JP2011007902A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of obtaining a large optical deflection angle at driving voltage of small value.SOLUTION: The optical scanner 1 is equipped with a mirror part 2, a movable beam 3, a pair of driving parts 4a and 4b, and a fixed part 5. The mirror part 2 is equipped with a reflection surface 6 swinging around a swing axial line SW, and reflecting incident luminous flux to perform scanning. The movable beam 3 is equipped with a pair of supporting beams 7a and 7b, a pair of extending beams 8a and 8b, and four coupling beams 9a to 9d. The pair of supporting beams 7a and 7b extends from both sides of the mirror part 2 in an X-axis direction, that is, a direction parallel with the swinging axial line SW. The driving parts 4a and 4b are provided to extend over a pair of coupling beams 9a and 9b and the fixed part 5 respectively. The center of gravity GC of the mirror part 2 is positioned on the opposite side CS of the driving parts 4a and 4b with respect to an extension line XT.

Description

  The present invention relates to an optical scanner used in a laser printer, a projection display device, and the like.

  Conventionally, optical scanners are used in laser printers, projection display devices, and the like. As this optical scanner, there are generally those using a polygon mirror and those using a MEMS (Micro-Electro-Mechanical Systems) mirror. Among these, an optical scanner using a MEMS mirror is an integral part of a mirror part, a beam that supports the mirror part and transmits a driving force to the mirror part, and a fixed frame that is connected to the beam and surrounds the mirror part and the beam. Because it is manufactured by molding, etc., it is suitable for light and small optical scanners compared to polygon mirrors.

  FIG. 9 is an exploded perspective view of the optical scanner 101 using the MEMS mirror disclosed in Patent Document 1. In FIG. The optical scanner 101 includes a base table 102 and a vibrating body 105. The base 102 includes a pair of support portions 103a and 103b, a pair of recesses 104a and 104b, and an intermediate recess 104c. The support part 103 a and the support part 103 b are formed on the upper surface of the base table 102. The concave portions 104a and 104b are formed between the support portion 103a and the support portion 103b. The intermediate recess 104c is formed between the recess 104a and the recess 104b. The recess 104a and the recess 104b are formed adjacent to the support portions 103a and 103b, respectively. The vibrating body 105 is disposed on the base table 102 configured as described above.

  The vibrating body 105 includes a mirror unit 106, support beams 107a and 107b, extended beams 108a and 108b, connecting beams 109a, 109b, 109c, and 109d, a fixing unit 110, and driving units 111a and 111b. . The mirror unit 106 has a reflecting surface 106a. The support beam 107a and the support beam 107b are connected to the mirror unit 106 and face each other with the mirror unit 106 interposed therebetween. The extended beam 108a is connected to the support beam 107a and extends to both sides of the support beam 107a. The extension beam 108b is connected to the support beam 107b and extends to both sides of the support beam 107b. The connecting beams 109 a and 109 c are connected to both ends of the extended beam 108 a, extended toward the fixed portion 110, and connected to the fixed portion 110. The connecting beams 109b and 109d are connected to the extended beams 108a and 108b, extend toward the fixed portion 110, and are connected to the fixed portion 110. The fixed portion 110 is an outer frame that surrounds the outer periphery of the mirror portion 106, the support beams 107a and 107b, the extended beams 108a and 108b, and the connecting beams 109a to 109d. The fixed part 100 is disposed on the support parts 103 a and 103 b of the base table 102. The drive unit 111a is provided across the connecting beam 109a and the fixed unit 110. The drive unit 111b is provided across the connecting beam 109b and the fixed unit 110.

  The drive units 111a and 111b are composed of a piezoelectric body and two electrodes sandwiching the piezoelectric body. The piezoelectric bodies of the drive units 111a and 111b are polarized by applying a voltage to the electrodes of the drive units 111a and 111b, respectively. The polarized piezoelectric bodies of the drive units 111a and 111b expand and contract in the longitudinal direction of the connecting beams 109a and 109b, respectively. A drive voltage having a magnitude and polarity according to the waveform of the drive signal supplied to the drive units 111a and 111b is applied to the electrodes of the drive units 111a and 111b. That is, for example, when drive signals having the same phase are supplied to the drive units 111a and 111b, drive voltages having the same polarity are applied to the electrodes of the drive units 111a and 111b. When a drive voltage having the same polarity is applied to the electrodes of the drive units 111a and 111b, when one of the piezoelectric bodies of the drive units 111a and 111b extends toward the mirror unit 106, the other also extends, and one of them is a mirror. When contracting away from the portion 106, the other contracts. As the piezoelectric bodies of the drive units 111a and 111b expand and contract, the connecting beams 109a and 109b bend vertically in the thickness direction of the connecting beams 109a and 109b, respectively. The bending of the connecting beams 109a and 109b causes the extending beams 108a and 108b, the support beams 107a and 107b, and the mirror unit 106 to swing. As the mirror unit 106 swings, the reflecting surface 106a swings, and the reflecting surface 106a reflects the incident light beam while swinging. As described above, the optical scanner 101 scans the light beam incident on the reflecting surface 106a.

  In the optical scanner 101 as described above, as a method of obtaining a large optical deflection angle, it is possible to increase the expansion and contraction of the piezoelectric bodies of the drive units 111a and 111b. Since the expansion / contraction amount of the piezoelectric body depends on the magnitude of the voltage applied to the electrodes of the driving units 111a and 111b, a large driving voltage is applied to the electrodes of the driving units 111a and 111b in order to obtain a large optical deflection angle. It is necessary to Therefore, the method of increasing the expansion and contraction of the piezoelectric bodies of the drive units 111a and 111b has a problem that the drive units 111a and 111b cannot be driven with a small drive voltage.

JP 2003-57586 A

  The present invention has been made to solve the above-described problems, and is an optical scanner that reflects and scans an incident light beam, and has a reflecting surface that can swing around a swing axis. A pair of mirror support beams extending from both sides of the mirror portion in a direction parallel to the swing axis, and a pair of first connection portions connected to each of the pair of mirror support beams, A pair of extending beams extending from the first connecting portion to both sides of the mirror support beam in a direction parallel to the reflecting surface and perpendicular to the swing axis, and the pair of extending beams A movable beam having four second coupling portions coupled to each of both ends, and four coupling beams extending from the second coupling portion in a direction away from the mirror portion in parallel to the swing axis. A fixed portion connected to the four connecting beams, and the front of the four connecting beams An optical scanner comprising: a pair of connecting beams positioned on one side with respect to an extension line connecting a pair of mirror support beams; and a pair of drive units for driving the movable beam, The object is to obtain a large optical deflection angle with a small driving voltage.

  In order to achieve the above object, the present invention according to claim 1 is an optical scanner that reflects and scans an incident light beam, and includes a mirror portion having a reflecting surface that can swing around a swing axis. A pair of mirror support beams extending from both sides of the mirror portion in a direction parallel to the swing axis, and a pair of first connection portions connected to each of the pair of mirror support beams; A pair of extended beams extending from the first connecting portion to both sides of the mirror support beam in a direction perpendicular to the swing axis, and both ends of the pair of extended beams. A movable beam having four second coupling portions coupled to each other, and four coupling beams extending from the second coupling portion in a direction away from the mirror portion in parallel to the swing axis; The fixed portion connected to the four connecting beams, and the pair of mirrors of the four connecting beams. A pair of connecting beams positioned on one side with respect to the extension line connecting the support beams and the fixed portion, and a pair of driving portions for driving the movable beam, The center of gravity is located on a side opposite to the pair of driving units with respect to the extension line.

  According to a second aspect of the present invention, in the first aspect of the present invention, the pair of driving units each include a piezoelectric body that expands and contracts on a plane parallel to the reflecting surface and parallel to the swing axis. A pair of electrodes provided on both sides of the piezoelectric body, wherein the piezoelectric bodies of the pair of drive units are on a plane parallel to the reflecting surface and in a direction parallel to the swing axis. And a drive control section for supplying a drive signal having the same phase to the pair of drive sections so as to extend or contract together.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the branch width between the pair of connecting beams facing each other across the extension line is a plane parallel to the reflecting surface of the mirror portion. The distance between the center of gravity of the mirror portion and the extension line is less than half of the mirror width in the direction perpendicular to the swing axis and is half the branch width. It is characterized in that the length is reduced from.

  In this invention of Claim 4, in the invention in any one of Claims 1-3, The one side end of the said mirror part located in the opposite side to the said pair of drive part with respect to the said extension line, The distance between the extension line and the extension line is different from the distance between the extension line and the other end of the mirror portion located on the same side as the pair of drive units. The center of gravity of the mirror part is located on the opposite side to the pair of driving parts with respect to the extension line.

  In this invention of Claim 5, in the invention in any one of Claims 1-3, when the said mirror part has a hole, a groove | channel, or a weight, the gravity center of the said mirror part is with respect to the said extension line. And it is located on the opposite side to a pair of above-mentioned drive part, It is characterized by the above-mentioned.

  The inventors have developed and improved the optical scanner described below. The optical scanner is an optical scanner that reflects and scans an incident light beam, and includes a mirror portion having a reflecting surface that can swing around a swing axis, and the mirror in a direction parallel to the swing axis. A pair of mirror support beams extending from both sides of the part, and a pair of first connection parts connected to each of the pair of mirror support beams, on the plane parallel to the reflecting surface and the swing axis A pair of extending beams extending from the first connecting portion to both sides of the mirror support beam, and four second connecting portions connected to both ends of the pair of extending beams. A movable beam having four connecting beams extending from the second connecting portion in a direction away from the mirror portion in parallel with the swing axis, and a fixed portion connected to the four connecting beams; Of the four connecting beams, one piece with respect to an extension line connecting the pair of mirror support beams It provided across a pair of connecting beams and the fixed portion located, and a pair of drive unit for driving the movable beam. Hereinafter, the optical scanner is referred to as a “bifurcated optical scanner”. The present inventor performs a numerical analysis on the bifurcated optical scanner, thereby positioning the center of gravity of the mirror portion on the side opposite to the pair of drive portions with respect to the extension line, thereby providing a constant deflection angle. It was confirmed that the drive voltage required to obtain was reduced. In addition, the present inventor compared the case where the center of gravity of the mirror part is located on the same side as the pair of driving parts with respect to the extension line, compared to the case where the center of gravity of the mirror part is on the extension line with respect to the bifurcated optical scanner. It was also confirmed that a larger driving voltage is required to obtain a constant deflection angle.

  According to the optical scanner of claim 1, by positioning the center of gravity of the mirror portion of the bifurcated optical scanner on the side opposite to the pair of drive portions with respect to the extension line, it is possible to apply a large drive voltage without applying a large drive voltage. A large optical deflection angle of the optical scanner can be obtained. Therefore, a large optical deflection angle of the bifurcated optical scanner can be obtained with a small driving voltage.

  According to the optical scanner of the second aspect, the same phase drive control system that is optimal for the bifurcated optical scanner that supplies the same phase drive signal to the pair of drive units is adopted, and the mirror unit of the bifurcated optical scanner is provided. By positioning the center of gravity on the side opposite to the pair of drive units with respect to the extension line, a large optical deflection angle of the optical scanner can be obtained without applying a large drive voltage. Therefore, a large optical deflection angle of the bifurcated optical scanner can be obtained with a small driving voltage.

  As the inventor conducts numerical analysis to increase the distance between the center of gravity of the mirror portion of the bifurcated optical scanner and the extension line, the driving voltage required to obtain a constant deflection angle gradually increases. It has been confirmed that after falling and reaching a certain minimum value, it rises or converges to a certain minimum convergence value.

  On the basis of the fact that the change in the driving voltage is confirmed, according to the optical scanner of claim 3, the distance between the center of gravity of the mirror portion and the extension line is set so that the half of the branch width is equal to the mirror width. By reducing the length from half, the drive voltage required to obtain a constant deflection angle becomes a minimum value or a value near the minimum convergence value, and the large optical deflection angle of the optical scanner is made as much as possible. Can be obtained with a small driving voltage.

  According to the optical scanner of claim 4, by positioning the center of gravity of the mirror portion of the bifurcated optical scanner on the side opposite to the pair of drive units with respect to the extension line, even without applying a large drive voltage, A large optical deflection angle of the optical scanner can be obtained. Therefore, a large optical deflection angle of the bifurcated optical scanner can be obtained with a small driving voltage.

  According to the optical scanner of claim 5, by positioning the center of gravity of the mirror part of the bifurcated optical scanner on the side opposite to the pair of drive parts with respect to the extension line, even without applying a large drive voltage, A large optical deflection angle of the optical scanner can be obtained. Therefore, a large optical deflection angle of the bifurcated optical scanner can be obtained with a small driving voltage.

1 is a partial top view of an optical scanner 1 according to an embodiment of the present invention. 2 is a partially enlarged top view of the optical scanner 1. FIG. It is explanatory drawing for demonstrating the structure of the drive part 4a which concerns on this embodiment. It is explanatory drawing for demonstrating the drive signal DS which concerns on this embodiment. It is explanatory drawing for demonstrating rocking | fluctuation of the mirror part 2 which concerns on this embodiment. It is a figure which shows the relationship between offset amount OS and drive voltage which concern on this embodiment at the time of setting branch width WD = 200 micrometers between the connection beam 9a and the connection beam 9c. It is a figure which shows the relationship between offset amount OS and drive voltage which concern on this embodiment in the case of setting said branch width WD = 300, 400, 500 micrometers. It is a figure which shows the manufacturing process of the structure which concerns on this embodiment. It is a figure which shows the usage example in the retinal scanning display 201 of the said optical scanner 1. FIG. It is a figure which shows the conventional optical scanner 101. FIG.

  Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings.

[Optical scanner appearance]
FIG. 1 is a partial top view showing the appearance of the optical scanner 1 of the present embodiment. In FIG. 1, a part of the optical scanner 1 is omitted for simplification. The optical scanner 1 is a resonance type optical scanner. As shown in FIG. 1, the optical scanner 1 includes a mirror unit 2, a movable beam 3, a pair of drive units 4 a and 4 b, and a fixed unit 5. The mirror part 2 in this embodiment is an example of the mirror part of this invention. The movable beam 3 in this embodiment is an example of the movable beam of the present invention. The drive units 4a and 4b in the present embodiment are an example of the drive unit of the present invention. The fixing part 5 in the present embodiment is an example of the fixing part of the present invention. The fixed portion 5 is an outer frame that surrounds the mirror portion 2 and the movable beam 3 as disclosed in Japanese Patent Application Laid-Open No. 2003-57586, but FIG. 1 shows the movable beam 3 and the fixed portion for simplification. Only the fixing part 5 in the vicinity of the connecting part to 5 is shown. In addition, the mirror part 2, the movable beam 3, the drive parts 4a and 4b, and the fixed part 5 are arrange | positioned on the base stand which is not shown in figure.

  The mirror unit 2 includes a reflecting surface 6 that can swing around the swing axis SW and that reflects and scans an incident light beam. Hereinafter, for simplification, as shown in FIG. 1, the direction parallel to the swing axis SW when the optical scanner 1 is stationary is defined as the X axis, on the plane parallel to the reflecting surface 6, and the swing axis SW. A direction perpendicular to the Y axis is defined as the Y axis, and a direction perpendicular to the reflecting surface 6 is defined as the Z axis. The definitions of the directions of the X axis, the Y axis, and the Z axis are common to other drawings. The reflective surface 6 in the present embodiment is an example of the reflective surface of the present invention.

  As shown in FIG. 1, the movable beam 3 extends from both sides of the mirror portion 2 in the X-axis direction. As shown in FIG. 1, the movable beam 3 includes a pair of support beams 7a and 7b, a pair of extended beams 8a and 8b, and four connecting beams 9a to 9d. The pair of support beams 7a and 7b extend from both sides of the mirror portion 2 in the X-axis direction, that is, in a direction parallel to the swing axis SW. Of the four connecting beams 9a to 9d, the pair of connecting beams 9a and 9b are located on one side SS with respect to the extension line XT connecting the pair of support beams 7a and 7b. The pair of connecting beams 9c and 9d are located on the other side CS with respect to the extension line XT. The drive units 4a and 4b are provided across the pair of connecting beams 9a and 9b and the fixed unit 5, respectively. The support beams 7a and 7b in this embodiment are an example of the mirror support beam of the present invention. The extended beams 8a and 8b in this embodiment are an example of the extended beam of the present invention. The connecting beams 9a to 9d in the present embodiment are examples of the connecting beam of the present invention.

  The mass distribution with respect to the XY plane of the mirror unit 2 is substantially uniform. In the present embodiment, the center of gravity GC is the point of action of the resultant force of gravity acting on the mass in a system in which the mass is distributed with a spatial spread like the mirror unit 2, that is, the center of mass. As shown in FIG. 1, with respect to the extension line XT, the distance CD between the one end CE of the mirror part 2 located on the side CS opposite to the drive parts 4a and 4b and the extension line XT is an extension line. With respect to XT, the distance SD is larger than the distance SD between the other end SE of the mirror unit 2 located on the same side SS as the drive units 4a and 4b and the extension line XT. In this way, the offset amount OS = CD−SD is set to a positive value in the Y-axis direction shown in FIG. 1, so that the center of gravity GC of the mirror unit 2 is extended line XT as shown in FIG. 1. On the other hand, it is located on the side CS opposite to the drive units 4a and 4b. The swing axis SW passes near the center of gravity GC, and when the offset amount OS = 0 μm, the swing axis SW and the extension line XT substantially coincide with each other, and both pass near the center of gravity GC. One side end CE in the present embodiment is an example of one side end of the present invention. The other side end SE in the present embodiment is an example of the other side end of the present invention.

  The structure of the optical scanner 1 will be described in detail with reference to FIG. FIG. 2 is a partially enlarged top view of the optical scanner 1. In FIG. 2, only the support beam 7a, the extension beam 8a, the connection beams 9a and 9c, and the drive unit 4a are shown for simplification, but the support beam 7b, the extension beam 8b, the connection beams 9b and 9d, The drive unit 4b also has the same configuration as the support beam 7a, the extended beam 8a, the connecting beams 9a and 9c, and the drive unit 4a. As shown in FIG. 2, the support beam 7a extends from one side surface of the mirror unit 2 in the X-axis direction. As shown in FIG. 2, the extended beam 8a has a first connecting portion CP1 connected to the support beam 7a, and extends from the first connecting portion CP1 to both sides of the support beam 7a in the Y-axis direction. As shown in FIG. 2, the connecting beams 9a and 9c have a pair of second connecting portions CP2 that are connected to both ends of the extending beam 8a. Further, as shown in FIG. 2, the connecting beams 9 a and 9 c have a pair of third connecting portions CP <b> 3 that are connected to the fixing portion 5. The connecting beams 9a and 9c extend from the second connecting part CP2 toward the third connecting part CP3 in the direction away from the mirror part 2 in the X direction. The first connecting portion CP1 and the second connecting portion CP2 in the present embodiment are examples of the first connecting portion and the second connecting portion of the present invention, respectively.

[Structure of drive unit]
The structure of the drive units 4a and 4b will be described in detail with reference to FIG. In FIG. 3, only the drive unit 4a is shown as a representative, but the drive unit 4b has the same configuration as the drive unit 4a. As shown in FIG. 3, the drive unit 4a is a laminated body in which a thin plate-like piezoelectric body 10a is sandwiched between an upper electrode 11a and a lower electrode 12a. The piezoelectric body 10a is composed of lead zirconate titanate (hereinafter referred to as “PZT”) that is deformed by voltage application. Similarly to the drive unit 4a, the drive unit 4b includes a piezoelectric body 10b (not shown), an upper electrode 11b, and a lower electrode 12b. The piezoelectric bodies 10a and 10b in the present embodiment are examples of the piezoelectric body of the present invention. The upper electrodes 11a and 11b and the lower electrodes 12a and 12b in the present embodiment are examples of the electrode of the present invention.

  The upper electrodes 11 a and 11 b and the lower electrodes 12 a and 12 b are connected to the drive control unit 60 by lead wires 50. A drive signal having the same phase is supplied from the drive control unit 60 to the drive units 4 a and 4 b through the lead wire 50. By supplying drive signals of the same phase from the drive control unit 60 to the drive units 4a and 4b, the same polarity is provided between the upper electrode 11a and the lower electrode 12a and between the upper electrode 11b and the lower electrode 12b. A voltage is applied. When the voltage is applied in this way, the piezoelectric bodies 10a and 10b extend or contract together in the X-axis direction. The drive control unit 60 in the present embodiment is an example of the drive control unit of the present invention.

[Drive optical scanner]
The driving of the optical scanner 1 will be described with reference to FIGS. FIG. 4 is a diagram illustrating in-phase drive signals DS supplied from the drive control unit 60 to the drive units 4a and 4b. In FIG. 4, the vertical axis represents the voltage Vt applied between the upper electrodes 11a, 11b and the lower electrodes 12a, 12b of the drive units 4a, 4b, and the horizontal axis represents the time Tm. The drive control unit 60 generates a drive signal DS for driving the drive units 4a and 4b, and supplies the drive signal DS to the drive units 4a and 4b. The drive signals DS supplied to the drive unit 4a and the drive unit 4b need only have at least the same phase, but in the present embodiment, the drive signals DS supplied to the drive unit 4a and the drive unit 4b are Have the same amplitude and the same phase. Due to the periodicity of the drive signal DS, the piezoelectric bodies 10a and 10b of the drive units 4a and 4b extend or contract together in the X-axis direction. That is, for example, at times Tm1 to Tm2 indicated by broken lines and arrows in FIG. 4, the voltage Vt applied to the upper electrodes 11a and 11b and the lower electrodes 12a and 12b gradually increases. As the voltage Vt gradually increases, the piezoelectric bodies 10a and 10b both contract in the X-axis direction. In addition, in the time Tm3 to Tm4 indicated by the alternate long and short dash line and the arrow in FIG. 4, the voltage Vt applied to the upper electrodes 11a and 11b and the lower electrodes 12a and 12b gradually decreases. When the voltage Vt gradually decreases, the piezoelectric bodies 10a and 10b both extend in the X-axis direction. Thus, due to the periodicity of the drive signal DS, the piezoelectric bodies 10a and 10b of the drive units 4a and 4b both expand or contract in the X-axis direction.

  FIG. 5 is a diagram illustrating a state in which the optical scanner 1 is driven and the mirror unit 2 swings around the swing axis SW. FIG. 5 shows only the mirror unit 2 and the movable beam 3 for simplification. FIG. 5 shows the optical scanner 1 having an offset amount OS close to 0 μm for simplification. In FIG. 5, an optical scanner 1 indicated by a two-dot chain line indicates the optical scanner 1 at rest. An optical scanner 1 indicated by a solid line shows the optical scanner 1 when the optical scanner 1 is driven and the mirror portion 2 reaches a certain swing angle Φ. As is well known, the swing angle of the mirror unit 2 corresponds to the optical swing angle of the optical scanner 1. The movable beam 3 is shown with a simplified structure. The drive signal DS having the same phase shown in FIG. 4 is supplied from the drive control unit 60 to the drive units 4a and 4b, so that the drive units 4a and 4b are driven, and the piezoelectric bodies 10a and 10b are moved together in the X-axis direction. Stretch or shrink. As a result of the expansion and contraction of the piezoelectric bodies 10a and 10b, the portions in the vicinity of the drive portions 4a and 4b of the connecting beams 9a and 9b bend upward or downward in the Z-axis direction. Due to the periodicity of the in-phase drive signal DS shown in FIG. 5, the voltage applied between the upper electrode 11a and the lower electrode 12a and between the upper electrode 11b and the lower electrode 12b periodically changes. This periodic voltage change causes a periodic bending upward or downward in the Z-axis direction in the vicinity of the driving portions 4a and 4b of the connecting beams 9a and 9b. Due to the periodic bending of the connecting beams 9a and 9b in the vicinity of the drive portions 4a and 4b, the movable beam 3 is twisted and oscillated around the swing axis SW. Due to the torsional vibration of the movable beam 3, the mirror unit 2 swings about the swing axis SW. The reflecting surface 6 of the mirror unit 2 reflects the incident light beam while swinging about the swing axis SW. In this way, the light beam is reflected by the reflecting surface 6 so that the light beam is scanned. As described above, when the drive signal DS having the same phase is supplied from the drive control unit 60 to the drive units 4a and 4b, the optical scanner 1 is driven, and the optical scanner 1 receives the light beam incident on the reflection surface 6 as a result. Reflect and scan. Note that the upper side and the lower side in the Z-axis direction are the positive region side and the negative region side of the Z-axis, respectively, and are not strictly limited to a direction parallel to the Z-axis direction.

[Analysis result]
An analysis result by simulation of a change in the driving voltage of the optical scanner 1 when the offset amount OS is changed will be described. First, the dimensions of each part of the optical scanner 1 set in the simulation will be described with reference to FIG. The width MR of the mirror part 2 in the Y-axis direction is a width MR = 1000 μm. The branch width WD between the pair of connecting beams 9a and 9c facing each other across the extension line XT was simulated with four set values of the branch width WD = 200 μm, 300 μm, 400 μm, and 500 μm. The width between the pair of connecting beams 9b and 9d is also the same as the branch width WD between the pair of connecting beams 9a and 9c. Further, as shown in FIG. 1, the width MR of the mirror section 2 in the Y-axis direction is the sum of the distance CD and the distance SD. The sign of the offset amount OS follows the sign in the Y-axis direction shown in FIG. That is, when the center of gravity GC of the mirror unit 2 is located on the opposite side CS to the extension line XT, the offset amount OS> 0 μm, and the pair of drive units 4a, 4b When located on the same side SS, the offset amount OS <0 μm. Further, as shown in FIG. 1, since the absolute value of the offset amount OS needs to be less than or equal to half the width MR of the mirror portion 2 in the Y-axis direction, the offset amount OS is −500 μm or more and 500 μm or less. There is a need.

  An analysis result is demonstrated using FIG. 6A, FIG. 6B, and a table | surface. The numerical values such as the drive voltage and the resonance frequency described in FIGS. 6A and 6B and the table are all obtained when the optical deflection angle of the optical scanner 1, that is, the oscillation angle of the mirror unit 2 is set to 25 degrees. It is a numerical value. Table 1 shows the relationship between the offset amount OS, the drive voltage, and the resonance frequency when the branch width WD is set to 200 μm. As shown in Table 1 and FIG. 6A, it can be seen that when the offset amount OS> 0 μm, the drive voltage is reduced compared to the case where the offset amount OS = 0 μm. It can also be seen that when the offset amount OS> 0 μm, the drive voltage can be suppressed smaller as the offset amount OS is larger. On the other hand, as shown in Table 1, it can be seen that when the offset amount OS <0 μm, a very large drive voltage is applied compared to the case where the offset amount OS = 0 μm. Therefore, the center of gravity GC of the mirror portion is located on the extension line XT only when the center of gravity GC of the mirror portion is located on the side CS opposite to the pair of drive portions 4a and 4b with respect to the extension line XT. It can be seen that a large optical deflection angle of the optical scanner 1 can be obtained with a small driving voltage as compared with the optical scanner. On the other hand, when the center of gravity GC of the mirror part is located on the same side SS as the pair of drive parts 4a and 4b with respect to the extension line XT, the conventional optical scanner in which the center of gravity GC of the mirror part is located on the extension line XT In comparison, it can be seen that a large drive voltage is required to obtain a large optical deflection angle of the optical scanner 1.

  As shown in Table 1, when the offset amount OS> 0 μm, the resonance frequency of the optical scanner 1 gradually increases as the offset amount OS increases from 0 μm, and reaches a maximum value near the offset amount OS = 400 μm. = Small in the region exceeding 400 μm. As shown in Table 1 and FIG. 6A, in the region where the offset amount OS exceeds about 400 μm, even if the offset amount OS is increased, the drive voltage is not reduced so much. Further, when the resonance frequency is reduced, the resolution of the image is lowered when the optical scanner 1 is applied to an image display device such as a retinal scanning display. Therefore, in order to maintain the constant resonance frequency while reducing the drive voltage of the optical scanner 1 as much as possible, the offset amount OS is changed from 100 μm, which is half of the branch width WD = 200 μm, to the width MR of the mirror portion 2 = 1000 μm. It is desirable to set the length from 500 μm which is half, that is, a value in the vicinity of 400 μm.

  Tables 2, 3, and 4 show the relationship between the offset amount OS, the drive voltage, and the resonance frequency when the branch width WD is set to 300, 400, and 500 μm, respectively. As shown in Table 2 and FIG. 6B, when the branch width WD = 300 μm is set, the drive voltage of the optical scanner 1 gradually decreases as the offset amount OS increases from 0 μm, and is a minimum value near the offset amount OS = 350 μm. And gradually increases in the region exceeding the offset amount OS = 350 μm. However, the drive voltage at the offset amount OS = 450 μm is smaller than the offset amount OS = 0 μm. Therefore, it can be seen that when the offset amount OS> 0 μm, the drive voltage is reduced as compared with the case where the offset amount OS = 0 μm.

  As shown in Table 3 and FIG. 6B, when the branch width WD is set to 400 μm, the drive voltage of the optical scanner 1 gradually decreases as the offset amount OS increases from 0 μm, and is a minimum value near the offset amount OS = 300 μm. And gradually increases in a region exceeding the offset amount OS = 300 μm vicinity. However, the drive voltage at the offset amount OS = 450 μm is smaller than the offset amount OS = 0 μm. Therefore, it can be seen that when the offset amount OS> 0 μm, the drive voltage is reduced as compared with the case where the offset amount OS = 0 μm.

  As shown in Table 4 and FIG. 6B, when the branch width WD is set to 500 μm, the drive voltage of the optical scanner 1 gradually decreases as the offset amount OS increases from 0 μm, and is a minimum value near the offset amount OS = 200 μm. And gradually increases in a region exceeding the offset amount OS = 200 μm vicinity. The drive voltage at the offset amount OS = 450 μm is larger than the offset amount OS = 0 μm. However, when the offset amount OS> 0 μm, the offset amount OS <400 μm, the offset amount OS = 0 μm. In comparison, it can be seen that the drive voltage is reduced.

  As shown in Tables 2, 3, and 4, it can be seen that a larger drive voltage is applied when the offset amount OS <0 μm than when the offset amount OS = 0 μm. Therefore, when the branch width WD is set to 300, 400, and 500 μm, similarly to the case where the branch width WD is set to 200 μm, the center of gravity GC of the mirror portion is a pair of drive units 4a, Only when it is located on the side CS opposite to 4b, a large optical deflection angle of the optical scanner 1 is obtained with a small driving voltage as compared with the conventional optical scanner in which the center of gravity GC of the mirror portion is located on the extension line XT. You can see that On the other hand, when the center of gravity GC of the mirror part is located on the same side SS as the pair of drive parts 4a and 4b with respect to the extension line XT, the conventional optical scanner in which the center of gravity GC of the mirror part is located on the extension line XT In comparison, it can be seen that a large drive voltage is required to obtain a large optical deflection angle of the optical scanner 1.

  As shown in Table 2, when the branch width WD = 300 μm is set and the offset amount OS> 0 μm, the resonance frequency of the optical scanner 1 gradually increases as the offset amount OS increases from 0 μm. = Maximum value in the vicinity of 350 μm, and gradually decreases in the region exceeding the offset amount OS = 350 μm. As shown in Tables 3 and 4, when the branch width WD is set to 400 and 500 μm, and the offset amount OS> 0 μm, the resonance frequency of the optical scanner 1 increases as the offset amount OS increases from 0 μm. It becomes smaller gradually. As shown in Table 2, Table 3, Table 4, and FIG. 6B, when the branch width WD is set to 300, 400, and 500 μm, the offset amount OS = 350, 300, in the region that exceeds the vicinity of 250 μm, As the offset amount OS increases, the drive voltage gradually increases. Therefore, in order to maintain the constant resonance frequency while reducing the drive voltage of the optical scanner 1 as much as possible, the offset amount OS is set to be half the branch width WD and half the width MR of the mirror portion 2. It is desirable to set the lengths subtracted from 350, 300, and 250 μm, respectively.

[Method of manufacturing structure]
A structure manufacturing method according to the present embodiment will be described with reference to FIG. The structure refers to the substrate of the mirror unit 2, the movable beam 3, and the fixed unit 5. The reflecting surface 6 is usually formed by forming a metal film made of gold or the like on the substrate of the mirror unit 2.

  First, as shown in FIG. 7, a plate-like silicon substrate having elasticity is prepared as a material to be etched (step S1, hereinafter referred to as S1). Next, a photoresist is applied to both sides of the silicon substrate, and a resist film is formed on both sides of the silicon substrate. (S2). When the resist film is formed, a photolithography technique is used, and a predetermined pattern light is exposed to the resist film. By exposing the predetermined pattern light, unnecessary portions of the resist film are removed. Thereby, mask patterns are formed on both surfaces of the silicon substrate, respectively (S3). When the mask pattern is formed, the laminated body of the silicon substrate and the mask pattern is immersed in an etching tank containing an etching solution, and wet etching is performed (S4). When wet etching is performed, the laminated body of the silicon substrate and the mask pattern is taken out from the etching tank (S5), and then the mask pattern is peeled off from both surfaces of the silicon substrate (S6). A structure having a predetermined shape is manufactured by the above manufacturing method.

[Optical scanner usage example]
An example of use of the optical scanner 1 according to this embodiment in the retinal scanning display 201 will be described with reference to FIG. The retinal scanning display 201 is a form of a head mounted display device (hereinafter referred to as “HMD”). The retinal scanning display 201 is mounted on the wearer's head and in the vicinity thereof, guides image light to the wearer's eyes, and scans the wearer's retina in a two-dimensional direction so that an image corresponding to the image information is obtained. It is comprised so that it may be visually recognized by the wearer. The optical scanner 1 according to this embodiment is used for the resonant deflection element 261 and the deflection element 281 shown in FIG. However, the drive control unit 60 corresponds to the horizontal scanning control circuit 262 and the vertical scanning control circuit 282.

  The retinal scanning display 201 includes a light beam generation unit 220, a horizontal scanning unit 260, and a vertical scanning unit 280.

  The light flux generation unit 220 generates image light based on the image information S supplied from the outside, and supplies the generated image light to the horizontal scanning unit 260. The horizontal scanning unit 260 scans the image light generated by the light beam generation unit 220 in the horizontal direction, and supplies the image light scanned in the horizontal direction to the vertical scanning unit 280 via the relay optical system 270. The vertical scanning unit 280 scans the image light supplied from the horizontal scanning unit 260 in the vertical direction via the relay optical system 270, and the image light scanned in the vertical direction via the relay optical system 290. To the pupil Ea.

  The light beam generation unit 220 includes a signal processing circuit 221, a light source unit 230, and a light combining unit 240.

  The signal processing circuit 221 receives image data S supplied from the outside. Based on the image data S, the signal processing circuit 221 generates blue, red, and green image signals, a B video signal, an R video signal, and a G video signal that are elements for synthesizing images, and the light source unit 230. To supply. The signal processing circuit 221 supplies a horizontal synchronization signal for driving the horizontal scanning unit 260 to the horizontal scanning unit 260 and supplies a vertical synchronization signal for driving the vertical scanning unit 280 to the vertical scanning unit 280.

  The light source unit 230 functions as an image light output unit that converts the B video signal, the R video signal, and the G video signal supplied from the signal processing circuit 221 into image light. The light source unit 230 includes a B laser 234 that generates blue image light and a B laser driver 231 that drives the B laser 234, an R laser 235 that generates red image light, and an R laser driver 232 that drives the R laser 235. A G laser 236 that generates green image light, and a G laser driver 233 that drives the G laser 236.

  The light combining unit 240 is supplied with the three image lights output from the light source unit 230, and generates arbitrary image light by combining the three image lights into one image light. The light combining unit 240 includes collimating optical systems 241, 242, and 243, dichroic mirrors 244, 245, and 246 for combining the collimated image light, and a coupling optical system 247 that guides the combined image light to the transmission cable 250. And. Laser beams emitted from the lasers 234, 235, and 236 are collimated by collimating optical systems 241, 242, and 243, respectively, and then incident on dichroic mirrors 244, 245, and 246. Thereafter, the dichroic mirrors 244, 245, and 246 selectively reflect or transmit each image light with respect to the wavelength. The collimating optical system 251 converts the image light emitted through the transmission cable 250 into parallel light and guides it to the horizontal scanning unit 260.

  The collimated image light is converted into two-dimensionally scanned image light by the horizontal scanning unit 260, the relay optical system 270, the vertical scanning unit 280, and the relay optical system 290. The horizontal scanning unit 260 reciprocally scans the image light that has been collimated by the collimating optical system 251 in the horizontal direction for image display. The relay optical system 270 is provided between the horizontal scanning unit 260 and the vertical scanning unit 280 and guides the image light scanned by the horizontal scanning unit 260 to the vertical scanning unit 280. The vertical scanning unit 280 reciprocates in the vertical direction the image light scanned in the horizontal direction by the horizontal scanning unit 260. The relay optical system 290 emits image light scanned (two-dimensionally scanned) in the horizontal direction and the vertical direction to the pupil Ea.

  The horizontal scanning unit 260 includes a resonance type deflection element 261 and a horizontal scanning control circuit 262. The optical scanner 1 according to the present embodiment is used for the resonance type deflection element 261. The resonant deflection element 261 has a reflection surface for scanning the image light in the horizontal direction. The horizontal scanning control circuit 262 resonates the resonance type deflection element 261 based on the horizontal synchronization signal supplied from the signal processing circuit 221. The relay optical system 270 relays image light between the horizontal scanning unit 260 and the vertical scanning unit 280. The light scanned in the horizontal direction by the resonance type deflection element 261 is converged on the reflection surface of the deflection element 281 in the vertical scanning unit 280 by the relay optical system 270.

  The vertical scanning unit 280 includes a deflection element 281 and a vertical scanning control circuit 282. The optical scanner 1 according to this embodiment is used for the deflection element 281. The deflection element 281 scans the image light guided by the relay optical system 270 in the vertical direction. The vertical scanning control circuit 282 swings the deflection element 281 based on the vertical synchronization signal supplied from the signal processing circuit 221. The image light scanned in the horizontal direction by the resonance type deflection element 261 and scanned in the vertical direction by the deflection element 281 is emitted to the relay optical system 290 as scanning image light scanned two-dimensionally.

  The relay optical system 290 relays image light between the vertical scanning unit 280 and the wearer's pupil Ea. The image light scanned in the horizontal direction by the resonance type deflection element 261 and scanned in the vertical direction by the deflection element 281 is converged on the pupil Ea of the wearer by the relay optical system 290. In this way, the wearer can visually recognize an image corresponding to the image information.

(Modification)
In the present embodiment, with respect to the extension line XT, the distance CD between the one end CE of the mirror unit 2 located on the side CS opposite to the drive parts 4a and 4b and the extension line XT is the extension line XT. On the other hand, it is larger than the distance SD between the other side end SE of the mirror part 2 located on the same side SS as the drive parts 4a and 4b and the extension line XT. As a result, the center of gravity GC of the mirror unit 2 is located on the side CS opposite to the drive units 4a and 4b with respect to the extension line XT. However, the present invention is not limited to this, and by providing a hole, groove, or weight in the mirror part 2, the center of gravity GC of the mirror part 2 is positioned on the side CS opposite to the drive parts 4a and 4b with respect to the extension line XT. You may comprise.

  In the present embodiment, the structure is formed by a technique using wet etching, but is not limited thereto, and may be formed by dry etching, for example.

  In this embodiment, as shown in FIG. 7, the structure is manufactured by one mask pattern formation and one wet etching. However, the structure is not limited to this, and these manufacturing steps may be performed a plurality of times. Good.

  In this embodiment, the mask pattern for manufacturing the structure is formed by directly applying a photoresist to a silicon substrate and then exposing to a predetermined pattern light. After heating the substrate and forming a silicon thermal oxide film on both sides of the silicon substrate, a resist is applied on the silicon thermal oxide film, and then a predetermined pattern light is exposed to form a resist film having a predetermined shape, The mask pattern may be formed by removing an excess portion of the silicon thermal oxide film using hydrofluoric acid or the like.

  In the present embodiment, the retinal scanning display 201 is shown as an example of use of the optical scanner 1, but the present invention is not limited to this, and it may be used for an electrophotographic multifunction device, a laser printer, a barcode reader, or the like.

DESCRIPTION OF SYMBOLS 1 Optical scanner 2 Mirror part 3 Movable beam 4a, 4b Drive part 5 Fixed part 6 Reflecting surface 7a, 7b Support beam 8a, 8b Extension beam 9a-9d Connection beam 10a, 10b Piezoelectric body 11a, 11b Upper electrode 12a, 12b Lower part Electrode 60 Drive controller SW Swing axis XT Extension line OS Offset amount

Claims (5)

An optical scanner that reflects and scans an incident light beam,
A mirror portion having a reflecting surface that can swing around a swing axis;
A pair of mirror support beams extending from both sides of the mirror portion in a direction parallel to the swing axis, and a pair of first connection portions connected to each of the pair of mirror support beams; A pair of extending beams extending from the first connecting portion to both sides of the mirror support beam on a parallel plane and in a direction perpendicular to the swing axis, and both ends of the pair of extending beams A movable beam having four second coupling parts coupled to the first coupling part and extending from the second coupling part in a direction away from the mirror part in parallel to the swing axis;
A fixing part connected to the four connecting beams;
A pair of drives for driving the movable beam provided across the pair of connection beams located on one side with respect to the extension line connecting the pair of mirror support beams among the four connection beams and the fixed portion. And comprising
The center of gravity of the mirror part is located on the opposite side to the pair of driving parts with respect to the extension line. Each of the pair of driving units includes a piezoelectric body that extends and contracts in parallel with the reflection axis and parallel to the swing axis, and a pair of electrodes that are provided on both sides of the piezoelectric body. ,
Drive in phase with the pair of drive units so that the piezoelectric bodies of the pair of drive units extend or contract together on a plane parallel to the reflecting surface and in a direction parallel to the swing axis. The optical scanner according to claim 1, further comprising a drive control unit that supplies a signal. The branch width between the pair of connecting beams opposed across the extension line is smaller than half of the mirror width of the mirror portion on a plane parallel to the reflection surface and perpendicular to the swing axis,
The distance between the center of gravity of the mirror part and the extension line is a length obtained by subtracting half the branch width from half the mirror width. The optical scanner described in.   The distance between the one end of the mirror unit located on the opposite side of the pair of drive units with respect to the extension line and the extension line is such that the pair of drive units with respect to the extension line The center of gravity of the mirror part is opposite to the pair of driving parts with respect to the extension line because the distance between the other side end of the mirror part located on the same side and the extension line is different. The optical scanner according to claim 1, which is located in   The center of gravity of the mirror part is located on the opposite side to the pair of driving parts with respect to the extension line by the mirror part having a hole, a groove, or a weight. 4. The optical scanner according to any one of 3.