JP7477344B2 - Mirror Device - Google Patents

Description

The present invention relates to a mirror device that oscillates a mirror having a reflective surface.

A scanning device is known that emits deflected light toward a predetermined area and detects the light returning from the predetermined area to obtain various information about objects located within the predetermined area.

As such a scanning device, one has been proposed in which a movable mirror member, such as a MEMS (Micro Electro Mechanical System) mirror that deflects light, is subjected to an external force, such as magnetic force, to cause the mirror to vibrate back and forth around a torsion bar as a twisting rotation axis (see, for example, Patent Document 1). In such an optical scanning device, the mirror member oscillates at a resonance frequency determined by the moment of inertia of the mirror member and the spring constant of the torsion bar.

However, the spring constant of the torsion bar changes with temperature, so the resonant frequency of the mirror material also changes with temperature.

Therefore, in the optical scanning device described above, the mirror member is covered with a cover member to thermally isolate the mirror member.

JP 2009-69676 A

However, when the mirror member is covered with the cover member described above, although it is possible to slow down the temperature change in response to a sudden temperature change in the external environment, the cover member alone cannot actually keep the temperature around the mirror member constant.

Therefore, even in such an optical scanning device, the resonant frequency of the mirror member changes due to the effect of temperature changes in the external environment.

Therefore, one of the objectives of the present invention is to provide a mirror device that can oscillate a mirror member at a desired resonant frequency regardless of changes in the environmental temperature.

The invention described in claim 1 comprises a mirror body that can swing around one axis, has a reflecting surface formed on one side, a first permanent magnet provided in the center of the other side, and a pair of second permanent magnets arranged on the other side across the one axis; a drive unit that includes a first yoke that is arranged in an area on the other side of the mirror body and has a pair of ends that face each other across the first permanent magnet; and an adjustment unit that includes a pair of second yokes that are arranged in an area on the other side of the mirror body and each have ends that face each of the pair of second permanent magnets.

The invention described in claim 7 is a mirror device having a mirror body with a reflecting surface formed on one side and a permanent magnet provided in the center of the other side, capable of swinging around one axis, and a drive unit including a yoke wound with a coil, the drive unit having a pair of ends that are arranged in the area on the other side of the mirror body and face each other across the first permanent magnet, the drive unit applies a current in which a DC component corresponding to the swing frequency of the mirror body when swinging is superimposed on an AC current to the coil wound around the yoke.

1 is a diagram showing an overall configuration of a mirror scanner as a mirror device according to a first embodiment; FIG. 4 is a block diagram showing an example of the internal configuration of a mirror drive circuit and an oscillation frequency adjustment circuit. FIG. FIG. 4 is a waveform diagram showing an example of a swing detection signal. 5A and 5B are diagrams illustrating the positional relationship between a mirror body and each yoke during oscillation. 10A and 10B are diagrams illustrating other positional relationships between the mirror body and each yoke during oscillation. 11A and 11B are diagrams for explaining the state of each yoke when the resonant frequency of the mirror body is higher than a reference frequency, and the effect on the mirror body. 13 is another diagram for explaining the state of each yoke when the resonant frequency of the mirror body is higher than the reference frequency, and the effect on the mirror body. FIG. 11A and 11B are diagrams for explaining the state of each yoke when the resonant frequency of the mirror body is equal to or lower than a reference frequency, and the effect on the mirror body. 13 is another diagram for explaining the state of each yoke when the resonant frequency of the mirror body is equal to or lower than the reference frequency, and the effect on the mirror body. FIG. FIG. 11 is a diagram illustrating an example of an overall configuration of a mirror scanner as a mirror device according to a second embodiment. 13 is a block diagram showing another example of the internal configuration of the mirror driving circuit. FIG.

The following is a detailed description of preferred embodiments of the present invention. In the following description of each embodiment and in the accompanying drawings, the same reference numerals are used for substantially the same or equivalent parts.

Figure 1 is a diagram showing an example of the overall configuration of a mirror scanner 100 according to a first embodiment as a mirror device. The mirror scanner 100 is, for example, a magnetically driven MEMS (Micro Electro Mechanical System) device, and has a plate-shaped mirror section 10 that deflects light, and a magnetic circuit 20 that is a magnetic field generating source that generates a magnetic field for oscillating the mirror section 10.

Figure 2 is a plan view of the mirror unit 10 viewed from the direction of the white arrow shown in Figure 1.

As shown in FIG. 2, the mirror section 10 has a mirror body 10S having a light reflecting surface RF, an annular frame body 10W surrounding the mirror body 10S, and a torsion bar 10T that supports the mirror body 10S in a state in which it can swing about a swing axis AY (shown by a dashed line).

As shown in Figures 1 and 2, permanent magnets 13, 15a, and 15b are fixed to the surface of the mirror body 10S opposite the light reflecting surface RF.

The permanent magnet 13 is fixed at the center position on the surface of the mirror body 10S opposite the light reflecting surface RF.

Permanent magnets 15a and 15b are fixed to the surface opposite the light reflecting surface RF at positions spaced apart from each other with permanent magnet 13 in between.

In the embodiment shown in FIG. 1, the surface of each of the permanent magnets 13, 15a, and 15b that is fixed to the mirror body 10S is a south pole, and the opposing surface is a north pole.

The magnetic circuit 20 includes yokes 21, 31a, and 31b made of a soft magnetic material, such as electromagnetic steel plate, a mirror drive circuit 25, and an oscillation frequency adjustment circuit 26. As shown in FIG. 1, the yokes 21, 31a, and 31b are arranged in the magnetic field of the permanent magnets 13, 15a, and 15b in the area on the side opposite the light reflecting surface RF of the mirror section 10. As shown in FIG. 1, coils 23, 33a, and 33b are wound individually around each of the yokes 21, 31a, and 31b, respectively.

The yoke 21 has, for example, a C-shape or a U-shape, and is installed so that its pair of ends sandwich the permanent magnet 13 in a non-contact manner, as shown in FIG. 1. The yoke 21 functions as an electromagnet that generates an AC magnetic field from its pair of ends when an AC current flows through the coil 23 wound around the yoke 21.

The yoke 31a has, for example, a rod shape, and is installed so that one end 34a is positioned opposite the permanent magnet 15a and out of contact with it, as shown in FIG. 1. When a direct current flows through the coil 33a wound around the yoke 31a, the yoke 31a functions as an electromagnet that generates a magnetic field of a north pole or south pole from its end 34a. For example, when a negative direct current flows through the coil 33a, a magnetic field of a south pole is generated from the end 34a of the yoke 31a, and when a positive direct current flows through the coil 33a, a magnetic field of a north pole is generated from the end 34a of the yoke 31a.

The yoke 31b has, for example, a rod shape, and is installed so that one end 34b is positioned opposite the permanent magnet 15b in a non-contact state as shown in FIG. 1. When a direct current flows through the coil 33b wound around the yoke 31b, the yoke 31b functions as an electromagnet that generates a magnetic field of a north pole or south pole from its end 34b. For example, when a negative direct current flows through the coil 33b, a south pole magnetic field is generated from the end 34b of the yoke 31b, and when a positive direct current flows through the coil 33b, a north pole magnetic field is generated from the end 34b of the yoke 31b.

The mirror drive circuit 25 generates an alternating magnetic field by generating a magnetic field of a north pole and a magnetic field of a south pole at each of a pair of ends of the yoke 21, and reversing the polarity of the magnetic field generated at each of the pair of ends. At this time, when the alternating magnetic field is applied to the permanent magnet 13, the mirror body 10S resonates around the oscillation axis AY, and the mirror body 10S oscillates.

The oscillation frequency adjustment circuit 26 generates a magnetic field of a north pole or a magnetic field of a south pole at the ends 34a and 34b of the pair of yokes 31a and 31b. The oscillation frequency adjustment circuit 26 adjusts the oscillation frequency during oscillation of the mirror body 10S by generating an attractive or repulsive force between the yoke 31a (31b) and the permanent magnet 15a (15b) using the generated magnetic field.

Figure 3 is a block diagram showing an example of the internal configuration of the mirror drive circuit 25 and the oscillation frequency adjustment circuit 26.

As shown in FIG. 3, the mirror drive circuit 25 includes an AC current source 250. The AC current source 250 generates an AC current for oscillating the mirror body 10S around the oscillation axis AY and supplies the AC current to the coil 23 of the yoke 21.

The oscillation frequency adjustment circuit 26 includes a vibration sensor 252, a control unit 253, and variable DC current sources 254 and 255.

The vibration sensor 252 detects the swaying state of the mirror body 10S and supplies a sway detection signal FD having a signal waveform corresponding to the swaying to the control unit 253.

Figure 4 is a waveform diagram showing an example of the vibration detection signal FD.

As shown in FIG. 4, the oscillation detection signal FD follows the oscillation of the mirror body 10S, and its signal level periodically changes between a maximum value and a minimum value around a central level Q.

The control unit 253 supplies the variable DC current source 254 with a power on/off signal GON1 that sets the variable DC current source 254 to an off state during a period when the signal level of the oscillation detection signal FD is higher than the center level Q shown in FIG. 4, and sets the variable DC current source 254 to an on state during a period when the signal level of the oscillation detection signal FD is lower than the center level Q, for example. The control unit 253 also supplies the variable DC current source 255 with a power on/off signal GON2 that sets the variable DC current source 255 to an on state during a period when the signal level of the oscillation detection signal FD is higher than the center level Q, and sets the variable DC current source 255 to an off state during a period when the signal level of the oscillation detection signal FD is lower than the center level Q.

Furthermore, the control unit 253 measures the frequency at which the mirror body 10S oscillates as the oscillation frequency based on the oscillation detection signal FD. Then, when the measured oscillation frequency is higher than a predetermined reference frequency, the control unit 253 supplies the variable DC current sources 254 and 255 with a current control signal CR that prompts them to generate, for example, a negative DC current. On the other hand, when the measured oscillation frequency is equal to or lower than the reference frequency, the control unit 253 supplies the variable DC current sources 254 and 255 with a current control signal CR that prompts them to generate a positive DC current.

The variable DC current source 254 is in the ON state while the power on/off signal GON1 indicates the ON state, generates a DC current IG1 of the polarity dictated by the current control signal CR, and supplies this to the coil 33a of the yoke 31a. On the other hand, while the power on/off signal GON1 indicates the OFF state, the variable DC current source 254 stops generating the DC current IG1.

The variable DC current source 255 is in the ON state while the power on/off signal GON2 indicates the ON state, generates a DC current IG2 of the polarity prompted by the current control signal CR, and supplies this to the coil 33b of the yoke 31b. On the other hand, while the power on/off signal GON2 indicates the OFF state, the variable DC current source 255 stops generating the DC current IG2.

The operation of the mirror scanner 100 shown in Figure 1 is described below.

First, the yoke 21 generates an AC magnetic field in which one of its pair of ends becomes a north pole and the other a south pole, and then one of the pair of ends becomes a south pole and the other a north pole, alternating in response to the AC current supplied from the mirror drive circuit 25. When the AC magnetic field is applied to the permanent magnet 13 of the mirror body 10S, attractive and repulsive forces are generated alternately between the pair of ends of the yoke 21 and the permanent magnet 13. This causes the mirror body 10S to oscillate around the oscillation axis AY. At this time, the torsion bar 10T supporting the mirror body 10S twists, causing the mirror body 10S to resonate at a frequency based on the spring constant of the torsion bar 10T. In other words, the mirror body 10S oscillates around the oscillation axis AY at a resonant frequency corresponding to the spring constant of the torsion bar 10T.

Figures 5A and 5B show the positional relationship between the mirror body 10S and the yoke 21, yokes 31a and 31b during oscillation.

Note that Fig. 5A shows the positional relationship between the mirror body 10S and the yoke 21, yokes 31a and 31b when the signal level of the vibration detection signal FD shown in Fig. 4 is at its maximum value. On the other hand, Fig. 5B shows the positional relationship between the mirror body 10S and the yoke 21, yokes 31a and 31b when the signal level of the vibration detection signal FD is at its minimum value.

Here, if the angle of the mirror body 10S when the permanent magnet 13 is not receiving an AC magnetic field is taken as the base angle J0, when the permanent magnet 13 receives an AC magnetic field, the mirror body 10S oscillates at a swing angle θ with respect to the base angle J0, as shown in Figures 5A and 5B.

In the state shown in FIG. 5A, of the variable DC current sources 254 and 255, the variable DC current source 255 is in the ON state. As a result, of the yokes 31a and 31b, only the yoke 31b functions as an electromagnet, and a magnetic field is generated from the end 34b of the yoke 31b. At this time, no magnetic field is generated from the end 34a of the yoke 31a.

On the other hand, in the state shown in FIG. 5B, of the variable DC current sources 254 and 255, the variable DC current source 254 is in the ON state. As a result, of the yokes 31a and 31b, only the yoke 31a functions as an electromagnet, and a magnetic field is generated from the end 34a of the yoke 31a. At this time, no magnetic field is generated from the end 34b of the yoke 31b.

In other words, each of the yokes 31a and 31b functions as an electromagnet when the opposing permanent magnets (15a, 15b) approach as the mirror body 10S oscillates.

When the oscillation frequency of the mirror body 10S based on the oscillation detection signal FD is higher than a predetermined reference frequency, the variable DC current source 254 (255) supplies a negative DC current IG1 (IG2) to the coil 33a (33b) of the yoke 31a (31b). This causes the end 34a (34b) of the yoke 31a (31b) to generate a magnetic field of the S pole, generating an attractive force between the yoke 31a (31b) and the permanent magnet 15a (15b).

Figures 6A and 6B are diagrams for explaining the state of yokes 31a and 31b when the oscillation frequency of mirror body 10S is higher than a predetermined reference frequency, and the effect on mirror body 10S. Note that Figure 6A shows the positional relationship between mirror body 10S, yoke 21, yokes 31a and 31b similar to Figure 5A, and Figure 6B shows the positional relationship between mirror body 10S, yoke 21, yokes 31a and 31b similar to Figure 5B.

When the permanent magnet 15b approaches the end 34b of the yoke 31b due to the oscillation of the mirror body 10S, a magnetic field of the south pole is generated from the end 34b of the yoke 31b, as shown in FIG. 6A. As a result, the yoke 31b generates an attractive force against the permanent magnet 15b, which generates a magnetic field of the north pole.

On the other hand, when the permanent magnet 15a approaches the end 34a of the yoke 31a due to the oscillation of the mirror body 10S, a magnetic field of the south pole is generated from the end 34a of the yoke 31a, as shown in FIG. 6B. As a result, the yoke 31a generates an attractive force against the permanent magnet 15a, which generates a magnetic field of the north pole.

In other words, when the environmental temperature around the mirror section 10 drops, the spring constant of the torsion bar 10T increases, causing the resonant frequency of the mirror body 10S to fluctuate in the higher direction.

In such a case, a magnetic field that generates an attractive force on the permanent magnet 15a (15b) is generated in the yoke 31a (31b). At this time, the larger the deflection angle of the mirror body 10S, the narrower the gap between the yoke 31a (31b) and the permanent magnet 15a (15b) becomes, and the stronger the attractive force becomes. This reduces the apparent spring constant of the torsion bar 10T that supports the mirror body 10S, and the resonant frequency of the mirror body 10S decreases.

This operation therefore makes it possible to suppress the increase in the resonant frequency of the mirror body 10S that occurs as the environmental temperature decreases.

On the other hand, when the resonant frequency of the mirror body 10S based on the oscillation detection signal FD is equal to or lower than a predetermined reference frequency, the variable DC current source 254 (255) supplies a negative DC current IG1 (IG2) to the coil 33a (33b) of the yoke 31a (31b). This causes the end 34a (34b) of the yoke 31a (31b) to generate a magnetic field of the N pole, generating a repulsive force between the yoke 31a (31b) and the permanent magnet 15a (15b).

Figures 7A and 7B are diagrams for explaining the state of yokes 31a and 31b when the resonant frequency of mirror body 10S is equal to or lower than a predetermined reference frequency, and the effect on mirror body 10S. Note that Figure 7A shows the positional relationship between mirror body 10S, yoke 21, yokes 31a and 31b similar to Figure 5A, and Figure 7B shows the positional relationship between mirror body 10S, yoke 21, yokes 31a and 31b similar to Figure 5B.

As shown in FIG. 7A, when the permanent magnet 15b approaches the end 34b of the yoke 31b due to the oscillation of the mirror body 10S, an N-pole magnetic field is generated from the end 34b of the yoke 31b. As a result, the yoke 31b generates a repulsive force against the permanent magnet 15b that generates the N-pole magnetic field.

On the other hand, as shown in FIG. 7B, when the permanent magnet 15a approaches the end 34a of the yoke 31a due to the oscillation of the mirror body 10S, an N-pole magnetic field is generated from the end 34a of the yoke 31a. As a result, the yoke 31a generates a repulsive force against the permanent magnet 15a that generates the N-pole magnetic field.

In other words, when the environmental temperature around the mirror section 10 increases, the spring constant of the torsion bar 10T decreases, causing the resonant frequency of the mirror body 10S to fluctuate in a lower direction.

In such a case, a magnetic field that generates a repulsive force against the permanent magnet 15a (15b) is generated in the yoke 31a (31b). At this time, the larger the deflection angle of the mirror body 10S, the narrower the gap between the yoke 31a (31b) and the permanent magnet 15a (15b) becomes, and the stronger the repulsive force becomes. This increases the apparent spring constant of the torsion bar 10T that supports the mirror body 10S, and increases the resonant frequency of the mirror body 10S.

This operation therefore makes it possible to prevent the resonant frequency of the mirror body 10S from becoming lower as the environmental temperature increases.

As described above in detail, in the mirror scanner 100, the resonant frequency of the mirror body 10S can be adjusted by the adjustment section including the oscillation frequency adjustment circuit 26, the yokes 31a and 31b, and the permanent magnets 15a and 15b fixed to the mirror body 10S.

Therefore, the mirror scanner 100 makes it possible to maintain the resonant frequency of the mirror body 10S at the desired reference frequency regardless of changes in the environmental temperature.

In the above embodiment, the surfaces of the permanent magnets 15a and 15b facing the ends 34a and 34b of the yokes 31a and 31b are both N poles, but they may be S poles, or one may be an S pole and the other an N pole. In this case, the polarity of the magnetic field generated at the ends 34a and 34b of the yokes 31a and 31b can be controlled in accordance with the polarity of the surfaces of the permanent magnets 15a and 15b facing the ends 34a and 34b of the yokes 31a and 31b.

In addition, in the above embodiment, the polarity of the magnetic field generated at the ends 34a and 34b of the yokes 31a and 31b is switched based on the oscillation frequency of the mirror body 10S. However, when the mirror scanner 100 is used in an environment with little temperature fluctuation, the polarity of the magnetic field generated at the ends 34a and 34b of the yokes 31a and 31b may be fixed to either the north pole or the south pole based on the environmental temperature.

In the above embodiment, one of the variable DC current sources 254 and 255 is set to an operating state and the other to a stopped state, following the oscillation of the mirror body 10S, for example, as shown in Figures 6A and 6B, but the variable DC current sources 254 and 255 may be set to an operating state at all times.

In short, the mirror scanner 100 may include the following mirror body, driving unit, and adjustment unit. That is, the mirror body (10S) can swing around one axis (AY), has a reflecting surface (RF) formed on one surface, a first permanent magnet (13) provided in the center of the other surface, and a pair of second permanent magnets (15a, 15b) arranged on either side of the above-mentioned one axis on the other surface. The driving unit (21, 23, 25) has a first yoke (21) arranged in an area on the other surface side of the mirror body and has a pair of ends facing each other with the first permanent magnet (13) in between. The adjustment unit (26, 31a, 31b, 33a, 33b) includes a pair of second yokes (31a, 31b) arranged in an area on the other surface side of the mirror body and each of which has ends (34a, 34b) facing each of the pair of second permanent magnets (15a, 15b).

Figure 8 is a diagram showing an example of the overall configuration of a mirror scanner 100A, which is a second embodiment of a mirror device according to this embodiment.

The mirror scanner 100A uses a mirror section 10 that does not include the permanent magnets 15a and 15b shown in FIG. 1, and uses a mirror drive circuit 25A instead of the mirror drive circuit 25. The magnetic circuit 20 does not include the oscillation frequency adjustment circuit 26 and yokes 31a and 31b shown in FIG. 1, and uses a mirror drive circuit 25A instead of the mirror drive circuit 25.

Figure 9 is a block diagram showing an example of the internal configuration of the mirror drive circuit 25A.

In FIG. 9, the vibration sensor 252 detects the swaying state of the mirror body 10S and supplies a sway detection signal FD having a signal waveform corresponding to the swaying, as shown in FIG. 4, to the control unit 253A.

The control unit 253A measures the resonant frequency during the oscillation of the mirror body 10S as the oscillation frequency based on the oscillation detection signal FD. Then, based on this oscillation frequency, the control unit 253A determines the amount of DC offset current to be superimposed on the AC current supplied to the coil 23, and supplies an offset signal DCO indicating this offset current amount to the AC current source 250A. For example, the higher the measured resonant frequency, the more the control unit 253A supplies to the AC current source 250A an offset signal DCO indicating a larger DC offset current.

The AC current source 250A generates an AC current for oscillating the mirror body 10S around the oscillation axis AY shown in FIG. 2. The AC current source 250A supplies the coil 23 of the yoke 21 with an offset superimposed AC current, which is a DC offset current having an offset current amount indicated by the offset signal DCO, superimposed on the AC current generated as described above.

When the offset superimposed AC current described above flows through the coil 23, the yoke 21 generates an AC magnetic field from its pair of ends. This generates alternating attractive and repulsive forces between the pair of ends of the yoke 21 and the permanent magnet 13, causing the mirror body 10S to oscillate around the oscillation axis AY. At this time, the torsion bar 10T supporting the mirror body 10S twists, causing the mirror body 10S to resonate at a frequency based on the spring constant of the torsion bar 10T. In other words, the mirror body 10S oscillates in the circumferential direction of the oscillation axis AY at a resonant frequency corresponding to the spring constant of the torsion bar 10T.

When the environmental temperature changes, the spring constant of the torsion bar 10T changes, causing the resonant frequency of the mirror body 10S to fluctuate.

However, in the mirror scanner 100A, even if the resonant frequency of the mirror body 10S fluctuates due to changes in the environmental temperature, the fluctuation in the resonant frequency is suppressed by superimposing an offset current corresponding to the resonant frequency on the AC current that oscillates the mirror body 10S.

Therefore, the mirror scanner 100A makes it possible to maintain the resonant frequency of the mirror body 10S at a predetermined reference frequency regardless of changes in the environmental temperature.

In the above embodiment, a DC current corresponding to the measured oscillation frequency of the mirror body 10S is superimposed on the AC current as an offset current, but the amount of the superimposed offset current may be changed in accordance with the phase of the oscillation detection signal FD. For example, at the maximum and minimum values of the oscillation detection signal FD as shown in FIG. 4, the amount of the superimposed offset current is maximized, and the amount of current is gradually reduced toward the center level Q.

In short, the mirror scanner 100A may include the following mirror body and drive unit. That is, the mirror body (10S) has a reflective surface (RF) formed on one side and a permanent magnet (13) provided in the center of the other side, and is installed in a state in which it can swing around one axis (AY). The drive unit (25A) is arranged in the area on the other side of the mirror body, has a pair of ends facing each other across the permanent magnet, includes a yoke (21) around which a coil (23) is wound, and applies a current in which a DC component corresponding to the resonant frequency due to the swing of the mirror body is superimposed on an AC current to the coil wound around the yoke.

10 Mirror section 10S Mirror body 13, 15a, 15b Permanent magnet 21, 31a, 31b Yoke 23, 33a, 33b Coil 25 Mirror drive circuit 26 Oscillation frequency adjustment circuit 100 Mirror scanner 250 AC current source 252 Vibration sensor 253 Control section 254, 255 Variable DC power supply

Claims (7)

a mirror body that is oscillating around one axis, has a reflecting surface formed on one surface, a first permanent magnet provided at the center of the other surface, and a pair of second permanent magnets disposed on both sides of the one axis on the other surface;
a drive unit including a first yoke disposed in an area on the other surface side of the mirror body and having a pair of ends facing each other with the first permanent magnet interposed therebetween, the drive unit generating a magnetic field in the first yoke to oscillate the mirror body ;
a pair of second yokes arranged in the area on the other surface side of the mirror body, each having an end facing each of the pair of second permanent magnets , and an adjustment unit that adjusts the oscillation frequency of the mirror body when it oscillates by generating a magnetic field in the second yokes . the driving unit generates a magnetic field of an N pole and a magnetic field of an S pole at the pair of ends of the first yoke, respectively, and inverts the polarity of the magnetic field generated at each of the pair of ends to resonate the mirror body around the one axis, thereby oscillating the mirror body;
The mirror device according to claim 1, characterized in that the adjustment unit generates a north pole magnetic field or a south pole magnetic field at the end of each of the pair of second yokes, and adjusts the oscillation frequency of the mirror body when it oscillates by generating an attractive or repulsive force between the pair of second yokes and the pair of second permanent magnets using the generated magnetic field. the adjustment unit includes a sensor that detects a swing state of the mirror body and generates a swing detection signal having a signal waveform corresponding to the swing;
3. The mirror device according to claim 2, wherein a magnetic field of a north pole or a magnetic field of a south pole is generated at the end of each of the pair of second yokes so as to generate an attractive force between the pair of second yokes and the pair of second permanent magnets when the oscillation frequency of the mirror body based on the oscillation detection signal is higher than a predetermined reference frequency, and to generate a repulsive force between the pair of second yokes and the pair of second permanent magnets when the oscillation frequency is equal to or lower than the reference frequency. The mirror device according to claim 3, characterized in that when one of the pair of second permanent magnets approaches one of the pair of second yokes due to the oscillation of the mirror body, the adjustment unit stops generation of a magnetic field in the other of the pair of second yokes, and when the other of the pair of second permanent magnets approaches the other of the pair of second yokes, the adjustment unit stops generation of a magnetic field in the one of the second yokes. a coil is wound around each of the first yoke and the pair of second yokes,
the driving unit includes an AC source that applies an AC current to the coil wound around the first yoke;
5. The mirror device according to claim 3, wherein the adjustment section includes first and second DC current sources that apply DC currents to the coils wound around the pair of second yokes, respectively. The mirror device according to claim 5, characterized in that the adjustment unit controls the first and second DC current sources to supply a first DC current to the coils wound around the pair of second yokes as the DC current when the oscillation frequency is higher than the reference frequency, and controls the first and second DC current sources to supply a second DC current having a polarity different from that of the first DC current to the coils wound around the pair of second yokes as the DC current when the oscillation frequency is equal to or lower than the reference frequency. a mirror body having a reflecting surface formed on one side and a permanent magnet provided at the center of the other side, the mirror body being oscillating around one axis;
a driving unit including a yoke around which a coil is wound, the driving unit having a pair of ends disposed in an area on the other surface side of the mirror body and facing each other across the permanent magnet,
The mirror device is characterized in that the driving unit applies a current to the coil wound around the yoke, the current being a DC current superimposed on an AC current, the current amount of which corresponds to the magnitude of the oscillation frequency when the mirror body oscillates.

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