Electromagnetic wave deflection device and electromagnetic wave scanning device

Abstract

This electromagnetic wave deflection device comprises a mirror that reflects electromagnetic waves, a first drive unit, a second drive unit, and a weight. The first drive unit inclines the mirror using a first axis as an inclination axis. The second drive unit inclines the mirror using a second axis that intersects the first axis as an inclination axis. The weight is disposed on at least one of the first drive unit and the second drive unit so that the resonant frequency of the second drive unit is not a natural number multiple of the resonant frequency of the first drive unit.

Description

Electromagnetic wave deflection device and electromagnetic wave scanning device Cross-reference to related applications

[0001] This application claims priority from Japanese Patent Application No. 2022-54373 (filed March 29, 2022), the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to an electromagnetic wave deflection device and an electromagnetic wave scanning device.

[0003] 2. Description of the Related Art There is known an optical deflector that prevents the position of the rotation axis from shifting when the mirror is rotated (see, for example, Japanese Patent Application Laid-Open No. 2003-222294).

[0004] Japanese Patent Application Laid-Open No. 2016-9050

[0005] An electromagnetic wave deflection device according to an embodiment of the present disclosure includes a mirror that reflects electromagnetic waves, a first driver, a second driver, and a weight. The first driver tilts the mirror about a first axis as a tilt axis. The second driver tilts the mirror about a second axis that intersects with the first axis as a tilt axis. The weight is disposed on at least one of the first driver or the second driver such that the resonant frequency of the second driver is different from the resonant frequency of the first driver by a natural number multiple.

[0006] An electromagnetic wave scanning device according to an embodiment of the present disclosure includes the electromagnetic wave deflection device and an irradiation device that makes electromagnetic waves incident on the electromagnetic wave deflection device.

[0007] Fig. 2 is a plan view showing a configuration example of an electromagnetic wave deflection device according to an embodiment of the present disclosure; Fig. 3 is a plan view showing a configuration example of an electromagnetic wave deflection device in a case where a mirror overlaps a second driving unit; Fig. 4 is a cross-sectional view taken along line A-A in Fig. 2; Fig. 5 is a plan view showing a configuration example of an electromagnetic wave deflection device in a case where a weight is positioned around the opening of a first driving unit; Fig. 6 is a plan view showing a configuration example of an electromagnetic wave deflection device in a case where the second driving unit has a plurality of folding units;

[0008] (Configuration Example of Electromagnetic Wave Deflection Device 1) As shown in FIG. 1 , an electromagnetic wave deflection device 1 according to one embodiment includes a substrate 40 and a mirror 30. The mirror 30 has a reflective surface that reflects incident electromagnetic waves. The substrate 40 includes a first driving unit 10 and a second driving unit 20. The first driving unit 10 includes a first support unit 12 and a first actuator 14. The second driving unit 20 includes a second support unit 22 and a second actuator 24. The first support unit 12 is located between two second support units 22 aligned in the X-axis direction. The second support unit 22 supports the first support unit 12. The substrate 40 has a frame-shaped outer frame portion, and the second support unit 22 is connected to this outer frame portion. In other words, the substrate 40 includes an outer frame, the first support unit 12, and the second support unit 22. The outer frame portion of the substrate 40, the first support portion 12, and the second support portion 22 may be formed by a manufacturing process based on MEMS (Micro Electro Mechanical Systems) technology. The X-axis direction corresponds to one of the surface directions of the substrate 40. The Y-axis direction corresponds to a direction perpendicular to the X-axis direction. The Z-axis direction corresponds to a direction perpendicular to the surface of the substrate 40.

[0009] The first support 12 supports the mirror 30 and a mirror support 32 that supports the mirror 30. The first support 12 has, for example, a rectangular shape with an opening inside. In other words, the first support 12 has a frame shape. The mirror support 32 is configured as a beam extending in the Y-axis direction within the opening inside the first support 12. The opening inside the first support 12 may be rectangular. The mirror support 32 has an elongated beam shape, and its ends are connected to one side of the opening inside the first support 12 and the opposite side. The mirror 30 is positioned on the mirror support 32 via a columnar member 32A and is configured to be tiltable around the mirror support 32 as an axis. The mirror 30 may be formed on a substrate 40 by a manufacturing process based on MEMS technology. The mirror support 32 may be formed on the substrate 40 or integrally with the substrate 40 by a manufacturing process based on MEMS technology. The mirror 30 may be supported by two mirror supports 32 on the side that forms the opening of the first support 12, without using the columnar member 32A. The axis around which the mirror 30 tilts, when it is tilted around the mirror support 32, is represented as a first axis 16 that extends in the Y-axis direction.

[0010] The first actuator 14 is located on the first support 12. The first actuators 14 may be located on both sides of the mirror support 32 in the longitudinal direction. The first actuators 14 may be located symmetrically with the longitudinal direction of the mirror support 32 as the axis of symmetry. The first actuator 14 may be located along the edge of the opening inside the first support 12. The first actuator 14 is configured to be expandable and contractible in the Y-axis direction. The first actuator 14 may be configured as, for example, a piezoelectric element or a motor. The expansion and contraction of the first actuator 14 in the Y-axis direction generates vibrations in the edges forming the opening of the first support 12. The vibrations of the edges of the opening of the first support 12 are transmitted to the mirror 30 through the mirror support 32. The vibrations transmitted to the mirror 30 cause the mirror 30 to resonate on the mirror support 32 in a tilting direction about the first axis 16. The mirror 30 oscillates around the first axis 16 by resonating in a tilting direction around the first axis 16. If an electromagnetic wave is incident on the mirror 30 from the positive direction of the Z axis, the electromagnetic wave reflected by the mirror 30 oscillating around the first axis 16 is scanned in the X axis direction.

[0011] The second support section 22 may be configured in a so-called meander shape (folded shape). When configured in a meander shape, the second support section 22 includes a portion extending in the Y-axis direction and a folded portion. The folded portion extends in the X-axis direction and connects the portions extending in the Y-axis direction. The portion extending in the Y-axis direction may be longer than the folded portion. The second support section 22 connects the first support section 12 to the outer frame portion of the substrate 40. When the first support section 12 is a rectangle having sides extending in the X-axis direction and the Y-axis direction, the second support section 22 connects one end of the side extending in the Y-axis direction to the substrate 40. Note that the second support section 22 is not limited to a meander shape. The second actuator 24 is located in a portion of the second support section 22 extending in the Y-axis direction. The second actuator 24 has a shape that extends elongated in the Y-axis direction. The second actuator 24 is configured to be expandable and contractible in the Y-axis direction. The second actuator 24 may be configured as, for example, a piezoelectric element or a motor. As the second actuator 24 expands and contracts in the Y-axis direction, the portion of the second support 22 extending in the Y-axis direction tilts around an axis along the X-axis direction. The tilt axis of the second support 22 is represented as the second axis 26. The second axis 26 is assumed to be an axis intersecting the first axis 16. As the portion of the second support 22 extending in the Y-axis direction tilts around the second axis 26, the first support 12 tilts around the second axis 26. As the first support 12 tilts around the second axis 26, the mirror 30 supported by a mirror support 32 located in an opening inside the first support 12 tilts around the second axis 26. The tilt angle of the mirror 30 around the second axis 26 is controlled according to the amount of expansion and contraction of the second actuator 24. If an electromagnetic wave is incident on the mirror 30 from the positive direction of the Z axis, the electromagnetic wave reflected by the mirror 30, whose tilt angle is controlled around the second axis 26, is scanned in the Y axis direction.

[0012] The mirror 30 oscillates around the first axis 16 by resonating at a resonance frequency specific to the first drive unit 10. Meanwhile, regardless of the resonance of the first drive unit 10, the mirror 30 tilts around the second axis 26 by deforming the second drive unit 20 through expansion and contraction of the second actuator 24, causing the first drive unit 10 to tilt around the second axis 26. The tilt angle of the mirror 30 around the second axis 26 can be controlled by the amount of expansion and contraction of the second actuator 24.

[0013] The second drive unit 20 is configured to be tiltable around the second axis 26 so as to tilt the first drive unit 10 and the mirror 30 supported by the second drive unit 20 around the second axis 26. In this case, the second drive unit 20 oscillates so as to tilt around the second axis 26 when resonating due to transmission of vibrations from the outside. If the resonant frequency of the second drive unit 20 matches the resonant frequency of the first drive unit 10 or a natural number multiple thereof (1, 2, 3, etc.), the second drive unit 20 is likely to resonate due to vibrations at the resonant frequency of the first drive unit 10 transmitted from the first drive unit 10 to the second drive unit 20. The second drive unit 20 oscillates around the second axis 26 due to resonance. When the second drive unit 20 resonates, the electromagnetic wave deflection device 1 cannot control the tilt angle of the second drive unit 20 around the second axis 26 by the amount of expansion and contraction of the second actuator 24.

[0014] Conversely, if the resonant frequency of the second drive unit 20 is different from a frequency that is a natural number multiple (1, 2, 3, ...) of the resonant frequency of the first drive unit 10, the second drive unit 20 is less likely to resonate even if vibrations at the resonant frequency of the first drive unit 10 are transmitted to the second drive unit 20. For example, if the resonant frequency of the second drive unit 20 is a frequency that is half an odd multiple (1.5, 2.5, 3.5, ...) of the resonant frequency of the first drive unit 10, the second drive unit 20 will hardly resonate when vibrations at the resonant frequency of the first drive unit 10 are transmitted to the second drive unit 20.

[0015] Therefore, the electromagnetic wave deflection device 1 according to this embodiment is configured so that the resonant frequency of the second drive unit 20 is different from a natural number multiple of the resonant frequency of the first drive unit 10, so that the second drive unit 20 is less likely to resonate due to vibration of the first drive unit 10. In this case, the second drive unit 20, the first drive unit 10 supported by the second drive unit 20, and the mirror 30 are less likely to resonate around the second axis 26. In other words, when the mirror 30 is made to resonate around the main axis (first axis 16), resonance around the secondary axis (second axis 26) intersecting the main axis can be reduced.

[0016] As shown in FIG. 2 , in a plan view of the substrate 40 of the electromagnetic wave deflection device 1 (when viewed in the positive direction of the Z axis), the mirror 30 may overlap the second drive unit 20. As shown in the cross-sectional view of FIG. 3 , the mirror 30 may tilt clockwise toward the positive direction of the X axis and move to the position of mirror 30A. Furthermore, when the second drive unit 20 resonates, the second support unit 22 may be displaced in the positive direction of the Z axis and move to the position of second support unit 22A. In this case, the mirror 30A may collide with the second support unit 22A. By configuring the electromagnetic wave deflection device 1 so that the second drive unit 20 is less likely to resonate around the second axis 26, the mirror 30 is less likely to collide with the second support unit 22. As a result, the reliability of the electromagnetic wave deflection device 1 may be improved.

[0017] Furthermore, the first driver 10 supporting the mirror 30 may be affected by resonance around the second axis 26 in the second driver 20. If resonance around the second axis 26 in the second driver 20 is transmitted to the first driver 10, the mirror 30 supported by the first driver 10 may vibrate around the second axis 26. If the mirror 30 vibrates around the second axis 26, it becomes difficult to control the tilt angle of the mirror 30 around the second axis 26. Therefore, by configuring the electromagnetic wave deflection device 1 so that the second driver 20 is less likely to resonate around the second axis 26, the electromagnetic wave deflection device 1 can more easily control the tilt angle of the mirror 30 around the second axis 26. As a result, the reliability of the electromagnetic wave deflection device 1 can be improved.

[0018] The resonant frequency of the second drive unit 20 is determined by the elastic modulus of the second support unit 22 and the moment of inertia around the second axis 26. The smaller the elastic modulus of the second support unit 22, the lower the resonant frequency. Therefore, the resonant frequency of the second drive unit 20 may be adjusted by adjusting the elastic modulus of the second support unit 22. The elastic modulus of the second support unit 22 may be adjusted by the material of the second support unit 22 or the shape of the second support unit 22.

[0019] Furthermore, the larger the moment of inertia of the second support unit 22 about the second axis 26, the lower the resonant frequency. The resonant frequency of the second drive unit 20 may be adjusted by adjusting the moment of inertia of the second support unit 22 about the second axis 26. The moment of inertia of the second support unit 22 about the second axis 26 is determined as the sum of the products of the distances of each part of the second support unit 22 from the second axis 26 and the masses of each part. As shown in FIG. 1 , the electromagnetic wave deflection device 1 according to this embodiment includes a weight 50 at a folded portion of the second support unit 22 away from the second axis 26 in order to adjust the resonant frequency of the second drive unit 20. The larger the mass of the weight 50 or the farther the position of the weight 50 is from the second axis 26, the lower the resonant frequency of the second drive unit 20.

[0020] When the weight 50 is installed on the second driving unit 20, it may be arranged so as not to overlap the second actuator 24 in a plan view of the substrate 40. In this way, the output of the second actuator 24 can more easily tilt the first driving unit 10 and the mirror 30. As a result, the weight 50 is less likely to reduce the energy efficiency when tilting the mirror 30 about the second axis 26.

[0021] The electromagnetic wave deflection device 1 may be configured so that the resonant frequency of the second drive unit 20 is lower than the resonant frequency of the first drive unit 10. In this case, the resonant frequency of the second drive unit 20 is a value that is far from any natural number multiple of the resonant frequency of the first drive unit 10. By doing so, the second drive unit 20 is less likely to resonate. In other words, when resonating on the main axis, resonance on the secondary axis that intersects the main axis can be reduced.

[0022] As shown in FIG. 4 , the weight 50 may be installed on the first drive unit 10. In the example of FIG. 4 , the weight 50 is arranged so as to surround the opening of the first support unit 12. The position of the weight 50 is not limited to this, and the weight 50 may be arranged on at least a portion of the first support unit 12. For example, the weight 50 may be arranged along at least one side of the opening of the first support unit 12. The weight 50 may be arranged along a side of the edge of the opening of the first support unit 12 that is aligned with the first axis 16, or along a side that intersects with the first axis 16. The weight 50 may be arranged along each of two opposing sides of the opening. The weight 50 may be arranged along each of the two left and right sides of the opening (sides that are aligned with the first axis 16), or along each of the two top and bottom sides of the opening (sides that intersect with the first axis 16).

[0023] When the weight 50 is installed on the first driving unit 10, it may be arranged so as not to overlap the first actuator 14 in a plan view of the substrate 40. The weight 50 may also be arranged so as to be farther from the mirror support 32 than the first actuator 14. This makes it easier for the output of the first actuator 14 to be transmitted to the mirror 30. As a result, the energy efficiency when vibrating the mirror 30 is less likely to be reduced by the weight 50.

[0024] 5, when the second drive unit 20 has multiple turning portions, the weight 50 may be disposed at each turning portion. The weight 50 may not be disposed at all turning portions, but may be disposed at only some of the turning portions. The weight 50 may be disposed only at turning portions close to the first drive unit 10. The weight 50 may be disposed only at turning portions of the second drive unit 20 that connect to portions of the substrate 40 that overlap with the mirror 30 in a plan view. The weight 50 may be disposed so that the resonant frequency around the second axis 26 of the portion of the second drive unit 20 that connects to the first drive unit 10 is different from the resonant frequency of the first drive unit 10.

[0025] The first drive unit 10 or the second drive unit 20 on the substrate 40 can vibrate in various vibration modes. The vibration modes can be a first mode (secondary axis sweep), a second mode (another form of secondary axis sweep), a third mode (meander alternating vibration), a fourth mode (meander simultaneous vibration), a fifth mode (major axis sweep), or a sixth mode (another form of major axis sweep). The first mode is a mode in which the second support unit 22 vibrates around the X axis, with the portion where the second support unit 22 connects to the outer frame of the substrate 40 as a fulcrum. The second mode is a mode in which the second support unit 22 vibrates around the X axis, with the portion on the opposite side of the Y axis from the portion where the second support unit 22 connects to the outer frame of the substrate 40 as a fulcrum. The third mode is a mode in which the portions of the second support unit 22 located on the positive and negative sides of the X axis across the first support unit 12 vibrate in opposite directions along the Z axis. The fourth mode is a mode in which both portions of the second support unit 22 located on the positive and negative sides of the X-axis, sandwiching the first support unit 12, vibrate in the same direction along the Z-axis. The fifth mode is a mode in which the first support unit 12 vibrates so that the tilt direction of the mirror 30 coincides with the tilt direction of the mirror 30 when tilted around the Y-axis. The sixth mode is a mode in which the first support unit 12 vibrates so that the tilt direction of the mirror 30 is opposite to the tilt direction of the mirror 30 when tilted around the Y-axis. The direction in which the electromagnetic wave deflection device 1 reflects electromagnetic waves is determined by the vibration of the mirror 30 in the first drive unit 10. Therefore, the electromagnetic wave deflection device 1 is configured so that the mirror 30 vibrates in a predetermined vibration mode in the first drive unit 10. At this time, it is required that the vibration of the second drive unit 20 does not interfere with the vibration of the mirror 30 in the predetermined vibration mode. The second drive unit 20 may vibrate in a mode that interferes with the vibration of the mirror 30 in the predetermined vibration mode. Therefore, the weight 50 may be arranged on the second driving unit 20 so as to prevent the second driving unit 20 from vibrating in a mode that inhibits the mirror 30 from vibrating in a predetermined vibration mode. When the electromagnetic wave deflection device 1 vibrates in the first and fifth modes described above as predetermined vibration modes, the fourth mode vibration may occur as an inhibiting mode in resonance with the fifth mode vibration. The weight 50 may be arranged on the second driving unit 20 so as to prevent the fourth mode vibration from occurring.

[0026] The weight 50 may be formed by thickening at least a portion of the first support section 12 or the second support section 22. The thickened portion of the first support section 12 or the second support section 22 is heavier than the other portions. That is, the weight 50 may be provided as a thick portion of the first support section 12 or the second support section 22. The weight 50 may be configured as a component separate from the substrate 40. In this case, the weight 50 may be bonded to the first support section 12 or the second support section 22. The weight 50 may be provided on one or both surfaces of the first support section 12 or the second support section 22. When the mirror 30 is large enough to overlap the first actuator 14 or the second actuator 24 in the Z-axis direction, providing the weight 50 on the back surface (i.e., the surface opposite to the side on which the mirror 30 is located) reduces interference between the weight 50 and the mirror 30. In other words, the mirror 30 may have a size that overlaps the first actuator 14 or the second actuator 24 in a direction perpendicular to the reflective surface of the mirror 30. The weight 50 may be disposed on the surface of the first driving unit 10 or the second driving unit 20 opposite to the side on which the mirror 30 is located.

[0027] (Electromagnetic Wave Scanning Device) The electromagnetic wave deflection device 1 may be used in combination with an irradiation device that irradiates electromagnetic waves. In this case, the electromagnetic waves may be incident on the mirror 30 of the electromagnetic wave deflection device 1 from the irradiation device and scanned by the mirror 30 that rotates around the first axis 16 or the second axis 26 as the rotation axis. A configuration in which the electromagnetic wave deflection device 1 and the irradiation device are combined is also called an electromagnetic wave scanning device. The irradiation device may be configured as a light source that emits various types of light, such as visible light, infrared light, or ultraviolet light. The irradiation device may be configured to emit various types of electromagnetic waves, such as millimeter waves or terahertz waves.

[0028] The drawings illustrating the embodiments of the present disclosure are schematic, and the dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones.

[0029] Although the embodiments according to the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art could make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications or alterations are included in the scope of the present disclosure. For example, the functions included in each component can be rearranged so as not to be logically inconsistent, and multiple components can be combined into one or divided. It should be understood that these modifications are also included in the scope of the present disclosure.

[0030] In this disclosure, descriptions such as "first" and "second" are identifiers for distinguishing the configuration. In this disclosure, the configurations distinguished by descriptions such as "first" and "second" can have their numbers interchanged. For example, the first axis 16 can have its identifiers "first" and "second" interchanged with the second axis 26. The identifiers are interchanged simultaneously. The configurations remain distinguished even after the identifiers are interchanged. Identifiers may be deleted. A configuration from which an identifier has been deleted is distinguished by a symbol. The identifiers "first" and "second" in this disclosure should not be used solely to interpret the order of the configurations or to justify the existence of an identifier with a smaller number.

[0031] In this disclosure, the X-axis, Y-axis, and Z-axis are provided for convenience of explanation and may be interchanged. The configurations according to this disclosure have been described using an orthogonal coordinate system formed by the X-axis, Y-axis, and Z-axis. The positional relationship between the components according to this disclosure is not limited to an orthogonal relationship.

[0032] REFERENCE SIGNS LIST 1 Electromagnetic wave deflection device 10 First drive unit (12: first support unit, 14: first actuator, 16: first axis) 20 Second drive unit (22: second support unit, 24: second actuator, 26: second axis) 30 Mirror (32: mirror support unit, 32A: columnar member) 40 Substrate 50 Weight

Claims

1. A mirror that reflects electromagnetic waves; a first drive unit that tilts the mirror about a first axis; a second drive unit that tilts the mirror about a second axis that intersects with the first axis; a weight disposed on at least one of the first drive unit and the second drive unit such that a resonant frequency of the second drive unit is different from a natural number multiple of a resonant frequency of the first drive unit; An electromagnetic wave deflection device comprising:

2. the weight is disposed on at least one of the first drive section or the second drive section such that a resonant frequency of the second drive section is lower than a resonant frequency of the first drive section; 2. An electromagnetic wave deflection device according to claim 1.

3. the first driving unit includes a first support unit that supports the mirror and a first actuator that is disposed on the first support unit, the weight is disposed on the first support portion so as not to overlap the first actuator; 2. An electromagnetic wave deflection device according to claim 1.

4. the second driving unit includes a second support unit that supports the first support unit, and a second actuator that is disposed on the second support unit; the weight is disposed on the second support portion so as not to overlap the second actuator; 4. An electromagnetic wave deflection device according to claim 3.

5. the mirror has a size such that it overlaps with the first actuator or the second actuator in a direction perpendicular to a reflecting surface of the mirror; The weight is disposed on a surface of the first driving unit or the second driving unit opposite to a surface on which the mirror is located.

5. An electromagnetic wave deflection device according to claim 4.

6. the weight is disposed on the second drive unit so as not to cause the second drive unit to vibrate in a mode that inhibits the mirror from vibrating in a predetermined vibration mode; 2. An electromagnetic wave deflection device according to claim 1.

7. 7. A method for manufacturing a semiconductor device comprising: a first deflection device for deflecting an electromagnetic wave from a first light source to a second light source; Electromagnetic wave scanning device.