JP2011175177A - Optical scanning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enlarge a scanning zone in an optical scanning device constructing a three-degree-of-freedom coupled vibration system. <P>SOLUTION: In the optical scanning device 1, the three-degree-of-freedom coupled vibration system, which performs torsional vibration with a large rotation angle when a specific periodic external force is applied, is composed of a mirror 13, an inner gimbal 12, an outer gimbal 11, a support part 3, elastic coupling parts 16a and 16b, elastic coupling parts 15a and 15b, and elastic coupling parts 14a and 14b. When a voltage is applied between comb electrode parts 17, 19 and comb electrode parts 4a, 4b, so that the specific periodic external force works on the outer gimbal 11, a three-degree-of-freedom torsional vibrator is set to a resonance condition. Subsequently the optical scanning device 1 is constructed in such a way that inequality ä(torsion spring constant K1 of mirror 13)/(moment I1 of inertia of mirror 13)¾>¾(torsion spring constant K3 of outer gimbal 11)/(moment I3 of inertia of outer gimbal 11)} holds for the purpose of enlarging an amplitude angle of the mirror 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical scanning device that scans a light beam.

In recent years, various optical scanning devices using MEMS (Micro Electro Mechanical System) technology have been proposed for the purpose of downsizing the optical scanning device (see, for example, Patent Document 1).
In contrast, the applicant of the present application provides a third frame having a mirror surface portion formed on the surface, a second frame provided with a predetermined gap with respect to the third frame, and a predetermined gap with respect to the second frame. And a 0th frame provided with a predetermined gap with respect to the first frame, and the third frame, the second frame, and the first frame are respectively connected to the respective rotation shafts. An optical scanning device having a three-degree-of-freedom coupled vibration system has been proposed (see, for example, Patent Document 2).

  In the optical scanning device configured as described above, the three-degree-of-freedom torsional vibrator can be brought into a resonance state by applying an inherent periodic excitation force to the first frame. Then, by superimposing periodic excitation forces corresponding to the vibrations of the second frame and the third frame, the second frame and the third frame are vibrated at different frequencies and amplitudes, respectively. The light can be scanned two-dimensionally by reflecting the light at the mirror surface.

JP 2006-167860 A JP 2008-129068 A

  However, the optical scanning device described in Patent Document 2 has a problem that the scanning range is small because the two frames of the second frame and the third frame are vibrated by the vibration of only the first frame.

  The present invention has been made in view of these problems, and an object of the present invention is to increase the scanning range in an optical scanning device configured with a three-degree-of-freedom coupled vibration system.

  In order to achieve the above object, an optical scanning device according to claim 1, further comprising: a reflecting portion having a reflecting surface for reflecting the light beam; and an elastically deformable first elastic connecting portion connected to the reflecting portion. A first support portion that supports the reflection portion in a swingable manner with the first elastic connection portion as a rotation axis, and a second elastic connection portion that is elastically deformable connected to the first support portion, and has a second elasticity. A second support part that pivotably supports the first support part about the connection part as a rotation axis; and a third elastic connection part that is elastically deformable connected to the second support part. A third support portion that pivotally supports the second support portion as a rotation shaft, and includes a reflection portion, a first support portion, a second support portion, a third support portion, a first elastic coupling portion, and a second elasticity. The coupling part and the third elastic coupling part are coupled with three degrees of freedom torsionally vibrate at a large rotation angle when an inherent periodic external force is applied. Constitute the dynamic system.

  For this reason, the optical scanning device according to claim 1 has a torsional freedom degree with respect to the first elastic connecting portion, the second elastic connecting portion, and the third elastic connecting portion with the third support portion as a fixed end. A torsional vibrator with a degree of freedom.

  A three-degree-of-freedom torsional vibrator theoretically has three vibration modes. That is, the three vibration modes have different resonance frequencies, and the ratios of the angular amplitudes of the torsional vibrations of the reflection part, the first support part, and the second support part with respect to each resonance frequency are different (this is called a vibration mode). . Therefore, when the angular amplitude of the second support portion increases in a certain vibration mode, the angular amplitude of the reflection portion and the first support portion increases according to the ratio of the angular amplitude in the vibration mode.

Then, the external force application means applies a periodic external force unique to the three-degree-of-freedom coupled vibration system. As a result, the torsional vibrator having three degrees of freedom can be brought into a resonance state.
Further, if a periodic excitation force having a frequency corresponding to each of the three vibration modes is given, each vibration mode can be excited. In addition, if a plurality of periodic excitation forces with a plurality of frequencies are superimposed and applied, a plurality of vibration modes can be excited simultaneously.

  Accordingly, the periodic excitation force corresponding to the vibration mode having a large angular amplitude of the reflecting portion and the periodic excitation force corresponding to the vibration mode having a large angular amplitude of the first support portion are superimposed and given. The laser beam reflected by the part can be scanned two-dimensionally.

FIG. 3 is a graph showing an example of the relationship between the amplitude angle of the reflecting portion and the torsion spring constant of the third elastic coupling portion.
As shown in FIG. 3, the magnitude of the amplitude angle of the reflecting portion varies greatly according to the torsion spring constant of the third elastic coupling portion. In FIG. 3, the maximum value of the amplitude angle of the reflecting portion (see point P1 in FIG. 3) is about 3.5 times the minimum value of the amplitude angle of the reflecting portion (see point P2 in FIG. 3). Become. That is, by adjusting the value of the torsion spring constant of the third elastic coupling portion, the amplitude angle of the reflection portion can be increased and the scanning range can be increased.

FIG. 5 is a graph showing an example of the relationship between the amplitude angle of the reflection portion and the amplitude angle of the first support portion and “(torsion spring constant of the third elastic coupling portion) / (moment of inertia of the second support portion)”. is there.
In FIG. 5, a curved line L1 indicates the amplitude angle of the reflecting part when the phase angle difference between the second supporting part and the reflecting part is 0 degrees (ie, in-phase), and a curved line L2 indicates the second supporting part. Shows the amplitude angle of the reflection portion when the difference in phase angle between the reflection portion and the reflection portion is 180 degrees (that is, reverse phase), and the curve L3 shows the amplitude angle of the first support portion. The broken line L4 indicates the magnitude of “(the torsion spring constant of the second elastic coupling portion) / (the moment of inertia of the first support portion)” (in FIG. 5, about 5E + 07). 1 (torsion spring constant of the elastic connecting portion) / (moment of inertia of the reflecting portion) ”(in FIG. 5, about 1.6E + 10).

  As shown in FIG. 5, the amplitude angle of the reflection portion is “(torsion spring constant of the third elastic coupling portion) / (moment of inertia of the second support portion)” (“torsion spring constant of the first elastic coupling portion)”. / (Maximum moment of inertia of the reflecting portion) "

  For this reason, in order to increase the amplitude angle of the reflecting portion, the torsion spring constant of the first elastic connecting portion and the torsion spring constant of the third elastic connecting portion are set to K1 and K3, respectively, and the inertia moment of the reflecting portion, and The moment of inertia of the second support portion may be configured to satisfy the relational expression expressed by the following expression (1) as I1 and I3, respectively.

(K1 / I1)> (K3 / I3) (1)
FIGS. 6A and 6B show the amplitude angle of the reflection portion and the amplitude angle of the first support portion and “(torsion spring constant of the third elastic coupling portion) / (inertia moment of the second support portion)”. It is a graph which shows an example of a relationship.

  As shown in FIG. 6A, according to “(torsion spring constant of the third elastic coupling portion) / (moment of inertia of the second support portion)”, “(torsion spring constant of the third elastic coupling portion) / In order of increasing (the moment of inertia of the second support portion), the region R1 in which the second support portion and the reflection portion are in reverse phase (hereinafter also referred to as reverse phase region R1), and the second support portion and the reflection portion are arranged. The region is divided into a region R2 (hereinafter also referred to as an unstable region R2) that is in phase or a reverse phase and a region R3 (hereinafter also referred to as an inphase region R3) in which the second support portion and the reflective portion are in phase.

  For this reason, in the optical scanning device according to claim 1, the in-phase vibration and the second oscillation are caused by the torsional vibration of the optical scanning device so that the phase angle difference between the second support portion and the reflection portion becomes 0 degree. 2 The torsional vibration of the optical scanning device so that the difference in phase angle between the support portion and the reflection portion is 180 degrees is referred to as anti-phase vibration, and the optical scanning device has a value of (K3 / I3). Accordingly, in-phase vibration generation state where only in-phase vibration is generated, in-phase vibration generation state where only anti-phase vibration occurs, in-phase vibration generation state, in-phase vibration or vibration state where anti-phase vibration occurs When transitioning to any one of the vibration states, it is preferable that the value is set to a value (K3 / I3) that does not result in an unstable vibration state.

Thereby, the operation of the optical scanning device becomes relatively stable, and the disturbance of the light beam scanning can be suppressed.
Further, as shown in FIG. 6B, the amplitude angle of the first support portion is the maximum value in the reverse phase region R1, and the amplitude angle of the first support portion in the reverse phase region R1 is the same phase region R3. It is larger than the amplitude angle of the first support portion at.

For this reason, in the optical scanning device according to claim 2, it is preferable that the value is set to a value of (K3 / I3) at which the anti-phase vibration is generated as described in claim 3.
Accordingly, the optical scanning device can be operated in a state where the amplitude angle of the first support portion is relatively large, and the scanning range can be expanded when performing light beam scanning in two dimensions.

  As shown in FIG. 5, the amplitude angle of the first support portion is “(torsion spring constant of the third elastic connecting portion) / (moment of inertia of the second supporting portion)”. The maximum value is obtained when “torsion spring constant) / (moment of inertia of the first support portion)” is greater than “.

  Therefore, in order to increase the amplitude angle of the first support portion and increase the scanning range, the optical scanning device according to any one of claims 1 to 3, wherein Furthermore, it is preferable that the torsion spring constant of the second elastic coupling portion is K2 and the moment of inertia of the first support portion is I2, so that the relational expression expressed by the following equation (2) is satisfied.

  (K3 / I3)> (K2 / I2) (2)

1 is a plan view showing a configuration of an optical scanning device 1. FIG. 2 is a block diagram showing an electrical configuration of the optical scanning device 1. FIG. 6 is a graph showing an example of a relationship between a mirror amplitude angle and a torsion spring constant K3 of the outer gimbal 11. 5 is a graph showing an example of a relationship between a mirror amplitude angle or an inner gimbal amplitude angle and “(torsion spring constant K3 of the outer gimbal 11) / (moment of inertia I3 of the outer gimbal 11)”. 12 is a first graph showing an example of a relationship between a mirror amplitude angle and an inner gimbal amplitude angle and “(torsion spring constant K3 of outer gimbal 11) / (moment of inertia I3 of outer gimbal 11)”. FIG. 5 is a second and third graph showing an example of the relationship between the mirror amplitude angle and the inner gimbal amplitude angle and “(torsion spring constant K3 of the outer gimbal 11) / (moment of inertia I3 of the outer gimbal 11)”.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view showing a configuration of an optical scanning device 1 according to an embodiment to which the present invention is applied.
The optical scanning device 1 is manufactured, for example, by processing an SOI (Silicon On Insulator) wafer by a semiconductor process, and as shown in FIG. 1, a light beam scanning unit 2 that scans a light beam, and a light beam scanning. A support unit 3 that supports the unit 2, a drive unit 4 that applies a rotational driving force to the light beam scanning unit 2, and an angle detection unit 5 that detects a rotation angle of the light beam scanning unit 2.

  The light beam scanning unit 2 includes an outer gimbal 11, an inner gimbal 12, a mirror 13, elastic connecting portions 14a and 14b, elastic connecting portions 15a and 15b, elastic connecting portions 16a and 16b, comb electrode portions 17, 18, 19, 20.

  Among these, the mirror 13 has a circular shape, and a mirror surface portion of an aluminum thin film is formed on the surface. The inner gimbal 12 has a rectangular frame shape, and a mirror 13 is disposed in the frame. The outer gimbal 11 has a rectangular frame shape, and the inner gimbal 12 is arranged in the frame.

  The elastic connecting portion 16 a is made of an elastically deformable material, and is disposed within the frame of the inner gimbal 12 to connect the mirror 13 and the inner gimbal 12. The elastic connecting portion 16b is made of an elastically deformable material, and is disposed in the frame of the inner gimbal 12. The mirror 13 and the inner gimbal 12 are connected to the opposite side of the elastic connecting portion 16a with the mirror 13 in between. Link. The elastic connecting portion 16 a and the elastic connecting portion 16 b are arranged on the same straight line passing through the center of gravity JS of the mirror 13 and serve as the rotation axis k of the mirror 13. As a result, the mirror 13 is configured to be capable of torsional vibration about the rotation axis k.

  The elastic connecting portion 15 a is made of an elastically deformable material, and is disposed in the frame of the outer gimbal 11 to connect the inner gimbal 12 and the outer gimbal 11. The elastic connecting portion 15b is made of an elastically deformable material, and is arranged in the frame of the outer gimbal 11. The inner gimbal 12 and the outer gimbal 11 are disposed on the opposite side of the inner connecting gimbal 12 from the elastic connecting portion 15a. And The elastic connecting portion 15 a and the elastic connecting portion 15 b are arranged on the same straight line passing through the center of gravity JS of the mirror 13 and the inner gimbal 12 and serve as the rotation axis j of the mirror 13. As a result, the inner gimbal 12 is configured to be capable of torsional vibration about the rotation axis j.

  The elastic connecting portion 14 a is made of an elastically deformable material, and connects the upper side 11 a of the outer gimbal 11 and the support portion 3. The elastic connecting portion 14b is made of an elastically deformable material, and connects the lower side 11b of the outer gimbal 11 and the support portion 3 on the opposite side of the elastic connecting portion 14a across the outer gimbal 11. The elastic coupling portion 14 a and the elastic coupling portion 14 b are arranged on the same straight line passing through the center of gravity JS of the mirror 13, the inner gimbal 12, and the outer gimbal 11, and serve as the rotation axis i of the outer gimbal 11. As a result, the outer gimbal 11 is configured to be torsionally vibrated around the rotation axis i.

  The comb electrode portion 17 is formed in a comb shape along the left side 11 c of the outer gimbal 11. Further, the comb electrode portion 18 is formed in a comb shape along the left side 11 c above the comb electrode portion 17.

  Further, the comb electrode portion 19 is formed in a comb shape along the right side 11 d of the outer gimbal 11. Further, the comb electrode portion 20 is formed in a comb shape along the right side 11 d above the comb electrode portion 17.

  Next, the support portion 3 includes an upper support portion 3a connected to an end portion of the elastic connection portion 14a on the side not connected to the upper side 11a, and an end portion of the elastic connection portion 14b on the side not connected to the lower side 11b. It is comprised from the lower side support part 3b connected.

  Further, the driving unit 4 is formed in a comb-teeth electrode portion 4a formed in a comb-teeth shape that meshes with the comb-teeth electrode unit 17 with a predetermined interval, and in a comb-teeth shape that meshes with the comb-teeth electrode unit 19 with a predetermined interval. And the comb electrode portion 4b.

  Further, the angle detection unit 5 is formed in a comb-teeth shape that is meshed with the comb-teeth electrode unit 18 with a predetermined interval and a comb-teeth shape that is meshed with the comb-teeth electrode unit 20 with a predetermined interval. It is comprised from the comb-tooth electrode part 5b made.

Next, the electrical configuration of the optical scanning device 1 will be described. FIG. 2 is a block diagram showing an electrical configuration of the optical scanning device 1.
As shown in FIG. 2, the optical scanning device 1 includes a drive signal generation circuit 31 that outputs a pulse voltage as a drive signal for rotationally driving the light beam scanning unit 2, and the drive output by the drive signal generation circuit 31. Amplifying circuit 32 that amplifies the signal and applies it to comb-tooth electrode portions 4a and 4b, and C− that converts the capacitance between comb-tooth electrode portions 5a and 5b and comb-tooth electrode portions 19 and 20 into a voltage value. From the V conversion circuits 33a and 33b (hereinafter, the CV conversion circuits 33a and 33b are collectively referred to as the CV conversion circuit 33), the semiconductor laser 34 serving as a light source of the light beam, and the CV conversion circuit 33. A control circuit 35 that monitors the output voltage, controls the semiconductor laser 34 based on the voltage value, and controls the drive signal generation circuit 31 is provided.

Next, the operation principle of the optical scanning device 1 will be described.
The optical scanning device 1 is a three-degree-of-freedom torsional vibrator having a degree of freedom of twisting with respect to the rotation axes i, j, and k with the support portion 3 as a fixed end.

  A three-degree-of-freedom torsional vibrator theoretically has three vibration modes. That is, the three vibration modes have different resonance frequencies, and the ratio of the angular amplitude of the torsional vibration of each frame to each resonance frequency is different (this is called a vibration mode). Hereinafter, these three vibration modes are referred to as vibration mode 1, vibration mode 2, and vibration mode 3, respectively.

  When a voltage is applied to the comb electrode portions 4a and 4b, an electrostatic force is generated between the comb electrode portions 17 and 19. Further, while the outer gimbal 11 vibrates for one cycle, the comb electrode portions 17 and 19 come closest to the comb electrode portions 4a and 4b twice. For this reason, if a periodic electrostatic force close to twice the resonance frequency is applied, the three-degree-of-freedom torsional vibrator can be brought into a resonance state (hereinafter, an excitation force for making the resonance state is referred to as a periodic excitation force). Further, every time the comb electrode portions 17 and 19 approach the comb electrode portions 4a and 4b, a periodic excitation force can be applied.

  If a periodic excitation force having a frequency corresponding to each of vibration mode 1, vibration mode 2, and vibration mode 3 is applied, the respective vibration modes can be excited. In addition, if a plurality of periodic excitation forces with a plurality of frequencies are superimposed and applied, a plurality of vibration modes can be excited simultaneously.

Here, for example,
The resonance frequency f1 of vibration mode 1 is 1000 Hz,
The resonance frequency f2 of vibration mode 2 is 5000 Hz,
The resonance frequency f3 of vibration mode 3 is 40000 Hz,
The amplitude ratio r1 of the outer gimbal 11, the inner gimbal 12, and the mirror 13 in the vibration mode 1 is “1: −20: 0.5”,
The amplitude ratio r2 of the outer gimbal 11, the inner gimbal 12, and the mirror 13 in the vibration mode 2 is “1: 0.01: −50”,
The amplitude ratio r3 of the outer gimbal 11, the inner gimbal 12, and the mirror 13 in the vibration mode 3 is “1: 0.02: −0.03”,
The operation of the three-degree-of-freedom torsional vibrator will be described.

  The amplitude ratio in each vibration mode is described in the order of the outer gimbal 11, the inner gimbal 12, and the mirror 13 from the left. For example, when the amplitude of the outer gimbal 11 is “1”, the amplitude ratio r1 indicates that the amplitude of the inner gimbal 12 is “−20” and the amplitude of the mirror 13 is “0.5”.

  In the resonance state of the three-degree-of-freedom torsional vibrator, the phase angle between the frames is theoretically 0 degree or 180 degrees. Therefore, when describing the amplitude ratio, the sign is “+” when the phase angle difference is 0 degree, and the sign is “−” when the difference is 180 degrees. For example, the amplitude ratio r1 indicates that the phase angle difference between the outer gimbal 11 and the mirror 13 is 0 degree, and the phase angle difference between the outer gimbal 11 and the inner gimbal 12 is 180 degrees.

  When the resonance frequency and amplitude ratio of each vibration mode are designed as described above, in the vibration mode 1, mainly the inner gimbal 12 and the mirror 13 connected to the inner gimbal 12 are largely torsionally vibrated at 1000 Hz. Further, in the vibration mode 2, the mirror 13 is largely twisted and vibrated at 5000 Hz.

  For this reason, the laser beam is reflected by the mirror surface portion of the mirror 13 and the vibration mode 1 and the vibration mode 2 are simultaneously excited, so that the vibration mode 2 is in the main scanning direction (5000 Hz) and the vibration mode 1 is in the sub-scanning direction ( 1000 Hz), the laser beam can be scanned two-dimensionally.

Next, the operation of the optical scanning device 1 will be described.
When the drive signal generating circuit 31 outputs a drive signal based on the control by the control circuit 35, the voltage value of the drive signal is amplified by the amplifier circuit 32 and applied to the comb electrode portions 4a and 4b. Thereby, a pulse voltage is applied between the comb-tooth electrode portions 4a and 4b and the comb-tooth electrode portions 17 and 19 to generate an electrostatic attractive force that periodically changes, and the elastic coupling portions 14a and 14b are elastically deformed. By twisting, the light beam scanning unit 2 reciprocally vibrates about the elastic coupling portions 14a and 14b as the rotation axis i.

  Here, the drive signal generation circuit 31 outputs a drive signal having a frequency twice the resonance frequency of the vibration mode in which the angular amplitude of the mirror 13 is larger than that of the outer gimbal 11 and the inner gimbal 12. Thus, the vibration system composed of the light beam scanning unit 2 and the elastic coupling portions 14a and 14b resonates, and the light beam scanning unit 2 reciprocally vibrates at the resonance frequency.

  In this state, when the mirror 13 is irradiated with a light beam from the semiconductor laser 34, the light beam is emitted by being reflected by the mirror surface of the mirror 13. Scanning is performed in a direction corresponding to the rotation angle.

  On the other hand, with the reciprocal vibration of the outer gimbal 11, the distance between the comb electrode portions 5a and 5b and the comb electrode portions 18 and 20 also periodically changes. As a result, the capacitance between the comb electrode portions 5 a and 5 b and the comb electrode portions 18 and 20 changes according to the rotation angle of the outer gimbal 11. The control circuit 35 detects the rotation angle of the outer gimbal 11 based on these capacitances. As described above, in the resonance state of the three-degree-of-freedom torsional vibrator, since the phase angle between the frames is theoretically 0 degree or 180 degrees, the mirror is detected by detecting the rotation angle of the outer gimbal 11. Thirteen rotation angles can be detected.

  The optical scanning device 1 configured as described above includes a mirror 13 having a mirror surface portion that reflects a light beam, and elastically deformable elastic connecting portions 16 a and 16 b connected to the mirror 13. An inner gimbal 12 that supports the mirror 13 so as to be swingable about a rotation axis k, and elastically deformable elastic connection portions 15a and 15b connected to the inner gimbal 12, and the elastic connection portions 15a and 15b as rotation axes An outer gimbal 11 that swingably supports the inner gimbal 12 as j, and a support that swingably supports the outer gimbal 11 with the elastically deformable elastic connecting portions 14a and 14b connected to the outer gimbal 11 as the rotation axis i. Part 3, mirror 13, inner gimbal 12, outer gimbal 11, support part 3, elastic coupling parts 16 a and 16 b, elastic coupling parts 15 a and 15 b, and elastic coupling part 14 a, 4b constitute three degrees of freedom coupled vibration system of torsional vibration with a large rotation angle when the specific periodic external force acts.

  For this reason, the optical scanning device 1 has a three-degree-of-freedom torsion having a degree of freedom of twisting the elastic connecting portions 16a and 16b, the elastic connecting portions 15a and 15b, and the elastic connecting portions 14a and 14b with the support portion 3 as a fixed end. It is a vibrator.

  A three-degree-of-freedom torsional vibrator theoretically has three vibration modes. That is, the three vibration modes have different resonance frequencies, and the ratios of the angular amplitudes of the torsional vibrations of the mirror 13, the inner gimbal 12, and the outer gimbal 11 with respect to the respective resonance frequencies are different (this is called a vibration mode). Therefore, when the angular amplitude of the outer gimbal 11 increases in a certain vibration mode, the angular amplitude of the mirror 13 and the inner gimbal 12 increases according to the ratio of the angular amplitude in this vibration mode.

  Comb electrode portions 17 and 19 formed in a comb shape are provided on the outer gimbal 11, and comb electrode portions 4a and 4b formed in a comb shape that can mesh with the comb electrode portions 17 and 19 are provided. Is fixedly installed at a position where it can mesh with the comb electrode portions 17 and 19, and the drive signal generating circuit 31 applies a voltage between the comb electrode portions 17 and 19 and the comb electrode portions 4a and 4b. Thus, an electrostatic attractive force is generated between both electrode portions.

  For this reason, the drive signal generation circuit 31 applies a voltage between the comb electrode portions 17 and 19 and the comb electrode portions 4a and 4b to cause a specific periodic external force to act on the outer gimbal 11. The three-degree-of-freedom torsional vibrator can be brought into a resonance state.

  Further, if a periodic excitation force having a frequency corresponding to each of the three vibration modes is given, each vibration mode can be excited. In addition, if a plurality of periodic excitation forces with a plurality of frequencies are superimposed and applied, a plurality of vibration modes can be excited simultaneously.

  Therefore, by applying the periodic excitation force corresponding to the vibration mode with a large angular amplitude of the mirror 13 and the periodic excitation force corresponding to the vibration mode with a large angular amplitude of the inner gimbal 12 in a superimposed manner, the mirror 13 The laser beam reflected by can be scanned two-dimensionally.

  FIG. 3 is a graph showing an example of the relationship between the amplitude angle of the mirror 13 (hereinafter also referred to as the mirror amplitude angle) and the torsion spring constant K3 of the elastic coupling portions 14a and 14b. Hereinafter, the torsion spring constant K3 of the elastic connecting portions 14a and 14b is referred to as the torsion spring constant K3 of the outer gimbal 11.

  As shown in FIG. 3, the magnitude of the mirror amplitude angle varies greatly according to the torsion spring constant K <b> 3 of the outer gimbal 11. In FIG. 3, the maximum value of the mirror amplitude angle (see point P1 in FIG. 3) is about 3.5 times the minimum value of the mirror amplitude angle (see point P2 in FIG. 3). That is, by adjusting the value of the torsion spring constant K3 of the outer gimbal 11, the mirror amplitude angle can be increased and the scanning range can be increased.

  FIG. 4A is a graph showing an example of the relationship between the amplitude angle of the mirror 13 and “(the torsion spring constant K3 of the outer gimbal 11) / (the moment of inertia I3 of the outer gimbal 11)”. In FIG. 4A, a curve L1 indicates the mirror amplitude angle when the difference in phase angle between the outer gimbal 11 and the mirror 13 is 0 degree (that is, the same phase), and the curve L2 indicates the outer gimbal 11 and The mirror amplitude angle in the case where the phase angle difference from the mirror 13 is 180 degrees (ie, opposite phase) is shown.

  As shown in FIG. 4A, the magnitude of the mirror amplitude angle varies greatly according to “(the torsion spring constant K3 of the outer gimbal 11) / (the moment of inertia I3 of the outer gimbal 11)”. Further, in accordance with “(torsion spring constant K3 of outer gimbal 11) / (moment of inertia of outer gimbal 11 I3)”, (torsion spring constant of outer gimbal 11 K3) / (moment of inertia of outer gimbal 11 I3) ” A region R1 in which the outer gimbal 11 and the mirror 13 are in reverse phase (hereinafter also referred to as a reverse phase region R1) and a region R2 in which the outer gimbal 11 and the mirror 13 are in phase or in reverse phase (hereinafter, unstable) And the outer gimbal 11 and the mirror 13 are divided into regions R3 (hereinafter also referred to as in-phase regions R3).

  FIG. 4B shows the relationship between the amplitude angle of the inner gimbal 12 (hereinafter also referred to as the inner gimbal amplitude angle) and “(torsion spring constant K3 of the outer gimbal 11) / (moment of inertia I3 of the outer gimbal 11)”. It is a graph which shows an example. As shown in FIG. 4B, the magnitude of the inner gimbal amplitude angle varies greatly according to “(torsion spring constant K3 of the outer gimbal 11) / (moment of inertia I3 of the outer gimbal 11)”.

  5, 6A, and 6B show the relationship between the mirror amplitude angle and the inner gimbal amplitude angle and “(the torsion spring constant K3 of the outer gimbal 11) / (the moment of inertia I3 of the outer gimbal 11)”. It is a graph which shows an example. In addition, FIG.5, FIG.6 (a), FIG.6 (b) overlaps and shows FIG.4 (a) and FIG.4 (b).

  In FIG. 5, the broken line L4 indicates the magnitude of “(the torsion spring constant K2 of the elastic coupling portions 15a and 15b) / (inertial moment I2 of the inner gimbal 12)” (in FIG. 5, about 5E + 07). , “(The torsion spring constant K1 of the elastic coupling portions 16a and 16b) / (the moment of inertia I1 of the mirror 13)” (in FIG. 5, about 1.6E + 10). Hereinafter, “the torsion spring constant K2 of the elastic connecting portions 15a and 15b” is referred to as “the torsion spring constant K2 of the inner gimbal 12”, and “the torsion spring constant K1 of the elastic connecting portions 16a and 16b” is referred to as “the torsion spring constant of the mirror 13”. This is referred to as “K1”.

  As shown in FIG. 5, the mirror amplitude angle is “(torsional spring constant K3 of outer gimbal 11) / (inertial moment I3 of outer gimbal 11)” is “(torsional spring constant K1 of mirror 13) / (of mirror 13). In the region R4, which is less than the moment of inertia I1) ", the maximum value is obtained.

  Therefore, in order to increase the mirror amplitude angle, {(torsion spring constant K1 of mirror 13) / (moment of inertia I1 of mirror 13)}> {(torsion spring constant K3 of outer gimbal 11) / (outer gimbal 11 It is preferable to configure the optical scanning device 1 so that the moment of inertia I3)

  Further, as shown in FIG. 6A, the value of “(torsion spring constant K3 of the outer gimbal 11) / (moment of inertia I3 of the outer gimbal 11)” so as to exclude the unstable region R2 in the region R4. Is set, the operation of the optical scanning device 1 becomes relatively stable, and the disturbance of the light beam scanning can be suppressed.

  Further, as shown in FIG. 6B, in the region R4, “(the torsion spring constant K3 of the outer gimbal 11) / (the moment of inertia of the outer gimbal 11) is excluded so as to exclude the unstable region R2 and the in-phase region R3. By setting the value of “I3)”, the optical scanning device 1 can be operated in a region where the inner gimbal amplitude angle is relatively large, and the scanning range is expanded when performing two-dimensional light beam scanning. Can do.

  As shown in FIG. 5, the inner gimbal amplitude angle is “(torsion spring constant K3 of outer gimbal 11) / (moment of inertia I3 of outer gimbal 11)” is “(torsion spring constant K2 of inner gimbal 12) / ( The maximum value is obtained in a region larger than the moment of inertia I2) of the inner gimbal 12.

  For this reason, in order to increase the inner gimbal amplitude angle and increase the scanning range, {(torsion spring constant K3 of the outer gimbal 11) / (moment of inertia I3 of the outer gimbal 11)}> {( The optical scanning device 1 may be configured so that the torsion spring constant K2) / (the moment of inertia I2 of the inner gimbal 12)}.

  In the embodiment described above, the mirror 13 is the reflection part in the present invention, the elastic connection parts 16a and 16b are the first elastic connection part in the present invention, and the inner gimbal 12 is the first support part and the elastic connection parts 15a and 15b in the present invention. Is the second elastic connecting portion in the present invention, the outer gimbal 11 is the second supporting portion in the present invention, the elastic connecting portions 14a and 14b are the third elastic connecting portions in the present invention, the supporting portion 3 is the third supporting portion in the present invention, The drive unit 4 is an external force acting means in the present invention.

The in-phase region R3 is an in-phase vibration occurrence state in the present invention, the anti-phase region R1 is an anti-phase vibration occurrence state in the present invention, and the unstable region R2 is an unstable vibration state in the present invention.
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.

  For example, in the above-described embodiment, the outer gimbal 11 is reciprocally vibrated by generating an electrostatic attractive force between the comb-tooth electrode portions 4a and 4b and the comb-tooth electrode portions 17 and 19. However, the outer gimbal 11 may be reciprocally vibrated by piezoelectric driving or electromagnetic driving.

  DESCRIPTION OF SYMBOLS 1 ... Optical scanning device, 2 ... Light beam scanning part, 3 ... Support part, 4 ... Drive part, 4a, 4b ... Comb electrode part, 5 ... Angle detection part, 5a, 5b ... Comb electrode part, 11 ... Out Gimbal, 12 ... Inner gimbal, 13 ... Mirror, 14a, 14b, 15a, 15b, 16a, 16b ... Elastic connection part, 17, 18, 19, 20 ... Combine electrode part, 31 ... Drive signal generating circuit, 32 ... Amplification Circuit 33 ... CV conversion circuit 34 ... Semiconductor laser 35 ... Control circuit

Claims (4)

A reflecting portion having a reflecting surface for reflecting the light beam;
A first support part that has an elastically deformable first elastic connection part that is connected to the reflection part, and that supports the reflection part in a swingable manner with the first elastic connection part as a rotation axis;
A second support portion that has an elastically deformable second elastic connection portion that is connected to the first support portion, and that supports the first support portion in a swingable manner using the second elastic connection portion as a rotation axis;
A third support portion that has an elastically deformable third elastic connection portion that is connected to the second support portion, and that supports the second support portion in a swingable manner with the third elastic connection portion as a rotation axis. The reflection unit, the first support unit, the second support unit, the third support unit, the first elastic connection unit, the second elastic connection unit, and the third elastic connection unit are unique. A three-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when a periodic external force is applied,
Furthermore, an optical scanning device comprising an external force application means for applying the inherent periodic external force to the three-degree-of-freedom coupled vibration system,
The torsion spring constant of the first elastic coupling part and the torsion spring constant of the third elastic coupling part are respectively K1 and K3,
The moment of inertia of the reflecting portion and the moment of inertia of the second support portion are denoted as I1 and I3, respectively.
An optical scanning device configured to satisfy the relational expression represented by the following expression (1).
(K1 / I1)> (K3 / I3) (1) The optical scanning device vibrates in the torsional vibration so that the phase angle difference between the second support part and the reflection part becomes 0 degree, and the phase between the second support part and the reflection part. The torsional vibration of the optical scanning device so that the angle difference becomes 180 degrees is referred to as anti-phase vibration,
In the optical scanning device, in accordance with the value of (K3 / I3), the in-phase vibration generation state, which is a vibration state in which only the in-phase vibration is generated, and the reverse phase vibration generation, in which only the reverse phase vibration is generated. The state, the in-phase vibration or the anti-phase vibration is a vibration state where the unstable vibration state is generated,
The optical scanning device according to claim 1, wherein the value is set to the value of (K3 / I3) that does not cause the unstable vibration state. The optical scanning device according to claim 2, wherein the value is set to the value of (K3 / I3) at which the antiphase vibration is generated. The torsion spring constant of the second elastic coupling part is K2,
The moment of inertia of the first support part is I2,
4. The optical scanning device according to claim 1, wherein the optical scanning device is configured to satisfy a relational expression represented by the following expression (2): 5.
(K3 / I3)> (K2 / I2) (2)