Scanning device and control device

Abstract

To minimize reductions in phase-shift and maximum drive angle.SOLUTION: A scanning device 10 is provided comprising a scanning unit 15, a drive unit, and a control unit 16. The scanning unit comprises a mirror unit configured to swing about a first axis and a second axis. The scanning unit 15 reflects an incident electromagnetic wave on a reflective surface of the mirror unit. The drive unit resonantly drives the mirror unit about the first axis. The drive unit non-resonantly drives the mirror unit about the second axis. The control unit 16 controls a drive frequency for swinging the mirror unit about the first axis on the basis of the swinging of the mirror unit about the second axis.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a scanning device and a control device. [Background technology]

[0002] In distance measuring devices such as Lidar, a target is scanned by changing the radiation direction of a beam of light using a MEMS mirror. The MEMS mirror is a two-axis rotating mirror that is oscillated around one axis at a resonant frequency, thereby increasing the scanning speed and driving angle (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-048529 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a drive frequency having the same period as the resonance frequency is applied so as to oscillate at the resonance frequency, a phase shift occurs and the maximum drive angle decreases.

[0005] Therefore, an object of the present disclosure, which has been made in consideration of the above-described problems of the conventional technology, is to reduce the phase shift and the reduction in the maximum drive angle. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a scanning device according to a first aspect comprises: a scanning unit having a mirror unit that oscillates around a first axis and a second axis different from the first axis, and that reflects incident electromagnetic waves on a reflective surface of the mirror unit; a drive unit that resonantly drives the mirror unit around the first axis and non-resonantly drives the mirror unit around the second axis; and a control unit that controls a drive frequency for oscillating the mirror unit around the first axis based on the oscillation of the mirror unit around the second axis. [Effects of the Invention]

[0007] According to the scanning device of the present disclosure configured as described above, the phase shift and the decrease in the maximum drive angle are reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a functional block diagram showing a schematic configuration of an electromagnetic wave detection device including a scanning device according to an embodiment. [Figure 2] FIG. 2 is a configuration diagram of the scanning device of FIG. [Figure 3] FIG. 3 is a configuration diagram of the scanning unit in FIG. 2. [Figure 4] 3 is a layout diagram showing the layout of components on a path along which an electromagnetic wave travels from the second mirror to the second detection element in FIG. 2. FIG. [Figure 5] 5 is a view of the slit plate and extraction mirror in FIG. 4 as seen from the second detecting element side. [Figure 6] 10A and 10B are diagrams illustrating the swing of the reflecting surface in a first rotation direction caused by a first drive signal. [Figure 7] 10 is a diagram for explaining an angle change along a second rotation direction of the reflecting surface caused by a second drive signal. FIG. [Figure 8] 3 is a flowchart for explaining a frequency adjustment process performed by the control unit of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a scanning device to which the present disclosure is applied will be described with reference to the drawings.

[0010] 1, a scanning device 10 according to the first embodiment of the present disclosure may be used, for example, in an electromagnetic wave detection device 11. The electromagnetic wave detection device 11 may be configured to include the scanning device 10, a first detection unit 12, and a control device 13.

[0011] An overview of the electromagnetic wave detection device 11 will be described. Electromagnetic waves emitted from a scanning device 10 are irradiated onto an object ob. The electromagnetic waves irradiated onto the object ob are reflected by the object ob, and the reflected waves are incident on a first detection unit 12. A control device 13 generates information about the object ob based on the electromagnetic waves radiated by the scanning device 10 and the reflected waves detected by the first detection unit 12. The configuration of each part of the electromagnetic wave detection device 11 will be described in detail below.

[0012] 2, the scanning device 10 includes a first emitting unit (emitting section) 14, a scanning section 15, and a control section 16. The scanning device 10 may further include a second emitting unit 17, a second detecting section 18, a first mirror 19, and a second mirror 20.

[0013] In this specification, a mirror reflecting an electromagnetic wave may mean that the mirror reflects the electromagnetic wave with a reflectance of more than 50%. Furthermore, the reflectance of the mirror to the electromagnetic wave is preferably more than 70%, more preferably more than 80%, even more preferably more than 90%, and most preferably substantially 100%.

[0014] In this specification, a mirror that transmits an electromagnetic wave may mean that the mirror transmits the electromagnetic wave at a transmittance of more than 50%. Furthermore, the transmittance of the mirror to the electromagnetic wave is preferably more than 70%, more preferably more than 80%, even more preferably more than 90%, and most preferably substantially 100%.

[0015] The first emitter 14 may emit a first electromagnetic wave (electromagnetic wave) em1. The first electromagnetic wave em1 may include, for example, at least one of infrared light, visible light, ultraviolet light, and radio waves. In this embodiment, the first electromagnetic wave em1 may be invisible light such as infrared light. The first emitter 14 may emit the first electromagnetic wave em1 in a narrow beam shape, for example, 0.5°. Alternatively, the first emitter 14 may emit the first electromagnetic wave em1 in pulses. The first emitter 14 may switch between emitting and stopping the first electromagnetic wave em1 under the control of the control unit 16, which will be described later. The first emitter 14 includes a radiation source, for example, a laser diode (LD) or a light emitting diode (LED). The first emitter 14 may further include an optical element that collimates the first electromagnetic wave em1 emitted by the radiation source.

[0016] The scanning unit 15 may be located in the radiation path of the first electromagnetic wave em1 emitted by the first radiator 14. For example, the scanning unit 15 may be located in the radiation direction of the first electromagnetic wave em1 emitted by the first radiator 14. Alternatively, the scanning unit 15 may be located in a direction in which the first electromagnetic wave em1 emitted by the first radiator 14 is deflected using at least one mirror.

[0017] 3, the scanning unit 15 has a reflecting surface rs that reflects a first electromagnetic wave em1. The reflecting surface rs may also reflect a second electromagnetic wave em2, which will be described later. The reflecting surface rs may be capable of reflecting both the first electromagnetic wave em1 and the second electromagnetic wave em2.

[0018] The scanning unit 15 oscillates the reflecting surface rs around a first axis ax1 in accordance with a drive frequency. The drive frequency may be sent to the scanning unit 15 as a drive signal from the control unit 16, which will be described later. The scanning unit 15 oscillates the reflecting surface rs around a second axis ax2. The second axis ax2 may intersect with or be perpendicular to the first axis ax1. As will be described later, if the scanning unit 15 is a MEMS mirror, the second axis ax2 may be in a twisted relationship with the first axis ax1, depending on the structure of the MEMS mirror. The scanning unit 15 changes the radiation direction of the first electromagnetic wave em1 and the second electromagnetic wave em2 incident on the reflecting surface rs by combining the oscillation of the reflecting surface rs around the first axis ax1 and the oscillation of the reflecting surface rs around the second axis ax2.

[0019] The scanning unit 15 has a first resonant frequency with respect to the oscillation of the reflecting surface rs around the first axis ax1. In the scanning unit 15 of the present application, the first resonant frequency changes in response to the oscillation around the second axis ax2. A specific example of the scanning unit 15 in which the first resonant frequency changes in response to the oscillation around the second axis ax2 is described below. Alternatively, in the scanning unit 15 of the present application, the first resonant frequency may change in response to the scanning speed based on the oscillation around the second axis ax2. The first resonant frequency may change in response to the scanning speed, particularly in a configuration in which the second drive signal increases and decreases stepwise, as described below.

[0020] The scanning unit 15 may be, for example, a MEMS (Micro Electro Mechanical Systems) mirror and may include a frame 21, a third mirror 22, a first holding unit 23, a second holding unit 24, and driving units (first driving unit, second driving unit) not shown. The frame 21 may be, for example, a rectangular frame or may have any shape such as a ring. In this embodiment, the frame 21 is a rectangular frame. The third mirror 22 may have a reflecting surface rs. The scanning unit 15 oscillates the third mirror 22 around a first axis ax1 in accordance with the driving frequency, thereby causing the reflecting surface rs to oscillate around the first axis ax1. The scanning unit 15 oscillates the third mirror 22 around a second axis ax2, thereby causing the reflecting surface rs to oscillate around the second axis ax2.

[0021] The first holding unit 23 may be fixed to the frame 21. The first holding unit 23 may be fixed to the inside of the frame 21 on both sides of the center. The first holding unit 23 may hold the third mirror 22 via the second holding unit 24. A first driving unit is installed on the first holding unit 23. The first holding unit 23 holds the third mirror 22 (reflecting surface rs) so that it can oscillate around the first axis ax1. The reflecting surface rs may be oscillated around the first axis ax1 by applying to the first driving unit a driving frequency having the same period as the resonance frequency of the scanning unit 15 around the first axis ax1. The first driving unit is, for example, a piezoelectric element.

[0022] The second holding unit 24 is connected to the third mirror 22. The second holding unit 24 may also be connected to the first holding unit 23. A second driving unit is provided on the second holding unit 24. The second driving unit may oscillate the reflecting surface rs around the second axis ax2. The second holding unit 24 holds the third mirror 22 (reflecting surface rs) so that it can oscillate around the second axis ax2. The second driving unit is, for example, a piezoelectric element.

[0023] 2, the second radiator 17 may radiate a second electromagnetic wave em2. The second electromagnetic wave em2 may include, for example, at least one of infrared light, visible light, ultraviolet light, and radio waves. The band of the second electromagnetic wave em2 may be different from the band of the first electromagnetic wave em1.

[0024] The second radiator 17 may emit the second electromagnetic wave em2 in a narrow beam shape, for example, 0.5°. Alternatively, the second radiator 17 may emit a continuous wave of the second electromagnetic wave em2. The second radiator 17 includes a radiation source such as an LD (Laser Diode) or an LED (Light Emitting Diode). The second radiator 17 may further include an optical element that collimates the second electromagnetic wave em1 emitted by the radiation source.

[0025] The first mirror 19 may be located on the radiation path of the first electromagnetic wave em1 emitted by the first radiator 14 and on the radiation path of the second electromagnetic wave em2 emitted by the second radiator 17. The first mirror 19 may transmit the first electromagnetic wave em1. The first mirror 19 may reflect the second electromagnetic wave em2 toward the scanning unit 15.

[0026] The second mirror 20 may be located closer to the object than the scanning unit 15. The second mirror 20 may further be located so as to overlap the traveling path of at least a part or all of the electromagnetic waves deflected by the scanning unit 15. The second mirror 20 may transmit the first electromagnetic wave em1. The second mirror 20 may reflect the second electromagnetic wave em2.

[0027] The second detector 18 may generate a signal for estimating the deflection direction of the first electromagnetic wave em1 by the scanner 15. Specifically, the second detector 18 may include an extraction mirror 25, a first detector element 26, and a second detector element 27.

[0028] The extraction mirror 25 may be located within the reflection range rr of the second electromagnetic wave em2 by the second mirror 20. The extraction mirror 25 may overlap only a portion of the first primary corresponding direction pcd1 in the reflection range rr. In other words, the extraction mirror 25 does not need to cover the entire reflection range rr in the first primary corresponding direction pcd1. The first primary corresponding direction pcd1 is a direction corresponding to the first rotation direction rd1 of the second electromagnetic wave em2 about the first axis ax1 reflected by the second mirror 20. Therefore, a portion of the second electromagnetic wave em2 reflected by the second mirror 20 and swung in the first primary corresponding direction pcd1 may be reflected by the extraction mirror 25, and another portion may pass through without entering the extraction mirror 25.

[0029] Furthermore, the extraction mirror 25 may overlap the entire second primary corresponding direction pcd2 in the reflection range rr. The second primary corresponding direction pcd2 is a direction corresponding to the second rotation direction rd2 of the second electromagnetic wave em2 about the second axis ax2 reflected by the second mirror 20. In other words, the extraction mirror 25 may cover the entire reflection range rr in the second primary corresponding direction pcd2.

[0030] The first detection element 26 may be provided in a region where the second electromagnetic wave em2 swung in the first primary corresponding direction pcd1 passes through without being incident on the extraction mirror 25. A plurality of first detection elements 26 may be positioned so as to be aligned along the first primary corresponding direction pcd1. Each first detection element 26 may detect the second electromagnetic wave em2 when the radiation direction of the second electromagnetic wave em2 is directed toward an arbitrary point in the first primary corresponding direction pcd1. The first detection element 26 may transmit a detection signal to the control unit 16 when it detects the second electromagnetic wave em2.

[0031] Note that a cylindrical lens may be provided farther from the second mirror 20 than the extraction mirror 25 and closer to the first detection element 26. The cylindrical lens may bend the second electromagnetic wave em2 in the second primary corresponding direction pcd2.

[0032] The second detection element 27 may be provided in a direction in which the second electromagnetic wave em2 swung in the first primary corresponding direction pcd1 is reflected by the extraction mirror 25. As shown in FIG. 4, the second detection element 27 may have a slit plate 28 between it and the extraction mirror 25, for example.

[0033] 5, the slit plate 28 may have a slit sl formed therein that is inclined with respect to both the first secondary corresponding direction scd1 and the second secondary corresponding direction scd2. The first secondary corresponding direction scd1 and the second secondary corresponding direction scd2 are directions corresponding to the first primary corresponding direction pcd1 and the second primary corresponding direction pcd2 of the second electromagnetic wave em2, respectively, reflected by the extraction mirror 25. The second detecting element 27 may detect the second electromagnetic wave em2 passing through the slit sl. The second detecting element 27 may transmit a detection signal to the control unit 16 when detecting the second electromagnetic wave em2.

[0034] Specifically, the first detection element 26 and the second detection element 27 may each include a single element such as an APD (Avalanche PhotoDiode) or a PD (PhotoDiode).

[0035] The control unit 16 includes one or more processors and a memory. The processor may include at least one of a general-purpose processor that loads a specific program to execute a specific function and a dedicated processor specialized for a specific process. The dedicated processor may include an application-specific integrated circuit (ASIC). The processor may include a programmable logic device (PLD). The PLD may include a field-programmable gate array (FPGA). The control unit 16 may include at least one of a system-on-a-chip (SoC) and a system in a package (SiP) in which one or more processors work together.

[0036] The control unit 16 may further include a storage unit. The storage unit may include any storage device, such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The storage unit may store various programs that cause the control unit 16 to function and various information used by the control unit 16.

[0037] The control unit 16 controls the first emitting unit 14 and the scanning unit 15. Furthermore, the control unit 16 may estimate the radiation direction of the first electromagnetic wave em1 based on the detection signal obtained from the second detecting unit 18.

[0038] The control unit 16 may control the oscillation of the scanning unit 15 about the first axis ax1 and the second axis ax2 by transmitting drive signals to the scanning unit 15. Specifically, the drive signals may include a first drive signal transmitted to a first drive unit installed in the first holding unit 23 and a second drive signal transmitted to a second drive unit installed in the second holding unit 24.

[0039] As shown in FIG. 6, the first drive signal has a continuous sinusoidal waveform. The continuous sinusoidal first drive signal causes the third mirror 22 to continuously oscillate around the first axis ax1. The continuous oscillation of the third mirror 22 causes the radiation direction of the first electromagnetic wave em1 to continuously change back and forth along the first rotation direction rd1. The control unit 16 may resonantly drive the reflecting surface rs around the first axis ax1 by generating the drive frequency of the sinusoidal first drive signal so that it is the same as the resonant frequency of the scanning unit 15 around the first axis ax1. Here, resonant driving refers to resonating at a natural vibration frequency (resonant frequency) determined by the structure, mass, spring constant, etc. of the MEMS mirror.

[0040] As shown in FIG. 7, the signal strength of the second drive signal may repeatedly increase and decrease in a stepped manner. The second drive signal, which repeatedly increases and decreases the signal strength in a stepped manner, causes the third mirror 22 to oscillate discretely around the second axis ax2. That is, the third mirror 22 performs non-resonant driving, which gradually changes the angle of the reflecting surface rs around the second axis ax2 to correspond to the signal strength of the second drive signal. Here, non-resonant driving refers to oscillating the reflecting surface rs around the second axis ax2 without resonating at a natural vibration frequency (resonant frequency) determined by the structure, mass, spring constant, etc. of the MEMS mirror. The discrete oscillation of the third mirror 22 causes the radiation direction of the first electromagnetic wave em1 to discretely change back and forth along the second rotation direction rd2. The drive frequency of the second drive signal, which repeatedly increases and decreases the signal strength in a stepped manner, may be fixed based on a fixed frame rate or may vary according to an adjustable frame rate. The period of the second drive signal may be longer than the period of the first drive signal.

[0041] Furthermore, the control unit 16 may calculate the deflection directions of the first electromagnetic wave em1 and the second electromagnetic wave em2 based on the drive signal to the scanning unit 15 and the detection signal obtained from the second detecting unit 18. The deflection directions correspond to the orientation of the reflecting surface rs at which the scanning unit 15 changes the radiation direction of the first electromagnetic wave em1 and the second electromagnetic wave em2. The control unit 16 may calculate the deflection directions of the first electromagnetic wave em1 and the second electromagnetic wave em2 as the directions of the first rotation direction rd1 and the second rotation direction rd2 components. A method for calculating the deflection directions will be described in detail below.

[0042] As described above, the first drive signal has a sinusoidal waveform that causes the scanning unit 15 to oscillate along the first rotation direction rd1. Therefore, the times at which the multiple first detection elements 26 detect the second electromagnetic wave em2 correspond to specific phases in the drive signal for the first rotation direction rd1, in other words, specific deflection directions in the first primary corresponding direction pcd1. Therefore, the control unit 16 may identify the time at which the beam deflects in a specific direction in the first primary corresponding direction pcd1 based on the phase correlation and the detection signals acquired from the first detection elements 26. Furthermore, the control unit 16 may estimate the deflection direction in the first primary corresponding direction pcd1 based on the time at which the beam deflects in a specific direction in the first primary corresponding direction pcd1, the elapsed time since the most recent detection signal was acquired, and the drive signal. The control unit 16 may estimate the deflection direction in the first rotation direction rd1 based on the deflection direction in the first primary corresponding direction pcd1.

[0043] As described above, the second drive signal repeatedly increases and decreases in a stepped manner, causing the scanning unit 15 to periodically and repeatedly move back and forth along the second rotation direction rd2. Therefore, the interval between two points in time at which the second detection element 27 consecutively detects the second electromagnetic wave em2 corresponds to a specific phase of the drive signal in the second rotation direction rd2, in other words, a specific direction in the second secondary corresponding direction scd2. Note that, as described above, because the slit sl is inclined with respect to the second secondary corresponding direction scd2, the specific direction along the second secondary corresponding direction scd2 changes depending on the deflection direction in the first secondary corresponding direction scd1. Therefore, the control unit 16 may identify the point in time at which the deflection occurs in a specific direction in the second secondary corresponding direction scd2 based on the correspondence relationship with the phase based on the deflection direction in the first primary corresponding direction scd1 and the detection signal acquired from the second detection element 27. Furthermore, the control unit 16 may estimate the deflection direction in the second secondary corresponding direction scd2 based on the time point at which the deflection occurs in a specific direction in the second secondary corresponding direction scd2, the elapsed time from the time point at which the detection signal is acquired, and the drive signal. The control unit 16 may estimate the deflection direction in the second rotation direction rd2 based on the deflection direction in the second secondary corresponding direction scd2.

[0044] The control unit 16 may transmit the estimated deflection directions in the first rotation direction rd1 and the second rotation direction rd2 to the control device 13 as information.

[0045] The control unit 16 changes the drive frequency of the first drive signal in response to a first change corresponding to the oscillation of the reflecting surface rs around the second axis ax2. The first change may be a change in the angle of the reflecting surface rs as viewed from the second axis ax2 due to the oscillation around the second axis ax2. The angle of the reflecting surface rs as viewed from the second axis ax2 is, for example, the angle as viewed from the second axis ax2 with respect to a reference direction of the normal to the reflecting surface rs. The reference direction is, for example, the normal direction when no voltage is applied to the second drive unit. Alternatively, the first change may be a change in the scanning speed due to the oscillation around the second axis ax2.

[0046] The control unit 16 may change the drive frequency of the first drive signal in accordance with the first change at a predetermined time point.

[0047] The predetermined time point (first time point) may be the time point when the angular velocity of the oscillation of the reflecting surface rs around the first axis ax1 becomes minimal. Specifically, the time point when the angular velocity of the oscillation becomes minimal is the time point when the first electromagnetic wave em1 is reflected toward both ends of the oscillation along the first rotation direction rd1. Note that the predetermined time point (first time point) may be set to a period when the angular velocity of the oscillation of the reflecting surface rs around the first axis ax1 becomes equal to or less than a first threshold value. The first threshold value may be set to, for example, an angular velocity at which the angular velocity of the oscillation of the reflecting surface rs around the first axis ax1 becomes 5 percent greater than the minimal value.

[0048] Alternatively, the predetermined time point (second time point) may be the time point at which the angular deviation of the reflecting surface rs from the first axis ax1 due to the oscillation around the first axis ax1 is minimized. The angle of the reflecting surface rs from the first axis ax1 is, for example, the angle from the first axis ax1 with respect to a reference direction of the normal to the reflecting surface rs. The reference direction is, for example, the normal direction when no voltage is applied to the first drive unit. Specifically, the time point at which the angular deviation from the first axis ax1 is minimized is the time point at which the first electromagnetic wave em1 is reflected toward the center of the oscillation along the first rotation direction rd1. Note that the predetermined time point (second time point) may be set to a period when the angular deviation of the reflecting surface rs from the first axis ax1 is equal to or less than a second threshold value. The first threshold value may be set to, for example, a deviation that is 5% greater than the value at which the angular deviation of the reflecting surface rs from the first axis ax1 is minimized.

[0049] The control unit 16 may change the drive frequency of the first drive signal so that the frequency corresponds to each angle of the reflecting surface rs caused by the swinging that changes stepwise around the second axis ax2. Each angle of the reflecting surface rs is the angle of the normal of the reflecting surface rs relative to the aforementioned reference direction as viewed from the second axis ax2. As described above, depending on the drive method for rotating the reflecting surface rs around the first axis ax1 and the second axis ax2, the first resonant frequency of the scanning unit 15 changes in response to the swinging around the second axis ax2. Therefore, the frequency corresponding to each angle may be the first resonant frequency corresponding to the angle of the reflecting surface rs around the second axis ax2.

[0050] The control unit 16 may change the drive frequency of the first drive signal using a deviation of a first resonance frequency measured in advance. The first resonance frequency measured in advance may be measured at any angle when the reflecting surface rs is viewed from the second axis ax2. The deviation of the first resonance frequency may be a deviation from a reference first resonance frequency. The reference first resonance frequency may be, for example, the first resonance frequency in a state where no drive signal is applied to the second drive unit.

[0051] The arbitrary angle may be the angle at the maximum change in the swing of the reflecting surface rs around the second axis ax2. Alternatively, the arbitrary angle may be each angle spaced at regular angle intervals in the swing around the second axis ax2. Alternatively, the arbitrary angle may be each angle corresponding to each position spaced at regular displacement intervals along the second rotation direction rd2 in a state in which the radial direction in the swing around the second axis ax2 is projected onto a plane.

[0052] The control unit 16 may estimate the first resonance frequency at an arbitrary angle by interpolation or extrapolation based on the first resonance frequency measured in advance for that angle and the angle of the reflecting surface rs as viewed from the second axis ax2. The control unit 16 may change the drive frequency of the first drive signal so that the drive frequency becomes the same as the estimated first resonance frequency.

[0053] Furthermore, the control unit 16 may change the drive frequency of the first drive signal so that the frequency corresponds to the ambient temperature. The control unit 16 may measure the first resonant frequency for any plurality of temperature values ​​in advance. The control unit 16 may estimate the first resonant frequency at that temperature by interpolation or extrapolation based on the first resonant frequency measured in advance for any plurality of temperature values ​​and the ambient temperature. The control unit 16 may change the drive frequency of the first drive signal so that the frequency corresponds to the estimated first resonant frequency.

[0054] The scanning device 10 may also be provided with a detection circuit that detects the phase difference between the phase of a continuous sinusoidal first drive signal that oscillates the scanning device 10 about the first axis ax1 and the phase of the angle of the reflecting surface rs about the first axis ax1, which is obtained based on detection signals from the multiple first detection elements 26. The control unit 16 may then change the drive frequency of the first drive signal so that the phase difference is a constant value at any angle of the reflecting surface rs as viewed from the second axis ax2. In this case, the constant value may be, for example, π / 2. Furthermore, for example, when the phase difference detected by the detection circuit is smaller than π / 2, the drive frequency may be increased, and when the phase difference is larger than π / 2, the drive frequency may be decreased.

[0055] The control unit 16 switches the first emitter 14 between emitting and extinguishing light. As shown in FIG. 6 , the control unit 16 may cause the first emitter 14 to emit pulsed light while the reflecting surface rs is tilted so that a sampling area excluding the vicinity of both ends of the oscillation in the first rotation direction rd1 is aligned with the radiation direction. Furthermore, the control unit 16 may cause the first emitter 14 to emit pulsed light while the above-described conditions for oscillation in the first rotation direction rd1 are satisfied after a stabilization time has elapsed since the signal strength of the second drive signal was changed. The control unit 16 may output a command to the first emitter 14 to emit light, and simultaneously transmit radiation information indicating that radiation has been completed to the control device 13.

[0056] 1, the first detector 12 may be provided so that a reflected wave from an object ob of an electromagnetic wave emitted by the scanning device 10 can be incident on the first detector 12. The first detector 12 may detect a first electromagnetic wave em1 that is the reflected wave. The first detector 12 may transmit detection information indicating that a reflected wave from the object has been detected to the control device 13.

[0057] More specifically, the first detection unit 12 includes elements that constitute a distance measurement sensor. For example, the first detection unit 12 includes a single element such as an APD (Avalanche PhotoDiode), a PD (PhotoDiode), or a distance measurement image sensor. Alternatively, the first detection unit 12 may include an element array such as an APD array, a PD array, a distance measurement imaging array, or a distance measurement image sensor.

[0058] The control device 13 may generate three-dimensional position information of any object point on the object ob based on the deflection direction and radiation information acquired from the scanning device 10 and the detection information acquired from the first detection unit 12.

[0059] Specifically, the control device 13 may acquire distance information of any object point on the target ob using ToF (Time of Flight) based on the time when the first emitting unit 14 emits the pulsed first electromagnetic wave em1 and the time when the first detecting unit 12 detects the first electromagnetic wave em1 after emission.

[0060] The control device 13 may generate three-dimensional position information of any object point based on the deflection direction to the object point and distance information calculated as described above.

[0061] Next, the frequency adjustment process executed by the control unit 16 in this embodiment will be described with reference to the flowchart of Fig. 8. The frequency adjustment process starts, for example, when the signal strength of the second drive signal changes.

[0062] In step S100, the control unit 16 calculates the angle of the reflecting surface rs as viewed from the second axis ax2 based on the changed signal intensity. After the calculation, the process proceeds to step S101.

[0063] In step S101, the control unit 16 calculates the first resonance frequency corresponding to the angle calculated in step S100 by interpolation or extrapolation. After the calculation, the process proceeds to step S102.

[0064] In step S102, the control unit 16 determines whether or not it is a predetermined time point in the oscillation of the reflecting surface rs around the first axis ax1. If it is not the predetermined time point, the process returns to step S102. If it is the predetermined time point, the process proceeds to step S103.

[0065] In step S103, the control unit 16 changes the drive frequency of the first drive signal so that it has the same period as the first resonance frequency calculated in step S101. After the change, the frequency adjustment process ends.

[0066] The scanning device 10 of this embodiment, configured as described above, includes a scanning unit 15 having a mirror unit that oscillates around a first axis ax1 and a second axis ax2 different from the first axis ax1 and reflects incident electromagnetic waves on the mirror unit's reflecting surface rs; a driving unit that resonantly drives the mirror unit around the first axis ax1 and non-resonantly drives the mirror unit around the second axis ax2; and a control unit 16 that controls the driving frequency for oscillating the mirror unit around the first axis ax1 based on the oscillation of the mirror unit around the second axis ax2. As described above, even if a driving frequency with the same period as the resonant frequency is applied to the driving unit, phase shifts and a reduction in the maximum driving angle occur. The inventors of this application discovered that this phenomenon is due to the fact that, depending on the structure of the scanning unit, rotation of the reflecting surface around one axis affects the resonant frequency around the other axis. Therefore, the scanning device 10 configured as described above can bring the driving frequency closer to the resonant frequency that changes in response to the oscillation of the third mirror 22 (reflecting surface rs) around the second axis ax. Therefore, the scanning device 10 can reduce the phase shift and the decrease in the maximum drive angle compared to a configuration in which the third mirror 22 (reflecting surface rs) is oscillated at a constant drive frequency.

[0067] Furthermore, in the scanning device 10, the driving unit includes a first driving unit that is installed on the first holding unit 23 and oscillates the mirror unit about the first axis ax1, and a second driving unit that is installed on the second holding unit 24 and oscillates the mirror unit about the second axis ax2. With this configuration, the scanning device 10 changes the driving frequency applied to the first driving unit that oscillates the mirror unit about the first axis ax1, and can reduce phase shifts and reductions in the maximum driving angle compared to when a constant driving frequency is applied.

[0068] Furthermore, in the scanning device 10, the control unit 16 controls the drive frequency in accordance with the angle by which the reflecting surface rs oscillates around the second axis ax2. With this configuration, the scanning device 10 can set an appropriate drive frequency in accordance with the angle by which the reflecting surface rs oscillates around the second axis ax2.

[0069] Furthermore, in the scanning device 10, the control unit 16 controls the drive frequency at a first time point when the angular velocity of the reflecting surface rs due to oscillation around the first axis ax1 becomes equal to or less than a first threshold. With this configuration, the scanning device 10 controls the drive frequency within a certain range before and after the time point when the first electromagnetic wave em1 is reflected at two ends of the oscillation along the first rotation direction rd1. Therefore, the scanning device 10 can control the drive frequency at a timing when the first electromagnetic wave em1 is not used to measure distance information of any object point on the target ob, for example.

[0070] Furthermore, in the scanning device 10, the control unit 16 controls the drive frequency at a second time point when the deviation in angle of the reflecting surface rs due to the oscillation about the first axis ax1 becomes equal to or less than a second threshold. With this configuration, the scanning device 10 can control the drive frequency within a certain range before and after the time point when the first electromagnetic wave em1 is reflected toward the center of the oscillation along the first rotation direction rd1.

[0071] The scanning device 10 further includes a first radiator 14 that radiates electromagnetic waves, and the scanning unit 15 reflects the electromagnetic waves incident from the first radiator 14 at the reflecting surface rs of the mirror unit. With this configuration, the scanning device 10 can change the radiation direction of the electromagnetic waves radiated by the first radiator 14 in accordance with the swinging motion around the first axis ax1 and the second axis ax2.

[0072] The scanning device 10 further includes a detection unit 12 that detects the reflected waves that are generated when the electromagnetic waves are reflected by the reflecting surface rs of the scanning unit 15 and then reflected by an object. With this configuration, the scanning device 10 can acquire distance information of any object point on the object, for example, by ToF, based on the time when the first radiator 14 radiates the electromagnetic waves and the time when the detector 12 detects the electromagnetic waves after the radiation.

[0073] The control device 13 configured as described above controls the scanning device 10, which includes a mirror unit that oscillates about a first axis ax1 and a second axis ax2 different from the first axis ax1, a drive unit that resonantly drives the mirror unit about the first axis ax1 and non-resonantly drives the mirror unit about the second axis ax2, and a scanning unit 15 that reflects incident electromagnetic waves on the reflecting surface rs of the mirror unit, and includes a control unit 16 that controls the drive frequency for oscillating the mirror unit about the first axis ax1 based on the oscillation of the mirror unit about the second axis ax2. With this configuration, the control device 13 can reduce phase shifts and decreases in the maximum drive angle in the scanning unit 15 included in the scanning device 10, compared to a configuration in which the third mirror 22 (reflecting surface rs) is oscillated at a constant drive frequency.

[0074] Although the embodiment of the scanning device 10 has been described above, the drawings illustrating the embodiment according to the present disclosure are schematic, and the dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones.

[0075] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art could make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications or alterations are included in the scope of the present disclosure. For example, the functions included in each component can be rearranged so as not to cause logical inconsistencies, and multiple components can be combined or divided into one.

[0076] All of the features described in this disclosure and / or all steps of all of the disclosed methods or processes may be combined in any combination except combinations in which these features are mutually exclusive. Furthermore, each feature described in this disclosure may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly denied. Thus, unless expressly denied, each disclosed feature is only one example of a generic series of identical or equivalent features.

[0077] Furthermore, embodiments of the present disclosure are not limited to the specific configurations of any of the above-described embodiments, but rather extend to any novel feature or combination thereof described herein, or any novel method or process step or combination thereof described herein.

[0078] In this disclosure, descriptions such as "first" and "second" are identifiers for distinguishing the configuration. In this disclosure, the configurations distinguished by descriptions such as "first" and "second" can have their numbers interchanged. For example, the first electromagnetic wave can have its identifiers "first" and "second" interchanged with the second electromagnetic wave. The identifiers are interchanged simultaneously. The configurations remain distinguished even after the identifiers are interchanged. The identifiers may be deleted. A configuration from which the identifiers have been deleted is distinguished by a symbol. The identifiers "first" and "second" in this disclosure should not be used solely to interpret the order of the configurations or to justify the existence of an identifier with a smaller number. [Explanation of symbols]

[0079] 10 Scanning Device 11 Electromagnetic wave detection device 12 First detection unit 13 Control device 14 First radiating part 15 Scanning unit 16 Control Unit 17 Second radiating part 18 Second detection unit 19 The First Mirror 20 The Second Mirror 21 frames 22 The Third Mirror 23 First holding part 24 Second holding part 25 Extraction mirror 26 First detector element 27 Second detector element 28 Slit Plate ax1 1st axis ax2 2nd axis em1 First electromagnetic wave em2 Second electromagnetic wave ob target pcd1 First primary correspondence direction pcd2 Second primary correspondence direction rd1 First rotation direction rd2 Second rotation direction rs reflective surface scd1 First secondary correspondence direction scd2 Secondary correspondence direction

Claims

1. a scanning unit having a mirror unit that oscillates around a first axis and a second axis different from the first axis, and that reflects incident electromagnetic waves on a reflective surface of the mirror unit; a drive unit that resonantly drives the mirror unit around the first axis and non-resonantly drives the mirror unit around the second axis; a control unit that controls a drive frequency for oscillating the mirror unit around the first axis based on the oscillation of the mirror unit around the second axis, Scanning device.

2. 2. The scanning device according to claim 1, The scanning unit a second holding portion that holds the mirror portion so that the mirror portion can swing around the second axis; a first holding portion that holds the mirror portion via the second holding portion so that the mirror portion can swing around the first axis; Scanning device.

3. 3. The scanning device according to claim 2, The drive unit is a first drive unit that is installed on the first holder and that swings the mirror unit around the first axis; a second drive unit that is installed on the second holder and that swings the mirror unit around the second axis, Scanning device.

4. 2. The scanning device according to claim 1, the control unit controls the drive frequency in accordance with an angle by which the reflecting surface oscillates around the second axis. Scanning device.

5. 5. The scanning device according to claim 4, the control unit controls the drive frequency at a first time point when an angular velocity of the reflecting surface due to the swinging about the first axis becomes equal to or less than a first threshold value. Scanning device.

6. 6. The scanning device according to claim 5, The first time point is a time point at which the angular velocity becomes a minimum. Scanning device.

7. 6. The scanning device according to claim 5, the control unit controls the drive frequency at a second time point when a deviation in angle of the reflecting surface due to the swing around the first axis becomes equal to or smaller than a second threshold value. Scanning device.

8. 8. The scanning device according to claim 7, The second time point is the time point at which the deviation is minimum. Scanning device.

9. 2. The scanning device of claim 1, a radiation unit that radiates electromagnetic waves, the scanning unit reflects the electromagnetic wave incident from the radiation unit on a reflecting surface of the mirror unit; Scanning device.

10. 10. The scanning device of claim 9, The scanning unit further includes a detection unit that detects a reflected wave that is generated when the electromagnetic wave is reflected by an object after being reflected by the reflection surface of the scanning unit. Scanning device.

11. A control device for controlling a scanning device including a scanning unit that includes a mirror unit that oscillates around a first axis and around a second axis different from the first axis, and a driving unit that resonantly drives the mirror unit around the first axis and non-resonantly drives the mirror unit around the second axis, and that reflects incident electromagnetic waves on a reflective surface of the mirror unit, a control unit that controls a drive frequency for oscillating the mirror unit around the first axis based on the oscillation of the mirror unit around the second axis, Control device.

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