JP2021025938A - Angle detection device - Google Patents

Abstract

To provide an angle detection device which is strong at change in surrounding environment and change with time and saves a space.SOLUTION: An angle detection device includes a mirror which has a first surface for reflecting light and a second surface located on a side opposite to the first surface and is configured to be rockable aound a rocking shaft from a reference attitude, a light source which emits laser light advancing in parallel to the second surface of the mirror in the reference attitude, a photodetector which is provided on the optical path of the laser light emitted from the light source and advanced, and an angle calculation part which calculates a rocking angle from the reference attitude on the basis of the light receiving result of the photodetector.SELECTED DRAWING: Figure 1B

Description

The present invention relates to an angle detection device, and more particularly to an angle calculation device for calculating a swing angle from a reference posture of a mirror swinging around a swing axis.

There is known a scanning device that obtains various information about an object located in the predetermined region by emitting light toward a predetermined region while deflecting the light and detecting the light returned from the predetermined region. There is. In such a scanning device, a movable mirror such as a MEMS (Micro Electro Mechanical System) mirror is provided as a portion for deflecting light.

In a scanning device having such a movable mirror, the emitted light is deflected by changing the angle of the mirror to change the incident direction and the reflected direction of the light ray with respect to the mirror. Therefore, in order to know where the emitted light is illuminating in a predetermined region, it is necessary to detect the angle of the mirror with respect to the reference posture.

As a method of detecting the angle of the mirror, for example, a strain sensor provided on the movable part of the mirror detects a part of the deformation of the movable part as the magnitude of the strain, and the piezoresistive effect or the piezoelectric effect is used to detect the mirror. The angle of is calculated. Further, a method of irradiating a mirror with light and detecting a change in the reflection direction of the light reflected by the mirror with a quadrant detector to detect the angle of the mirror has been proposed (for example, Patent Document 1). ..

Japanese Unexamined Patent Publication No. 2012-198511

In the method of calculating the angle of the mirror using the detection result of the strain sensor as described above, since the change in the physical characteristics of the material in the moving part or the like is used, the detection sensitivity has temperature dependence and the repeated strain. Due to the deterioration of the material due to the occurrence of the above, the detection sensitivity changes. Therefore, there is a problem that the angle of the mirror cannot be calculated accurately.

Further, in the method of detecting the angle of the mirror by utilizing the change in the reflection direction of the light reflected by the mirror as in the above prior art document, it is necessary to inject the light at a relatively angle with respect to the mirror. A considerable amount of space is required in the direction perpendicular to the light reflecting surface of the mirror. For this reason, there is a problem that the required volume around the mirror becomes large, and the scanning area of the light by the scanning device is limited by the presence of a laser, a detector, or the like that irradiates the light for angle detection.

As described above, in the detection of the angle of the mirror using the strain sensor, one example of the problem is that accurate calculation cannot be performed due to temperature dependence and timekeeping deterioration of the material. Further, when detecting the angle of the mirror based on the change in the reflection direction of the reflected light from the mirror, a large space for providing a detector or the like is required, which limits the scanning area of the scanning device. It is given as an example of the problem.

The present invention has been made in view of the above points, and one of the objects of the present invention is to provide a space-saving angle detection device that is resistant to changes in the surrounding environment and changes over time.

The invention according to claim 1 has a first surface that reflects light and a second surface that is located on the side opposite to the first surface, and swings around a swing axis from a reference posture. On an optical path of a mirror configured to be movable, a light source that emits a laser beam that travels parallel to the second surface of the mirror in the reference posture, and a laser beam that travels from the light source. It is characterized by having a provided light detector and an angle calculation unit that calculates a swing angle from the reference posture based on a light receiving result of the light detector.

The invention according to claim 9 has a first surface that reflects light and a second surface that is located on the side opposite to the first surface, and swings around a swing axis from a reference posture. A mirror configured to be movable and a laser in a direction passing through the region from the outside of a region located directly below the second surface when viewed from a direction perpendicular to the first surface of the mirror in the reference posture. Light detection that has a light source that emits light and a light receiving surface that receives the laser light that has passed through the region, and is arranged so that the amount of the laser light received by the light receiving surface changes due to the swing of the mirror. It is characterized by having a device and an angle calculation unit that calculates the swing angle of the mirror from the reference posture based on the light reception result of the light detector.

It is a figure which shows the whole structure of the angle detection apparatus of this Example. It is sectional drawing of the angle detection apparatus of this Example. It is a figure which shows typically the state of the laser light irradiation in the reference posture of a mirror. It is a figure which shows typically the state of irradiation of the laser beam when the mirror is tilted toward the 1st photodetector. It is a figure which shows typically the state of the laser light irradiation when the mirror is tilted toward the laser light emitting part side. It is a graph which shows the relationship between the light intensity detected when a mirror swings, and time. It is a graph which shows the relationship between the standardized light intensity and a swing angle. It is a figure which shows typically the case where the laser light reflected by the mirror is incident on the 1st photodetector. It is a figure which shows typically the state of irradiation of the laser light in the modification. It is a figure which shows typically the relationship of the phase difference between the waveform of a drive signal and the inclination of a mirror. It is a top view which shows typically the state that a laser beam passes a part of the back surface of a mirror in a modification. It is sectional drawing which shows typically how the laser beam passes a part of the back surface of a mirror in a modification. It is a figure which shows typically the mode that the detector receives the reflected light which reflected the laser beam by the mirror for tilt detection in the modification. It is a figure which shows typically the shape of the mirror and the light receiving part in the modification. It is a figure which shows typically the shape of the mirror and the light receiving part in the modification. It is a figure which shows typically the shape of the mirror and the light receiving part in the modification. It is a figure which shows typically the shape of the mirror and the light receiving part in the modification. It is a figure which shows typically the shape of the mirror and the light receiving part in the modification. It is a figure which shows typically the shape of the mirror and the light receiving part in the modification.

Preferred embodiments of the present invention will be described in detail below. In the description and the accompanying drawings in the following examples, substantially the same or equivalent parts are designated by the same reference numerals.

FIG. 1A is a perspective view showing the overall configuration of the angle detection device 10 according to the present embodiment. The angle detection device 10 is a device that detects a swing angle (hereinafter, also referred to as a swing angle) from a reference posture of a mirror swinging around a swing axis.

The angle detection device 10 includes a MEMS mirror 10 that performs light deflection, a laser light emitting unit 21 that emits laser light, a first photodetector 22 and a second photodetector 23 that receive the laser light, and a first light. It has an angle calculation unit 24 that calculates the swing angle of the MEMS mirror 10 based on the light reception results of the detector 22 and the second photodetector 23.

The MEMS mirror 10 is a MEMS (Micro Electro Mechanical System) mirror including a mirror that deflects light by periodically swinging. The MEMS mirror 10 includes a support portion 11 and a movable portion 12 oscillatingly supported by the support portion 11. The support portion 11 is fixed to a housing portion (not shown).

The movable portion 12 has a mirror portion 13 supported by the support portion 11 in a swingable state around the swing shaft CA. The mirror portion 13 is connected to and supported by the support portion 11 by a torsion bar 14 extending along the swing shaft CA. The support portion 11 and the movable portion 12 are made of a semiconductor material, and can be formed by, for example, processing a semiconductor wafer.

A light reflecting surface is formed on the first main surface of the mirror portion 13. On the other hand, the second main surface of the mirror portion 13, which is the main surface opposite to the first main surface, has a black color and is subjected to antireflection processing such as providing fine grooves. .. Further, a permanent magnet (not shown) is provided on the second main surface of the mirror portion 13. When a magnetic field is applied to the permanent magnet so that the torsion bar 14 is twisted in its circumferential direction, the mirror portion 13 swings around the swing shaft CA while being supported by the support portion 11.

The mirror portion 13 swings around the swing shaft CA in a basic posture in which the first main surface and the second main surface are supported so as to be horizontal. In this embodiment, the mirror unit 13 periodically swings in a range of a predetermined angle about the reference posture. For example, if the clockwise direction is the + direction and the counterclockwise direction is the − direction from the normal direction of the first main surface in the basic posture, the mirror unit 13 is the normal direction of the first main surface. The angle AG formed by the normal and the normal in the reference posture swings periodically in the range of AG ≦ ± θmax (for example, ± 15 °). In the following description, the maximum angle θmax indicating the limit of the swing angle is also referred to as the maximum swing angle.

The laser light emitting unit 21 is provided on the second main surface side of the mirror unit 13 in the reference posture. The laser beam emitting unit 21 is, for example, located outside the MEMS mirror 10 (that is, in a direction parallel to the second main surface of the mirror unit 13 in the reference posture, the distance from the center of the mirror unit 13 is larger than the outer edge of the MEMS mirror 10. From a distant position), the laser beam is emitted so as to pass over the second main surface of the mirror portion 13.

The first photodetector 22 is composed of a photodiode such as an APD (Avalanche PhotoDiode). The first photodetector 22 is provided on an optical path in which the laser light emitted from the laser light emitting unit 21 passes over the second main surface of the mirror unit 13 and travels. For example, the first photodetector 22 is the second main surface side of the mirror portion 13 in the reference posture, and is the mounting region of the MEMS mirror 10 (that is, the first main surface side of the mirror portion 13 in the reference posture). Is "upper" and the second main surface side is "lower"), and is provided at a position facing the laser beam emitting portion 21 with a region directly below the MEMS mirror 10).

Like the first photodetector 22, the second photodetector 23 is composed of a photodiode. In the second light detector 23, when the mirror portion 13 swings in one direction, the laser beam reflected by the end portion of the mirror portion 13 is incident, and when the mirror portion 13 swings in the other direction. Is provided at a position where the laser beam is not incident. For example, the second photodetector 23 is arranged on the second main surface side of the mirror unit 13 in the reference posture and at a position close to the laser light emitting unit 21.

The angle calculation unit 24 calculates the angle of the mirror unit 13 with respect to the reference posture based on the light reception result of the first photodetector 22. Further, the angle calculation unit 24 detects in which direction the mirror unit 13 is tilted from the reference posture based on the light receiving result of the second photodetector 23.

FIG. 1B is a cross-sectional view of the angle calculation device 100 along the XX line. Here, the positional relationship of each portion when the mirror portion 13 is in the reference posture is shown.

The laser beam emitting unit 21 emits laser light from the outside of the outer edge portion of the MEMS mirror 10 toward the center portion of the mirror portion 13 on the second main surface S2 side of the mirror portion 13 so that the center portion thereof is emitted. It is arranged so that the outlet faces in the direction of. The lens 25 is provided in the vicinity of the front side of the emission port of the laser beam emission unit 21 (that is, the side toward the center of the mirror unit 13).

The first photodetector 22 has a light receiving surface in the direction of the central portion of the mirror unit 13 so as to receive the laser light emitted from the laser light emitting unit 21 and passed over the second main surface of the mirror unit 13. It is placed facing.

The second photodetector 23 faces the second main surface S2 of the mirror unit 13 so as to receive the laser light emitted from the laser light emitting unit 21 and reflected by the side end of the mirror unit 13. It is arranged with the light receiving surface facing.

Next, the angle detection operation executed by the angle detection device 100 of this embodiment will be described with reference to FIGS. 2A, 2B, 2C, 3A and 3B.

FIG. 2A is a diagram schematically showing the state of emitting and receiving laser light when the mirror unit 13 is in the reference posture. Here, the direction perpendicular to the first main surface S1 and the second main surface S2 of the mirror portion 13 is shown as a normal NL. The laser light LL emitted from the laser light emitting unit 21 (shown by a broken line in FIG. 2A) passes through the lens 25 and travels in parallel on the second main surface S2 of the mirror unit 13, and the first It is incident on the photodetector 22. The amount of light of the laser beam LL incident on the first photodetector 22 is the largest as compared with the state in which the mirror portion 13 is swung. That is, in this state, the light intensity detected by the first photodetector 22 is maximized.

2B shows a state in which the first main surface S1 of the mirror portion 13 is tilted in the direction in which the first photodetector 22 is located from the state of the reference posture shown in FIG. 2A, that is, the normal line NL is in the direction A in FIG. 2A. It shows a state in which the mirror portion 13 is tilted so as to change. In this state, a part of the laser light LL emitted from the laser light emitting unit 21 irradiates the second main surface S2 of the mirror unit 13, and its progress is hindered. Therefore, the amount of light of the laser beam LL incident on the first photodetector 22 is smaller than that in the state where the mirror portion 13 is in the reference posture.

FIG. 2C shows a state in which the first main surface S1 of the mirror unit 13 is tilted in the direction in which the laser beam emitting unit 21 is located from the state of the reference posture shown in FIG. 2A, that is, the normal NL changes in the B direction of FIG. 2A. The mirror portion 13 is tilted so as to be tilted. In this state, a part of the laser light LL emitted from the laser light emitting unit 21 irradiates the first main surface S1 or the side end portion of the mirror unit 13, and its progress is hindered. Therefore, the amount of light of the laser beam LL incident on the first photodetector 22 is smaller than that in the state where the mirror portion 13 is in the reference posture. Further, among the laser light LL emitted from the laser light emitting unit 21, the laser light reflected at the side end portion of the mirror unit 13 on the laser light emitting unit 21 side is incident on the second light detector 23.

Next, a method in which the angle calculation unit 24 shown in FIG. 1 calculates the swing angle of the mirror unit 13 based on the light reception result of the first photodetector 22 and the light reception result of the second photodetector 23 will be described.

FIG. 3 is a graph showing the relationship between the swing angle of the mirror unit 13 and the light intensity and time of the laser light detected by the first photodetector 22 and the second photodetector 23. Here, the light intensity of the laser light detected by the first photodetector 22 is shown as D1, and the light intensity of the laser light detected by the second photodetector 23 is shown as D2.

When the mirror unit 13 is in the reference posture (indicated as a swing angle SA = 0), the light intensity of the laser light detected by the first photodetector 22 is maximized. On the other hand, the swing angle of the mirror portion 13 is the maximum, that is, the angle formed by the normal NL of the first main surface SL of the mirror portion 13 and the normal NL direction of the first main surface S1 in the reference posture is the maximum swing angle. In a certain state (shown as swing angle SA = max), the light intensity of the laser beam detected by the first photodetector 22 becomes the minimum. In this way, since the value of the detected light intensity changes according to the swing angle, the angle calculation unit 24 can calculate the swing angle based on the magnitude of the light intensity.

Further, when the mirror portion 13 is tilted in the A direction shown in FIG. 2A, the laser beam is not incident on the second photodetector 23, and when the mirror portion 13 is tilted in the B direction shown in FIG. 2A, the second light detection is performed. Laser light is incident on the vessel 23. As shown as D2 in FIG. 3A, the light intensity of the laser beam is detected by the second photodetector 23 only when it is tilted in one direction. Therefore, the angle calculation unit 24 can determine the direction of inclination of the mirror unit 13 based on whether or not the light intensity of the laser light is detected by the second photodetector 23.

The angle calculation unit 24 sets the light intensity standardized based on the maximum value of the light intensity of the laser light detected by the first light detector 22 as the standardized light intensity, and sets the standardized light intensity and the swing angle acquired in advance. The swing angle of the mirror unit 13 is calculated from the above relationship.

Next, the formula for calculating the standardized light intensity will be described. Here, the maximum value of the swing angle of the mirror unit 13 is 15 degrees, and the first light is detected when the direction of the first photodetector 22 is viewed from the laser light emitting unit 21 in the state where the swing angle is maximum. The case where the outer edge of the mirror portion 13 is in contact with the lower end of the light receiving portion of the device 22 will be described as an example.

First, assuming that the mirror portion 13 is a circular mirror having a diameter of d mm, there is a possibility that the laser light emitted from the laser light emitting portion 21 is incident on the lower half of the first main surface S1 of the mirror portion 13. area of a portion) becomes ^{S = (d 2/8)} π.

When the mirror portion 13 swings and tilts, and the angle formed by the normal direction of the first main surface S1 and the normal direction in the reference posture is θ, the laser beam is emitted when the mirror portion 13 is tilted. the area of the portion that blocks is expressed as ^{S (θ) = (d 2} /8) πsinθ.

Assuming that the laser light is incident on the first main surface S1 of the mirror unit 13 when θ = 15 °, the portion of the laser light emitted from the laser light emitting unit 21 that is not blocked by the mirror unit 13. The amount of light I (θ) of is expressed by the following mathematical formula 1 (Equation 1).

Here, I ₀ is the amount of laser light incident on the first photodetector 22 when the mirror unit 13 is in the reference posture. By dividing this light intensity I (θ) by I ₀ , a normalized light intensity “regulation I (θ)” as represented by the following equation 2 (Equation 2) can be obtained.

FIG. 3B is a graph showing the relationship between the normalized light intensity and the swing angle. In the range of the swing angle of ± 15 °, the value of the normalized light intensity changes linearly according to the change of the swing angle.

The angle calculation unit 24 calculates the normalized light intensity based on the light intensity of the laser light detected by the first photodetector 22, and calculates the swing angle based on the relational expression shown by the above equation 2. .. By using the standardized light intensity calculation formula as described above, the swing angle of the mirror unit 13 is stabilized regardless of the maximum light intensity value (that is, the light intensity when the mirror unit 13 is in the reference posture). Can be calculated.

As described above, in the angle detection device 100 of this embodiment, the angle calculation unit 24 calculates the swing angle of the mirror unit 13 based on the light intensity of the laser beam detected by the first photodetector 22. Further, the angle calculation unit 24 determines in which direction the mirror unit 13 is tilted, based on whether or not a light intensity equal to or higher than a predetermined value is detected by the second photodetector 23.

According to this configuration, unlike the case where the angle is calculated using the strain sensor, the swing angle of the mirror unit 13 can be calculated without being affected by the temperature dependence and the deterioration of the material over time. .. Therefore, it is possible to stably calculate the swing angle with high accuracy.

Further, the laser light emitting unit 21, the first light detector 22, and the second light detector 23 are provided on the side opposite to the light reflecting surface of the mirror 10 (that is, the second main surface side of the mirror unit 13). , The laser beam is emitted and received in a direction parallel to the second main surface of the mirror portion 13 in the reference posture. Therefore, since much space is not required in the direction perpendicular to the light reflecting surface of the mirror 10, the angle detection device can be configured in a space-saving manner.

That is, according to the angle detection device of the present embodiment, it is possible to realize angle detection that is space-saving and resistant to changes in the surrounding environment and changes over time (that is, robust).

The present invention is not limited to the above embodiment. For example, in the above embodiment, in order to prevent the reflection of the laser light on the second main surface of the mirror portion 13, the second main surface of the mirror portion 13 has a black color and a fine groove is provided. An example was explained. However, the present invention is not limited to this, and an antireflection structure may be formed on the second main surface of the mirror portion 13. For example, fine protrusions may be formed on the second main surface, or a paint having low reflectance may be applied. Further, on the contrary, the mirror portion 13 itself may be formed of a material having a low reflectance, and the first main surface may be processed to have the reflectivity only.

Further, in addition to the antireflection processing as described above, even if it is further provided with a configuration for suppressing the laser light reflected by the second main surface of the mirror portion 13 from being incident on the first photodetector 22. good.

FIG. 4A is a diagram schematically showing how the laser light reflected by the second main surface of the mirror unit 13 is incident on the first photodetector 22. In this way, when the laser light reflected by the second main surface of the mirror unit 13 is incident on the first light detector 22, the laser light emitted from the laser light emitting unit 21 is directly directed to the first light detector 22. Since the light intensity of the incident portion is added to the light intensity of the incident portion reflected by the second main surface of the mirror unit 13 and the first light detector 22 is incident, the angle may not be calculated. ..

FIG. 4B is a diagram schematically showing a configuration for suppressing the laser light reflected by the second main surface of the mirror unit 13 from entering the first photodetector 22. A second lens 26 is provided between the side end portion of the mirror portion 13 near the first photodetector 22 and the first photodetector 22. Further, a shield 27 having an opening (aperture) is provided between the second lens 26 and the first photodetector 22.

The laser beam reflected by the second main surface of the mirror portion 13 is focused by the second lens 26 at a position different from the opening of the shield 27. Therefore, the laser beam does not pass through the opening of the shield 27 and does not enter the first photodetector 22. On the other hand, the laser light emitted from the laser light emitting unit 21 and traveling in the direction parallel to the second main surface in the reference posture of the mirror unit 13 without being reflected by the second main surface of the mirror unit 13 (hereinafter, The parallel light) is focused by the second lens 26 at the position of the opening of the shield 27. Therefore, the laser beam is incident on the first photodetector 22. According to such a configuration, the incident of the laser light reflected by the second main surface of the mirror portion 13 on the first light detector 22 can be restricted, and only the parallel light can be incident on the first light detector 22. Therefore, it is possible to accurately detect the angle.

Further, in the above embodiment, an example in which the light receiving result of the second photodetector 23 is used to determine which side the mirror portion 13 is tilted to has been described. However, unlike this, for example, a strain sensor may be provided in the movable portion 12, and the method of tilting may be determined by utilizing the piezoresistive effect or the like. The sensor result of the strain sensor is affected by temperature dependence and deterioration of the material over time, but accuracy such as angle calculation is not necessary to determine which side the mirror unit 13 is tilted to. Therefore, the determination can be made using a distortion sensor.

Further, when a rotational torque is directly applied to the MEMS mirror 10 and the mirror portion 13 is oscillating in resonance or non-resonance (for example, a permanent magnet is adhered to the second main surface of the mirror portion 13 from the outside. In the case of swinging the mirror with the magnetic field of (1), it is possible to determine the direction of inclination of the mirror unit 13 based on the waveform of the drive voltage or the drive current.

FIG. 5 is a diagram showing the relationship between the waveform of the drive signal and the swing of the mirror unit 13. For example, in the case of the direct drive type resonance operation, the mirror unit 13 generates a magnetic field corresponding to the drive signal from the magnetic field generation source to which the drive signal including the resonance frequency is applied, and the magnetic field acts on the permanent magnet. As a result, the mirror portion 13 swings in a resonant state. In such a swing operation, the swing of the mirror unit 13 has a waveform whose phase is delayed by 90 ° from the waveform of the drive signal, as shown in FIG. Therefore, it is possible to determine the direction of inclination of the mirror unit 13 based on the drive signal on the assumption that the phase is delayed by 90 °.

Further, the angle detection device of the above embodiment can detect the swing angle of the mirror unit 13 without using the entire surface of the second main surface of the mirror unit 13. FIG. 6A is a top view schematically showing how the laser light emitted from the laser light emitting unit 21 travels along a part of the second main surface of the mirror unit 13, and FIG. 6B is a cross-sectional view thereof. Is. In this way, by arranging the laser light emitting unit and the first photodetector so as to calculate the angle using the laser light that has passed through a part of the second main surface of the mirror unit 13, the mirror unit 13 Even when the permanent magnet 30 is fixed to the second main surface, it is possible to calculate the angle without being affected by the permanent magnet 30.

Further, in the above-described embodiment, an example in which the first photodetector 22 directly receives the laser light emitted from the laser light emitting unit 21 has been described. However, the first photodetector 22 may be configured to receive the light that is once reflected by the mirror or the like. FIG. 7 is a diagram showing an angle detection device having such a configuration. A tilt detection mirror 21 is provided at a position facing the laser beam emitting portion 21 with the mounting region of the MEMS mirror 10 interposed therebetween. The photodetector 32 is provided at a position where the laser beam reflected by the tilt detection mirror 21 is incident. Also in the angle detection device having such a configuration, it is possible to calculate the swing angle of the mirror unit 13 based on the light intensity of the laser light detected by the photodetector 32 as in the above embodiment.

Further, in the above embodiment, the case where the mirror portion 13 is circular has been described as an example, but the shape of the mirror portion 13 is not limited to this. For example, the mirror portion 13 may have a square shape such as a square or a rectangle.

8 (A) to 8 (F) are diagrams schematically showing the relationship between the light receiving surface of the first photodetector 22 seen from the laser light emitting unit 21 and the portion where the laser light is blocked by the mirror unit 13. ..

FIG. 8A shows a state in which the mirror portion 13 is circular and the mirror portion 13 is most tilted (that is, a state in which the swing angle is maximum) as in the above embodiment, and the edge of the mirror portion is first. It shows a case where it comes into contact with the lower side of the light receiving surface of the photodetector 22. The above-mentioned standardized light intensity calculation formula assumes a case where the mirror portion 13 is circular in this way. However, by using a standardized strength calculation formula different from this, it is possible to calculate the swing angle of the mirror portion 13 even when the mirror portion 13 has a square shape, for example.

When the mirror unit 13 has a square shape and the mirror unit 13 blocks the progress of a part of the laser beam as shown in FIG. 8B, the first light detection unit according to the swing angle of the mirror unit 13 Since the amount of laser light incident on 22 changes, the swing angle of the mirror unit 13 can be calculated based on the change in light intensity. However, as shown in FIG. 8C, the mirror unit 13 blocks the progress of the laser beam almost entirely, and as shown in FIG. 8D, the mirror unit 13 is from the light receiving surface of the first photodetector 22. When the state of protrusion is reached, the amount of laser light incident on the first photodetector 22 does not change, so that the swing angle of the mirror unit 13 cannot be calculated based on the light intensity. Therefore, as shown in FIG. 8E, the light receiving surface of the first photodetector 22 is enlarged so that the first photodetector 22 is not completely covered even when the mirror portion 13 is most tilted. This makes it possible to sufficiently calculate the swing angle even when the shape of the mirror portion 13 is square. Further, by increasing the area of the laser beam irradiation region by using a lens or the like, the progress of the laser beam may not be completely blocked by the mirror portion 13. Further, as shown in FIG. 8 (F), even when the mirror portion 13 is circular, the light receiving surface of the first photodetector 22 is enlarged to reduce the region where the progress of the laser beam is blocked by the mirror portion 13. You may do so.

Further, the series of processes described in the above embodiment can be performed by computer processing according to a program stored in a recording medium such as a ROM.

100 Angle detection device 10 MEMS mirror 11 Support part 12 Movable part 13 Mirror part 14 Torsion bar 21 Laser light emission part 22 First photodetector 23 Second photodetector 24 Angle calculation part 25 Lens 30 Permanent magnet 31 Mirror for tilt detection 32 Photodetector

Claims (9)

A mirror having a first surface that reflects light and a second surface that is located on the opposite side of the first surface and is configured to swing around a swing axis from a reference posture.
A light source that emits a laser beam that travels parallel to the second surface of the mirror in the reference posture.
A photodetector provided on the optical path of the laser beam emitted from the light source and traveling.
An angle calculation unit that calculates the swing angle from the reference posture based on the light reception result of the photodetector,
An angle detection device characterized by having. The angle calculation unit is characterized in that it calculates a swing angle from the reference posture by comparing the light reception result of the photodetector with the light reception result when the mirror is in the reference posture. The angle detection device according to 1. The angle calculation unit standardizes the light intensity of the laser beam detected by the photodetector using the light intensity detected by the photodetector when the mirror is in the reference posture, and standardizes the standard. The angle detection device according to claim 1 or 2, wherein the swing angle from the reference posture is calculated based on the standardized light intensity, which is the standardized light intensity. A second light detector provided at a position where the laser beam is incident when the mirror swings in one direction from the reference posture and the laser beam is not incident when the mirror swings in the other direction. Have,
The angle calculation unit according to any one of claims 1 to 3, wherein the angle calculation unit determines the swing direction of the mirror from the reference posture based on the light receiving result of the second detector. Angle detector. The mirror has a permanent magnet fixed to the second surface and swings so as to resonate with a magnetic field generated by a magnetic field source that operates in response to the application of a drive signal.
The angle detection device according to any one of claims 1 to 3, wherein the angle calculation unit determines the swing direction of the mirror from the reference posture based on the signal waveform of the drive signal. .. The angle detection device according to any one of claims 1 to 5, wherein an antireflection structure is formed on the second surface of the mirror. A laser beam arranged between the light source and the light detector and reflected by the second surface of the mirror and a laser beam traveling without being reflected by the second surface are placed at different positions. With a focusing lens
It is characterized by having a shielding portion which is provided close to a light receiving surface of the photodetector and shields at least a part of laser light reflected by the second surface of the mirror and collected by the lens. The angle detection device according to any one of claims 1 to 6. It has a second mirror that reflects laser light that has passed over the second surface of the mirror.
The angle detection device according to any one of claims 1 to 7, wherein the detector is arranged at a position where it can receive a laser beam reflected by the second mirror. A mirror having a first surface that reflects light and a second surface that is located on the opposite side of the first surface and is configured to swing around a swing axis from a reference posture.
A light source that emits laser light in a direction that passes through the region from the outside of a region located directly below the second surface when viewed from a direction perpendicular to the first surface of the mirror in the reference posture.
A photodetector having a light receiving surface that receives the laser light that has passed through the region and arranged so that the amount of the laser light received by the light receiving surface changes due to the swing of the mirror.
An angle calculation unit that calculates the swing angle of the mirror from the reference posture based on the light reception result of the photodetector.
An angle detection device characterized by having.

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