WO2024087891A1 - Radar à onde continue à modulation de fréquence et procédé d'auto-détection pour l'état de mode longitudinal d'une source de lumière - Google Patents

Radar à onde continue à modulation de fréquence et procédé d'auto-détection pour l'état de mode longitudinal d'une source de lumière Download PDF

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WO2024087891A1
WO2024087891A1 PCT/CN2023/117011 CN2023117011W WO2024087891A1 WO 2024087891 A1 WO2024087891 A1 WO 2024087891A1 CN 2023117011 W CN2023117011 W CN 2023117011W WO 2024087891 A1 WO2024087891 A1 WO 2024087891A1
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self
signal
light source
test
detection
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PCT/CN2023/117011
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English (en)
Chinese (zh)
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汪洋
向少卿
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上海禾赛科技有限公司
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Publication of WO2024087891A1 publication Critical patent/WO2024087891A1/fr

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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
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • 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
    • G01S17/50—Systems of measurement based on relative movement of target
    • G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • 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
    • G01S7/497—Means for monitoring or calibrating

Definitions

  • the embodiments of the present invention relate to the field of radar technology, and in particular to a frequency modulated continuous wave radar and a method for self-checking the longitudinal mode state of a light source.
  • Narrow linewidth tunable light source is a key component of laser radar, especially frequency modulated continuous wave (FMCW) laser radar.
  • FMCW laser radar emits frequency modulated continuous laser as detection light. There is a certain frequency shift between the echo signal reflected by the obstacle and the corresponding detection light signal. By measuring the frequency shift, the distance and speed information of the obstacle can be obtained, thereby realizing space detection.
  • the narrow linewidth light source commonly used in FMCW LiDAR is usually an external cavity laser (ECL).
  • ECL external cavity laser
  • lasers with short external cavities are not easy to meet the linewidth requirements; while lasers with long external cavities have narrow linewidth, but small mode spacing, and are easily affected by changes in environmental conditions such as temperature to produce mode hopping, multi-longitudinal mode competition and other states.
  • the longitudinal mode refers to the light wave mode that oscillates stably along the axis of the resonant cavity
  • the linewidth refers to the frequency (or wavelength) range corresponding to when the light intensity drops to half of the maximum value.
  • Multi-longitudinal modes refer to the existence of multiple relatively stable light wave modes in the resonant cavity.
  • multi-longitudinal mode competition will occur, that is, the light source outputs lasers of multiple frequencies (or wavelengths), the detection unit cannot obtain normal beat frequency signals, and the FMCW LiDAR cannot operate normally. Therefore, it is necessary to detect the longitudinal mode state of the light source of the FMCW LiDAR.
  • the existing longitudinal mode state detection usually requires the use of external equipment such as FP scanning interferometer or spectrometer, which is not only expensive, but can only be detected when the laser radar is not working, and the detection efficiency is low.
  • This detection method is not applicable to many laser radar application scenarios, such as vehicle-mounted laser radar systems. Therefore, it is necessary for those skilled in the art to realize the detection of the longitudinal mode state of the light source of the frequency modulated continuous wave radar without the help of external equipment.
  • an embodiment of the present invention provides a frequency modulated continuous wave radar and a self-detection method for the longitudinal mode state of a light source, which can detect the longitudinal mode state of the light source of the frequency modulated continuous wave radar without the aid of external equipment, thereby reducing the detection cost and improving the detection efficiency.
  • An embodiment of the present invention provides a frequency modulated continuous wave radar, including:
  • a light source adapted to emit a frequency-modulated light signal in a preset period, wherein at least one period is a self-test period, and the frequency-modulated light signal emitted by the light source in the self-test period is a self-test signal;
  • the detection module is adapted to detect the self-detection signal to determine the longitudinal mode state of the light source.
  • the self-test signal is a fixed-frequency modulated optical signal.
  • the modulation frequency of the fixed-frequency modulation makes the selfie signal frequency between at least two longitudinal modes of the light source smaller than the bandwidth of the detection module, and the selfie signal frequency between different sidebands of the same longitudinal mode greater than the bandwidth of the detection module.
  • the frequency modulated continuous wave radar does not transmit an optical signal to the external space during the self-test period, and the detection module is suitable for completing the detection of the longitudinal mode state within one self-test period.
  • the detection module is adapted to determine that the light source is in a multi-longitudinal mode state when a Selfie signal of the self-test signal is detected.
  • the light source is adapted to emit a frequency modulated light signal at a preset period, wherein at least two adjacent periods are self-test periods;
  • the detection module is suitable for completing the detection of the longitudinal mode state within at least two adjacent self-detection cycles.
  • the modulation frequencies of the self-test signals emitted in at least two adjacent self-test cycles are different.
  • the detection module is adapted to determine that the light source is in a multi-longitudinal mode state when a Selfie signal is detected in at least two self-timer cycles and the frequencies of the Selfie signals in different self-timer cycles are different.
  • the light source further has a detection period, and the frequency modulated light signal emitted by the light source during the detection period is a detection signal, which is suitable for detecting the external space of the frequency modulated continuous wave radar.
  • the detection signal is a linear frequency modulated optical signal or a nonlinear frequency modulated optical signal.
  • the light source comprises:
  • a laser emitting unit adapted to emit laser light
  • the modulation unit is suitable for modulating the laser to obtain a frequency modulated optical signal.
  • the frequency modulated continuous wave radar further includes: a first light splitting unit, adapted to split the frequency modulated light signal into a local oscillator light signal and an outgoing signal, wherein the local oscillator light signal is transmitted to the detection module.
  • a first light splitting unit adapted to split the frequency modulated light signal into a local oscillator light signal and an outgoing signal, wherein the local oscillator light signal is transmitted to the detection module.
  • the FMCW radar further comprises: an isolation unit, the isolation unit comprising at least Three ports, wherein the first port is suitable for receiving the outgoing signal; the second port allows the outgoing signal to be emitted to the external space and receives the echo signal of the outgoing signal reflected by an obstacle; and the third port is coupled to the detection module so that the echo signal is transmitted to the detection module.
  • the detection module includes:
  • a detection unit adapted to receive the local oscillator optical signal, or the local oscillator optical signal and the echo signal, and convert the optical signal into an electrical signal
  • the processing unit is adapted to receive the electrical signal and obtain the longitudinal mode state of the light source based on the electrical signal.
  • the FMCW radar further includes: a control module, adapted to trigger the processing unit to obtain the longitudinal mode state of the light source based on a self-check start instruction.
  • the embodiment of the present invention further provides a method for self-checking the longitudinal mode state of a light source, comprising:
  • the light source emits a frequency modulated light signal in a preset period, wherein at least one period is a self-test period, and the light source emits a self-test signal in the self-test period;
  • the self-test signal is detected to determine the longitudinal mode state of the light source.
  • the self-test signal is a fixed-frequency modulated optical signal.
  • the modulation frequency of the fixed-frequency modulation makes the selfie signal frequency between at least two longitudinal modes of the light source smaller than the bandwidth of the detection module, and the selfie signal frequency between different sidebands of the same longitudinal mode greater than the bandwidth of the detection module.
  • the detecting the self-test signal to determine the longitudinal mode state of the light source includes:
  • the frequency modulated continuous wave radar does not transmit light signals to the external space during the self-test period.
  • the detecting the self-test signal to determine the longitudinal mode state of the light source includes:
  • the modulation frequencies of the self-test signals of the at least two adjacent self-test cycles are different, wherein when the frequencies of the self-test signals detected in at least two adjacent self-test cycles are different, it is determined that the light source is in a multi-longitudinal mode state.
  • a light source emits at least one period of a frequency modulated light signal as a self-test signal, and a detection module detects the self-test signal.
  • the longitudinal mode state of the light source can be accurately determined without the aid of any external equipment, thereby effectively reducing the detection cost.
  • the detection process of the longitudinal mode state of the light source is performed during radar detection. Therefore, the longitudinal mode state of the light source can be quickly determined without affecting the normal operation of the radar, and the detection efficiency is high.
  • the self-timer signal between the longitudinal modes of the light source can be frequency-reduced, that is, the frequency of the self-timer signal between multiple longitudinal modes of the light source is lower, so that the detection module can detect the self-timer signal between the longitudinal modes of the light source even when the bandwidth is small, and determine the longitudinal mode state of the light source based on the self-timer signal, thereby reducing the design difficulty and hardware cost of the radar; on the other hand, it can prevent the self-timer signal between different sidebands of the same longitudinal mode from interfering with the self-timer signal between multiple longitudinal modes of the light source, avoid misjudging different sidebands of the same longitudinal mode as multiple longitudinal modes, and thus obtain accurate detection results
  • the FMCW radar does not transmit optical signals to the external space during the self-test period, no echo signals reflected from the external space are generated during the detection process, which can effectively avoid interference signals during the detection process, thereby improving the accuracy of the detection result.
  • the detection module when it detects the Selfie signal of the self-test signal, it can determine that the light source is in a multi-longitudinal mode state. Not only does it not require the aid of any external equipment, but the radar's own detection system can also be used to detect the longitudinal mode state of the light source without the need for hardware changes, thereby reducing the detection cost.
  • the light source is suitable for emitting a frequency-modulated light signal in a preset period, wherein at least two adjacent periods are self-test periods, and the detection module is suitable for completing the detection of the longitudinal mode state in at least two adjacent self-test periods.
  • the detection module obtains the detection results of the longitudinal mode state of the light source in multiple self-test periods, it can avoid interference caused by reflected echoes from external space obstacles and improve the accuracy of detection.
  • the detection module detects a Selfie signal in at least two self-check cycles and the Selfie signal frequencies in different self-check cycles are different, it can be determined that the light source is in a multi-longitudinal mode state, thereby avoiding interference caused by reflection echoes from external space obstacles and improving the accuracy of the detection result.
  • the entire detection process does not require the use of any external equipment, and the detection of the longitudinal mode state of the light source can be achieved using the radar's own detection system, without the need for hardware changes, so the detection cost can be reduced.
  • the light source also has a detection cycle, and the frequency-modulated light signal emitted by the light source during the detection cycle is a detection signal, which is suitable for detecting the external space of the frequency-modulated continuous wave radar. Therefore, the longitudinal mode state of the light source can be detected at any time without affecting the normal operation of the radar, and the longitudinal mode state of the radar light source can be monitored in real time.
  • FIG1 shows a schematic structural diagram of a frequency modulated continuous wave radar in an embodiment of the present invention
  • FIG2a is a schematic diagram showing an emission signal of a single longitudinal mode light source in an embodiment of the present invention.
  • FIG2b shows the modulation spectrum of the transmission signal shown in FIG2a
  • FIG2c is a schematic diagram showing a transmission signal of a multi-longitudinal mode light source in an embodiment of the present invention.
  • FIG2d shows a modulation spectrum of the transmission signal shown in FIG2c according to an embodiment of the present invention
  • FIG3a is a schematic diagram showing the spectrum of an outgoing signal and an echo signal of a fixed-frequency modulated optical signal in an embodiment of the present invention
  • FIG3 b shows a schematic diagram of the spectrum of an outgoing signal and an echo signal of another fixed-frequency modulated optical signal in an embodiment of the present invention
  • FIG4 shows a timing diagram of longitudinal mode state detection of a light source based on a single-cycle self-test signal in an embodiment of the present invention
  • FIG5 shows a timing diagram of longitudinal mode state detection of a light source based on a multi-cycle self-test signal in an embodiment of the present invention
  • 6a to 6c are schematic diagrams showing the spectrum of the detection signal in the embodiment of the present invention.
  • FIG7 shows a schematic diagram of the structure of another FMCW radar in an embodiment of the present invention.
  • FIG8 shows a schematic diagram of a specific structure of a frequency modulated continuous wave radar in an embodiment of the present invention
  • FIG. 9 is a schematic diagram showing the steps of a method for self-checking the longitudinal mode state of a light source of a FMCW radar according to an embodiment of the present invention.
  • the narrow linewidth light source commonly used in current frequency modulated continuous wave lidar is usually an external cavity laser, among which the laser with a short external cavity is not easy to meet the linewidth requirements; and although the linewidth of the laser with a long external cavity is narrow, the mode spacing is small, and it is easy to produce mode hopping, multi-longitudinal mode competition and other conditions due to changes in environmental conditions such as temperature.
  • the detection unit cannot obtain the normal beat frequency signal, and the frequency modulated continuous wave lidar cannot operate normally.
  • the laser output by the light source contains multiple longitudinal modes (frequencies or wavelengths). If the response bandwidth of the detection unit is large enough, the selfie signal between the longitudinal modes of the light source can be detected.
  • the lowest selfie signal frequency is the longitudinal mode interval. Taking the FMCW radar using an external cavity laser ECL with a cavity length of 30 mm as an example, its longitudinal mode interval is about 3.3 GHz. If the selfie signal between its longitudinal modes is to be obtained, the response bandwidth of the FMCW radar detection unit is at least 3.3 GHz, and the sampling rate of the analog-to-digital converter is at least 6.6 GS/s.
  • the existing FMCW radar usually needs to use external equipment such as FP (Fabry–Pérot) scanning interferometer or spectrometer to detect the longitudinal mode state, which has high detection cost and low efficiency.
  • FP Fabry–Pérot
  • an embodiment of the present invention provides a frequency modulated continuous wave radar, which transmits at least one period of frequency modulated light signal as a self-test signal through a light source, and detects the self-test signal through a detection module.
  • the longitudinal mode state of the light source can be accurately determined without the aid of any external equipment, thereby effectively reducing the detection cost.
  • the detection process of the longitudinal mode state of the light source is carried out during radar detection, so the longitudinal mode state of the light source can be quickly judged without affecting the normal operation of the radar, and the detection efficiency is high.
  • an embodiment of the present invention provides a frequency modulated continuous wave radar.
  • the frequency modulated continuous wave radar LA includes: a light source A1 and a detection module A2, wherein:
  • the light source A1 is suitable for emitting a frequency-modulated light signal in a preset period, wherein at least one period is a self-test period, and the frequency-modulated light signal emitted by the light source A1 in the self-test period is a self-test signal.
  • the detection module A2 is adapted to detect the self-detection signal to determine the longitudinal mode state of the light source.
  • the frequency modulated continuous wave radar provided in the embodiment of the present invention transmits a self-test signal within a self-test period.
  • the detection module detects the self-test signal and can obtain different detection information, thereby determining the longitudinal mode state of the light source.
  • the light source A1 emits at least one period of frequency modulated light signal as a self-test signal, and the self-test signal is detected by the detection module A2.
  • the longitudinal mode state of the light source A1 can be accurately determined without the aid of any external equipment, thereby effectively reducing the detection cost.
  • the detection process of the longitudinal mode state of the light source A1 is carried out during the detection period of the radar LA. Therefore, the longitudinal mode state of the light source A1 can be quickly determined without affecting the normal operation of the radar LA, and the detection efficiency is high.
  • the self-test signal can be modulated at a fixed frequency, so that a single-frequency longitudinal mode Selfie signal can be obtained, so that the frequency modulated continuous wave radar can obtain accurate detection results of the longitudinal mode state of the light source.
  • the embodiment of the present invention does not limit the self-test signal to a fixed-frequency modulated optical signal. If the frequency interval between the longitudinal mode sidebands of the light source is small, the self-test signal may also be a non-fixed-frequency modulated optical signal.
  • the modulation frequency of the fixed frequency modulation can be set to meet the following conditions: the self-test signal frequency between at least two longitudinal modes of the light source A1 is less than the bandwidth of the detection module A2, and the self-test signal frequency between different sidebands of the same longitudinal mode is greater than the bandwidth of the detection module A2.
  • the Selfie signal between the longitudinal modes of the light source can be frequency-reduced, that is, the frequency of the self-timer signal between the multiple longitudinal modes of the light source is relatively low, so that the detection module can detect the self-timer signal between the longitudinal modes of the light source even when the bandwidth is small, and determine the longitudinal mode state of the light source based on the self-timer signal, thereby reducing the design difficulty and hardware cost of the radar; on the other hand, it can prevent the self-timer signal between different sidebands of the same longitudinal mode from interfering with the self-timer signal between the multiple longitudinal modes of the light source, avoid misjudging different sidebands of the same longitudinal mode as multiple longitudinal modes, thereby obtaining accurate detection results of the longitudinal mode state of the light source.
  • Figure 2a shows a schematic diagram of a transmission signal of a single longitudinal mode light source (unmodulated), wherein the single longitudinal mode light source transmits a longitudinal mode n with a light frequency of ⁇ n,0
  • Figure 2b shows a modulation spectrum of the transmission signal shown in Figure 2a.
  • the transmission signal generates sidebands such as ⁇ n,-1 , ⁇ n,+1 , and ⁇ n,+2 after modulation.
  • the frequency of the self-timer signal between different sidebands of the longitudinal mode n can be large, which is not within the response bandwidth of the detection module of the frequency modulated continuous wave radar, and the detection module cannot obtain the self-timer signal between different sidebands of the longitudinal mode n.
  • the multi-longitudinal mode light source transmits two longitudinal modes n and m with optical frequencies of ⁇ n ,0 and ⁇ m ,0 respectively, and FIG2d shows the modulation spectrum of the transmission signal shown in FIG2c.
  • each longitudinal mode generates multi-order sidebands after modulation. If the modulation frequency of the fixed frequency modulation is appropriate, the frequencies of the different sidebands of the longitudinal modes n and m can be close, so that the beat signal frequency between the longitudinal modes n and m can enter the response bandwidth of the detection module of the frequency modulated continuous wave radar.
  • the carrier ⁇ m ,0 of the longitudinal mode m and the +1-order sideband ⁇ n ,+1 of the longitudinal mode n are examples of the carrier ⁇ m ,0 of the longitudinal mode m and the +1-order sideband ⁇ n ,+1 of the longitudinal mode n.
  • the following specifically describes the method for determining the modulation frequency. Based on the different characteristics of the modulation results of the signals emitted by the above-mentioned different mode light sources, it can be assumed that the light source A1 is in a multi-longitudinal mode state, and its longitudinal mode interval is ⁇ 0 . Take any two longitudinal modes n and m, the optical frequencies are ⁇ n and ⁇ m respectively, and set their modulation frequency to ⁇ (t).
  • the sideband frequencies of the longitudinal modes n and m after modulation are as follows:
  • the frequency of the self-timer signal between the sidebands (ie, ⁇ 0 ) needs to be greater than the response bandwidth of the detection module A2: ⁇ 0 >B (5)
  • the frequency modulated light signal obtained by modulating the light emitted by the light source with a frequency within the range of formula (6) can be used as a self-test signal, satisfying that the self-test signal frequency between at least two longitudinal modes is less than the bandwidth of the detection module, and the self-test signal frequency between different sidebands of the same longitudinal mode is greater than the bandwidth of the detection module.
  • the frequency difference between different sidebands of the multiple longitudinal modes falls within the response bandwidth of the detection module, that is, the detection module of the frequency modulated continuous wave radar can detect the self-test signal of the self-test signal, and at this time it can be determined that the light source is in a multi-longitudinal mode state. On the contrary, if the self-test signal of the self-test signal is not detected, it can be determined that the light source is in a single longitudinal mode state.
  • the FMCW radar LA may be configured not to emit optical signals to the external space during the self-test period, and the detection module A2 completes the detection of the longitudinal mode state within one self-test period.
  • the FMCW radar since the FMCW radar does not transmit optical signals to the external space during the self-test period, no echo signals reflected from the external space are generated during the detection process, which can effectively avoid interference signals during the detection process, thereby improving the accuracy of the detection result.
  • the solid line represents the fixed-frequency modulated optical signal emitted by the frequency-modulated continuous wave radar to the external space
  • the dotted line represents the echo signal of the fixed-frequency modulated optical signal reflected by an obstacle at a certain distance.
  • the distance of the obstacle only causes a time delay of the optical signal, but does not cause a frequency change.
  • the beat signal between the output signal and the echo signal is zero. Therefore, the fixed-frequency modulated optical signal cannot detect the time delay caused by the distance.
  • the solid line represents the fixed-frequency modulated optical signal emitted by the frequency-modulated continuous wave radar to the external space
  • the dotted line represents the echo signal generated by the fixed-frequency modulated optical signal reflected by a moving obstacle at a certain distance.
  • the echo signal reflected by the moving obstacle produces a Doppler frequency shift relative to the emitted fixed-frequency modulated optical signal, and the beat signal frequencies of the two are also within the response bandwidth of the detection module.
  • the beat signal of the emitted fixed frequency modulated light signal and the echo signal can be detected. Therefore, if the detection module A2 detects the echo signal of the moving obstacle while detecting the self-test signal, it will interfere with the detection and cause the misjudgment of the longitudinal mode state of the light source.
  • the channel for the frequency modulated continuous wave radar LA to transmit the light signal to the external space can be closed to ensure that the frequency modulated continuous wave radar LA does not transmit the light signal to the external space during the self-test period.
  • the channel through which the FMCW radar LA transmits light signals to the external space may also be blocked, so that the FMCW radar LA cannot transmit light signals to the external space during the self-test period.
  • the embodiment of the present invention does not limit the specific closing or shielding method, as long as the FMCW radar LA does not transmit light signals to the external space during the self-test period.
  • the detection module A2 can determine that the light source is in a multi-longitudinal mode state when detecting the self-timer signal of the self-test signal.
  • the frequency modulated continuous wave radar does not transmit light signals to the external space during the self-test period, and there is no beat signal interference of the echo signal.
  • the self-timer signal detected by the detection module corresponds to the self-timer signal between the sidebands of multiple longitudinal modes of the light source.
  • the multi-longitudinal mode state of the light source can be determined according to the detection results within one self-test period. Not only does it not require the use of any external equipment, but the detection system of the radar itself can also be used to detect the longitudinal mode state of the light source without the need for hardware changes, so the detection cost can be reduced.
  • the detection period N is a self-test period
  • the light source A1 transmits a self-test signal in the detection period N
  • the frequency modulated continuous wave radar LA does not transmit a light signal to the external space, which is represented by the light emission state OFF. If the self-timer signal is detected in the detection period N, it can be determined that the light source is in a multi-longitudinal mode state.
  • each cycle includes two frequency detection segments, and the beat signal frequency detected by each frequency detection segment forms a frequency group.
  • the detection cycle N includes two frequency groups ⁇ f 1 ⁇ N , ⁇ f 2 ⁇ N . If an obvious self-beating signal appears in the detection cycle N, the frequencies in the beat signal frequency groups ⁇ f 1 ⁇ N , ⁇ f 2 ⁇ N detected by the detection module A2 are the same, and it is determined that the light source is in a multi-longitudinal mode state. Otherwise, it is determined that the light source is in a single longitudinal mode state.
  • the source A1 emits a self-test signal of at least two adjacent cycles
  • the detection module A2 needs to complete the detection of the longitudinal mode state within at least two adjacent self-test cycles.
  • the longitudinal mode state of the light source can be determined by comparing the self-timer signals obtained in two self-test cycles; on the other hand, since the detection module A2 obtains the detection results of the longitudinal mode state of the light source in multiple self-test cycles, it can avoid the interference caused by the reflected echo from external space obstacles and improve the accuracy of detection.
  • the modulation frequencies of the self-test signals emitted in at least two adjacent self-test cycles may be set to be different.
  • the self-timer signal frequency between longitudinal modes is related to the modulation frequency
  • the modulation frequencies of the self-timer signals emitted in different self-test cycles are different
  • the self-timer signal frequencies between longitudinal modes detected in different cycles are also different.
  • the Doppler frequency shift generated by a moving obstacle is, on the one hand, not related to the modulation frequency; on the other hand, it is limited by acceleration in a short time ( ⁇ s level), so it can be considered that the speed of the obstacle is almost unchanged, so the Doppler frequency shift generated by the moving obstacle is also almost unchanged. In other words, the Doppler frequency shift detected in different self-test cycles is the same.
  • the detection module A2 can determine that the light source is in a multi-longitudinal mode state when it detects a self-timer signal in at least two self-check cycles and the frequencies of the self-timer signals in different self-check cycles are different, thereby avoiding interference caused by reflection echoes from external space obstacles and improving the accuracy of the detection results.
  • the entire detection process does not require the use of any external equipment, and the detection of the longitudinal mode state of the light source can be achieved using the radar's own detection system without hardware changes, thereby reducing the detection cost; further, there is no need to control the frequency modulated continuous wave radar LA not to emit light signals to the external space during the self-check cycle, thereby reducing the complexity of detection.
  • FIG5 a timing diagram of longitudinal mode state detection of a light source based on a multi-cycle self-test signal as shown in FIG5
  • two consecutive detection cycles N and detection cycle N+1 are self-test cycles
  • the light source A1 emits a self-test signal in the detection cycle N and the detection cycle N+1
  • And emit light signals to the external space and the light emission state is ON.
  • the self-test signals emitted in detection cycle N and detection cycle N+1 are fixed-frequency modulated, and the modulation frequencies are different. If self-timer signals are detected in detection cycle N and detection cycle N+1, and the Selfie signal frequencies are different, it can be determined that the light source is in a multi-longitudinal mode state.
  • each cycle includes two frequency detection segments, and the beat signal frequency detected by each frequency detection segment forms a frequency group.
  • the detection period N includes two frequency groups ⁇ f 1 ⁇ N and ⁇ f 2 ⁇ N
  • the detection period N+1 includes two frequency groups ⁇ f 1 ⁇ N+1 and ⁇ f 2 ⁇ N+1 .
  • the frequencies in the beat signal frequency groups ⁇ f 1 ⁇ N and ⁇ f 2 ⁇ N are the same, the frequencies in the beat signal frequency groups ⁇ f 1 ⁇ N+1 and ⁇ f 2 ⁇ N+1 are the same, and the frequencies between ⁇ f 1 ⁇ N and ⁇ f 2 ⁇ N and ⁇ f 1 ⁇ N+1 and ⁇ f 2 ⁇ N+1 are different, it is determined that the light source is in a multi-longitudinal mode state; otherwise, it is determined that the light source is in a single longitudinal mode state.
  • the same frequency is the Doppler frequency shift caused by the moving obstacle.
  • the light source A1 may also have a detection period, and the frequency modulated light signal emitted by the light source A1 during the detection period is a detection signal, which is suitable for detecting the external space of the frequency modulated continuous wave radar LA. Therefore, the frequency modulated continuous wave radar LA can detect the longitudinal mode state of the light source A1 at any time without affecting the normal operation of the radar, and monitor the longitudinal mode state of the radar light source A1 in real time.
  • the detection signal may be a linear frequency modulated optical signal or a nonlinear frequency modulated optical signal.
  • the detection signal can be a linear frequency modulated optical signal, as shown in Figures 6a and 6b; wherein the linear frequency modulated optical signal shown in Figure 6a includes two adjacent frequency sweeping segments, namely an upper frequency sweeping segment whose frequency increases over time and a lower frequency sweeping segment whose frequency decreases over time, and the linear frequency modulated optical signal shown in Figure 6b includes an upper frequency sweeping segment, a non-frequency sweeping segment (the frequency of the optical signal does not change over time) and a lower frequency sweeping segment.
  • the detection signal can also be a nonlinear frequency modulated optical signal, that is, the frequency of the optical signal changes nonlinearly with time. Linear change, as shown in Figure 6c.
  • the present invention does not limit the modulation form of the detection signal, as long as it can detect the distance and speed of the obstacle.
  • the FMCW radar LA1 includes: a light source B1 and a detection module B2, wherein the light source B1 includes: a laser emitting unit B11 and a modulation unit B12, wherein:
  • the laser emitting unit B11 is suitable for emitting laser.
  • the modulation unit B12 is suitable for modulating the laser to obtain a frequency modulated optical signal.
  • the detection module B2 is suitable for detecting the longitudinal mode state of the light source.
  • the frequency modulated continuous wave radar LA1 in the above embodiment is used, and at least one cycle of laser is emitted by the laser emitting unit B11, and the laser is modulated by the modulation unit B12, and the obtained frequency modulated light signal is used as a self-test signal.
  • the detection module B2 obtains the longitudinal mode state of the light source B1 based on the self-timer signal of the self-test signal without the help of any external device.
  • the detection of the longitudinal mode state of the light source is shared with the detection system of the frequency modulated continuous wave radar itself for obstacle detection, without any hardware modification, which can effectively reduce the detection cost; in addition, the detection process of the longitudinal mode state of the light source B1 is carried out during the radar detection period, so the longitudinal mode state of the light source can be quickly judged without affecting the normal operation of the radar, and the detection efficiency is high.
  • the FMCW radar LA1 may further include: a first light splitting unit B3 adapted to split the FMC light signal into a local oscillator light signal and an outgoing signal, wherein the local oscillator light signal is transmitted to the detection module B2 .
  • the frequency modulated continuous wave radar LA1 may also include: an isolation unit B4, the isolation unit B4 includes at least three ports, wherein the first port is suitable for receiving the outgoing signal; the second port allows the outgoing signal to be emitted to the external space, and receives the echo signal of the outgoing signal reflected by an obstacle; the third port is coupled to the detection module B2 so that the echo signal is transmitted to the detection module B2.
  • the detection module B2 includes: a detection unit B21 and a processing unit B22, wherein:
  • the detection unit B21 is adapted to receive the local oscillator optical signal, or the local oscillator optical signal and the echo signal, and convert the optical signal into an electrical signal.
  • the processing unit B22 is adapted to receive the electrical signal and obtain the longitudinal mode state of the light source based on the electrical signal.
  • the frequency modulated continuous wave radar does not emit an outgoing signal to the external space during the self-test period, and therefore does not receive an echo signal during the self-test period.
  • the detection unit B21 receives the local oscillation light signal of the self-test signal transmitted by the isolation unit B4, obtains the Selfie signal of the local oscillation light signal, and converts it into an electrical signal.
  • the processing unit B22 detects the longitudinal mode state of the light source based on the electrical signal.
  • the frequency modulated continuous wave radar transmits an outgoing signal to the external space during the self-test period, so an echo signal reflected by an obstacle may be received during the self-test period.
  • the detection unit B21 receives the local oscillator light signal and the echo signal transmitted by the isolation unit B4, obtains the beat signal, and converts it into an electrical signal.
  • the processing unit B22 detects the longitudinal mode state of the light source based on the electrical signal.
  • the FMCW radar LA1 may further include: a control module B5 adapted to trigger the processing unit B22 to obtain the longitudinal mode state of the light source B1 based on a self-check start instruction.
  • the frequency modulated continuous wave radar LA2 includes: a light source C1, a detection module C2, a first light splitting unit C3 and an isolation unit C4, and a control module C5;
  • the light source C1 includes: a laser C11 and a modulator C12, wherein:
  • the laser C11 is suitable for emitting laser.
  • the laser C11 is an external cavity laser.
  • the modulator C12 is coupled to the laser C11 and is suitable for modulating the laser to obtain a frequency modulated optical signal.
  • the first light splitting unit C3 is coupled to the modulator C12, and is adapted to split the frequency modulated light signal into a local oscillator light signal and an output signal, wherein the local oscillator light signal is transmitted to the detection module C2.
  • the first light splitting unit C3 may be a coupler.
  • the isolation unit C4 may be a circulator, which includes three Ports, wherein the first port C41 is coupled to the first splitter unit C3 and is suitable for receiving the outgoing signal; the second port C42 allows the outgoing signal to be emitted to the external space and receives the echo signal of the outgoing signal reflected by an obstacle; the third port C43 is coupled to the detection module C2 so that the echo signal is transmitted to the detection module C2.
  • the isolation unit C4 may also be a polarization beam splitter.
  • the detection module C2 includes: a detection unit and a processing unit, wherein:
  • the detection unit is adapted to receive the local oscillator optical signal, or the local oscillator optical signal and the echo signal, and convert the optical signal into an electrical signal.
  • the processing unit is adapted to receive the electrical signal and obtain the longitudinal mode state of the light source based on the electrical signal.
  • the detection unit includes a second light splitting unit C21 and a photodetector.
  • the second light splitting unit C21 can be a coupler.
  • the photodetector includes a detector C22 and a detector C23.
  • the second light splitting unit C21 divides the received optical signal into two paths, which are transmitted to the detectors C22 and C23 respectively.
  • the detectors C22 and C23 convert the optical signal into an electrical signal respectively, and transmit it to the processing unit.
  • the processing unit is a signal processing unit (Signal Processing Unit, SPU).
  • SPU Signal Processing Unit
  • control module C5 may be a main processor (MPU), which is adapted to trigger the processing unit to obtain the longitudinal mode state of the external cavity laser B11 based on a self-check start instruction.
  • control module C5 is also adapted to control the light source C1 to emit a self-check signal during the self-check cycle.
  • the frequency modulated continuous wave radar in the above embodiment is used, and at least one cycle of laser is emitted by the laser C11, and the laser is modulated by the modulator C12, and the obtained frequency modulated light signal is used as the self-test signal.
  • the self-test signal is divided into a local oscillator light signal and an outgoing signal through the coupler C3, and the local oscillator light signal and/or the echo signal of the local oscillator light signal and the outgoing signal reflected by the obstacle are transmitted to the detection module C2 by the isolation unit C4, wherein the coupler C21 performs light splitting and transmits them to the detector C22 and the detector C23 respectively, and the two detectors generate electrical signals with the same DC and opposite AC phases, and the processing unit C24 receives and processes the electrical signals to obtain the longitudinal mode state of the laser C11.
  • the detection of the longitudinal mode state of the light source is also consistent with the self-test signal of the frequency modulated continuous wave radar. It can be shared with the detection system used for obstacle detection without any hardware modification, which can effectively reduce the detection cost.
  • the detection process of the longitudinal mode state of laser C11 is carried out during radar detection, so the longitudinal mode state of laser C11 can be quickly judged without affecting the normal operation of the radar, and the detection efficiency is high.
  • the embodiment of the present invention further provides a method for self-checking the longitudinal mode state of a light source of a frequency modulated continuous wave radar.
  • a method for self-checking the longitudinal mode state of a light source of a frequency modulated continuous wave radar Referring to the schematic diagram of the steps of the method for self-checking the longitudinal mode state of a light source of a frequency modulated continuous wave radar shown in FIG. 9 , the following steps can be used to perform self-checking the longitudinal mode state of the light source:
  • step A the light source emits a frequency-modulated light signal in a preset period, wherein at least one period is a self-test period, and the light source emits a self-test signal in the self-test period.
  • Step B obtaining the self-test signal.
  • Step C detecting the self-test signal to determine the longitudinal mode state of the light source.
  • the longitudinal mode state of the light source By adopting the above-mentioned self-detection method for the longitudinal mode state of the light source, by controlling the light source to emit at least one period of frequency-modulated light signal as a self-detection signal, and detecting the self-detection signal, the longitudinal mode state of the light source can be accurately determined without the aid of any external equipment, thereby effectively reducing the detection cost; in addition, the detection process of the longitudinal mode state of the light source is carried out during radar detection, so the longitudinal mode state of the light source can be quickly judged without affecting the normal operation of the radar, and the detection efficiency is high.
  • the self-test signal in order to avoid interference of the modulation signal itself on the detection result, can be modulated at a fixed frequency, so as to obtain a single-frequency longitudinal mode self-timer signal, so that the frequency modulated continuous wave radar can obtain accurate detection results of the longitudinal mode state of the light source.
  • the embodiment of the present invention does not limit the self-test signal to a fixed-frequency modulated optical signal. If the frequency interval between the longitudinal mode sidebands of the light source is small, the self-test signal may also be a non-fixed-frequency modulated optical signal.
  • the modulation frequency of the fixed frequency modulation when the self-test signal is modulated at a fixed frequency, can be set to meet the following conditions: the frequency of the Selfie signal between at least two longitudinal modes of the light source is less than the bandwidth of the detection module, and the frequency of the self-timer signal between different sidebands of the same longitudinal mode is greater than the bandwidth of the detection module.
  • the specific implementation example of determining the modulation frequency of the fixed frequency modulation can be referred to the specific example of the frequency modulated continuous wave radar mentioned above, which will not be repeated here.
  • the Selfie signal between the longitudinal modes of the light source can be frequency-reduced, that is, the frequency of the self-timer signal between the multiple longitudinal modes of the light source is low, so that the detection module can detect the self-timer signal between the longitudinal modes of the light source even when the bandwidth is small, and determine the longitudinal mode state of the light source based on the Selfie signal.
  • the detection module can detect the self-timer signal between the longitudinal modes of the light source even when the bandwidth is small, and determine the longitudinal mode state of the light source based on the Selfie signal.
  • it can prevent the selfie signals between different sidebands of the same longitudinal mode from interfering with the selfie signals between multiple longitudinal modes of the light source, and avoid misjudging different sidebands of the same longitudinal mode as multiple longitudinal modes, thereby obtaining accurate detection results of the longitudinal mode state of the light source.
  • the Selfie signal of the self-test signal when the Selfie signal of the self-test signal is detected within the self-test cycle, it can be determined that the light source is in a multi-longitudinal mode state. Specifically, if there are multiple longitudinal modes in the light emitted by the light source, the frequency difference between different sidebands of the multiple longitudinal modes falls within the response bandwidth of the detection module, that is, the detection module of the frequency modulated continuous wave radar can detect the self-timer signal of the self-test signal. At this time, it can be determined that the light source is in a multi-longitudinal mode state. Conversely, if the self-timer signal of the self-test signal is not detected, it can be determined that the light source is in a single longitudinal mode state. Not only does it not require the aid of any external equipment, but the detection system of the radar itself can also be used to detect the longitudinal mode state of the light source without the need for hardware changes, so the detection cost can be reduced.
  • the frequency modulated continuous wave radar in order to avoid interference signals during the detection process, can be set not to transmit light signals to the external space during the self-test period, and the detection module completes the detection of the longitudinal mode state within one self-test period.
  • the specific implementation example of setting the frequency modulated continuous wave radar not to transmit light signals to the external space during the self-test period can be referred to the specific example of the frequency modulated continuous wave radar mentioned above, which will not be repeated here.
  • the FMCW radar since the FMCW radar does not transmit optical signals to the external space during the self-test period, no echo signals reflected from the external space are generated during the detection process, which can effectively avoid interference signals during the detection process, thereby improving the accuracy of the detection result.
  • a Selfie signal of the self-test signal when a Selfie signal of the self-test signal is detected within at least two adjacent self-test cycles, it can be determined that the light source is in a multi-longitudinal mode state.
  • the longitudinal mode state of the light source can be determined by comparing the self-timer signals obtained in two adjacent self-test cycles; on the other hand, since the detection results of the longitudinal mode state of the light source are obtained in multiple self-test cycles, the interference caused by the reflected echo from external space obstacles can be avoided, thereby improving the accuracy of detection.
  • the modulation frequencies of the self-test signals emitted in at least two adjacent self-test cycles can be set to be different.
  • the frequencies of the self-test signals detected in at least two adjacent self-test cycles are different, it can be determined that the light source is in a multi-longitudinal mode state.
  • the detection system of the radar itself can be used to detect the longitudinal mode state of the light source without hardware modification, so the detection cost can be reduced; further, there is no need to control the frequency modulated continuous wave radar not to emit light signals to the external space during the self-test period, thereby reducing the detection complexity.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Optical Radar Systems And Details Thereof (AREA)

Abstract

Des modes de réalisation de la présente invention concernent un radar à onde continue modulée en fréquence et un procédé d'auto-détection pour un état de mode longitudinal d'une source de lumière. Le radar à onde continue modulée en fréquence comprend : une source de lumière appropriée pour transmettre un signal optique modulé en fréquence dans une période prédéfinie, au moins une période étant une période d'auto-détection, et le signal optique modulé en fréquence transmis par la source de lumière dans la période d'auto-détection étant un signal d'auto-détection; et un module de détection approprié pour détecter le signal d'auto-détection de façon à déterminer l'état de mode longitudinal de la source de lumière. En utilisant la solution, la détection de l'état de mode longitudinal de la source de lumière du radar à onde continue modulée en fréquence peut être réalisée sans dispositif externe, de telle sorte que le coût de détection est réduit, et l'efficacité de détection est améliorée.
PCT/CN2023/117011 2022-10-24 2023-09-05 Radar à onde continue à modulation de fréquence et procédé d'auto-détection pour l'état de mode longitudinal d'une source de lumière WO2024087891A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02263126A (ja) * 1989-04-04 1990-10-25 Toshiba Corp レーザ出力光監視装置
US4982082A (en) * 1989-11-21 1991-01-01 Hughes Aircraft Company Frequency detector for discriminating multi-longitudinal mode laser operation
JP2004061126A (ja) * 2002-07-24 2004-02-26 Nippon Telegr & Teleph Corp <Ntt> 光周波数測定装置および測定方法
CN109031337A (zh) * 2018-09-28 2018-12-18 深圳市速腾聚创科技有限公司 激光雷达及其测距方法
CN115015953A (zh) * 2022-06-06 2022-09-06 长沙思木锐信息技术有限公司 微波驱动的fmcw激光雷达探测装置及其探测方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02263126A (ja) * 1989-04-04 1990-10-25 Toshiba Corp レーザ出力光監視装置
US4982082A (en) * 1989-11-21 1991-01-01 Hughes Aircraft Company Frequency detector for discriminating multi-longitudinal mode laser operation
JP2004061126A (ja) * 2002-07-24 2004-02-26 Nippon Telegr & Teleph Corp <Ntt> 光周波数測定装置および測定方法
CN109031337A (zh) * 2018-09-28 2018-12-18 深圳市速腾聚创科技有限公司 激光雷达及其测距方法
CN115015953A (zh) * 2022-06-06 2022-09-06 长沙思木锐信息技术有限公司 微波驱动的fmcw激光雷达探测装置及其探测方法

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