WO2023281978A1 - 測距装置および測距方法 - Google Patents

測距装置および測距方法 Download PDF

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Publication number
WO2023281978A1
WO2023281978A1 PCT/JP2022/023314 JP2022023314W WO2023281978A1 WO 2023281978 A1 WO2023281978 A1 WO 2023281978A1 JP 2022023314 W JP2022023314 W JP 2022023314W WO 2023281978 A1 WO2023281978 A1 WO 2023281978A1
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Prior art keywords
light
light emission
distance
pulse
unit
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Ceased
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PCT/JP2022/023314
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English (en)
French (fr)
Japanese (ja)
Inventor
智成 吉田
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Denso Corp
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Denso Corp
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Priority to CN202280045917.6A priority Critical patent/CN117616304A/zh
Publication of WO2023281978A1 publication Critical patent/WO2023281978A1/ja
Priority to US18/405,592 priority patent/US20240230899A9/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/4808—Evaluating distance, position or velocity data
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/484—Transmitters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/4861—Circuits for detection, sampling, integration or read-out
    • G01S7/4863—Detector arrays, e.g. charge-transfer gates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/4865—Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/487—Extracting wanted echo signals, e.g. pulse detection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/487—Extracting wanted echo signals, e.g. pulse detection
    • G01S7/4873—Extracting wanted echo signals, e.g. pulse detection by deriving and controlling a threshold value

Definitions

  • the disclosure in this specification relates to a ranging device and a ranging method for measuring the distance to a target object.
  • a rangefinder there is a technology that uses light pulses to measure the distance to a target object based on the time of flight (TOF) of the light pulses. Specifically, part of the light emitted from the light source of the range finder is reflected by the target object and returns to the detector of the range finder. Then, the distance to the target object is estimated (see Patent Literature 1, for example).
  • TOF time of flight
  • the light intensity of the reflected light pulse is too high, and the light receiving element is affected. It may exceed the detection range. If the intensity of the reflected light pulse exceeds the detection range of the light-receiving element, the position of the peak of the reflected light pulse cannot be determined, resulting in a problem of reduced distance measurement accuracy.
  • the disclosed object has been made in view of the above-mentioned problems, and aims to provide a distance measuring device and a distance measuring method that are excellent in measurement accuracy.
  • the present disclosure employs the following technical means to achieve the aforementioned objectives.
  • the range finder disclosed herein is a range finder that irradiates a target area with light and measures the distance to a target object in the target area, and irradiates the target area with light.
  • a light emission control unit that controls the light emitting unit, a detection information acquisition unit that acquires detection information obtained by the light receiving unit that detects light from the target area, and a distance calculation unit that calculates the distance to the target object using the detection information. and wherein the light emission control unit controls the light emitting unit to irradiate a plurality of light pulses having different light emission intensities per unit measurement time at different light emission times, and the distance calculation unit controls the plurality of light pulses as targets.
  • a distance measuring device that calculates a distance using the detection timing of a plurality of response pulses generated by being reflected by an object.
  • a ranging method disclosed herein is a ranging method for measuring the distance to a target object in a target area, wherein processing performed by at least one processor includes a plurality of measurements per unit measurement time. controlling the light emitting unit to irradiate the target region with light pulses having different light emission intensities at different light emission times; obtaining detection information obtained by the light receiving unit that detects the light from the target region; calculating the distance to the target object using detection timings of a plurality of response pulses generated by reflection of the light pulse contained in the target object.
  • the light pulse has a plurality of different emission intensities and different emission times per unit measurement time. You can get a pulse. Therefore, the distance can be calculated using the detection timings of a plurality of response pulses included in the detection information. For example, even if the detection timing of one response pulse is unclear due to saturation, noise, etc., if the detection timing of other response pulses is clear, the other response pulses can be used to measure the distance. This makes it possible to realize a distance measuring device and a distance measuring method with excellent measurement accuracy.
  • FIG. 1 is a block diagram showing a distance measuring device 100 according to a first embodiment
  • FIG. 4 is a diagram showing functional blocks of the signal processing device 20;
  • FIG. 11 shows a saturated response pulse;
  • FIG. 10 is a diagram showing another example of response pulses;
  • 4 is a flowchart showing processing of the signal processing device 20;
  • FIG. 4 is a diagram showing multipath detection processing;
  • FIG. 4 is a diagram for explaining a distance measurement range;
  • FIG. 5 is a diagram for explaining detection processing of multiple reflection;
  • FIG. 5 is a diagram for explaining another example of a light emission sequence;
  • FIG. 4 is a diagram for explaining a light emission sequence for each pixel 14;
  • FIG. 4 is a diagram for explaining a light emission sequence for each frame;
  • FIG. 8 is a diagram for explaining another example of the light emission sequence for each pixel 14;
  • FIG. 8 is a diagram for explaining still another example of the light emission sequence for each pixel 14;
  • FIG. 1 A first embodiment of the present disclosure will be described with reference to FIGS. 1 to 17.
  • FIG. The distance measuring device 100 of this embodiment irradiates a target area with light and measures the distance to the target object 101 in the target area.
  • the distance measuring device 100 includes an optical sensor 10 and a signal processing device 20, as shown in FIG.
  • a distance measuring device 100 of this embodiment is mounted on a vehicle and measures the distance to a target object 101 around the vehicle.
  • the ranging device 100 is also called a LiDAR (Light Detection and Ranging/Laser Imaging Detection and Ranging) device.
  • the distance measuring device 100 measures the distance to the reflection point by detecting reflected light from the reflection point with respect to irradiation of light.
  • Range finder 100 is installed in a vehicle having at least one of an advanced driving support function and an automatic driving function, for example.
  • the distance measuring device 100 is communicably connected to the in-vehicle ECU 30 via an in-vehicle LAN.
  • the in-vehicle ECU 30 is an electronic control device that uses the measurement result of the distance measuring device 100 for processing such as advanced driving assistance and automatic driving.
  • the optical sensor 10 irradiates light and detects reflected light.
  • the optical sensor 10 measures the time of flight of light by measuring the time difference between the emission time of light from the light source and the arrival time of reflected light.
  • the optical sensor 10 includes a light emitting section 11 , a light receiving section 12 and a control circuit 13 .
  • the light emitting unit 11 emits light toward the target area.
  • Light emitting unit 11 is a light source that emits laser light toward the outside of the vehicle, and is realized by, for example, a laser element. Under the control of the control circuit 13, the light emitting unit 11 emits intermittent pulsed beams of laser light. The light emitting unit 11 causes the movable optical member to scan the laser light in accordance with the irradiation timing of the laser light.
  • the light receiving unit 12 detects light from the target area.
  • the light receiving unit 12 is configured to detect light from the surroundings of the vehicle, and has a plurality of light receiving elements.
  • the light-receiving element is an imaging element that detects light including reflected light from the target object 101 with respect to laser light irradiation by the light-emitting unit 11 .
  • the target object 101 is, for example, a vehicle and features around the vehicle. In the following, the reflected light from the target object 101 for this laser beam irradiation is simply referred to as "reflected light".
  • the light receiving element is set to have a high sensitivity to the vicinity of the wavelength of the laser light emitted by the light emitting section 11 .
  • the light receiving elements are arranged in a one-dimensional or two-dimensional array.
  • the number of light receiving elements corresponds to the number of pixels.
  • a single photon avalanche diode (SPAD) is adopted. When one or more photons are incident on the SPAD, the electron doubling action due to avalanche doubling produces an electrical pulse.
  • a SPAD can output an electric pulse, which is a digital signal, without going through an AD conversion circuit.
  • the control circuit 13 performs an irradiation function of scanning laser light and a reflected light detection function of detecting reflected light.
  • the control circuit 13 controls irradiation and scanning of the laser light by the light emitting section 11 .
  • the control circuit 13 reads the electric pulse output by the light receiving element of the light receiving section 12 .
  • control circuit 13 sequentially exposes and scans each of the plurality of scanning lines of the light receiving element as the laser light is irradiated. As a result, the control circuit 13 acquires the number of electric pulses for each time within the exposure time output from each light receiving element as detection data. Then, the control circuit 13 generates detection information that associates the elapsed time from the laser light irradiation time with the detection time of each detection signal within the exposure time indicated by the detection data. The control circuit 13 outputs the generated detection information to the signal processing device 20 .
  • the signal processing device 20 generates a point cloud image of the target object 101 based on the detection information from the optical sensor 10 .
  • the signal processing device 20 is a control device and, as shown in FIG. 1, a computer including at least one memory 21 and at least one processor 22 .
  • the memory 21 non-temporarily stores or stores computer-readable programs and data.
  • the memory 21 is implemented by at least one type of non-transitory tangible storage medium, such as semiconductor memory, magnetic medium, and optical medium.
  • the memory 21 stores various programs executed by the processor 22, such as a range finding program and an image processing program, which will be described later.
  • the processor 22 includes, as a core, at least one of CPU (Central Processing Unit), GPU (Graphics Processing Unit), RISC (Reduced Instruction Set Computer)-CPU, and the like.
  • Processor 22 executes a plurality of instructions contained in, for example, a ranging program stored in memory 21 .
  • the signal processing device 20 implements a distance measurement method for measuring the distance to the target object 101 in the target area by executing the distance measurement program.
  • the signal processing device 20 also executes image processing for generating a point cloud image of the target object 101 from the detection result of the optical sensor 10 by executing an image processing program.
  • a plurality of functional units are constructed by causing the processor 22 to execute a plurality of programs and a plurality of instructions.
  • the signal processing device 20 has, as functional units, a light emission control unit 23, a distance calculation unit 26, a detection information acquisition unit 24, a waveform comparison unit 27, and an image generation unit 25, as shown in FIG.
  • the light emission control section 23 controls the light emission section 11 .
  • the light emission control unit 23 gives an operation command to the optical sensor 10 .
  • the control circuit 13 controls the light emitting section 11 based on the operation command.
  • the light emission control section 23 controls the number of light pulses emitted by the light emitting section 11 per unit measurement time, the waveform shape, and the light emission intensity. A light pulse emitted by the light emitting unit 11 will be described later.
  • the detection information acquisition unit 24 acquires the detection information obtained by the light receiving unit 12 .
  • the detection information acquiring unit 24 determines whether or not the waveform information of the detected reflected wave is valid for the newly acquired detection information. For example, the detection information acquiring unit 24 determines whether the waveform information is valid based on the magnitude of the S/N ratio of the waveform, the amplitude of the waveform, and the like. When determining that the waveform information is not valid, the detection information acquisition unit 24 rejects the acquired detection information.
  • the detection information acquisition unit 24 acquires detection information for all pixels in each control cycle. The detection information acquisition unit 24 sequentially provides each acquired detection information to the distance calculation unit 26 .
  • the distance calculation unit 26 calculates the distance to the target object 101 using the detection information.
  • the distance calculator 26 calculates the distance using detection timings of a plurality of response pulses generated by reflection of the light pulse from the target object 101 . Specifically, the distance calculator 26 calculates the distance to the reflection point.
  • a reflection point is a point where laser light irradiation is reflected by the target object 101 .
  • a reflection point can also be said to be an emission point of reflected light.
  • the distance calculation unit 26 sequentially provides the calculated distance value to the reflection point to the image generation unit 25 .
  • the image generation unit 25 converts the distance value to the reflection point calculated by the distance calculation unit 26 into three-dimensional coordinate information.
  • the image generator 25 converts the distance value into a three-dimensional coordinate value based on the focal length of the optical system, the number of light receiving elements, the size of the light receiving elements, and the like.
  • a three-dimensional coordinate value is a coordinate system centered on the distance measuring device 100 .
  • the image generation unit 25 converts all the distance values into a three-dimensional coordinate system and generates a point cloud image including coordinate information of the reflection points corresponding to the respective light receiving elements.
  • the emitted light is characterized in that it has a plurality of light pulses, two in this embodiment, with different light emission intensities per unit measurement time and different light emission times.
  • a unit measurement time is the generation time of one histogram.
  • the unit measurement time is the time set for receiving the reflected light after the light is emitted.
  • the unit measurement time is set based on, for example, the upper limit of distance measurement.
  • the light emission intensity of the preceding optical pulse is greater than that of the latter optical pulse.
  • the light emission time of the light pulse in the former stage and the light pulse in the latter stage do not overlap and are shifted in terms of time.
  • the former-stage optical pulse is sometimes referred to as the first emitted pulse 41
  • the latter-stage optical pulse is sometimes referred to as the second emitted pulse 42 .
  • the first embodiment is also characterized in that the first emitted pulse 41 and the second emitted pulse 42 have different emission waveforms.
  • the second emitted pulse 42 has a flatter shape than the first emitted pulse and is asymmetrical. In contrast, in the comparative example, there is only one light pulse per unit measurement time.
  • a light emission time is assigned to each pixel.
  • Light emission is controlled so that all pixels have the same light emission pattern.
  • the light emission pattern is a combination of the number of light pulses per unit measurement time, the light emission intensity of the light pulses, and the waveform shape of the light pulses. Therefore, for example, the period for the first pixel p and the period for the second pixel p+1 are controlled to have the same light emission pattern.
  • FIG. 5 to 7 Since the emitted light has two light pulses as described above, under ideal conditions the reflected light also has two response pulses, as shown in FIG.
  • the front-stage response pulse may be referred to as a first response pulse 43 and the rear-stage response pulse may be referred to as a second response pulse 44 .
  • the vertical axis indicates the response power.
  • Response power corresponds to light intensity.
  • the light receiving element is a SPAD, so the response power corresponds to the number of responses.
  • the light-receiving unit 12 has a structure in which, when one or more photons, which are light particles, are incident on a pixel, SPADs are arranged for each pixel by multiplication like an avalanche to output one large electrical pulse signal. Since one photon can be multiplied into many electrons, one photon can be detected, and the number of output electrical pulse signals is the number of responses.
  • peak values are obtained by sampling.
  • the control circuit 13 counts the number of electric pulses output from each light receiving element at each sampling.
  • the control circuit 13 then generates a histogram that records the number of electrical pulses for each sampling.
  • Each class of the histogram indicates the time of flight of light (Time of Flight, TOF), which is the elapsed time for each sampling from the emission time of the light emitting unit 11 .
  • the sampling frequency therefore corresponds to the time resolution of the TOF measurement.
  • the peak value is used to calculate the distance, as shown in FIG. Further, as shown in FIG. 6, since the first response pulse 43 is saturated and the peak value cannot be detected with high accuracy, the peak value of the second response pulse 44 is used to calculate the distance.
  • Saturation as shown in FIG. 6 means the upper limit of the light receiving intensity of each light receiving element.
  • each light receiving element is a SPAD
  • the received light intensity corresponding to the number of responses of the SPAD in each light receiving element is acquired. If the distance is calculated using the saturated first response pulse 43, the distance is calculated by regarding the sampling time when the maximum number of responses is obtained as the peak value.
  • Whether or not it is saturated can be determined using sampling values. For example, (1) when there are a predetermined number of K1 or more maximum responses, (2) when there are a predetermined number of K2 or more maximum responses, and when the half-value width is a predetermined T1 [ns] or more, and (3 ) When there are K3 or more maximum responses and the bottom width is equal to or greater than a predetermined T2 [ns], it is determined that saturation has occurred.
  • the determination conditions (1) to (3) may be used individually, or may be used in combination. Also, the values of K1, K2 and K3 may be different or the same. Also, the values of T1 and T2 may be different or the same. These values are determined, for example, by preliminary experiments and simulations.
  • the distance calculator 26 calculates the signal-to-noise ratio (S/N ratio) of the first response pulse 43 and the second response pulse 44. calculate. If the calculated signal-to-noise ratio (hereinafter sometimes simply referred to as SN) satisfies a predetermined condition, it is assumed that the waveform is suitable with little noise. It can be judged that the noise becomes less as the SN becomes larger. SN can be calculated by the following equations (1) to (4).
  • lmax is the maximum value that the light receiving element can take
  • lpeak is the peak value of the response pulse
  • lamb is the minimum value of the response pulse.
  • FIG. 8 shows processing of a distance measurement program that is repeatedly executed in a short period of time by the distance calculation unit 26 when the power of the distance measurement device 100 is turned on.
  • the first response pulse 43 is called Echo A
  • the second response pulse 44 is called Echo B.
  • step S1 it is determined whether or not echo A is saturated. If saturated, the process proceeds to step S2, and if not saturated, the process proceeds to step S10. In step S2, it is determined whether or not the echo B is saturated. If saturated, the process proceeds to step S3, and if not saturated, the process proceeds to step S5.
  • the saturation determination method described above is used to determine saturation.
  • step S3 both echo A and echo B are saturated, so the distance is calculated using echo A and echo B, and the process proceeds to step S4. Since both response pulses are saturated, the distance is calculated at each response pulse and the distance is calculated by averaging or the like. In step S4, a first flag is given, and this flow ends. Flags will be described later.
  • step S5 it is determined whether or not the SN of echo B is equal to or greater than the threshold. If the SN is equal to or greater than the threshold, the process proceeds to step S6. . In step S8, since echo B is not saturated and the reliability of SN is high, echo B is used to calculate the distance, and the process proceeds to step S7. In step S7, a second flag is given, and this flow ends.
  • step S8 echo B is not saturated, but the reliability of SN is low, so the saturated echo A is used to calculate the distance, and the process proceeds to step S9.
  • step S9 a third flag is given, and this flow ends.
  • step S10 since echo A is not saturated, it is determined whether or not the SN of echo B is above the threshold. Otherwise, the process moves to step S13.
  • step S11 Echo A and Echo B are not saturated and the reliability of SN of Echo B is high, so the distance is calculated using Echo A and Echo B, and the process proceeds to Step S12. Since the first emitted pulse 41 has a higher emission intensity, it is estimated that the echo B based on the second emitted pulse 42 is not saturated when the echo A based on the first emitted pulse 41 is not saturated. There is In step S12, a fourth flag is given, and this flow ends.
  • step S13 echo A is not saturated, but the SN of echo B is not above the threshold. Therefore, it is determined whether the SN of echo A is above the threshold. If not, the process moves to step S14, and if it is not equal to or greater than the threshold value, the process moves to step S16.
  • step S14 Echo A and Echo B are not saturated, but the SN reliability of Echo B is low and the SN reliability of Echo A is high. Therefore, only Echo A is used to calculate the distance. move to In step S15, a fifth flag is given, and this flow ends.
  • step S16 echo A and echo B are not saturated, but since the reliability of SN of echo A and echo B is low, it is determined that there is no target object 101, and the process proceeds to step S17.
  • step S17 a sixth flag is given, and this flow ends.
  • the first to sixth flags are response pulse information regarding Echo A and Echo B.
  • the response pulse information includes information such as the detection timing of each echo, received light intensity and SN.
  • the response pulse information is indicated by six flags.
  • the first to sixth flags are given as information for roughly classifying the reflection intensity from the target object 101 for use in subsequent processing.
  • the reflection intensity becomes weaker in order from the first flag to the sixth flag. For example, in the first flag, since echo A and echo B are saturated, the reflection intensity is the strongest, and there is a high possibility that the target object 101 is a high-brightness object, so using saturated echo A and echo B calculating the distance.
  • the distance calculation unit 26 calculates the distance using the detection timing of the response pulse having a peak value below the upper detection limit of the light receiving unit 12 among the plurality of response pulses included in the detection information.
  • a response pulse having a peak value below the upper limit of detection is synonymous with a non-saturated response pulse.
  • steps S6, S11 and S14 in FIG. 8 when echo A and echo B are not saturated, the distance is calculated using the response pulse that is not saturated. This is for improving the distance measurement accuracy.
  • the distance calculation unit 26 selects, among a plurality of response pulses included in the detection information, response pulses having a peak value below the upper detection limit of the light receiving unit 12 and having a signal-to-noise ratio of a predetermined value.
  • the distance is calculated using the detection timing of the response pulse greater than the confidence value. Specifically, as shown in steps S6, S11 and S14 in FIG. 8, the distance is calculated when SN is equal to or greater than the threshold value. This is because response pulses with less noise are used to improve distance measurement accuracy.
  • the distance calculation unit 26 determines that, among the plurality of response pulses included in the detection information, if there is no response pulse having a peak value below the upper detection limit of the light receiving unit 12, The distance is calculated using the detection timing of all response pulses. Specifically, as shown in step S3 of FIG. 8, echo A and echo B are saturated, so echo A and echo B are used to calculate the distance. A saturated echo lowers the detection accuracy, but the use of two echoes can suppress the lowering of the detection accuracy.
  • the shape of the response pulse will be explained.
  • the shapes of the first emitted pulse 41 and the second emitted pulse 42 are different, and in the emitted light of the second embodiment, the first emitted pulse 41 and the second emitted pulse
  • the shape of the pulse 42 is similar.
  • the light emission control unit 23 controls the light emission unit 11 to irradiate a plurality of light pulses having different light emission intensities and the same waveform shape per unit measurement time.
  • the same waveform shape also includes a similar shape.
  • the reflected light has the same shape as the outgoing light if it is a single pass.
  • the waveform comparison unit 27 of the signal processing device 20 compares the waveform shapes of the plurality of response pulses included in the detection information and the plurality of light pulses emitted by the light emitting unit 11 in chronological order. Then, the waveform comparison unit 27 determines the presence or absence of multipath.
  • the waveform shapes of the first output pulse 41 and the first response pulse 43 are the same, and the waveform shapes of the second output pulse 42 and the second response pulse 44 are different.
  • the waveform shapes of the first output pulse 41 and the first response pulse 43 are the same, and the waveform shapes of the second output pulse 42 and the second response pulse 44 are also the same.
  • the waveform comparison unit 27 can determine whether or not there is multipath based on the emitted light of the first embodiment. This is because, in the case of multipath, the reflected light on the detour route indicated by the dashed line has a longer route length, so that it arrives at the light receiving section 12 later than the second response pulse 44 on the straight route indicated by the solid line. This is because the first response pulse 43 on the detour route shown may arrive early.
  • Emission intensity is also called emission power.
  • the first emitted pulse 41 has a higher emission intensity than the second emitted pulse 42 .
  • the same range-finding range as in the comparative example with only the first emitted pulse 41 can be maintained.
  • the number of times of sampling from the light emission start time to the upper limit of distance measurement is determined, and the second emitted pulse 42 is emitted later than the first emitted pulse 41. Therefore, the delay Therefore, the distance range including the second emitted pulse 42 is smaller than that of the comparative example using only the first emitted pulse 41 .
  • the distance measurement range is the same as in the comparative example.
  • the second emitted pulse 42 can be used to measure the distance with higher accuracy.
  • the first emitted pulse 41 has a higher emission intensity than the second emitted pulse 42, but the intensity relationship is not limited to this. Contrary to the first embodiment, the emission intensity of the second emitted pulse 42 may be higher than that of the first emitted pulse 41 .
  • the first emitted pulse 41 has a lower emission intensity than the second emitted pulse 42 and has different waveform shapes.
  • a high-brightness reflector 102 is a target object 101 having a high-brightness surface.
  • the multiple reflection by the internal reflector and the high-brightness reflector 102 means that the emitted light does not make one round trip, but two round trips by the internal reflector and the high-brightness reflector 102 . , may enter the light receiving section 12 . Therefore, the multiple reflection by the high-intensity reflector 102 is a phenomenon in which pseudo echoes are visible when the emission intensity is high.
  • the second response pulse 44 becomes a pseudo echo in the comparative example.
  • the pseudo echo and the second response pulse 44 of reflected light may or may not be mixed depending on the sampling time. It cannot be determined whether it is the response pulse 44 or not. This is because the emission intensity of the pseudo echo is weak and the emission intensity of the second emitted pulse 42 of the first embodiment is also small.
  • the emission intensity of the second emitted pulse 42 is high, it is possible to distinguish between the first response pulse 43 of the pseudo echo and the second response pulse 44 of the reflected light.
  • the intensity of the second response pulse 44 of the reflected light is high, so that they appear to disappear. Therefore, in the third embodiment, the influence of pseudo echo can be suppressed.
  • the emitted light provides an interval of a predetermined time T3 between the first emitted pulse 41 and the second emitted pulse 42 .
  • the predetermined time T3 is set to a time during which the light receiving section 12 can separate and process the first emitted pulse 41 and the second emitted pulse 42 . If the predetermined time T3 is too short, the first response pulse 43 and the second response pulse 44 cannot be separated.
  • the predetermined time T3 is preferably equal to or greater than the width of the waveform obtained by convolving the response function of the SPAD and the transfer function of the light emission waveform, for example.
  • the SPAD's response function is dead-time dependent.
  • the wavelengths of the first emitted pulse 41 and the second emitted pulse 42 of emitted light may be the same or different.
  • the same device can be used, which simplifies the circuit.
  • the same wavelength includes the case where at least part of the wavelength band overlaps without being completely the same.
  • the sensitivity can be adjusted by the transmittance in addition to the emission intensity by using different bandpass filters for each wavelength in the light receiving section 12 .
  • “Different wavelengths” means that the wavelength bands do not overlap and the wavelength bands are different, the wavelength bands partially overlap but the peak wavelengths are different, and the wavelength bands partially overlap but half or more of the wavelength bands are different. include. This facilitates extension of the dynamic range. Specifically, when the wavelengths of the first emitted pulse 41 and the second emitted pulse 42 are the same, the reflected light of the first emitted pulse 41 and the second emitted pulse 42 pass through the same band-pass filter.
  • the transmittance in the band-pass filter is the same as that of the reflected light of the pulse 42 .
  • the wavelengths of the first emitted pulse 41 and the second emitted pulse 42 are different, they are passed through different bandpass filters. Therefore, by varying the transmittance of the band-pass filter, the transmittance of the reflected light of the first output pulse 41 and the transmittance of the reflected light of the second output pulse 42 can be adjusted separately. This makes it easier to detect the first response pulse 43 and the second response pulse 44 .
  • the emitted light may be emitted in the same light emission pattern for each pixel 14, and as shown in FIGS. good too.
  • the light emission control unit 23 may control the light emission unit 11 so as to irradiate light with a different light emission pattern for each divided region obtained by dividing the target region.
  • One divided area corresponds to one pixel 14 .
  • All the pixels 14 can form a point cloud image of the target region because all the sub-regions are combined to form the target region.
  • FIGS. 14 to 17 the same light emission patterns are indicated by the same hatching for easy understanding.
  • the period for a certain first pixel p and the period for another second pixel p+1 are controlled to have different emission patterns.
  • the emission pattern using the emitted light of the first embodiment is used in the period for the first pixel p
  • the emission pattern using the emitted light of the third embodiment is used in the period for the second pixel p+1.
  • the light emission pattern may be controlled so that the light emission pattern differs from frame to frame.
  • Two types of light emission patterns may be alternately switched so that the light emission patterns are different in adjacent frames.
  • control may be performed so that the pixels 14 adjacent to the left and right have different light emission patterns, and the pixels 14 adjacent to the upper and lower sides have the same light emission pattern.
  • the pixels 14 adjacent to the left and right may have the same light emission pattern, and the pixels 14 adjacent to the upper and lower sides may have different light emission patterns.
  • the dynamic range can be expanded without lowering the FPS.
  • power consumption can be reduced as a whole.
  • the light pulse has a plurality of different emission intensities per unit measurement time. 12 can obtain multiple response pulses. Therefore, the distance can be calculated using the detection timings of a plurality of response pulses included in the detection information. For example, even if the detection timing of one response pulse is unclear due to saturation, noise, etc., if the detection timing of other response pulses is clear, the other response pulses can be used to measure the distance. This makes it possible to realize the distance measuring device 100 and the distance measuring method with excellent measurement accuracy.
  • the distance calculator 26 calculates the distance using the detection timing of the response pulse having a peak value below the upper detection limit of the light receiver 12 among the multiple response pulses included in the detection information. Since the distance is calculated by the response pulse having the peak value, the distance can be calculated with high accuracy.
  • the distance calculation unit 26 uses, among the plurality of response pulses included in the detection information, response pulses having a peak value below the upper detection limit of the light receiving unit 12 and having a signal-to-noise ratio of a predetermined reliability value. The distance is calculated using the detection timing of the response pulse described above. Therefore, since a highly reliable response pulse having a peak value and an SN higher than the reliability value is used, the distance can be calculated with high accuracy.
  • the distance calculation unit 26 calculates all of the response pulses included in the detection information. The distance is calculated using the detection timing of the response pulse of . If all the response pulses are saturated, the precision will drop with one response pulse, but using a plurality of response pulses can suppress the drop in precision.
  • the waveform comparison unit 27 compares the waveform shapes of the plurality of response pulses included in the detection information and the plurality of waveform shapes emitted by the light emitting unit 11 in chronological order.
  • the waveform comparison unit 27 can determine the presence or absence of multipath by comparing waveform shapes. As a result, the distance can be calculated by excluding multipath detection information, and the influence of multipath can be suppressed.
  • the distance measurement method includes controlling the light emitting unit 11 to irradiate a target region with light pulses having a plurality of different light emission intensities per unit measurement time, and detecting light from the target region.
  • the distance to the target object 101 is calculated using the detection timing of a plurality of response pulses generated by the light pulses included in the detection information being reflected by the target object 101. including doing As a result, the distance can be calculated with high accuracy as described above.
  • the number is not limited to two, and may be three or more.
  • the light receiving unit 12 is configured using a SPAD, it is not limited to the SPAD, and may be another image sensor such as a CMOS sensor.
  • the functions realized by the signal processing device 20 in the first embodiment described above may be realized by hardware and software different from those described above, or a combination thereof.
  • the signal processor 20 may, for example, communicate with other controllers, and the other controllers may perform some or all of the processing.
  • the signal processor 20 can be implemented by digital circuitry, including numerous logic circuits, or by analog circuitry.
  • the signal processing device 20 may be a locator ECU that estimates the vehicle's own position.
  • the signal processing device 20 may be an ECU that controls advanced driving assistance or automatic driving of the vehicle.
  • the signal processing device 20 may be an ECU that controls communication between the vehicle and the outside world.
  • the signal processing device 20 may be configured to further include an FPGA (Field-Programmable Gate Array), an NPU (Neural Network Processing Unit), an IP core with other dedicated functions, and the like.
  • FPGA Field-Programmable Gate Array
  • NPU Neurological Network Processing Unit
  • IP core IP core with other dedicated functions, and the like.
  • Such a signal processing device 20 may be individually mounted on a printed circuit board, or may be mounted on an ASIC (Application Specific Integrated Circuit), FPGA, or the like.
  • ASIC Application Specific Integrated Circuit
  • the distance measuring device 100 is used in a vehicle, but it is not limited to being mounted in the vehicle, and at least part of it may not be mounted in the vehicle.

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