Scanner, distance measuring device, movable body mounted system, method for controlling scanner, and program

Abstract

To provide a scanner that can prevent a reduction in control performance even when the transfer characteristics of a biaxial MEMS mirror change.SOLUTION: A scanner (1) has: scanning means (400) that scans an electromagnetic wave in a two-dimensional way; update means (1300) that updates a transfer function matrix of the scanning means (400); and control means (1100) that controls the scanning means (400) on the basis of the updated transfer function matrix.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a scanning device, a distance measuring device, a mobile body-mounted system, a method for controlling a scanning device, and a program.

Background Art

[0002] A two-axis MEMS (Micro Electro Mechanical Systems) mirror is used as a scanner device (scanning device) for LiDAR (Light Detection And Ranging). In order to obtain point cloud information at a predetermined angle, it is desirable to control the MEMS mirror stably and with high precision. In order to stably and quickly converge the tilt displacement of the MEMS mirror to the target displacement, it is desirable to set a controller in consideration of the transfer characteristics of the MEMS mirror.

[0003] Patent Document 1 discloses a method for improving scanning accuracy by measuring the transfer characteristics of each mirror at startup and performing scanning control based on the measured transfer characteristics in a scanner device having two one-axis mirrors (an X-axis mirror and a Y-axis mirror).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of a scanning device having a two-axis MEMS mirror, crosstalk components (a transmission component from a horizontal drive signal to a vertical displacement and a transmission component from a vertical drive signal to a horizontal displacement) exist in the transfer characteristics. Therefore, in the method disclosed in Patent Document 1, when the transfer function of the crosstalk component changes due to environmental changes or aging changes, the control performance (control stability, accuracy, or response speed) may deteriorate.

[0006] Therefore, an object of the present invention is to provide a scanning device capable of suppressing a decrease in control performance even when the transfer characteristics of a two-axis MEMS mirror change.

Means for Solving the Problems

[0007] A scanning device according to one aspect of the present invention includes scanning means for two-dimensionally scanning an electromagnetic wave, updating means for updating a transfer function matrix of the scanning means, and control means for controlling the scanning means based on the transfer function matrix.

[0008] Other objects and features of the present invention will be described in the following embodiments.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a scanning device capable of suppressing a decrease in control performance even when the transfer characteristics of a two-axis MEMS mirror change.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8(A)

Figure 8(B)

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] (LiDAR device) First, the LiDAR device (scanning device, distance measuring device) 1 in this embodiment will be described. FIG. 1 is a block diagram of the LiDAR device 1. The LiDAR device 1 appropriately controls the irradiation direction (scanning direction) of pulsed light as an electromagnetic wave emitted repeatedly to scan the surrounding space, observes the reflected pulsed light from an object (body) existing in the surrounding space, and generates information about the object from the result. The information about the object includes the TOF (Time of Flight) delay time (distance to the object), the probability of the existence of the object, or the reflectivity of the object, etc., which will be described later. In the following description, the pulsed light irradiated into the surrounding space is referred to as emitted light, the object for generating the above information is referred to as a target, and the reflected light from the object is referred to as signal light (signal electromagnetic wave).

[0013] The LiDAR device 1 includes a laser 100, a transmission optical system 200, a separation optical system 300, a MEMS mirror 400, a reception optical system 500, a reception circuit 600, a detection / distance measuring unit (distance measuring means) 700, a MEMS drive circuit 800, a MEMS monitoring circuit 900, and a scanning control unit 1000.

[0014] (Laser 100 to Detection / Distance Measuring Unit 700) Laser 100 as a light source (electromagnetic wave source) repeatedly outputs emitted light as laser light (electromagnetic wave) in response to a pulse trigger signal output by scanning control unit 1000. Transmission optical system 200 shapes the emitted light from laser 100 to an appropriate divergence angle and guides it to MEMS mirror 400. Separation optical system 300 guides the emitted light to MEMS mirror 400 and guides most of the signal light to receiving optical system 500. MEMS mirror 400 emits the emitted light in an appropriate direction and guides the signal light that has returned after the emitted light is irradiated onto a target in the surrounding space and reflected to separation optical system 300. Also, MEMS mirror 400 is controlled by scanning control unit 1000 so that the emitted light is emitted in an appropriate direction. MEMS mirror 400 is rotatable around two axes respectively and is a two-dimensional scanner (scanning means) that scans electromagnetic waves two-dimensionally.

[0015] Receiving optical system 500 has optical filter 510 and condenser lens 520. Receiving circuit 600 has APD (avalanche photodiode) 610, TIA (transimpedance amplifier) 620, and ADC (AD converter) 630. Receiving optical system 500 condenses the signal light onto APD 610. In addition to the signal light, background light (background electromagnetic wave) generated when the object is illuminated by the sun or the like also enters receiving optical system 500. Optical filter 510 is provided to selectively reduce the background light. Specifically, optical filter 510 has the characteristic of passing only the light components in a specific passband and blocking the passage of light components in other bands. The specific passband is determined based on the wavelength width of laser 100, the fluctuation width of the center wavelength due to temperature change, or the like.

[0016] The signal light and background light that have passed through receiving optical system 500 are photoelectrically converted by APD 610. TIA 620 converts the current signal output from APD 610 into a voltage signal. The analog voltage signal output by TIA 620 is converted into a digital signal by ADC 630.

[0017] The detection and ranging unit (ranging means) 700 acquires distance information to the object based on the signal electromagnetic wave reflected by the object. Specifically, the detection and ranging unit 700 uses the received signal, which is the signal output from the ADC 630, to detect the signal light component and estimate the TOF delay time, and outputs a detection flag and the estimated TOF delay time. The TOF delay time is the time from when light is emitted from the laser 100 until it is received (received) by the APD 610.

[0018] Next, with reference to FIG. 2, the MEMS mirror 400 and its control system will be described in detail. FIG. 2 is a block diagram of the scanning control unit 1000, the MEMS drive circuit 800, the MEMS monitoring circuit 900, and the MEMS mirror 400.

[0019] (MEMS mirror 400) In this embodiment, the MEMS mirror 400 as a scanner (two-dimensional scanner) is a two-axis MEMS mirror of an electromagnetic drive type. The MEMS mirror 400 has a mirror part, an X-axis torsion bar, and a Y-axis torsion bar (not shown). The mirror part is supported by the X-axis torsion bar and the Y-axis torsion bar.

[0020] The MEMS drive circuit (driving means) 800 drives the MEMS mirror 400 around two axes, for example, around the X-axis and the Y-axis (around the first axis, around the second axis). That is, the MEMS drive circuit 800 drives the MEMS mirror 400 around two axes based on a drive signal related to the horizontal direction (the first direction) (horizontal drive signal, the first drive signal) and a drive signal related to the second direction (vertical direction) (vertical drive signal, the second drive signal).

[0021] The X-axis torsion bar and the Y-axis torsion bar of the MEMS mirror 400 are twisted around the X-axis and the Y-axis based on the horizontal drive signal (horizontal drive signal) and the vertical drive signal (vertical drive signal) output from the MEMS drive circuit 800. As a result, the mirror part of the MEMS mirror 400 is driven to tilt in the horizontal direction and the vertical direction.

[0022] The MEMS mirror 400 also has an H inclination sensor (first sensor) 410 and a V inclination sensor (second sensor) 420. The H inclination sensor 410 detects the inclination in the horizontal direction and outputs a horizontal inclination sensor signal (first signal). The V inclination sensor 420 detects the inclination in the vertical direction and outputs a vertical inclination sensor signal (second signal).

[0023] The H inclination sensor 410 and the V inclination sensor 420 electrically detect the inclinations in the horizontal and vertical directions of the mirror unit, and output inclination sensor signals to the MEMS monitoring circuit 900. In this embodiment, the H inclination sensor 410 and the V inclination sensor 420 are each piezo sensors. The piezo sensor electrically detects the strain caused by the stress of the torsion bar.

[0024] Ideally, only the horizontal inclination of the MEMS mirror 400 is displaced by the horizontal drive signal, and only the vertical inclination is displaced by the vertical drive signal. However, in reality, there are transmission characteristics of crosstalk components such that the vertical inclination is slightly displaced by the horizontal drive signal. The relationship between the drive signals (Xh, Xv) input to the MEMS mirror 400 and the inclination displacements (Yh, Yv) is expressed as the following formula (1).

[0025]

Equation

[0026] Here, let the transfer function from the horizontal drive signal to the horizontal displacement (displacement in the first direction) be Ghh, the transfer function from the vertical drive signal to the horizontal displacement be Ghv, the transfer function from the horizontal drive signal to the vertical displacement (displacement in the second direction) be Gvh, and the transfer function from the vertical drive signal to the vertical displacement be Gvv. Also, the MEMS transfer function matrix G is expressed as the following formula (2).

[0027]

Equation

[0028] (MEMS drive circuit 800) The MEMS drive circuit 800 includes DACs (DA converters) 810 and 820, and amplifiers 830 and 840. The DACs 810 and 820 convert the horizontal drive signal and the vertical drive signal (digital signals) output by the scan control unit 1000 into analog signals. The amplifiers 830 and 840 amplify the horizontal drive signal and the vertical drive signal (analog signals) to a predetermined level and output them to the MEMS mirror 400.

[0029] (MEMS monitoring circuit 900) The MEMS monitoring circuit 900 includes amplifiers 910 and 920, and ADCs 930 and 940. The amplifiers 910 and 920 amplify the horizontal and vertical tilt sensor signals (analog signals) output by the H tilt sensor 410 and the V tilt sensor 420 to a predetermined level and output them to the ADCs 930 and 940 respectively. The ADCs 930 and 940 convert the amplified horizontal and vertical tilt sensor signals (analog signals) into digital signals and output them to the scan control unit 1000.

[0030] (Scan control unit 1000) The scan control unit 1000 functions as a control unit for controlling the MEMS mirror 400. As shown in FIG. 2, the scan control unit 1000 includes a normal scan control unit 1100, a transfer function measurement unit 1300, a mode switching control unit 1400, and a pulse trigger generation unit 1500.

[0031] The scan control unit 1000 can execute two modes: the normal mode and the transfer function measurement mode. The normal mode is a mode in which the space is scanned with electromagnetic waves as a LiDAR to acquire point cloud information. The transfer function measurement mode is a mode for updating the estimated MEMS transfer function matrix used for MEMS control in the normal mode.

[0032] When the mode is set to the normal mode by the mode switching control unit 1400, the normal scan control unit (control means) 1100 controls the horizontal and vertical tilt displacements of the MEMS mirror 400 based on the horizontal and vertical tilt sensor signals output by the MEMS mirror 400.

[0033] When the mode is set to the transfer function measurement mode by the mode switching control unit 1400, the transfer function measurement unit (update means) 1300 updates (estimates, measures) the transfer function matrix of the MEMS mirror 400 based on the horizontal and vertical inclination sensor signals output by the MEMS mirror 400. The normal scanning control unit 1100 controls the MEMS mirror 400 based on the updated transfer function matrix.

[0034] The mode switching control unit (decision means) 1400 determines the measurement timing (update timing) of the transfer function matrix by the transfer function measurement unit 1300. The mode switching control unit 1400 determines, for example, which mode of the normal mode (first mode) or the transfer function measurement mode (second mode) to execute (the measurement timing of the transfer function matrix) based on the vehicle information output by the vehicle information acquisition device 3001 described later.

[0035] When the mode is set to the normal mode by the mode switching control unit 1400, the pulse trigger generation unit 1500 outputs a pulse trigger toward the laser 100 at a predetermined timing.

[0036] (Control method of two-axis MEMS mirror) Next, a control method for the MEMS mirror (two-axis MEMS mirror) 400 will be described.

[0037] First, with reference to FIGS. 3(A), (B) and FIGS. 4(A), (B), an outline of the control algorithm of the MEMS mirror 400 in the normal mode will be described. FIGS. 3(A), (B) are diagrams showing the V target displacement waveform and the H target displacement waveform, respectively. In FIGS. 3(A), (B), the horizontal axis represents time, and the vertical axis represents the target displacement (V target displacement or H target displacement), respectively.

[0038] Since the target tilt displacement, actual displacement, and drive signal of the MEMS mirror 400 are repetitive signals, they can be expressed by Fourier series. For example, in this embodiment, the frame frequency is 24.6 Hz, and the target displacement waveform in the vertical direction (V target displacement radius) is a sawtooth wave with one frame period as shown in FIG. 3(A). Also, the target displacement waveform in the horizontal direction (H target displacement waveform) is a sine wave with a frequency of 1180 Hz as shown in FIG. 3(B).

[0039] Both of these can be expressed by Fourier harmonic coefficients (harmonic coefficients) with a fundamental frequency of 24.6 Hz (frame frequency). FIGS. 4(A) and (B) are diagrams showing the harmonic coefficients (V target harmonic coefficients, H target harmonic coefficients) of the target displacement waveforms in the vertical and horizontal directions, respectively. In this control algorithm, the harmonic coefficients of the drive signal (drive harmonic coefficients) are controlled so that the tilt displacement of the MEMS mirror 400, that is, the harmonic coefficients of the tilt sensor signal (observed harmonic coefficients), approach the harmonic coefficients of the target displacement waveform (target harmonic coefficients).

[0040] Hereinafter, the order of the harmonic coefficients will be represented using n. The maximum order N of the harmonic coefficients to be controlled may be determined in view of the bandwidth of the MEMS mirror 400. In this embodiment, N is 128 (3147 Hz). When the bandwidth of the MEMS mirror 400 is wider than that (when it responds to higher frequency signals), it is desirable to make the control order N larger.

[0041] Next, with reference to FIG. 5, the specific configuration of the normal scanning control unit 1100 for realizing the above control will be described. FIG. 5 is a configuration diagram of the normal scanning control unit 1100.

[0042] Normally, the scanning control unit 1100 includes a complex sine wave generation unit 1110, synchronous detection units 1120 and 1130, an H target harmonic coefficient memory unit 1140, a V target harmonic coefficient memory unit 1150, and an error coefficient correction unit 1160. The normal scanning control unit 1100 also includes an H drive coefficient memory unit 1170, a V drive coefficient memory unit 1180, a conjugate signal generation unit 1190, complex multiplication units 1200 and 1210, addition units 1220 and 1230, and real part acquisition units 1240 and 1250.

[0043] The complex sine wave generation unit 1110 includes complex sine wave generators 1111-1 to 1111-N and outputs complex sine waves from the first to the Nth order.

[0044] The synchronous detection unit 1120 includes complex multipliers 1121-1 to 1121-N and LPFs (low-pass filters) 1122-1 to 1122-N. Based on the horizontal inclination sensor signal output by the MEMS mirror 400, it obtains and outputs the observed harmonic coefficients from the first to the Nth order. Similarly, the synchronous detection unit 1130 includes complex multipliers 1131-1 to 1131-N and LPFs 1132-1 to 1132-N. Based on the vertical inclination sensor signal output by the MEMS mirror 400, it obtains and outputs the observed harmonic coefficients from the first to the Nth order.

[0045] The H target harmonic coefficient memory unit 1140 stores the horizontal target harmonic coefficients from the first to the Nth order in advance. Similarly, the V target harmonic coefficient memory unit 1150 stores the vertical target harmonic coefficients from the first to the Nth order in advance.

[0046] The error coefficient correction unit 1160 corrects the error coefficients (Eh, Ev), which are the differences between the horizontal and vertical observed harmonic coefficients and the target harmonic coefficients, by multiplying the inverse matrix ^G of the estimated MEMS transfer function matrix ^G described later from the left. -1 To perform correction of the error coefficients.

[0047] The H drive coefficient memory unit 1170 stores the first to Nth order horizontal drive harmonic coefficients in the previous frame. Similarly, the V drive coefficient memory unit 1180 stores the vertical drive harmonic coefficients in the previous frame, respectively. The conjugate signal generation unit 1190 outputs a signal obtained by taking the complex conjugate of the first to Nth order complex sine waves output by the complex sine wave generation unit 1110.

[0048] The complex multiplication unit 1200 has complex multipliers 1201-1 to 1201-N, and multiplies the first to Nth order horizontal drive harmonic coefficients by the first to Nth order complex sine waves, respectively. Similarly, the complex multiplication unit 1210 includes complex multipliers 1211-1 to 1211-N, and multiplies the first to Nth order vertical drive harmonic coefficients by the first to Nth order complex sine waves.

[0049] The addition unit 1220 sums up the first to Nth order complex signals output by the complex multiplication unit 1200. Similarly, the addition unit 1230 sums up the first to Nth order complex signals output by the complex multiplication unit 1210. The real part acquisition unit 1240 generates a horizontal drive signal by acquiring the real part of the complex signal output by the addition unit 1220. Similarly, the real part acquisition unit 1250 generates a vertical drive signal by acquiring the real part of the complex signal output by the addition unit 1230.

[0050] Next, with reference to FIG. 6, the specific processing of the normal scanning control unit 1100 will be described. FIG. 6 is a flowchart showing the processing of the normal scanning control unit 1100. The processing in FIG. 6 is executed when the normal scanning control unit 1100 acquires an execution instruction for the normal mode from the mode switching control unit 1400.

[0051] First, in step S601, the normal scanning control unit 1100 performs synchronous detection on the vertical and horizontal sensor signals for one frame period, and obtains the observed harmonic coefficients. The synchronous detection is performed by multiplying the first to Nth order complex sine waves (complex sine waves with frequencies from 1 times to N times the fundamental frequency of 24.6 Hz) by the tilt sensor signal and then smoothing (filtering with an LPF), as shown in FIG. 5.

[0052] Subsequently, in step S602, the normal scanning control unit 1100 calculates the difference (error coefficient) between the vertical and horizontal observed harmonic coefficients and the target harmonic coefficient. The error coefficient is calculated by subtracting the target harmonic coefficient from the observed harmonic coefficient.

[0053] Subsequently, in step S603, the normal scanning control unit 1100 updates the drive harmonic coefficient based on the error coefficient and the estimated MEMS transfer function matrix. Specifically, after multiplying the vertical and horizontal error coefficients (Eh, Ev) by the inverse matrix ^G of the estimated MEMS transfer function matrix ^G from the left, and subtracting the result from the drive harmonic coefficient of the previous frame, the drive harmonic coefficient of the next frame is generated. -1 That is, the drive harmonic coefficient of the next frame is generated by multiplying the vertical and horizontal error coefficients (Eh, Ev) by the inverse matrix ^G of the estimated MEMS transfer function matrix ^G from the left and then subtracting the result from the drive harmonic coefficient of the previous frame.

[0054] Here, the estimated MEMS transfer function matrix ^G is a matrix consisting of four elements as represented by the following equation (3).

[0055]

Equation

[0056] In Equation (3), let the estimation function of the transfer function from the horizontal drive signal to the horizontal displacement be ^Ghh, and the estimation function of the transfer function from the vertical drive signal to the horizontal displacement be ^Ghv. Also, let the estimation function of the transfer function from the horizontal drive signal to the vertical displacement be ^Gvh, and the estimation function of the transfer function from the vertical drive signal to the vertical displacement be ^Gvv. The estimated MEMS transfer function matrix ^G is sequentially updated by performing the MEMS transfer function measurement described later.

[0057] Subsequently, in step S604, the normal scanning control unit 1100 generates a drive signal (time-domain waveform) from the drive harmonic coefficient. As shown in FIG. 5, the drive signal is generated by multiplying complex sine waves from the first to the Nth order and then taking the real part thereof. Note that the above processing (steps S601 to S604) is repeatedly executed for each frame.

[0058] Here, during the execution of the process in the normal mode, the pulse trigger generation unit 1500 outputs a pulse trigger to the laser 100 at a predetermined timing.

[0059] (Method for estimating the transfer function matrix of a two-axis MEMS mirror) Next, with reference to FIG. 7, the specific configuration of the transfer function measurement unit 1300 for estimating the transfer function matrix of the MEMS mirror 400 will be described. FIG. 7 is a configuration diagram of the transfer function measurement unit 1300.

[0060] The transfer function measurement unit 1300 includes a complex sine wave generator 1310, synchronous detectors 1320 and 1330, a conjugate signal generation unit 1340, a real part acquisition unit 1350, a storage unit 1360, and a switch 1370. The complex sine wave generator 1310 outputs a complex sine wave exp(−jωt) with an angular frequency of ω = 2πfn.

[0061] The synchronous detector 1320 includes a complex multiplier 1321 and an LPF 1322, and obtains a complex coefficient based on the horizontal inclination sensor signal output by the MEMS mirror 400 and stores it in the storage unit 1360. Similarly, the synchronous detector 1330 includes a complex multiplier 1331 and an LPF 1332, and obtains a complex coefficient based on the vertical inclination sensor signal output by the MEMS mirror 400 and stores it in the storage unit 1360.

[0062] The conjugate signal generation unit 1340 obtains the complex conjugate of the complex sine wave output by the complex sine wave generator 1310. The real part acquisition unit 1350 obtains the real part of the complex sine wave output by the conjugate signal generation unit 1340. The storage unit 1360 stores the complex coefficients output by the synchronous detector 1320 and the synchronous detector 1330. The switch 1370 switches the output destination of the sine wave output by the real part acquisition unit 1350.

[0063] Next, with reference to FIGS. 8(A) and 8(B), the specific processing of the transfer function measurement unit 1300 will be described. FIGS. 8(A) and 8(B) are flowcharts showing the processing of the transfer function measurement unit 1300. The processing in FIGS. 8(A) and 8(B) is executed when the transfer function measurement unit 1300 acquires a measurement instruction for the transfer function from the mode switching control unit 1400.

[0064] (Acquisition of Estimated MEMS Transfer Functions ^Ghh and ^Gvh (FIG. 8(A)) First, in step S801, the transfer function measurement unit 1300 switches the switch 1370 to the horizontal drive signal side, so that the horizontal drive signal is in an outputtable state and the vertical drive signal is not output. Subsequently, in step S802, the transfer function measurement unit 1300 sets n, which represents the order of the frequency of the complex sine wave output by the complex sine wave generator 1310, to 1. Subsequently, in step S803, the complex sine wave generator 1310 outputs a complex sine wave exp(−jωt) whose angular frequency is ω = 2πfn. Here, fn = n × 24.6 Hz.

[0065] Subsequently, in step S804, the transfer function measurement unit 1300 outputs the complex sine wave output in step S803 as a horizontal drive signal via the conjugate signal generation unit 1340 and the real part acquisition unit 1350. Subsequently, in step S805, the transfer function measurement unit 1300 synchronously detects the horizontal and vertical inclination sensor signals respectively and obtains the complex coefficients respectively. The synchronous detection is performed by multiplying the complex sine wave output by the complex sine wave generator 1310 by the inclination sensor signal and then smoothing (filtering with an LPF).

[0066] Subsequently, in step S806, the transfer function measurement unit 1300 stores the complex coefficients obtained in step S805 in the storage unit 1360. Subsequently, in step S807, the transfer function measurement unit 1300 adds 1 to n.

[0067] Subsequently, in step S808, the transfer function measurement unit 1300 determines whether n is less than or equal to N. If the transfer function measurement unit 1300 determines that n is less than or equal to N, it returns to step S803. On the other hand, if the transfer function measurement unit 1300 determines that n is not less than or equal to N, it proceeds to step S809. Here, N is 128 in this embodiment. The transfer function measurement unit 1300 obtains the estimated MEMS transfer functions ^Ghh and ^Gvh through the above processing.

[0068] (Obtaining the estimated MEMS transfer functions ^Ghv and ^Gvv (Fig. 8(B)) First, in step S809, the transfer function measurement unit 1300 switches the switch 1370 to the vertical drive signal side, so that the vertical drive signal is in an output - enabled state and the horizontal drive signal is not output. Subsequently, in step S810, the transfer function measurement unit 1300 sets n, which represents the order of the frequency of the complex sine wave output by the complex sine wave generator 1310, to 1. Subsequently, in step S811, the complex sine wave generator 1310 outputs a complex sine wave exp( - jωt) with an angular frequency ω = 2πfn. Here, fn = n×24.6Hz.

[0069] Subsequently, in step S812, the transfer function measurement unit 1300 outputs the complex sine wave output in step S811 as a vertical drive signal through the conjugate signal generation unit 1340 and the real - part acquisition unit 1350. Subsequently, in step S813, the transfer function measurement unit 1300 synchronously detects the horizontal and vertical inclination sensor signals respectively and obtains the complex coefficients respectively. The synchronous detection is performed by multiplying the complex sine wave output by the complex sine wave generator 1310 by the inclination sensor signal and then smoothing (filtering with an LPF).

[0070] Subsequently, in step S814, the transfer function measurement unit 1300 stores the complex coefficients obtained in step S813 in the storage unit 1360. Subsequently, in step S815, the transfer function measurement unit 1300 adds 1 to n. Subsequently, in step S816, the transfer function measurement unit 1300 determines whether n is less than or equal to N. If the transfer function measurement unit 1300 determines that n is less than or equal to N, it returns to step S811. On the other hand, if the transfer function measurement unit 1300 determines that n is not less than or equal to N, it ends this flow. Here, N is 128 in this embodiment. The transfer function measurement unit 1300 acquires the estimated MEMS transfer functions ^Ghv and ^Gvv by the above processing. Here, during the execution of the processing in the transfer function measurement mode, no pulse trigger is output (no pulsed light is emitted).

[0071] The mode switching control unit 1400 determines whether to execute the normal mode or the transfer function measurement mode based on, for example, the vehicle information output from the vehicle information acquisition device 3001 (see FIG. 9). For example, when the gear selection of the vehicle is drive, the normal mode is executed, and when switching from drive to parking, the transfer function measurement mode is executed, etc.

[0072] Next, the effect of the scanning control unit 1000 in this embodiment will be described. The relationship between the input (drive signal) and output (tilt displacement) of the MEMS mirror 400 is as shown in Equation (1). From Equation (1), when trying to make the output (Yh, Yv) the target displacement (Rh, Rv), as represented by the following Equations (4) and (5), it is only necessary to multiply the inverse matrix of the MEMS transfer function matrix G from the left with respect to the target displacement (Rh, Rv) in advance and then input it.

[0073]

Equation

[0074]

Equation

[0075] Based on the above, in step S703, the error coefficient is multiplied by the inverse matrix of the estimated MEMS transfer function matrix ^G. Here, when the estimated MEMS transfer function matrix ^G is equal to the MEMS transfer function matrix G, the MEMS displacement immediately reaches the target displacement. However, in reality, there is a difference between the estimated MEMS transfer function matrix ^G and the MEMS transfer function matrix G, so it does not immediately become the target displacement. By repeating the process in FIG. 6, the MEMS displacement converges to the target displacement. Conversely, if the estimated MEMS transfer function matrix ^G is closer to the MEMS transfer function matrix G, the convergence of the MEMS displacement to the target displacement becomes faster.

[0076] The MEMS transfer function matrix G changes due to various environmental factors, aging deterioration, etc. In this embodiment, as described above, the process of updating the estimated MEMS transfer function matrix ^G is performed by sequentially measuring the MEMS transfer function matrix. Therefore, even when the MEMS transfer function matrix changes due to environmental factors, aging deterioration, etc., it is possible to prevent a decrease in the convergence speed (response speed), accuracy, and stability to the target displacement in normal scanning control.

[0077] The detection / distance measurement unit 700 and the scanning control unit 1000 include various processors such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The detection / distance measurement unit 700 and the scanning control unit 1000 are an example of a computer that executes a program. Note that the detection / distance measurement unit 700 and the scanning control unit 1000 are not limited to being realized by software based on a program, and may be realized by any combination of hardware, firmware, and software. Further, the detection / distance measurement unit 700 and the scanning control unit 1000 may be a user-programmable integrated circuit such as an FPGA (field-programmable gate array) or a microcontroller. Alternatively, it may be an ASSP (Application Specific Standard Produce) or an ASIC (Application Specific Integrated Circuit).

[0078] (Vehicle-mounted system) FIG. 9 is a block diagram of a vehicle-mounted system (driving support device) 3000 as a mobile body-mounted system including the LiDAR device 1 of this embodiment. The vehicle-mounted system 3000 is mounted on a mobile body such as an automobile (vehicle), and supports the driving (operation) of the vehicle based on information on the distance to an object such as an obstacle or a pedestrian around the vehicle acquired by the LiDAR device 1 as a distance acquisition device. As shown in FIG. 9, the vehicle-mounted system 3000 includes a LiDAR device 1, a vehicle information acquisition device 3001, a control device (ECU: Electronic Control Unit) 3002, and a warning device (warning unit) 3003.

[0079] The vehicle information acquisition device 3001 acquires vehicle information including gear selection information, vehicle speed, yaw rate, and steering angle of the vehicle, and outputs it to the LiDAR device 1. The control device 3002 controls the vehicle based on the distance information to the object output by the LiDAR device 1 and the vehicle information, and outputs a warning signal to the warning device 3003. The warning device 3003 performs a warning operation to the driver based on the warning signal output by the control device 3002.

[0080] FIG. 10 is a schematic diagram of a vehicle 3005 including the vehicle-mounted system 3000. FIG. 10 shows a case where the distance acquisition range of the LiDAR device 1 is set in front of the vehicle 3005. However, the distance acquisition range may be set other than in front, such as behind or on the side of the vehicle 3005.

[0081] FIG. 11 is a flowchart showing the process executed by the vehicle-mounted system 3000. First, in step S1101, when the pulsed light (emitted light) from the laser 100 shown in FIG. 1 irradiates an object around the vehicle, the LiDAR device 1 receives the reflected pulsed light (signal light) from the object and acquires the distance information to the object. Subsequently, in step S1102, the vehicle information acquisition device 3001 acquires vehicle information including gear selection information, vehicle speed, yaw rate, and steering angle of the vehicle.

[0082] Subsequently, in step S1103, the control device 3002 determines whether the distance to the object is within a preset distance range by using the distance information acquired in step S1101 and the vehicle information acquired in step S1102. Thereby, the control device 3002 can determine whether there is an object within the preset distance around the vehicle and can determine the possibility of collision between the vehicle and the object. Note that steps S1101 and S1102 may be performed in the reverse order of the above order or may be performed in parallel with each other. When the control device 3002 determines that there is an object within the preset distance, it proceeds to step S1104. In step S1104, the control device 3002 determines that "there is a possibility of collision". On the other hand, when the control device 3002 determines that there is no object within the preset distance, it proceeds to step S1105. In step S1105, the control device 3002 determines that "there is no possibility of collision".

[0083] In step S1106, since the control device 3002 determines that "there is a possibility of collision", it controls the vehicle to avoid or reduce the collision, such as turning on the brakes of the vehicle, turning off the accelerator, or steering. In step S1107, the control device 3002 notifies the warning device 3003 that "there is a possibility of collision". Thereby, the warning device 3003 emits a warning sound to the user (driver) of the vehicle, displays warning information on the display screen of a car navigation system or the like, or performs warning operations such as vibrating the seat belt or the steering wheel.

[0084] According to the in-vehicle system 3000, it is possible to obtain the detected distance information to the object and avoid or reduce the collision between the vehicle and the object. In particular, by applying the LiDAR device 1 of this embodiment to the in-vehicle system 3000, it is possible to suppress the decrease in angular accuracy due to environmental changes and aging changes, so that the collision can be more reliably avoided or reduced.

[0085] In addition to driving assistance, the in-vehicle system 3000 may also be applied to cruise control (including the full-vehicle-speed following function) and autonomous driving. Further, the in-vehicle system 3000 may be applied not only to vehicles such as automobiles but also to various moving bodies such as ships, aircraft, and industrial robots. Further, the LiDAR device 1 may be used not only in moving bodies but also in various systems and other devices that utilize information (such as distance) obtained from the LiDAR device 1 of advanced road traffic systems (ITS), monitoring systems, smartphones, etc.

[0086] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0087] According to each embodiment, it is possible to provide a scanning device, a distance measuring device, a moving body-mounted system, a control method for a scanning device, and a program that can suppress a decrease in control performance even when the transfer characteristics of a two-axis MEMS mirror change.

[0088] The disclosure of each embodiment includes the following configurations and methods. (Configuration 1) Scanning means for two-dimensionally scanning electromagnetic waves, Updating means for updating the transfer function matrix of the scanning means, A scanning device, comprising control means for controlling the scanning means based on the updated transfer function matrix. (Configuration 2) The scanning device according to Configuration 1, wherein the scanning means is a MEMS mirror that can rotate around two axes respectively. (Configuration 3) The scanning device further includes driving means for driving the scanning means, The driving means drives the MEMS mirror around the two axes based on a first driving signal related to a first direction and a second driving signal related to a second direction different from the first direction, according to the scanning device described in Configuration 2. (Configuration 4) The transfer function matrix is represented by using a transfer function from the first driving signal to a displacement in the first direction, a transfer function from the second driving signal to a displacement in the first direction, a transfer function from the first driving signal to a displacement in the second direction, and a transfer function from the second driving signal to a displacement in the second direction, according to the scanning device described in Configuration 3. (Configuration 5) The first driving signal is a horizontal driving signal, The second driving signal is a vertical driving signal, The displacement in the first direction is a horizontal displacement, The displacement in the second direction is a vertical displacement, according to the scanning device described in Configuration 4. (Configuration 6) The scanning means has a first sensor that detects an inclination angle in a first direction and outputs a first signal, and a second sensor that detects an inclination angle in a second direction different from the first direction and outputs a second signal, The control means, acquires respective harmonic coefficients of the first signal and the second signal, and controls the scanning means based on the harmonic coefficients, harmonic coefficients of a target displacement, and the transfer function matrix, according to the scanning device described in any one of Configurations 1 to 5. (Configuration 7) The scanning device according to any one of Configurations 1 to 6 further has a determination means for determining an update timing of the transfer function matrix by the update means. (Configuration 8) The determination means controls the update timing of the transfer function matrix based on vehicle information output by a vehicle information acquisition device, according to the scanning device described in Configuration 7. (Configuration 9) A scanning device according to any one of Configurations 1 to 8, and A distance measuring device, comprising distance measuring means for obtaining distance information to the object based on a signal electromagnetic wave reflected by the object. (Configuration 10) A mobile body-mounted system, characterized by having the distance measuring device according to Configuration 9. (Method 1) A step of two-dimensionally scanning an electromagnetic wave using scanning means; A step of updating the transfer function matrix of the scanning means; A method for controlling a scanning device, comprising a step of controlling the scanning means based on the updated transfer function matrix. (Configuration 11) A program, characterized in that a computer executes the method for controlling a scanning device according to Method 1.

[0089] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

Description of Reference Numerals

[0090] 1 LiDAR device (scanning device) 400 MEMS mirror (scanning means) 1100 Normal scanning control unit (control means) 1300 Transfer function measurement unit (updating means)

Claims

1. Scanning means for two-dimensionally scanning an electromagnetic wave, Updating means for updating the transfer function matrix of the scanning means, A scanning device comprising control means for controlling the scanning means based on the updated transfer function matrix.

2. The scanning device according to claim 1, wherein the scanning means is a MEMS mirror rotatable about two axes respectively.

3. The scanning device further comprises driving means for driving the scanning means, The driving means drives the MEMS mirror about the two axes based on a first driving signal regarding a first direction and a second driving signal regarding a second direction different from the first direction. The scanning device according to claim 2.

4. The transfer function matrix is represented by using a transfer function from the first driving signal to a displacement in the first direction, a transfer function from the second driving signal to a displacement in the first direction, a transfer function from the first driving signal to a displacement in the second direction, and a transfer function from the second driving signal to a displacement in the second direction. The scanning device according to claim 3.

5. The first driving signal is a horizontal driving signal, The second driving signal is a vertical driving signal, The displacement in the first direction is a horizontal displacement, The displacement in the second direction is a vertical displacement. The scanning device according to claim 4.

6. The scanning means has a first sensor for detecting an inclination angle in a first direction and outputting a first signal, and a second sensor for detecting an inclination angle in a second direction different from the first direction and outputting a second signal, The control means, Obtains harmonic coefficients of each of the first signal and the second signal, Controls the scanning means based on the harmonic coefficients, harmonic coefficients of a target displacement, and the transfer function matrix. The scanning device according to any one of claims 1 to 5.

7. The scanning device according to any one of claims 1 to 5, further comprising determining means for determining an update timing of the transfer function matrix by the updating means.

8. The determining means controls the update timing of the transfer function matrix based on vehicle information output by a vehicle information acquisition device. The scanning device according to claim 7.

9. A ranging device comprising the scanning device according to any one of claims 1 to 5, And ranging means for obtaining distance information to the object based on a signal electromagnetic wave reflected by the object.

10. A mobile body-mounted system comprising the distance measuring device according to claim 9.

11. Scanning electromagnetic waves two-dimensionally using scanning means; Updating the transfer function matrix of the scanning means; Controlling the scanning means based on the updated transfer function matrix, characterized by a control method for a scanning device having the steps.

12. A program characterized by causing a computer to execute the control method for a scanning device according to claim 11.

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