JP7152147B2 - rangefinder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rangefinder, and more particularly to a rangefinder that performs optical range finding.

2. Description of the Related Art Ranging devices are known that scan a target area with light to measure the distance to an object. Such a rangefinder has, for example, a light source that emits a laser pulse, a scanning mechanism that reflects and scans the laser pulse, and a light receiving section that receives the laser pulse reflected by an object. . Then, the distance measuring device measures the distance to the object based on the emitted laser pulse and the laser pulse received by the light receiving section.

For example, Patent Literature 1 discloses a light scanning unit that has a light reflecting surface and can perform Lissajous scanning of light incident on the light reflecting surface within a target area, and a pulsed light emitted from a light source that is reflected by an object. a light-receiving unit for receiving the reflected light, and a distance measuring unit for measuring the distance to the object based on the timing of emitting the pulsed light from the light source unit and the timing of receiving the reflected light from the light-receiving unit. A range device is disclosed.

JP 2011-53137 A

When the distance measuring device as described above is mounted on a moving object such as a vehicle, it may be required to perform measurement in a scanning mode according to the running state of the moving object. For example, depending on the driving conditions, it may be necessary to perform more detailed measurements on part of the target area.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points. One of the purposes is to provide a device.

According to a first aspect of the present invention, there is provided a distance measuring device mounted on a moving body that receives reflected light of projected light reflected by an object and measures a distance to the object, the distance measuring device comprising: and a scanning mode of the light emitting section between a first scanning mode and a second scanning mode capable of scanning more densely than the first scanning mode. and a control unit for switching between scanning modes, wherein the control unit acquires running state information indicating a running state of the moving body, and switches the scanning mode based on the running state information. .

An eleventh aspect of the present invention provides a reflecting member that is capable of swinging about two axes and capable of switching between a resonant mode and a non-resonant mode in operation mode about each axis, and the reflecting member. a light source that emits light toward the light source, a light receiving unit that receives the light reflected by the object after being reflected by the reflecting member, and based on the time when the light is emitted and the time when the light is received, the a distance measuring unit that calculates the distance to an object; It is characterized by switching based on state information.

1 is a block diagram showing the configuration of a distance measuring device according to an embodiment; FIG. 4 is a top view of the optical scanning unit according to the example; FIG. 3 is a cross-sectional view of an optical scanning unit according to an example; FIG. 4A and 4B are diagrams illustrating an example of waveforms of driving signals applied to an optical scanning unit and scanning trajectories of pulsed light by the optical scanning unit according to the embodiment; FIG. 4A and 4B are diagrams illustrating an example of waveforms of driving signals applied to an optical scanning unit and scanning trajectories of pulsed light by the optical scanning unit according to the embodiment; FIG. 4A and 4B are diagrams illustrating an example of waveforms of driving signals applied to an optical scanning unit and scanning trajectories of pulsed light by the optical scanning unit according to the embodiment; FIG. FIG. 5 is a diagram showing an example of contents of a scanning mode according to the embodiment; FIG. 5 is a diagram showing an example of running state information suitable for a scanning mode according to the embodiment; 4 is a flow chart showing an example of a routine executed by the distance measuring device according to the embodiment;

A configuration of a distance measuring device 10 according to an embodiment will be described with reference to FIG. The rangefinder 10 is an optical rangefinder that is mounted on a mobile object such as a vehicle and optically measures the distance to an object. FIG. 1 schematically shows an object OB whose distance is to be measured by the distance measuring device 10 together with the distance measuring device 10 for the sake of explanation. Also, paths of light related to measurement by the distance measuring device 10 are shown as L1, L2, and L3.

The light source 11 is, for example, a light-emitting element such as a laser diode, and emits pulsed light L1.

The optical system 12 is provided on the optical path of the pulsed light L1. The optical system 12 is an optical system including an optical member such as a collimator lens, and converts the pulsed light L1 emitted from the light source 11 into parallel light.

The beam splitter 13 is provided on the optical path of the pulsed light L1 emitted from the light source 11 and converted into parallel light by the optical system 12 . The beam splitter 13 is arranged so as to transmit or reflect incident light incident on the beam splitter 13 in a predetermined direction.

The optical scanning unit 15 is provided on the optical path of the pulsed light L1 emitted from the light source 11 and transmitted through the optical system 12 and the beam splitter 13 . The optical scanning unit 15 is a MEMS (Micro Electro Mechanical Systems) mirror having a light reflecting film 16 . The optical scanning unit 15 is configured to electromagnetically oscillate the light reflecting film 16 .

The light reflecting film 16 is a reflecting member having a light reflecting surface 16A. The pulsed light L1 emitted from the light source 11 and converted into parallel light by the optical system 12 passes through the beam splitter 13 and is reflected by the light reflecting surface 16A. The light reflecting surface 16A reflects the pulsed light L1 to generate scanning light (ranging light) L2.

When the light reflecting film 16 is electromagnetically oscillated, the direction of the light reflecting surface 16A changes, and the direction in which the pulse light L1 is reflected by the light reflecting surface 16A, that is, the direction in which the scanning light L2 is emitted changes. The optical scanning unit 15 scans a predetermined area with the scanning light L2 by changing the direction in which the scanning light L2 is emitted. That is, the light source 11 and the optical scanning section 15 function as a light emitting section that emits the scanning light L2.

For example, the predetermined area is an area determined according to the angular range in which the light reflecting film 16 can swing. In FIG. 1, the inside of the predetermined area is shown as a scanning target area R0. Further, in FIG. 1, a virtual plane separated from the optical scanning unit 15 by a predetermined distance in the scanning target region R0 is shown as a scanning target plane R1.

The scanning light L2 is emitted toward a scanning target region R0, which is a scanning target region. When an object OB (an object or fluid having the property of reflecting the pulsed light L1) exists on the optical path of the scanning light L2 in the scanning target region R0, the scanning light L2 is irradiated (projected) onto the object OB and reflected. be done. The reflected light L3, which is the scanning light L2 reflected by the object OB, returns to the light reflecting film 16. FIG. Then, the reflected light L3 is reflected by the light reflecting surface 16A and is reflected by the beam splitter 13 .

The light receiving section 18 is a photodetector arranged on the optical path of the reflected light L3 reflected by the beam splitter 13 . For example, the light receiving section 18 is a light receiving element such as a photodiode, and generates an electric signal as a light receiving signal based on the intensity of light incident on the light receiving section 18 . The generated received light signal is supplied to the controller 20 . Thus, the reflected light L3 reflected by the beam splitter 13 is received by the light receiving section 18 and detected.

The control unit 20 performs control necessary for the operation of the distance measuring device 10 . The control unit 20 includes a central processing unit (CPU) and a storage device such as an erasable/writable HDD (Hard Disk Drive).

The controller 20 includes a light source controller 20A. The light source control section 20A is a functional section that generates drive signals for driving the light source 11 . The light source 11 emits the pulsed light L1 according to the drive signal generated by the light source controller 20A.

The controller 20 also includes a scan controller 20B. The scanning control section 20</b>B is a functional section that generates a drive signal for causing the optical scanning section 15 to swing the light reflection film 16 and supplies the drive signal to the optical scanning section 15 . The drive signal causes the light reflecting film 16 to oscillate, and the direction in which the pulsed light L1 is reflected by the light reflecting surface 16A changes. The optical scanning unit 15 scans a predetermined area with the scanning light L2 by changing the reflection direction of the pulsed light L1 according to a signal from the scanning control unit 20B.

Further, the control section 20 includes a distance measuring section 20C. The distance measuring unit 20C is a functional unit that measures the distance between the light receiving unit 18 and the object OB based on the pulsed light L1 emitted by the light source 11 and the reflected light L3 received by the light receiving unit 18. For example, the distance measurement unit 20C performs distance measurement of the object OB using the time-of-flight method. That is, the distance measurement section 20C functions as a distance measurement section.

For example, the distance measurement unit 20C detects the object OB from the distance measurement device 10 based on the difference between the time (timing) when the light source 11 emits the pulsed light L1 and the timing when the light receiving unit 18 receives the reflected light L3. Measure (calculate) the distance to The light source control unit 20A supplies a signal indicating the timing at which the light source 11 emits the pulsed light L1 to the distance measurement unit 20C. Also, the timing at which the light receiving section 18 receives the reflected light L3 is specified based on the received light signal supplied from the light receiving section 18 .

Furthermore, the control unit 20 includes a determination unit 20D. The determination unit 20</b>D acquires, from the outside of the range finder 10 , running state information indicating the running state of the moving body on which the range finder 10 is mounted. For example, the determination unit 20D acquires the running state information from another device or GPS mounted on the mobile body. The determination unit 20D functions as an acquisition unit that acquires driving state information.

For example, the running state information includes the speed and acceleration of the moving object and the brightness around the moving object. The determination unit 20D acquires the measurement results of the velocity and acceleration of the mobile body from the mobile body or the speedometer and accelerometer mounted on the mobile body.

Further, for example, the running state information may include a distance to an object (for example, a preceding vehicle or the like) existing in the traveling direction of the moving object. The determination unit 20D acquires the measurement result of the distance from the moving body to the object from a distance measuring device such as a millimeter wave radar mounted on the moving body.

Further, the determination unit 20D determines whether or not it is necessary to switch the scanning pattern when the optical scanning unit 15 scans the scanning target region R0, based on the running state information. The scanning control section 20B controls the scanning pattern of the optical scanning section 15 according to the determination result of the determination section 20D.

A configuration example of the optical scanning unit 15 will be described with reference to FIGS. 2A and 2B. FIG. 2A is a schematic top view of the optical scanning unit 15. FIG. FIG. 2B is a cross-sectional view along line VV of FIG. 2A.

As shown in FIGS. 2A and 2B, the fixed part 21 includes a fixed substrate B1 and a fixed frame B2 which is an annular frame formed on the fixed substrate B1. As shown in FIG. 2B, the fixed substrate B1 has, on the top surface B1S of the fixed substrate B1, a projecting portion B1P having a frame-like planar shape in a region facing the fixed frame B2, and fixed on the projecting portion B1P. It has a configuration in which a frame B2 is placed.

The movable portion 22 is arranged inside the fixed frame B2 and includes a swing plate SY and a swing frame SX surrounding the swing plate SY. A circular light reflecting film 16 is provided on the rocking plate SY. Hereinafter, the upper surface of the light reflecting film 16, that is, the center of the light reflecting surface 16A will be described as AC.

The swing frame SX is connected to the fixed frame B2 by a first torsion bar TX. The first torsion bar TX is a pair of long plate-like structural portions extending along a first swing axis AX passing through the center AC of the light reflecting surface 16A and extending in the in-plane direction of the light reflecting surface 16A. be. When a force around the swing axis AX is applied to the swing frame SX, the first torsion bar TX is twisted, and the swing frame SX moves around the first swing axis AX, that is, the first swing axis AX. It oscillates as the central axis of oscillation. The swing frame SX has a line-symmetrical shape about the first swing axis AX.

The swing plate SY is connected to the swing frame SX by a second torsion bar TY. The second torsion bar TY passes through the center AC of the light reflecting film, extends in the in-plane direction of the light reflecting surface 16A, and extends along a second swing axis AY perpendicular to the first swing axis AX. It is a pair of long plate-like structural parts that extend in parallel with each other. When a force around the swing axis AY is applied to the swing frame SY, the second torsion bar TY is twisted, and the swing frame SY is centered around the second swing axis AY, that is, the second swing axis AY. It oscillates as the central axis of oscillation. The rocking plate SY has a line-symmetrical shape about the rocking axis AY.

Therefore, the rocking plate SY rocks around the rocking axes AX and AY that are perpendicular to each other. The direction in which the light reflection surface 16A faces is changed by the oscillation of the oscillation plate SY. That is, the light reflecting film 16 is a reflecting member having a reflecting surface and configured to be able to swing.

As described above, the movable part 22 is connected to the fixed frame B2, and the fixed frame B2 is placed on the protrusion B1P of the fixed substrate B1. Therefore, the movable part 22 is separated from the upper surface B1S of the fixed substrate B1. When the swing frame SX swings around the swing axis AX and the swing plate SY swings around the swing axis AY, the movable part 22 swings so as to be inclined with respect to the fixed frame B2. do. The projecting portion B1P is formed with a sufficient height such that the movable portion 22 does not come into contact with the upper surface B1S due to the swinging. In addition, for example, the fixed frame B2 and the movable portion 22 may be an integral structure formed by processing one semiconductor substrate.

The driving force generator 23 includes a permanent magnet MG1 and a permanent magnet MG2 arranged outside the projecting portion B1P on the fixed substrate B1, and a metal wire routed on the swing frame SX along the outer periphery of the swing frame SX. It includes a wiring (first coil) CX and a metal wiring (second coil) CY that is routed on the oscillating plate SY along the outer circumference of the oscillating plate SY.

The permanent magnet MG1 is a pair of magnet pieces arranged on the swing axis AX and facing each other with the movable portion 22 interposed therebetween. In addition, the permanent magnet MG2 is a pair of magnet pieces arranged on the swing axis AY and facing each other with the movable portion 22 interposed therebetween. Therefore, in this embodiment, four magnet pieces are arranged so as to surround the movable portion 22 .

Also, the two magnet pieces forming the permanent magnet MG1 are arranged so that the portions exhibiting opposite polarities face each other. Similarly, the two magnet pieces forming the permanent magnet MG2 are arranged such that the portions exhibiting opposite polarities face each other.

The scanning control section 20B is connected to the metal wirings CX and CY. The scanning control unit 20B supplies currents (driving signals) to the metal wires CX and CY. The drive force generation unit 23 generates an electromagnetic force for swinging the swing frame SX and the swing plate SY of the movable unit 22 by applying the drive signal.

Specifically, when a current flows through the metal wiring CX, interaction between the current and the magnetic field generated by the two magnet pieces of the permanent magnet MG1 arranged in the direction along the oscillation axis AY causes oscillation. A force around the swing axis AX is applied to the frame SX. Thereby, the first torsion bar TX is twisted around the swing axis AX, and the swing frame SX swings around the swing axis AX.

Further, when a current flows through the metal wiring CY, the interaction between the current and the magnetic field generated by the two magnet pieces of the permanent magnet MG2 arranged in the direction along the oscillation axis AX causes the oscillation plate SY to oscillate. A force is applied about the axis AY. Thereby, the second torsion bar TY is twisted about the swing axis AY, and the swing plate SY swings about the swing axis AY.

FIG. 3 shows driving signals DX and DY generated by the scanning control unit 20B when the optical scanning unit 15 scans by Lissajous scanning, which is the first scanning pattern, and scanning light scanned by the optical scanning unit 15 based on these signals. The relationship with the scanning trajectory of L2 is schematically shown.

In the following description, the drive signal DX is described as a drive signal generated by the scanning control section 20B and supplied to the metal wiring CX. As a result, the swing frame SX swings around the swing axis AX. Further, in the following description, the drive signal DY is described as a drive signal generated by the scanning control section 20B and supplied to the metal wiring CY. As a result, the rocking plate SY rocks around the rocking axis AY.

In the following description, it is assumed that the drive signal DX and the drive signal DY have the same amplitude (AMP=1 in the figure).

In FIG. 3, (a) shows a scanning trajectory TR when scanning is performed on the scanning target surface R1 shown in FIG. 1 so as to draw a Lissajous trajectory. AX1 and AY1 in the drawing correspond to the swing axis AX and the swing axis AY of the optical scanning unit 15, respectively. That is, the oscillation of the optical scanning unit 15 about the oscillation axis AX corresponds to the change in the scanning position in the direction along AY1 on the scanning target surface R1. Further, the oscillation of the optical scanning unit 15 about the oscillation axis AY corresponds to the change in the scanning position in the AX1 direction on the scanning target surface R1.

(b) of FIG. 3 schematically shows the waveform of the drive signal DX during the Lissajous scanning shown in (a) of FIG. _The drive signal DX in FIG. 3B is _a sine represented by the formula DX( _θ1 )=A1 sin( _θ1 + _B1 ) where A1 and _B1 are constants and θ1 is _a variable. It is a wave signal. The variable θ ₁ corresponds to the natural frequency of the swing frame SX and the swing plate SY supported by the fixed frame B2 by the first torsion bar TX of the optical scanning unit 15, and the drive signal DX is set to resonate. It is set to be a sine wave of the frequency that

FIG. 3(c) schematically shows the waveform of the driving signal DY during the Lissajous scanning shown in FIG. 3(a). The drive signal DY is a sinusoidal signal represented by the formula DY ₍ θ2) _{= A2} sin ₍ θ2 ₊ B2) where _A2 and B2 _are constants and θ2 is a variable. The variable θ ₂ is set so that the drive signal DY becomes a sine wave of a frequency that corresponds to the natural frequency of the oscillation plate SY of the optical scanning unit 15 and causes it to resonate.

Therefore, the swing frame SX and the swing plate SY are swung while resonating about the swing axis AX by the drive signal DX. That is, it is driven in a resonance mode operation mode centering on the swing axis AX. Further, the rocking plate SY is rocked while resonating about the rocking axis AY by the driving signal DY. That is, it is driven in a resonance mode operation mode centering on the swing axis AY. Accordingly, the rocking plate SY rocks about the rocking axis AX and rocks about the rocking axis AY. The direction in which the light reflection film 16 faces changes according to the oscillation of the oscillation plate SY. Therefore, the scanning light L2 (see FIG. 1) emitted from the light source and reflected by the light reflecting film 16 is emitted to the scanning target area R0 while changing the emission direction according to the oscillation of the oscillating plate SY.

As shown in FIG. 3, the trajectory TR of the point (spot position) at which the scanning light L2 reaches the scanning target surface R1 is determined by the oscillation of the oscillation plate SY around the oscillation axis AX and the oscillation axis AY as described above. Since it oscillates while swaying, it becomes a trajectory that draws a Lissajous curve. The Lissajous curve extends over the entire scanning target surface R1, the trajectory is concentrated at the ends of the scanning target surface R1 in the direction along AX1, and approaches the center of the scanning target surface R1 in the direction along AX1. As the distance increases, the distance between the loci tends to be wider than that at the end.

4A and 4B show drive signals DX and DY generated by the scanning control unit 20B when the optical scanning unit 15 scans the scanning light L2 by raster scanning, which is a second scanning pattern different from the scanning pattern in FIG. and the scanning trajectory of the scanning light L2 scanned by the optical scanning unit 15 based thereon.

As described above, the drive signal DX is a drive signal generated by the scanning control section 20B and supplied to the metal wiring CX. As a result, the swing frame SX swings around the swing axis AX. Further, the drive signal DY is a drive signal generated by the scanning control section 20B and supplied to the metal wiring CY. As a result, the rocking plate SY rocks around the rocking axis AY.

In FIG. 4A, (a) shows a scanning trajectory TR when scanning is performed by drawing a raster trajectory on the scanning target surface R1 shown in FIG. As in FIG. 3, AX1 and AY1 in the figure correspond to the swing axis AX and swing axis AY of the optical scanning unit 15, respectively. The oscillation of the optical scanning unit 15 about the oscillation axis AX corresponds to the change in the scanning position in the direction along AY1 on the scanning target surface R1. Further, the oscillation of the optical scanning unit 15 about the oscillation axis AY corresponds to the change in the scanning position in the AX1 direction on the scanning target surface R1.

(b) of FIG. 4A schematically shows the waveform of the drive signal DX during the raster scanning shown in (a) of FIG. 4A. The drive signal DX in (b) of FIG. 4A is a sine represented by the formula DX(θ ₁ )=A ₁ sin (θ ₁ +B ₁ ) where A ₁ and B ₁ are constants and θ ₁ is a variable. It is a wave signal. The variable θ ₁ corresponds to the natural frequency of the swing frame SX and the swing plate SY supported by the fixed frame B2 by the first torsion bar TX of the optical scanning unit 15, and the drive signal DX is set to resonate. It is set to be a sine wave of the frequency that

(c) of FIG. 4A schematically shows the waveform of the drive signal (second drive signal) DY during raster scanning shown in (a) of FIG. 4A. The drive signal DY is a sawtooth wave signal. The drive signal DY is generated to be a sawtooth wave having a frequency (non-resonance) that does not correspond to the natural frequency of the oscillation plate SY of the optical scanning unit 15 and does not resonate it. For example, the driving vibration DY is DY(θ2) _{= 2} /π[ _{sinA2θ2 +} 1/ _{2sin2A2θ2 + 1} , where _A2 is a constant, B2 is an arbitrary integer, and θ2 is a variable. /3 sin3A ₂ θ ₂ + 1/B ₂ sin B ₂ A ₂ θ ₂ ].

The drive signal DY is not limited to the sawtooth wave described above, and may be a triangular wave or a sine wave having a frequency (non-resonant) that does not correspond to the natural frequency of the oscillating plate SY of the optical scanning unit 15 and does not cause it to resonate. There may be.

During the raster scanning of FIG. 4A, the rocking plate SY is rocked while resonating about the rocking axis AX by the driving signal DX. Further, the rocking plate SY is rocked around the rocking axis AY by the drive signal DY without resonating. That is, the raster scanning in FIG. 4A is raster scanning in which the driving of the oscillating plate SY about the oscillating axis AY is in the non-resonant mode, and the driving of the oscillating plate SY about the oscillating axis AX is in the resonant mode.

Accordingly, the rocking plate SY rocks about the rocking axis AX and rocks about the rocking axis AY. The direction in which the light reflection film 16 faces changes according to the oscillation of the oscillation plate SY. Therefore, the scanning light L2 (see FIG. 1) emitted from the light source and reflected by the light reflecting film 16 is emitted to the scanning target area R0 while changing the emission direction according to the oscillation of the oscillating plate SY.

As described above, the rocking plate SY rocks while resonating about the rocking axis AX. Further, the amplitude of the drive signal DX is equivalent to the amplitude of the drive signal X shown in FIG. 3(b). In this case, the magnitude of rocking of rocking plate SY around rocking axis AX, ie, the angle, is the same as in the case shown in FIG. 3(a). Therefore, the scanning trajectory TR of the scanning light L2 on the scanning target surface R1 is drawn in a wide range in the direction along AY1.

Further, as described above, the rocking plate SY rocks around the rocking axis AY without resonating. Further, the amplitude of the drive signal DY is the same as the amplitude of the drive signal Y shown in FIG. 3(c). In this case, the magnitude of rocking plate SY about rocking axis AY, that is, the angle, is compared with the case where rocking plate SY resonates and rocks about rocking axis AY (FIG. 3). and become smaller. Therefore, the scanning trajectory TR of the scanning light L2 on the scanning target surface R1 is drawn in a narrow range along the AX1 direction.

Therefore, the scanning trajectory in (a) of FIG. 4A is drawn in the raster scanning area RAY, which is a narrow range along the direction along AX1. The scanning trajectory is concentrated in a narrow range along the direction along AX1 in the raster scanning area RAY. In this manner, the raster scanning area RAY can be scanned at a high density by raster scanning in which the oscillation plate SY is driven around the oscillation axis AY in the non-resonant mode.

In FIG. 4B, (a) shows a scanning trajectory TR by raster scanning of the scanning target surface R1 shown in FIG. AX1 and AY1 in the drawing correspond to the swing axis AX and the swing axis AY of the optical scanning unit 15, respectively. The oscillation of the optical scanning unit 15 about the oscillation axis AX corresponds to the change in the scanning position in the direction along AY1 on the scanning target surface R1. Further, the oscillation of the optical scanning unit 15 about the oscillation axis AY corresponds to the change in the scanning position in the AX1 direction on the scanning target surface R1.

(b) of FIG. 4B schematically shows the waveform of the driving signal DX during the raster scanning shown in (a) of FIG. 4B. The drive signal (first drive signal) DX in (b) of FIG. 4B is a sawtooth wave signal. The drive signal DX does not correspond to the natural frequencies of the swing frame SX and the swing plate SY supported by the fixed frame B2 by the first torsion bar TX of the optical scanning unit 15, and has a frequency that does not cause them to resonate. generated to be a sawtooth wave.

When A1 and B1 are arbitrary integers and θ1 is _a variable, the drive signal DX is DY(θ1)= _{2 /} π[ _sinA1θ1 + _{1 / 2sin2A1θ1} + _{1 / 3sin3A1θ1} + 1/B ₁ sin B ₁ A ₁ θ ₁ ].

(c) of FIG. 4B schematically shows the waveform of the drive signal (second drive signal) DY during the raster scanning shown in (a) of FIG. 4B. The drive signal DY is a sinusoidal signal represented by the formula DY ₍ θ2) _{= A2} sin ₍ θ2 ₊ B2) where _A2 and B2 _are constants and θ2 is a variable. The variable θ ₂ is set so that the drive signal DY becomes a sine wave of a frequency that corresponds to the natural frequency of the oscillation plate SY of the optical scanning unit 15 and causes it to resonate.

During the raster scanning of FIG. 4B, the rocking plate SY is rocked around the rocking axis AX by the driving signal DX without resonating. Further, the rocking plate SY is rocked while resonating about the rocking axis AY by the driving signal DY. That is, the raster scanning in FIG. 4B is raster scanning in which the driving of the oscillating plate SY about the oscillating axis AX is in the non-resonant mode and the driving of the oscillating plate SY about the oscillating axis AY is in the resonant mode.

Accordingly, the rocking plate SY rocks about the rocking axis AX and rocks about the rocking axis AY. That is, the oscillating plate SY provided with the light reflecting film 16 can oscillate about two axes. The direction in which the light reflection film 16 faces changes according to the oscillation of the oscillation plate SY. Therefore, the scanning light L2 (see FIG. 1) emitted from the light source and reflected by the light reflecting film 16 is emitted to the scanning target area R0 while changing the emission direction according to the oscillation of the oscillating plate SY.

As described above, the rocking plate SY rocks around the rocking axis AX without resonating. Further, the amplitude of the drive signal DX is equivalent to the amplitude of the drive signal DX shown in FIG. 3(b). In this case, the magnitude at which the rocking plate SY rocks about the rocking axis AX, that is, the angle is and FIG. 4A(b)). Therefore, the scanning trajectory TR of the scanning light L2 on the scanning target surface R1 is drawn in a narrow range in the direction along AY1.

Further, as described above, the rocking plate SY rocks while resonating about the rocking axis AY. Further, the amplitude of the drive signal DY is equivalent to the amplitude of the drive signal DY shown in (c) of FIG. In this case, the magnitude of rocking of rocking plate SY around rocking axis AY, ie, the angle, is the same as in the case shown in FIG. 3(a). Therefore, the scanning trajectory TR of the scanning light L2 on the scanning target surface R1 is drawn in a wide range along the AX1 direction.

Therefore, the scanning trajectory in (a) of FIG. 4B is drawn in the raster scanning area RAX, which is a narrow range in the direction along AY1. The scanning trajectory is concentrated in a narrow range in the direction along AY1 in the raster scanning area RAX. In this manner, the raster scanning area RAX can be scanned at a high density by raster scanning in which the oscillation plate SY is driven around the oscillation axis AX in the non-resonance mode.

As shown in FIGS. 4A and 4B, the optical scanning unit 15 causes the oscillation plate SY to resonate about one of the oscillation axis AX and the oscillation axis AY in scanning according to the second scanning pattern. It is driven to oscillate while rotating (resonant mode), and driven to oscillate about the other axis without resonating (non-resonant mode).

When the optical scanning unit 15 is driven by signals of the same amplitude, the scanning trajectory of the second scanning pattern is denser than the scanning trajectory of the first scanning pattern in a narrower area within the scanning target surface R1. The scanning trajectory becomes Therefore, the second scan pattern allows denser scanning than the first scan pattern.

The scanning control section 20B can switchably supply the driving signal DX and the driving signal DY corresponding to the first scanning pattern or the second scanning pattern to the optical scanning section 15 . Therefore, the scanning pattern of the scanning light L2 by the optical scanning unit 15 can be switched between the first scanning pattern and the second scanning pattern that enables denser scanning than the first scanning pattern.

The optical scanning unit 15 sets the oscillation of the oscillation plate SY centered on either of the oscillation axis AX and the oscillation axis AY to the non-resonant mode, so that a high-density scanning trajectory in a narrower range is obtained. Scanning patterns are good. For example, the scanning control unit 20B supplies the drive signal DY shown in (c) of FIG. 4A and the drive signal DX shown in (b) of FIG. Areas where areas RAX and RAY overlap can be locally scanned at higher densities.

An example of the scanning mode of the optical scanning unit 15 executed using either one or both of the Lissajous scanning as the first scanning pattern and the raster scanning as the second scanning pattern will be described with reference to FIG. 5A. . FIG. 5A shows specific scanning contents executed in each scanning mode.

As described above, the scanning pattern by the optical scanning unit 15 can be switched between Lissajous scanning and raster scanning. Further, in raster scanning by the optical scanning unit 15, vertical raster scanning for scanning the raster scanning area RAY shown in FIG. 4A and horizontal raster scanning for scanning the raster scanning area RAX shown in FIG. 4B are possible.

In the first scanning mode, only Lissajous scanning is used. In FIG. 5A, "Lissajous scanning" is described as a specific scanning content corresponding to the "first scanning mode".

In a second scanning mode, a scanning pattern is used that includes raster scanning. In FIG. 5A, "vertical raster scanning" for executing only vertical raster scanning and "horizontal raster scanning" for executing only horizontal raster scanning are described as the contents of the "second scanning mode".

“Combination of vertical raster scanning and horizontal raster scanning” in FIG. 5A indicates that vertical raster scanning and horizontal raster scanning are alternately repeated.

For example, in raster scanning, the start to end of one scan of the entire raster scanning area RAY is defined as one cycle of vertical raster scanning, and the start to end of one scan of the entire raster scanning area RAX is defined as one cycle of horizontal raster scanning. Assuming one cycle, vertical raster scanning with a predetermined cycle and horizontal raster scanning with a predetermined cycle can be alternately repeated. That is, vertical raster scanning and horizontal raster scanning can be combined in units of scanning cycles. As a result, it is possible to supplement and scan an area that can be scanned by horizontal raster scanning among the areas that cannot be scanned by vertical raster scanning.

Also, “combination of Lissajous scanning and raster scanning” in FIG. 5A indicates combining Lissajous scanning with one or both of vertical raster scanning and horizontal raster scanning. For example, the start to end of one scan of the entire scanning target surface R1 by Lissajous scanning may be defined as one period, and Lissajous scanning, vertical raster scanning, and horizontal raster scanning may be repeated at predetermined intervals. As a result, Lissajous scanning can compensate for the scanning of areas that are not scanned by vertical or horizontal raster scanning.

In other words, the second scanning mode is a scanning mode that performs scanning including raster scanning that enables denser scanning than Lissajous scanning. Therefore, a denser scan can be performed in the second scanning mode than in the first scanning mode. In this way, the control unit 20 sets the scanning mode of the scanning light for the scanning of the optical scanning unit 15 to the first scanning mode and the second scanning mode, which enables denser scanning than the first scanning mode. can be switched between.

With reference to FIG. 5B, the driving state information indicating the driving state of the mobile object acquired by the determination unit 20D in the range finder 10 and the criteria for determining the scanning mode suitable for each of the driving state information by the determination unit 20D will be described. . FIG. 5B shows items of "speed (km/h)", "distance to object (m)", and "surrounding brightness (lx)" as the running state information. For each item, an example of conditions when the first scanning mode is suitable and an example of conditions when the second scanning mode is suitable are described. For example, a table as shown in FIG. 5B is stored in a storage device (not shown) included in the control unit 20 .

"Speed (km/h)" indicates the traveling speed at which the moving object equipped with the range finder 10 is traveling. The determination unit 20D acquires information on the speed of the moving body on which the range finder 10 is mounted from the moving body or a device mounted on the moving body. In FIG. 5B, the first scanning mode is suitable when the speed of the moving body is less than 80 km/h, and the second scanning mode is suitable when the speed of the moving body is 80 km/h or more. shown to be suitable.

For example, when the speed of the moving object exceeds 80 km/h, the determination unit 20D of the control unit 20 causes the light scanning unit 15 to scan the scanning light based on the criteria shown in FIG. Switch from the scanning mode to the second scanning mode. For example, when the mobile body travels on a highway, it may be considered that dense scanning is more effective for the area in the traveling direction of the mobile body than for the periphery of the mobile body. In such a case, by switching to the second scanning mode, it is possible to perform distance measurement by scanning more suitable for the running state.

"Distance to object (m)" indicates the distance to an object existing in the moving direction of the moving object. The determination unit 20D acquires the distance measurement result from the distance measuring device 10 to the object from the mobile object or from a distance measuring device such as a millimeter wave radar mounted on the mobile object.

For example, the determination unit 20D determines that the first scanning mode is suitable when the distance to the object is 5 m or more, and the second scanning mode is suitable when the distance to the object is less than 5 m. determine that there is Then, when the distance to the object is less than 5 m, the scanning of the scanning light of the optical scanning unit 15 is switched from the first scanning mode to the second scanning mode based on the criteria shown in FIG. 5B.

"Ambient brightness (lx)" indicates the brightness around the moving object, that is, the illuminance. The determining unit 20D acquires information on the degree of brightness with which the moving object is illuminated from an illuminometer mounted on the moving object.

For example, when the brightness around the moving object is 1000 lx (lux) or more, the background light is strong when the light receiving unit 18 receives the light, and the reflected light reflected by the object around the moving object is detected. Accuracy may decrease. In such cases, it is effective to perform a denser scan. In such a case, the determination unit 20D determines that the running state is suitable for switching to the second scanning mode. Then, the control unit 20 switches the scanning of the scanning light of the optical scanning unit 15 from the first scanning mode to the second scanning mode.

In addition, the determination unit 20D determines that one or more items of the three items of running state information of speed, distance to an object, and ambient lightness shown in FIG. 5B meet the conditions suitable for the second scanning mode. First, it is determined that the running state is suitable for switching to the second scanning mode. Such determination is referred to as determination based on the OR condition.

Alternatively, the determination unit 20D determines that, when all the items of the running state information of the three items of the speed, the distance to the object, and the ambient brightness shown in FIG. 5B correspond to the conditions suitable for the second scanning mode, It may be determined that the driving state is suitable for switching to scanning mode 2. Such determination is referred to as determination under AND conditions.

Also, each item of the running state information may be restricted in relation to other items. For example, when the surrounding brightness is 100 lux or less, that is, when the surroundings are dark, it can be considered that wide range measurement over the entire scanning target surface R1 by Lissajous scanning (first scanning mode) is suitable. can. In such a case, the control unit 20 changes the scanning mode of the scanning light of the optical scanning unit 15 from the first scanning mode even if the condition suitable for the second scanning mode is satisfied for other driving state information. It is also possible not to switch to the second scanning mode.

In this manner, the determination unit 20D of the control unit 20 can determine whether or not to switch from the first scanning mode to the second scanning mode based on the traveling state information of the moving body. The scanning control section 20B of the control section 20 can change the driving signal supplied to the optical scanning section 15 based on the determination result of the determining section 20D, and switch the scanning mode of the optical scanning section 15. FIG.

Note that the determination unit 20D may acquire information on the distance to the object from the distance measurement unit 20C. Further, the determination unit 20D may make a determination based on the acceleration of the moving body in addition to the speed of the moving body. As a result, it is possible to make a determination that reflects the running state such as a curve or sudden braking while the mobile body is running.

Further, the running state information may include the rudder angle of the steering wheel of the moving body. For example, when the rudder angle of the steering wheel is greater than a predetermined value, it can be assumed that the moving object is turning right or left at an intersection. In such cases, a combination of broad scanning and fine scanning can be considered effective. In this case, the determination unit 20D determines that the running state is suitable for the second scanning mode, and the control unit 20 switches the scanning mode of the scanning light of the optical scanning unit 15 to the second scanning mode, and Lissajous. Scanning that combines scanning and raster scanning may be performed. As a result, it is possible to make a determination that reflects the running state of the moving object in more detail.

In addition, the running state information may include the number of times the steering wheel of the moving body is turned within a predetermined time period, that is, the meandering frequency. For example, if the steering wheel is frequently turned, it can be considered that the vehicle is frequently avoiding obstacles or traveling on a meandering road. In this case, the determination unit 20 determines that the second scanning mode is suitable for the running state, and if the moving object is traveling straight, that is, if the steering wheel of the moving object has not been turned within a predetermined time, , determine that the first scanning mode is suitable for running. Thereby, the control unit 20 can switch the scanning mode according to the running state.

Also, the running state information may include the weather around the mobile object. In this case, the determination unit 20 determines that the running state is suitable for the first scanning mode when the weather is fine, and determines that the running state is suitable for the second scanning mode when it is raining. Thereby, the control unit 20 can switch the scanning mode according to the weather.

Also, the running state information may include the number of objects (other moving bodies, pedestrians, obstacles, etc.) existing around the moving body. In this case, the determination unit 20 determines that the running state is suitable for the first scanning mode when the number of objects present in the surroundings is less than or equal to a predetermined number, and determines that the running state is suitable for the second scanning mode when the number or more of the objects is greater than or equal to the predetermined number. is a suitable running state. Thereby, the control unit 20 can switch the scanning mode according to the circumstances around the moving body.

It should be noted that when switching to the second scanning mode, which of the four scanning contents included in the second scanning mode is to be used may be determined in advance. It may be determined according to the degree. For example, when the speed is 80 to 90 Km/h, vertical raster scanning or horizontal raster scanning is used, and when the speed is 90 to 100 Km/h, a combination of vertical raster scanning and horizontal raster scanning is used, and the speed is 100 Km/h. , a method of performing a combination of Lissajous scanning and raster scanning can be exemplified.

In this embodiment, one optical scanning unit 15 is configured to be able to perform both the first scanning mode and the second scanning mode. good. For example, two MEMS mirrors may be provided and the first scanning mode and the second scanning mode may be executed using separate MEMS mirrors (in this case, the light source 11, the optical system 12, It is desirable that the beam splitter 13 and the light receiving section 18 are also provided for each optical scanning section). By doing so, it is possible to provide a MEMS mirror dedicated to Lissajous scanning and a MEMS mirror dedicated to raster scanning, so that, for example, in raster scanning in the second scanning mode, the scanning target surface R1 can be scanned over the entire area. can. Furthermore, when performing a combination of Lissajous scanning and raster scanning in the second scanning mode, scanning can be performed simultaneously with each scanning method. Note that even when there are three or more scanning modes, the same number of MEMS mirrors as the number of scanning modes can be provided, and scanning can be performed using separate MEMS mirrors for each scanning mode.

[Ranging routine]
An example of the distance measurement routine RT1 executed by the control unit 20 in the distance measurement device 10 mounted on a moving body will be described with reference to FIG. When a distance measurement start operation is accepted by a switch operation (not shown) or the like, the control unit 20 instructs the light source control unit 20A to emit the pulsed light L1, and starts the distance measurement routine RT1. At the same time, the control section 20 instructs the scanning control section 20B to start scanning control in the first scanning mode of the optical scanning section 15 . Further, the control unit 20 instructs the distance measurement unit 20C to start calculating the distance to the object OB.

When starting the ranging routine RT1, the control unit 20 determines whether or not the running state is suitable for the second scanning mode (step S11). In step S11, the determination unit 20D of the control unit 20 determines whether or not the running state is suitable for the second scanning mode, based on the running state information of the moving body on which the range finder 10 is mounted.

For example, in step S11, the determination unit 20D acquires information about the speed at which the moving body is running, and determines whether the running state is suitable for the second scanning mode based on the speed as the running state information. judge. Further, for example, the traveling state information may include the distance to the object and the brightness of the surroundings in addition to the speed information (see FIG. 5B).

If one or more items of each of the three pieces of driving state information correspond to conditions suitable for the second scanning mode, it is determined that the driving state is suitable for switching to the second scanning mode. Determined by OR conditions. For example, the determination unit 20D of the control unit 20 determines that the running state is suitable for the second scanning mode when the speed of the moving object exceeds 80 km/h.

Also, an AND condition for determining that the running state is suitable for switching to the second scanning mode when all the items of the running state information of the three items correspond to the conditions suitable for the second scanning mode. , it may be determined whether the driving conditions are suitable for the second scanning mode.

For example, the determination unit 20D determines that the second scanning mode is suitable when the speed of the moving object is 80 km/h or more, the distance to the object is less than 5 m, and the ambient brightness is 1000 lux or more. It is determined that the vehicle is in a running state.

When the controller 20 determines in step S11 that the running state is not suitable for the second scanning mode (step S11: NO), it ends the ranging routine RT1 and starts a new ranging routine RT1.

When the controller 20 determines in step S11 that the traveling state is suitable for the second scanning mode (step S11: YES), it starts scanning in the second scanning mode (step S12). In step S12, the control unit 20 instructs the scanning control unit 20B to perform control in the second scanning mode.

In step S12, the scanning control section 20B changes the driving signals DX and DY supplied to the optical scanning section 15 to shift the scanning mode of the optical scanning section 15 from Lissajous scanning to scanning including raster scanning. That is, in step S12, the scanning mode of the optical scanning unit 15 shifts to the second scanning mode that enables more dense scanning within the scanning target surface R1.

For example, in step S12, the scanning control unit 20B supplies a driving signal DY for oscillating the oscillating plate SY of the optical scanning unit 15 about the oscillating axis AY in a non-resonant mode, that is, a sawtooth wave driving signal DY. do. Further, in step S12, the scanning control unit 20B supplies a drive signal DX that causes the oscillation plate SX of the optical scanning unit 15 to oscillate in a resonance mode about the oscillation axis AX, that is, a sinusoidal drive signal DX. . In this manner, the scanning control unit 20B shifts the scanning pattern of the optical scanning unit 15 from Lissajous scanning to vertical raster scanning for scanning the raster scanning area RAY (see FIG. 4A).

For example, in step S12, the scanning control unit 20B outputs the driving signals DX and DY for realizing scanning by horizontal raster scanning, a combination of vertical raster scanning and horizontal raster scanning, or a combination of Lissajous scanning and raster scanning. (see FIG. 5A).

After executing step S12, the control unit 20 continues scanning in the second scanning mode for a predetermined time (step S13). For example, the predetermined time may be determined in advance based on the time required for scanning in the second scanning mode to be performed for a predetermined period.

After executing step S13, the control unit 20 determines whether or not the running state is suitable for continuing the second scanning mode (step S14). If the control unit 20 determines in step S14 that the running state is suitable for continuing the second scanning mode (step S14: YES), the process returns to step S13, and scanning in the second scanning mode is continued for a predetermined time. do.

When the control unit 20 determines in step S14 that the running state is not suitable for continuing the second scanning mode (step S14: NO), it terminates the distance measurement routine RT1 and starts a new distance measurement routine RT1. Start.

As described above in detail, according to the distance measuring device 10 of the present embodiment, the scanning of the optical scanning unit 15, which is a MEMS mirror, is performed based on the traveling state information of the moving body on which the distance measuring device 10 is mounted. It is possible to switch the scanning mode of the light between a first scanning mode, which is Lissajous scanning, and a second scanning mode, which includes raster scanning and allows for a denser scanning than the first scanning mode. .

Furthermore, in the second scanning mode, among a plurality of scanning patterns including raster scanning (vertical raster scanning, horizontal raster scanning) or a combination of scanning patterns (a combination of raster scanning and Lissajous scanning), Any suitable scan pattern or combination of scan patterns can be applied. In this manner, the scanning pattern can be freely changed based on the running state information.

Therefore, the distance measuring device 10 can perform distance measurement by scanning in a scanning mode suitable for the running state of the moving body. In other words, it is possible to measure the distance using a scanning pattern suitable for the running state of the moving object, following changes in the running state.

Therefore, according to the distance measuring apparatus of the present invention, the distance measuring apparatus is capable of measuring a part of the scanning target area in more detail depending on the situation while executing measurement of the entire scanning target area. can provide.

10 Distance measuring device 11 Light source 12 Optical system 13 Beam splitter 15 Light scanning unit 16 Light reflecting film 16A Light reflecting surface 18 Light receiving unit 20 Control unit 20A Light source control unit 20B Scan control unit 20C Distance measuring unit 20D Judging unit 21 Fixed unit 22 Movable Part 23 Driving Force Generating Part AX, AY Rocking Axis TX First Torsion Bar TY Second Torsion Bar

Claims (16)

A distance measuring device mounted on a moving body that receives reflected light of projected light reflected by an object and measures a distance to the object,
a light emitting unit that emits scanning light for scanning a predetermined area;
a control unit that switches the scanning mode of the light emitting unit between a first scanning mode and a second scanning mode that enables denser scanning than the first scanning mode,
The light emitting unit performs Lissajous scanning in the first scanning mode, performs scanning including scanning different from Lissajous scanning in the second scanning mode,
The distance measuring device, wherein the control unit acquires running state information indicating a running state of the moving object, and switches the scanning mode based on the running state information. 2. The distance measuring device according to claim 1, wherein the running state information includes the speed of the moving object. 3. The distance measuring device according to claim 1, wherein the running state information includes a distance to an object existing in the moving direction of the moving body. 4. The distance measuring device according to claim 1, wherein the running state information includes brightness around the moving body. 5. The distance measuring device according to any one of claims 1 to 4, wherein the running state information includes acceleration of the moving object. 6. The distance measuring device according to claim 1, wherein said running state information includes a steering angle of a steering wheel of said moving body. 7. The distance measuring device according to claim 1, wherein the running state information includes meandering frequency of the moving object. 8. The distance measuring device according to any one of claims 1 to 7, wherein the running state information includes weather around the moving object. the light emitting portion includes a reflecting member having a reflecting surface and capable of swinging;
a light source that emits light toward the reflecting surface of the reflecting member;
9. The distance measuring device according to claim 1 , wherein the scanning light is emitted by reflecting the light emitted from the light source on the reflecting surface. the reflecting member is swingable about two axes;
In the Lissajous scanning, the reflecting member is oscillated while resonating about both of the two axes, and in a scanning different from the Lissajous scanning, one of the two axes is the center. 10. The distance measuring device according to claim 9 , wherein said reflecting member is caused to oscillate without resonating. In the second scanning mode, the control section switches the scanning pattern of the light emitting section to a scanning pattern in which the reflecting member is oscillated about both of the two axes without resonating. 11. The distance measuring device according to claim 10, wherein 12. The light emitting section according to any one of claims 1 to 11 , wherein in the second scanning mode, the Lissajous scanning and scanning different from the Lissajous scanning are alternately repeated at a predetermined cycle. The distance measuring device according to . 13. The distance measuring device according to claim 1 , wherein the switching of the scanning mode is performed for each one or more cycles of the scanning. 14. The distance measuring device according to any one of claims 1 to 13, wherein the light emitting section performs scanning including raster scanning in the second scanning mode. a reflecting member that is capable of swinging about two axes and capable of switching the operation mode about each axis between a resonant mode and a non-resonant mode;
a light source that emits light toward the reflecting member;
a light receiving unit that receives the light reflected by the object after being reflected by the reflecting member;
a distance measuring unit that calculates a distance to the object based on the time when the light is emitted and the time when the light is received;
an acquisition unit that acquires running state information indicating the running state of the moving body,
A distance measuring device, wherein each of the operation modes of the reflecting member centered on each axis is switched based on the running state information. A distance measuring device mounted on a moving body that receives reflected light of projected light reflected by an object and measures a distance to the object,
a light emitting unit that emits scanning light for scanning a predetermined area;
a control unit that switches the scanning mode of the light emitting unit between a first scanning mode and a second scanning mode that enables denser scanning than the first scanning mode,
The control unit acquires running state information indicating a running state of the mobile object, and switches the scanning mode based on the running state information,
The light emitting section includes a reflecting member having a reflecting surface and capable of swinging, and a light source that emits light toward the reflecting surface of the reflecting member. The scanning light is emitted by being reflected on a reflective surface,
In the first scanning mode, the light emitting section performs scanning with a first scanning pattern, and in the second scanning mode, the light emitting section performs a second scan that is denser than the first scanning pattern. scanning with a scanning pattern including the scanning pattern of
the reflecting member is swingable about two axes;
In scanning with the first scanning pattern, the reflecting member is resonated and oscillated about both of the two axes, and in scanning with the second scanning pattern, the two axes 2. A distance measuring device characterized in that the reflecting member is oscillated about one of the axes without resonating.

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