Scanning device and control device

Abstract

To stabilize changes in rotation angle.SOLUTION: A scanning device 10 is provided comprising a scanning unit 15 and a control unit 16. The scanning unit 15 changes orientation of a reflective surface in directions including a first direction and a second direction. When changing the orientation of the reflective surface from the first direction to the second direction, the control unit 16 at least outputs a third drive signal to the scanning unit 15 and outputs a second drive signal to the scanning unit 15. The third drive signal changes the orientation of the reflexive surface from the first direction to a third direction. The second drive signal changes the orientation of the reflexive surface to the second direction. The second drive signal is output so as to reduce swinging of the reflective surface caused by the third drive signal.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 object is scanned by changing the direction of radiation of a beam of light using a MEMS mirror. The MEMS mirror performs scanning by changing the rotation angles of the horizontal and vertical axes of a two-axis rotating mirror (see Patent Document 1). [Prior art documents] [Patent documents]

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

[0004] In such a configuration, the change in the rotation angle around one axis may become unstable.

[0005] Therefore, an object of the present disclosure, which has been made in consideration of the above-described problems of the conventional art, is to stabilize changes in the rotation 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 that changes the orientation of the reflecting surface in a plurality of directions including a first direction and a second direction; a control unit that, when changing the orientation of the reflective surface from the first direction to the second direction, outputs to the scanning unit at least a third drive signal that changes the orientation of the reflective surface from the first direction to a third direction, and outputs to the scanning unit a second drive signal that changes the orientation of the reflective surface to the second direction; The second drive signal is output so as to reduce the vibration of the reflecting surface caused by the third drive signal.

[0007] A control device according to a second aspect comprises: A control device for controlling a scanning device including a scanning unit that changes the orientation of a reflective surface in a plurality of directions including a first direction and a second direction, a control unit that, when changing the orientation of the reflective surface from the first direction to the second direction, outputs to the scanning unit at least a third drive signal that changes the orientation of the reflective surface from the first direction to a third direction, and outputs to the scanning unit a second drive signal that changes the orientation of the reflective surface to the second direction; The second drive signal is output so as to reduce the vibration of the reflecting surface caused by the third drive signal. [Effects of the Invention]

[0008] According to the scanning device of the present disclosure configured as described above, the change in the rotation angle is stabilized. [Brief explanation of the drawings]

[0009] [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 graph showing the change over time in the direction of the reflecting surface when the drive signal is changed to a square shape. [Figure 8]10 is a graph showing the time change of each directional component of the reflecting surface due to a plurality of sub-rotations. [Figure 9] 10 is a graph showing a change over time in the direction obtained by adding up the directional components of the reflecting surface due to a plurality of sub-rotations. [Figure 10] 10 is a diagram for explaining a step-like change in angle along a second rotation direction of the reflecting surface caused by a second drive signal. FIG. [Figure 11] 3 is a flowchart for explaining an intensity adjustment process performed by the control unit of FIG. 2. [Figure 12] 3 is a flowchart for explaining a frequency adjustment process performed by the control unit of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a scanning device to which the present disclosure is applied will be described with reference to the drawings.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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%.

[0015] 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%.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The scanning unit 15 changes (oscillates) the orientation of the reflecting surface rs around a first axis ax1. The scanning unit 15 may oscillate the reflecting surface rs according to 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 changes (rotates) the orientation of the reflecting surface rs around a second axis ax2. The second axis ax2 intersects with the first axis ax1. The second axis ax2 may 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 rotation of the reflecting surface rs around the second axis ax2.

[0020] The scanning unit 15 may have a first resonant frequency for the rotation of the reflecting surface rs around the first axis ax1, and may have a second resonant frequency for the rotation of the reflecting surface rs around the second axis ax2.

[0021] In the scanning unit 15 of the present application, the first resonant frequency may change in response to rotation about the second axis ax2. A specific example of the scanning unit 15 in which the first resonant frequency changes in response to rotation about 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 a scanning speed based on rotation about 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.

[0022] 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 oscillating the reflecting surface rs around the first axis ax1. The scanning unit 15 rotates the third mirror 22 around a second axis ax2, thereby rotating the reflecting surface rs around the second axis ax2.

[0023] 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.

[0024] 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 rotate 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 rotate around the second axis ax2. The second driving unit is, for example, a piezoelectric element.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] 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.

[0040] The control unit 16 may control the oscillation of the scanning unit 15 about the first axis ax1 and the rotation of the scanning unit 15 about the second axis ax2 by transmitting a drive signal to the scanning unit 15. Specifically, the drive signal 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.

[0041] The reflecting surface rs may be controlled to oscillate around the first axis ax1. As shown in FIG. 6, the first drive signal may be a continuous sinusoidal wave. The continuous sinusoidal first drive signal may cause the third mirror 22 to continuously oscillate around the first axis ax1. The continuous oscillation of the third mirror 22 may cause 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.

[0042] Regarding rotation around the second axis ax2, in a device including the scanning device 10, i.e., in this embodiment, the electromagnetic wave detection device 11, the direction around the second axis ax2 in which a predetermined process is performed on the radiation of the first electromagnetic wave em1 reflected by the reflecting surface rs is discretely determined. In the electromagnetic wave detection device 11, for example, the predetermined process is distance measurement. In the electromagnetic wave detection device 11, the direction around the second axis ax2 in which distance measurement is performed is discrete. Among all the discretely determined directions, rotation between adjacent directions is performed by multiple sub-rotations. The adjacent directions are the directions that form the smallest angles with any one of the multiple discrete directions, and the arbitrary direction. The multiple sub-rotations are performed with a time lag so that the oscillations of the reflecting surface rs around the second axis ax2 caused by each of the multiple sub-rotations cancel each other out. Below, the oscillation due to rotation and the multiple sub-rotations are explained using specific examples.

[0043] The signal strength of the second drive signal corresponds to the direction of the reflecting surface rs around the second axis ax2. The direction of the reflecting surface rs may be the normal direction of the reflecting surface rs. However, as shown in Figure 7, when the signal strength is changed in a rectangular shape, the reflecting surface rs does not stop rotating in a direction corresponding to the changed signal strength, but oscillates around that direction. The change in a rectangular shape means that the strength does not change gradually, but rather the slope is steep. Furthermore, the oscillation gradually attenuates and converges to face that direction. The frequency of the oscillation is the same as the resonant frequency around the second axis ax2.

[0044] For the sake of convenience, two adjacent, discretely defined directions will be referred to as the first direction and the second direction. As shown in FIG. 8 , rotation from the first direction to the second direction may be performed, for example, by a first sub-rotation and a second sub-rotation. The first sub-rotation is a rotation that orients the reflecting surface rs in a third direction, for example, a direction that is half the angle between the first direction and the second direction. The second sub-rotation is a rotation that orients the reflecting surface rs in the second direction. The second sub-rotation starts half a period corresponding to the resonance frequency around the second axis ax2 after the first sub-rotation. In other words, the first sub-rotation starts half a period corresponding to the resonance frequency around the second axis ax2 before the second sub-rotation.

[0045] To perform the first sub-rotation, the control unit 16 transmits to the scanning unit 15 a third drive signal (second drive signal) that changes the direction of the reflecting surface rs in a third direction. The signal strength of the third drive signal (second drive signal) is switched from the first signal strength corresponding to the first direction to a signal strength for the first sub-rotation. The signal strength for the first sub-rotation is a signal strength corresponding to the third direction, for example, a direction corresponding to a half angle of the angle formed by the first direction and the second direction. By switching the signal strength, the reflecting surface rs rotates around the half angle direction so as to include a rotation component (see the directional component of the reflecting surface due to the first sub-rotation) that oscillates around the second axis ax2 due to the resonant frequency.

[0046] Furthermore, to perform the second sub-rotation, the signal strength of the second drive signal is switched from the signal strength for the first sub-rotation to the signal strength for the second sub-rotation. The signal strength for the second sub-rotation is a second signal strength corresponding to the second direction. By switching the signal strength, the reflecting surface rs rotates so as to include a rotation component (see the directional component of the reflecting surface due to the second sub-rotation) that oscillates at the resonant frequency around the second axis ax2 around the second direction.

[0047] The switching to the second drive signal for the second sub-rotation is performed before the oscillation of the reflecting surface rs caused by the first sub-rotation converges. The switching to the second drive signal is delayed by half a period of the resonant frequency around the second axis ax2 after the switching of the signal intensity for the first sub-rotation. Therefore, as shown in Figure 9, when the two rotation components are combined, they cancel each other out.

[0048] The predetermined processing described above may be performed after the amplitude of the oscillation of the reflecting surface rs, in other words, the maximum value of the angular change of the reflecting surface rs due to the oscillation, has attenuated to a value equal to or less than the value obtained by multiplying the angle between the first direction and the second direction by a coefficient α less than 1. The coefficient α may be determined based on the performance required of the scanning device 10. For example, the coefficient α is preferably equal to or less than 0.5, more preferably equal to or less than 0.3, and even more preferably equal to or less than 0.1. The time required from the start of the sub-rotation until the predetermined processing described in detail can be performed is referred to as the stabilization time in this specification.

[0049] In the above specific example, a configuration in which the plurality of sub-rotations is two has been described, but the number of sub-rotations is not limited to two. The rotation from the first direction to the second direction may be performed by three or more sub-rotations. When rotating the reflecting surface rs from the first direction to the second direction, other sub-rotations may be performed to change the reflecting surface rs to another direction in addition to the third direction described above, and each sub-rotation may be performed so as to cancel out the oscillation of the reflecting surface caused by the other sub-rotations. Also,

[0050] In the above specific example, the rotation angles of the first sub-rotation in which the reflecting surface rs changes from the first direction to the third direction and the second sub-rotation in which the reflecting surface rs changes from the third direction to the second direction are the same and are a division of the angle between the first direction and the second direction. Similarly, in a configuration in which the rotation from the first direction to the second direction is performed by three or more sub-rotations, the rotation angles of each sub-rotation may be the same or may be a division of the angle between the first direction and the second direction. Alternatively, the angles of the sub-rotations are not limited to a division of the angle between the first direction and the second direction, as long as the respective swings can be canceled out. For example, the rotation angle of the first sub-rotation in which the reflecting surface rs changes from the first direction to the third direction may be greater than the rotation angle when the reflecting surface rs changes from the first direction to the second direction.

[0051] In the above specific example, the time difference between the first sub-rotation and the second sub-rotation is a half period of the period corresponding to the resonance frequency around the second axis ax2, but it may be a sum of a half period and an integer multiple of that period. Alternatively, the time difference between each sub-rotation is not limited to the half period and an integer multiple of the period, as long as the respective oscillations can cancel each other out. For example, when the number of sub-rotations is set to three or more, the time difference between each sub-rotation may be a sum of a quarter period of the period corresponding to the resonance frequency around the second axis ax2 and an integer multiple of that period.

[0052] Overall, as shown in FIG. 10 , the second drive signal may repeatedly increase and decrease in a stepped manner. The stepped increase and decrease does not include sub-rotations, but corresponds to changes due to rotation between adjacent directions caused by multiple sub-rotations. The second drive signal, which repeatedly increases and decreases in a stepped manner, causes the third mirror 22 to rotate discretely around the second axis ax2. The discrete rotation 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 in a stepped manner, may be fixed based on a fixed frame rate or may change according to an adjustable frame rate. The period of the second drive signal may be longer than the period of the first drive signal.

[0053] In a configuration in which the frame rate is fixed, the second drive signal may have a predetermined drive frequency, and the time intervals of the stepwise unit increases and decreases may be predetermined based on the drive frequency. A unit increase or decrease refers to a change in signal strength to rotate between adjacent directions. In a configuration in which the frame rate is variable, the drive frequency and time intervals of the second drive signal may be modified by the control unit 16 in accordance with the changed frame rate. In either configuration, the time intervals of the multiple sub-rotations in the stepwise unit increases or decreases are determined as described above.

[0054] 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 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.

[0055] 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.

[0056] 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.

[0057] The control unit 16 may transmit the estimated deflection directions in the first rotation direction rd1 and the second rotation direction to the control device 13 as information.

[0058] The control unit 16 may change the drive frequency of the first drive signal in accordance with a first change corresponding to the rotation of the reflecting surface rs about 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 rotation about 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 rotation about the second axis ax2.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 rotation thereof changed 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 about the first axis ax1 and the second axis ax2, the first resonant frequency of the scanning unit 15 changes in response to the rotation about 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 about the second axis ax2.

[0063] 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.

[0064] The arbitrary angle may be the angle at the maximum change in the rotation 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 rotation 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 rotation around the second axis ax2 is projected onto a plane.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Next, the intensity adjustment process executed by the control unit 16 in this embodiment will be described using the flowchart in Fig. 11. The intensity adjustment process starts, for example, when a time interval of stepwise unit increase or decrease has elapsed after the signal intensity of the second drive signal has been changed.

[0074] In step S101, the control unit 16 changes the signal strength of the second drive signal to the signal strength for the first sub-rotation (third drive signal). After the change, the process proceeds to step S102.

[0075] In step S102, the control unit 16 determines whether or not a half period corresponding to the resonance frequency around the second axis ax2 has elapsed since the end of step S101. If not, the process returns to step S102. If yes, the process proceeds to step S103.

[0076] In step S103, the control unit 16 changes the signal strength of the second drive signal to the signal strength for the second sub-rotation, and after the change, the strength adjustment process ends.

[0077] Next, the frequency adjustment process executed by the control unit 16 in this embodiment will be described with reference to the flowchart of Fig. 12. The frequency adjustment process starts, for example, when the signal strength of the second drive signal changes.

[0078] In step S200, 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 S201.

[0079] In step S201, the control unit 16 calculates the first resonance frequency corresponding to the angle calculated in step S200 by interpolation or extrapolation. After the calculation, the process proceeds to step S202.

[0080] In step S202, 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 S202. If it is the predetermined time point, the process proceeds to step S203.

[0081] In step S203, 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 S201. After the change, the frequency adjustment process ends.

[0082] The scanning device 10 of this embodiment, configured as described above, includes a scanning unit 15 that changes the orientation of the reflecting surface rs in multiple directions, including the first direction and the second direction, and a control unit 16 that, when changing the orientation of the reflecting surface rs from the first direction to the second direction, outputs at least a third drive signal to the scanning unit 15 that changes the orientation of the reflecting surface rs from the first direction to the third direction and a second drive signal to the scanning unit 15 that changes the orientation of the reflecting surface rs to the second direction. The second drive signal is output to reduce the oscillation of the reflecting surface rs caused by the third drive signal. The scanning device 10 configured as described above can shorten the stabilization time by changing the orientation of the reflecting surface rs so that the oscillations cancel each other out. Therefore, the scanning device 10 stabilizes changes in the rotation angle around one axis.

[0083] The scanning device 10 further includes an emission unit 14 that emits electromagnetic waves em1, and the scanning unit 15 reflects the electromagnetic waves em1 incident from the emission unit 14 at a reflection surface rs. With this configuration, the scanning device 10 can change the radiation direction of the electromagnetic waves emitted by the emission unit 14 in accordance with the swinging motion around the first axis ax1 and the second axis ax2.

[0084] The scanning device 10 further includes a detection unit 12 that detects the reflected waves of the electromagnetic waves em1 that are reflected by the object after being reflected by the reflecting surface rs of the scanning unit 15. With this configuration, the scanning device 10 can obtain distance information of any object point on the object, for example, by ToF, based on the time when the emitting unit 14 emits the electromagnetic waves and the time when the detecting unit 12 detects the electromagnetic waves after emission.

[0085] The control device 13 of this embodiment, configured as described above, controls the scanning device 10, which includes a scanning unit 15 that changes the orientation of the reflecting surface rs in multiple directions, including a first direction and a second direction. When changing the orientation of the reflecting surface rs from the first direction to the second direction, the control device 13 includes a control unit 16 that outputs at least a third drive signal to the scanning unit 15 to change the orientation of the reflecting surface rs from the first direction to a third direction, and a second drive signal to the scanning unit 15 to change the orientation of the reflecting surface rs to the second direction. The second drive signal is output to reduce the oscillation of the reflecting surface rs caused by the third drive signal. With this configuration, the control device 13 can shorten the stabilization time by changing the orientation of the reflecting surface rs in the scanning unit 15 of the scanning device 10 so that the oscillations cancel each other out.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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]

[0091] 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 that changes the orientation of the reflecting surface in a plurality of directions including a first direction and a second direction; a control unit that, when changing the orientation of the reflective surface from the first direction to the second direction, outputs to the scanning unit at least a third drive signal that changes the orientation of the reflective surface from the first direction to a third direction, and outputs to the scanning unit a second drive signal that changes the orientation of the reflective surface to the second direction, the second drive signal is output so as to reduce the oscillation of the reflecting surface caused by the third drive signal. Scanning device.

2. 2. The scanning device according to claim 1, the control unit outputs the second drive signal to the scanning unit before the oscillation of the reflecting surface caused by the third drive signal converges. Scanning device.

3. 2. The scanning device according to claim 1, the control unit outputs the second drive signal to the scanning unit when a swing angle of the reflecting surface that changes in the second direction due to the swing caused by the third drive signal becomes maximum. Scanning device.

4. 2. The scanning device according to claim 1, The control unit outputting the second drive signal to the scanning unit during a period in which the orientation of the reflecting surface changes toward the first direction after the swing angle of the reflecting surface, which changes in the second direction due to the swing caused by the third drive signal, reaches a maximum; Scanning device.

5. 3. The scanning device according to claim 1, The control unit outputting the third drive signal to the scanning unit, and then outputting the second drive signal to the scanning unit with a time difference of a half period of a resonance frequency of the oscillation of the reflecting surface plus an integer multiple of the period of the resonance frequency; Scanning device.

6. 3. The scanning device according to claim 1, The control unit outputting the third drive signal to the scanning unit before a time equal to a half period of a resonance frequency of the oscillation of the reflecting surface plus an integer multiple of the period of the resonance frequency, the third drive signal being output to the scanning unit; Scanning device.

7. 3. The scanning device according to claim 1, the scanning unit directs the reflecting surface in the first direction, the third direction, and the second direction around a predetermined axis; a rotation angle of the reflecting surface from the first direction to the third direction is smaller than a rotation angle of the reflecting surface from the first direction to the second direction; Scanning device.

8. 3. The scanning device according to claim 1, the scanning unit directs the reflecting surface in the first direction, the third direction, and the second direction around a predetermined axis; a rotation angle of the reflecting surface from the first direction to the third direction is larger than a rotation angle of the reflecting surface from the first direction to the second direction; Scanning device.

9. 3. The scanning device according to claim 1, The control unit outputting a plurality of drive signals including the third drive signal to the scanning unit before outputting the second drive signal to the scanning unit; Each of the plurality of drive signals is output so as to cancel out the oscillation of the reflecting surface caused by the other drive signals. Scanning device.

10. 2. The scanning device of claim 1, further comprising a radiation unit that radiates electromagnetic waves, the scanning unit reflects the electromagnetic wave incident from the radiation unit on the reflection surface; Scanning device.

11. 11. A scanning device according to claim 10, a detection unit that detects a reflected wave that is formed by the electromagnetic wave reflected by the reflecting surface of the scanning unit and then reflected by an object; Scanning device.

12. A control device for controlling a scanning device including a scanning unit that changes the orientation of a reflective surface in a plurality of directions including a first direction and a second direction, a control unit that, when changing the orientation of the reflective surface from the first direction to the second direction, outputs to the scanning unit at least a third drive signal that changes the orientation of the reflective surface from the first direction to a third direction, and outputs to the scanning unit a second drive signal that changes the orientation of the reflective surface to the second direction, the second drive signal is output so as to reduce the oscillation of the reflecting surface caused by the third drive signal. Control device.

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