed. The results obtained by simulation are shown. FIG. 2B shows the temperature dependence of the resonance frequency when the structure 110 is formed of SUS430 in the optical scanner 100 shown in FIG. 1 and the material of the pedestal 120 (= linear expansion coefficient) is changed. The result obtained by actual measurement after actually manufacturing the optical scanner 100 is shown. Between FIG. 2A and FIG. 2B, even if the same material is used due to various uncertainties such as bonding conditions between the pedestal 120 and the structure 110 and manufacturing size variations, the temperature dependence The absolute value of sex is different. However, in either case, the tendency was found that the greater the linear expansion coefficient of the material of the pedestal 120, the greater the temperature dependence of the resonance frequency. More specifically, when the pedestal 120 is configured with SUS420, the temperature dependence of the resonance frequency was −0.5 to −0.6 [Hz / ° C.] in both simulation and measurement. The linear expansion coefficient (α = 10.3 × 10 ⁻⁶ [/ ° C.] of SUS420 is the linear expansion coefficient (α = 10.4 × 10 ⁻⁶ [/ ° C.]) of SUS430, which is a constituent material of the structure 110. Is almost equal to That is, the temperature dependence of the resonance frequency when the pedestal 120 is formed of SUS420 can be regarded as a value when the linear expansion coefficients of the structure 110 and the pedestal 120 are substantially the same. Since the Young's modulus decreases with increasing temperature, when the linear expansion coefficient of the structure 110 and the pedestal 120 is substantially the same, the temperature dependence of the resonance frequency shows a negative value (the higher the temperature, the lower the resonance frequency). ). And if the linear expansion coefficient of the base 120 becomes larger than the structure 110, the temperature dependence of the resonant frequency will be relieved. As described above, this is because the pair of torsion beam portions 112 are pulled by the thermal stress acting on the structure 110 due to the difference in the linear expansion coefficient between the structure 110 and the pedestal 120, and apparently a pair of torsion. This is because the rigidity of the beam portion 112 increases. According to the result of FIG. 2, when SECC and SUS309 are used for the pedestal 120, the temperature dependence of the resonance frequency is alleviated as compared to the case where the pedestal 120 is made of the same material as the structure 110. Since it is desirable that the temperature dependence of the resonance frequency is reduced, the material that minimizes the absolute value of the temperature dependence of the resonance frequency may be determined as a constituent material of the pedestal 120 based on this result. For example, according to the result of FIG. 2A, the pedestal 120 is formed using SECC. Further, according to the result of FIG. 2B, the pedestal 120 is formed using SECC or SUS309.

  By taking the linear expansion coefficient of the material of the pedestal 120 on the horizontal axis and the temperature dependence of the resonance frequency on the vertical axis, the correlation between the two is examined. As apparent from FIG. 3, there is a positive correlation, more specifically, a linear relationship between the linear expansion coefficient of the constituent material of the pedestal 120 and the temperature dependence of the resonance frequency. Note that the difference in the temperature dependence of the resonance frequency between the simulation and the actual measurement is shown in FIG. 3 as a difference in proportionality coefficient. Using this first-order proportional relationship (correlation), for example, a material that minimizes the absolute value of the temperature dependence of the resonance frequency can be selected as the material of the pedestal 120. Furthermore, for example, by determining the temperature dependence of the resonance frequency for at least two materials from the population, the proportionality coefficient between the linear expansion coefficient and the temperature dependence of the resonance frequency can be determined. In other words, if this proportionality coefficient is used, the material whose resonance frequency temperature dependence is minimized is based on only the value of the linear expansion coefficient, even for a material whose temperature dependence of the resonance frequency is not determined. Selection becomes possible.

Second Embodiment
FIG. 4 shows another preferred embodiment of the present invention. As shown in FIG. 4, the optical scanner 200 includes a structure 210 and a pedestal 220. The optical scanner 200 is different from the optical scanner 100 described above in the configuration of the base 220.

[Configuration of Optical Scanner 200]
The structure 210 includes a mirror portion 211, a pair of torsion beam portions 212, and a main body portion 213. A piezoelectric element 214 is provided on the upper surface of the main body portion 213. These structures included in the structure 210 are the same as the structures included in the structure 110 described above. Therefore, detailed description of the structure 210 is omitted.

  The pedestal 220 has a first layer 221 and a second layer 222. The constituent material of the first layer 221 and the constituent material of the second layer 222 are metals having different linear expansion coefficients. The second layer 222 has a rectangular shape in plan view, and has a rectangular hole cut out in a rectangular shape at the center. The second layer 222 is fixed to the fixed portion 213a of the structure 210, similarly to the first layer 121 in the above-described embodiment. The first layer 221 is formed in the same manner as the second layer 222 in plan view. The first layer 221 is fixed to the lower surface of the second layer 222. That is, one surface (upper surface) of the second layer 222 is fixed to the structure 210, and the other surface (lower surface) is fixed to the first layer 221. Note that the thickness of the second layer 222 is thinner than the thickness of the first layer 221. As an example, when the thickness of the first layer 221 is about 2 mm, the thickness of the second layer 222 is set to about 0.4 mm. In addition, the thickness of the structure 210 is about 0.1 mm, for example.

[Examination of constituent materials of pedestal 220]
In the first embodiment described above, it has been shown that the temperature dependence of the resonance frequency can be adjusted by changing the constituent material of the pedestal 120 and adjusting its linear expansion coefficient. Here, it is further shown that the temperature dependence of the resonance frequency can be further finely adjusted by configuring the pedestal 220 by stacking metal materials having different linear expansion coefficients.

FIG. 5 shows the result of the simulation for the temperature dependence of the resonance frequency when the material of the second layer 222 is combined with the material of the first layer 221 in the optical scanner 200 shown in FIG. FIG. As an example, as the material of the first layer 221, SUS420 (α = 10.3 × 10 -6 [/℃]),SECC(α=11.7×10 -6 [/ ℃]), SUS304 (α = 17.3 × 10 ⁻⁶ [/ ° C.]). As the material of the second layer 222, SUS430 (α = 10.4 × 10 ⁻⁶ [/ ° C.]), high-function spring steel (α = 14.0 × 10 ⁻⁶ [/ ° C.]), SUS304 ( α = 17.3 × 10 ⁻⁶ [/ ° C.]). Note that the structure 210 is formed of SUS430 as in the case of the optical scanner 100. Moreover, as high function spring steel, for example, HT2000 manufactured by Nisshin Steel Co., Ltd. can be used.

  FIG. 5 shows that the temperature dependence of the resonance frequency changes when the material of the first layer 221 is fixed and the material of the second layer 222 is changed. For example, when SUS430 and SUS304 are used for the second layer 222, the temperature dependence of the resonance frequency of both is about 0.2 [Hz / ° C.] regardless of the material of the first layer 221. There is a difference. The temperature dependence of the resonance frequency tends to increase as a material having a large linear expansion coefficient is used for the second layer 222. On the other hand, comparing the case where SUS420 and SUS304 are used for the first layer 221, regardless of the material of the second layer 222, the temperature dependence of both resonance frequencies is about 0.5 to 0.8 [Hz. / ° C]. In other words, the linear expansion coefficient of the entire pedestal 220 is roughly determined by the first layer 221 having a large thickness, and can be finely adjusted by selecting the material of the second layer 222. Utilizing this property, the material of the first layer 221 is selected so that the absolute value of the temperature dependency of the resonance frequency is minimized, and then the material of the second layer 222 is selected, so that the temperature of the resonance frequency is selected. The dependency can be made closer to 0. For example, when the first layer 221 is configured with SUS420, the temperature dependency of the resonance frequency is a negative value, and thus the second layer 222 is configured with a material having a larger linear expansion coefficient than the first layer 221. Thus, the temperature dependency of the resonance frequency can be further reduced. On the other hand, for example, when the first layer 221 is configured with SUS304, the temperature dependency of the resonance frequency is a positive value, and therefore the second layer 222 is configured with a material having a smaller linear expansion coefficient than the first layer 221. By doing so, the temperature dependence of the resonance frequency can be further reduced.

<Third Embodiment>
Based on the knowledge obtained above, it becomes possible to manufacture an optical scanner in which the temperature dependence of the resonance frequency is relaxed. Here, the process will be described with reference to FIGS.

  First, in step S1, the linear expansion coefficient of the first material constituting the optical scanner structure (structure 110 or structure 210 of the above-described embodiment) is acquired. The material constituting the structure is selected in advance according to, for example, the design value of the resonance frequency of the optical scanner. The linear expansion coefficient may be obtained by directly measuring the material, or may be obtained by utilizing an existing value such as a data sheet.

  Next, in step S2, the temperature dependence of the Young's modulus of the material constituting the structure is acquired. As described above, the Young's modulus of the structure affects the resonance frequency of the optical scanner. The higher the Young's modulus, the higher the resonant frequency. Therefore, by obtaining the temperature dependence of the Young's modulus, the temperature dependence of the resonance frequency of the optical scanner caused only by the structure can be understood. Note that the temperature dependence of the Young's modulus may be acquired by any method such as application of a mathematical formula using an existing value such as a data sheet as a coefficient, actual measurement, or the like.

  Next, in step S3, candidates for the second material constituting the pedestal are determined, and the linear expansion coefficient is obtained. First, a plurality of materials having different linear expansion coefficient values (for example, five types of materials shown as the second material in FIG. 2) exist as a candidate population as the second material. This population includes a material having a linear expansion coefficient larger than that of the first material constituting the structure. Note that a material having a linear expansion coefficient smaller than that of the first material may be included in this population. Then, from this population, one material (for example, SUS420) is determined as a candidate for the second material. Then, the linear expansion coefficient of the second material candidate is acquired. In addition, acquisition of a linear expansion coefficient may be achieved by arbitrary methods, such as using measurement and the value of a data sheet.

  Next, in step S4, the temperature dependence of the Young's modulus of the second material candidate determined in step S3 is acquired. Again, the temperature dependence of the Young's modulus may be obtained by any method such as a mathematical expression using a coefficient of an existing value such as a data sheet or an actual measurement.

  Next, in step S5, the temperature dependence of the resonance frequency in the optical scanner in which the second material candidate is used for the pedestal is determined. This step is achieved, for example, by actually creating an optical scanner and measuring the resonance frequency of the optical scanner while changing the ambient temperature in which the optical scanner is placed. The resonance frequency may be determined from, for example, the timing of the scanning light detected by the optical sensor disposed at the position where the light scanned by the optical scanner enters. Of course, even if it is not an actual measurement, the temperature dependence of the resonance frequency of the optical scanner may be obtained using simulation. Alternatively, if the temperature dependency of the resonance frequency is obtained for two or more second material candidates, based on the correlation between the temperature dependency of the resonance frequency and the linear expansion coefficient of the material. Thus, it is also possible to obtain the temperature dependence of the resonance frequency from the value of the linear expansion coefficient. For example, in FIG. 2, it is assumed that the temperature dependence of the resonance frequency is obtained by actual measurement in the case where the pedestal is configured by SUS420 and SUS304. In this case, a proportional coefficient between the linear expansion coefficient and the temperature dependence of the resonance frequency is determined using the linear expansion coefficients of SUS420 and SUS304 obtained in step S3. If this proportionality coefficient is used, for example, the temperature dependence of the resonance frequency can be determined when the pedestal is constituted by SECC, SUS309, and SUS316 that are not actually measured. That is, once the proportionality coefficient is determined, the temperature dependence of the resonance frequency when the material is used for the pedestal can be determined based only on the value of the linear expansion coefficient of the material. If further expanding, even if the material is not included in the population as a candidate for the second material (for example, a material not shown in FIG. 2), only the value of the linear expansion coefficient of the material is used. Based on this, the temperature dependence of the resonance frequency can be determined.

  Next, in step S6, it is determined whether or not the absolute value of the temperature dependence of the resonance frequency of the second material candidate determined in step S3 is the minimum. If the absolute value of the temperature dependence of the resonance frequency of the second material candidate is minimum (S6: Y), after the second material candidate is determined as the second material constituting the pedestal in step S7. The process proceeds to step S8. On the other hand, when the absolute value of the temperature dependence of the resonance frequency of the second material candidate is not minimum (S6: N), the process proceeds to step S8. For example, if SUS420 is first determined as the second material candidate in FIG. 2, there is no second material candidate determined before that, so the absolute value of the temperature dependence of the resonance frequency of SUS420 is minimized. (Step S6: Y). Therefore, SUS420 is determined as the second material constituting the pedestal (S7). On the other hand, if SECC is determined as the second material candidate after SUS420, the absolute value of the temperature dependence of the resonance frequency of SECC is smaller than the absolute value of the temperature dependence of the resonance frequency of SUS420. Therefore, the absolute value of the temperature dependence of the SECC resonance frequency is minimized (step S6: Y). Therefore, instead of SUS420, SECC is determined as the second material constituting the pedestal (S7). On the other hand, if SUS309 is determined as the second material candidate after SECC, the absolute value of the temperature dependence of the resonance frequency of SUS309 is larger than the absolute value of the temperature dependence of the resonance frequency of SECC. For this reason, the absolute value of the temperature dependence of the resonance frequency of SECC remains minimal (step S6: N). In this case, since step S7 is not performed, the second material constituting the pedestal remains SECC.

  Next, in step S8, it is determined whether other second material candidates still remain in the population. When other second material candidates still remain (S8: Y), the process returns to step S3, and steps S3 to S7 are performed on the other second material candidates. On the other hand, when no other second material candidates remain, in other words, when the study on all second material candidates included in the population is completed (S8: N), the process proceeds to step S9.

  Next, in step S9, it is determined whether or not the temperature dependence of the resonance frequency when using the pedestal material determined in step S7 is within the specification range. The range of this specification may be determined based on the performance of a printer such as a printer that uses an optical scanner or a scanning image display device. Alternatively, the performance of the optical scanner alone may be set to a predetermined value. When the temperature dependence of the resonance frequency falls within the specification range (S9: Y), an optical scanner is created using the base material (S11). That is, in this case, the above-described optical scanner 100 in which the pedestal is composed of a single layer is produced. On the other hand, when the temperature dependency of the resonance frequency does not fall within the specification range (S9: N), the temperature dependency of the resonance frequency is further reduced by forming the pedestal in a laminated structure as in the optical scanner 200 described above. Consideration is made (S10).

  Details of step S10 are shown in FIG. First, in step S100, it is determined whether or not the temperature dependence (obtained in step S5) of the resonance frequency of the second material determined in step S7 is a positive value. For example, in the case shown in FIG. 2, SECC is determined as the second material. When the pedestal is composed of SECC, the temperature dependency of the resonance frequency is negative (−0.162 [Hz / ° C. in simulation, −0.323 [Hz / ° C.] in actual measurement). Is denied (S100: N). In this case, step S102 is performed. On the other hand, if the temperature dependency of the resonance frequency is a positive value, the determination in step S110 is affirmed (S100: Y). In this case, step S101 is performed.

  In step S101, a material having a smaller linear expansion coefficient than the material of the first layer 221 is selected as the material of the second layer 222 of the base 220. As a result, the substantial linear expansion coefficient of the entire pedestal 220 can be reduced, and the temperature dependence of the resonance frequency can be brought close to zero. For example, if SUS304 is determined as the material of the first layer 221, high-function spring steel or SUS430, which is a material having a smaller coefficient of linear expansion than SUS304, is determined as the material of the second layer 222. (See FIG. 5). Thereafter, the study of the stacked structure of the pedestal is completed, and the process proceeds to step S11.

  In step S102, a material having a larger linear expansion coefficient than the material of the first layer 221 is selected as the material of the second layer 222 of the base 220. As a result, the substantial linear expansion coefficient of the entire pedestal 220 can be increased, and the temperature dependence of the resonance frequency can be brought close to zero. For example, if SECC is determined as the material of the first layer 221, high-function spring steel or SUS304, which is a material having a larger linear expansion coefficient than SECC, is determined as the material of the second layer 222. . Thereafter, the study of the stacked structure of the pedestal is completed, and the process proceeds to step S11.

  In step S11 of FIG. 6, an optical scanner is created. Here, when the determination in step S9 is affirmative (S9: Y), the optical scanner 100 including the pedestal 120 made of a single layer is formed. On the other hand, when the determination in step S9 is negative (S9: N), the optical scanner 200 including the base 220 having the first layer 221 and the second layer 222 is formed. Details of step S11 are shown in FIG.

  First, in step S110, a structure is formed. A metal plate (for example, SUS430) constituting the structure is divided into a size equal to the outer shape of the structure. Then, a resist film for masking is formed at positions corresponding to the mirror portion, the torsion beam portion, and the main body portion 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. Alternatively, the structure may be formed not by wet etching but by mechanical processing such as press processing.

  Next, in step S111, a bulk piezoelectric material provided with electrode layers on both surfaces of the piezoelectric element in advance is mounted on the structure. 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, a bulk piezoelectric material is placed on a conductive adhesive applied to the main body portion of the structure. After installation of the piezoelectric material, the conductive adhesive is cured by placing the structure in a heating furnace maintained at 100 to 200 ° C. for 30 to 60 minutes. This completes the mounting of the piezoelectric element.

  Next, in step S112, a pedestal is created. The outer shape of the pedestal can be obtained by performing removal processing such as etching or pressing on the metal plate that is a constituent material of the pedestal, as in the case of the structure. When the pedestal has a laminated structure of the first layer and the second layer, the metal plate for constituting the first layer and the metal plate for constituting the second layer are respectively subjected to removal processing. Is done. Note that the thicknesses of the first layer and the second layer are automatically set by processing a metal plate having a corresponding thickness. Thereafter, the first layer and the second layer are fixed by adhesion, welding, or the like.

  Next, in step S113, the base and the structure 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 and the base may be fixed by other fixing methods such as bonding using a thermosetting adhesive.

  In step S114, the signal line is connected to the piezoelectric element and the structure by wire bonding. This signal line is connected to an AC power source (not shown). Since the structure and the piezoelectric element are bonded by a conductive adhesive, a voltage is applied between the piezoelectric element and the structure via the signal line. This completes the optical scanner manufacturing process.

  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 optical scanner 200 described above, the pedestal 220 has a first layer 221 and a second layer 222. However, this embodiment does not exclude a configuration in which the pedestal has a laminated structure of three or more layers. When the pedestal is formed with a laminated structure of three or more layers, the materials for the third and subsequent layers may be determined after the materials for the first layer and the second layer are determined as described above.

  In the optical scanner 200 described above, the material of the second layer 222 is determined to reduce the temperature dependence of the resonance frequency using the type of the constituent material, more specifically, the linear expansion coefficient of the constituent material as a variable. However, other variables that determine the structure of the second layer 222 may be further introduced to reduce the temperature dependence of the resonance frequency. For example, as shown in FIG. 9, when the thickness of the second layer 222 changes, the temperature dependence of the resonance frequency also changes. In the example shown in FIG. 9, the structure 210 is made of SUS430, the first layer 221 of the base 220 is made of SECC, and the second layer 222 is made of SUS304. The thickness of the structure 210 is set to 100 μm, and the thickness of the first layer 221 is set to 2000 μm. As is apparent from FIG. 9, the temperature dependence of the resonance frequency increases as the second layer 222 becomes thicker. That is, for example, a step of determining the thickness of the second layer 222 may be performed after step S101 or step S102 shown in FIG. This makes it possible to determine the structure of the pedestal so that the absolute value of the temperature dependence of the resonance frequency is further reduced by using the variable of the pedestal thickness in addition to the variable of the linear expansion coefficient.

  In the above-described embodiment, the structure and the base are made of metal. However, the present invention is characterized in that the temperature dependence of the resonance frequency is relaxed by making the linear expansion coefficients of the structure and the pedestal different. Therefore, even if the pedestal or the structure is made of a nonmetal such as silicon, it is within the scope of the present invention. Similarly, the shapes of the structure and the pedestal are not limited to the above-described embodiments. Any type of optical scanner in which a flat plate-like structure having a mirror portion, a torsion beam portion, and a main body portion is fixed to a pedestal is included in the scope of the present invention. In the embodiment described above, a piezoelectric element 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 Optical scanner 110, 210 Structure 111, 211 Mirror part 112, 212 Torsion beam part 113, 213 Body part 113a, 213a Fixed part 113b, 213b Node connecting part 114, 214 Piezoelectric element 120, 220 Base 121, 221 First layer 222 second layer

Claims (8)

A mirror portion including a reflecting surface for reflecting light and configured to be swingable about a first axis;
A pair of torsion beam portions, one end of which is connected to both sides of the mirror portion and extends from the mirror portion parallel to the first axis;
A body portion connected to the other end of the pair of torsion beam portions, extending from the mirror portion and extending in a direction intersecting the first axis;
A flat plate-like structure composed of the first material;
A drive unit that is provided at least in the structure and configured to be able to swing the mirror portion around the first axis at a predetermined resonance frequency;
A pedestal to which the structure is fixed;
The structure is a part of the main body part and is fixed to at least the pedestal in a pair of fixed parts facing each other with the pair of torsion beam parts and the mirror part interposed therebetween,
The pedestal is constituted by a second material having a linear expansion coefficient different from that of the first material,
The linear expansion coefficient of the second material is larger than the linear expansion coefficient of the first material, and the absolute value of the temperature dependence of the resonance frequency is the value when the pedestal is formed of the first material. Set to a value smaller than the absolute value of the temperature dependence of the resonance frequency,
An optical scanner characterized by that. The pedestal is
A first layer composed of the second material;
A second layer configured by a third material provided between the first layer and the structure and having a linear expansion coefficient different from that of the second material;
The second layer is fixed to the fixed portion of the structure;
The first layer is fixed to the second layer;
The optical scanner according to claim 1. The second layer is configured to be thinner than the first layer.
The optical scanner according to claim 2. The first material and the second material are metals.
The optical scanner according to claim 1. The drive unit is
Provided in the body portion;
A piezoelectric element capable of swinging the mirror portion around the first axis via the main body portion and the pair of torsion beam portions by exciting plate waves in the main body portion;
The optical scanner according to claim 4. A method for manufacturing an optical scanner according to any one of claims 1 to 5,
As the second material constituting the pedestal from a population including a plurality of materials having values of linear expansion coefficients different from each other, the values being larger than the linear expansion coefficient of the first material constituting the structure A candidate determination step of determining a second material candidate that is a candidate material of
A dependency determining step for determining temperature dependency of a resonance frequency of the optical scanner when the second material candidate is used as the second material;
Among the two or more second material candidates whose temperature dependency is determined by the dependency determining step, the second material candidate whose absolute value of the temperature dependency is minimized is selected as the second material. A second material determination step determined as:
Using the second material determined by the second material determination step, the creation step of creating the optical scanner;
A method for manufacturing an optical scanner, comprising: An obtaining step of obtaining a linear expansion coefficient of the two or more second material candidates;
Determination of a relationship for determining a correlation between values of linear expansion coefficients of the two or more second material candidates and the temperature dependency of the two or more second material candidates determined by the dependency determination step. A further process,
In the second material determination step, based on the correlation determined in the relationship determination step, in addition to the two or more second material candidates, an absolute value of the temperature dependency from the population. A material having a coefficient of linear expansion corresponding to a value close to a minimum is determined as the second material;
The manufacturing method of the optical scanner of Claim 6. A determination step of determining whether or not the temperature dependence of the second material determined by the second material determination step is within a predetermined range;
When it is determined in the determination step that the temperature dependence does not fall within a predetermined range, a material used as the third material constituting the second layer of the pedestal is determined from the population. A third material determination step,
The third material determination step includes
When the temperature dependency is a negative value, a material having a larger linear expansion coefficient than the second material is determined as the third material,
If the temperature dependency is a positive value, a material having a smaller linear expansion coefficient than the second material is determined as the third material,
In the creation step, when it is determined in the determination step that the temperature dependency does not fall within a predetermined range, the second material is the first layer of the pedestal, and the third material is the second layer. Using the pedestal as a layer, the optical scanner is manufactured.
The manufacturing method of the optical scanner of Claim 6 or 7.

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