WO2023077801A1 - 激光雷达 - Google Patents

激光雷达 Download PDF

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Publication number
WO2023077801A1
WO2023077801A1 PCT/CN2022/097824 CN2022097824W WO2023077801A1 WO 2023077801 A1 WO2023077801 A1 WO 2023077801A1 CN 2022097824 W CN2022097824 W CN 2022097824W WO 2023077801 A1 WO2023077801 A1 WO 2023077801A1
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WIPO (PCT)
Prior art keywords
light
laser
external cavity
feedback device
semiconductor laser
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PCT/CN2022/097824
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English (en)
French (fr)
Inventor
吴世祥
李大汕
向少卿
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上海禾赛科技有限公司
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Publication of WO2023077801A1 publication Critical patent/WO2023077801A1/zh

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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
    • 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
    • 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
    • G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • 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
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • 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
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
    • 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
    • G01S7/495—Counter-measures or counter-counter-measures using electronic or electro-optical means
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Definitions

  • the invention relates to laser detection, in particular to a laser radar.
  • Lidar is a commonly used ranging sensor, which has the characteristics of long detection distance, high resolution, and low environmental interference. It is widely used in intelligent robots, drones, unmanned driving and other fields.
  • the working principle of lidar is to use the time it takes for the laser to go back and forth between the radar and the target, or the frequency shift caused by the frequency modulation continuous light going back and forth between the radar and the target to evaluate information such as the distance or speed of the target.
  • the distance measurement performance is an important technical indicator of lidar.
  • the distance measurement performance of lidar mainly depends on the signal-to-noise ratio level of the system. As ambient light is an important source of noise, suppressing ambient light has always been an important goal in lidar design.
  • the problem solved by the invention is how to suppress ambient light noise, thereby improving the signal-to-noise ratio of the laser radar and improving the performance of distance measurement.
  • the present invention provides a laser radar, including:
  • the emission unit includes: a narrow linewidth light source, the emission unit is suitable for generating detection light; the detection light emitted to the three-dimensional space is reflected to form echo light; an optical filter and a detection unit, the optical filter
  • the detection unit and the detection unit are sequentially located on the optical path of the echo light, the detection unit includes: a single photon detector, and the detection unit is suitable for receiving the echo light transmitted through the optical filter.
  • the linewidth of the narrow linewidth light source is within 1 nm.
  • the narrow linewidth light source includes: at least one of a narrow linewidth laser module and a narrow linewidth laser.
  • the narrow linewidth laser module includes: at least one semiconductor laser and an external cavity feedback device located on the light emitting path of the semiconductor laser.
  • the semiconductor laser includes: at least one of an edge emitting laser and a vertical cavity surface emitting laser.
  • the external cavity feedback device includes: a grating.
  • the grating includes: at least one of a volume Bragg grating and a volume fiber grating.
  • the incident surface of the external cavity feedback device is perpendicular to the optical axis of the light beam generated by the semiconductor laser.
  • the narrow linewidth laser module further includes: a collimating device, the collimating device is located on the optical path between the semiconductor laser and the external cavity feedback device to compress the beam divergence angle.
  • the divergence angle of the light beam incident on the external cavity feedback device is less than 10°.
  • the light beam generated by the semiconductor laser is vertically incident on the external cavity feedback device.
  • the reflectivity of the light exit front cavity surface of the semiconductor laser is less than a preset value so that the light reflected by the external cavity feedback device is projected into the semiconductor laser again.
  • the reflectivity of the light exit front cavity surface of the semiconductor laser is within 5%.
  • the distance between the semiconductor laser and the external cavity feedback device is smaller than a preset value to improve the feedback efficiency of the external cavity feedback device.
  • the distance between the semiconductor laser and the external cavity feedback device is less than 5mm.
  • the external cavity feedback device is a volume Bragg grating, and the thickness of the volume Bragg grating is smaller than a preset value to improve the feedback efficiency of the external cavity feedback device.
  • the thickness of the volume Bragg grating is within 5mm.
  • the narrow linewidth laser includes: at least one of a distributed feedback laser and a photonic crystal surface emitting laser.
  • the bandwidth of the optical filter is determined based on the wavelength of the detection light generated by the emitting unit to suppress ambient light.
  • the optical filter is an ultra-narrow-band optical filter.
  • the bandwidth of the filter is within 10nm.
  • it also includes: an outgoing transmission unit and a receiving transmission unit, the outgoing transmission unit is located on the optical path of the probe light, and the receiving transmission unit is located on the optical path of the echo light; the receiving transmission unit and the At least one of the outgoing transmission units has a telecentric design.
  • the receiving transmission unit includes a receiving aperture and a receiving optical assembly, the receiving aperture is located on the focal plane of the receiving optical assembly away from the detection unit; and/or, the outgoing transmission unit It includes an exit aperture and an exit optical assembly; the exit aperture is located on the focal plane of the emission optical assembly away from the emitting unit.
  • the receiving optical assembly includes: a positive-negative lens group to lengthen the focal length.
  • the echo light is vertically incident on the filter.
  • the single photon detector includes: at least one of a SiPM detector and a SPAD detector.
  • the emitting unit includes a narrow linewidth light source
  • the detecting unit includes a single photon detector.
  • the detection light width generated by the narrow-linewidth light source is very small and the wavelength is stable, which can provide enough space for the compression of the filter bandwidth, that is, the filter can be set as a filter with a relatively small bandwidth, which can effectively suppress the environment
  • Light, combined with the single photon detector in the detection unit, can effectively improve the signal-to-noise ratio; and the single-photon detector has lower circuit noise and dark noise, which can further improve the signal-to-noise ratio.
  • the incident surface of the external cavity feedback device is perpendicular to the optical axis of the beam generated by the semiconductor laser; the divergence angle of the beam generated by the semiconductor laser is compressed by a collimator; so that the beam generated by the semiconductor laser Incident to the external cavity feedback device as vertically as possible, so as to ensure the accuracy of the wavelength locked by the external cavity feedback device, effectively ensure the compression effect of the spectral bandwidth of the detection light, and then achieve the purpose of improving the signal-to-noise ratio.
  • the distance between the external cavity feedback device and the semiconductor laser and the length of the optical path of the probe light inside the external cavity feedback device are specially designed to meet their respective preset values, In order to effectively ensure the feedback efficiency of the external cavity feedback device.
  • the narrow linewidth light source may also be a narrow linewidth laser, such as at least one of a distributed feedback laser or a photonic crystal surface emitting laser.
  • the linewidth of the beam formed by the narrow-linewidth laser is relatively narrow. Directly using the narrow-linewidth laser as the light source can realize the integrated setting of the light source, which is conducive to the improvement of the integration of the laser radar.
  • the lidar further includes: an ultra-narrow-band filter. Since the emission unit includes a narrow-linewidth light source, its spectral bandwidth is extremely small, for example, less than 1 nm, and has a lower spectral temperature drift, so the bandwidth of the ultra-narrow-band filter is extremely small, for example, less than 10 nm, which can Effectively suppress ambient light noise, thereby achieving the purpose of improving the signal-to-noise ratio.
  • the echo light is vertically incident on the ultra-narrow-band filter to prevent the filter from changing the transmission wavelength when the echo light deviates from the vertical incidence, thereby ensuring that the bandwidth of the ultra-narrow-band filter is stable and effective. Suppresses return light loss caused by filter angle drift.
  • At least one of the receiving transmission unit and the outgoing transmission unit has a telecentric design.
  • the optical path of the telecentric design can make the echo light incident on the ultra-narrow-band filter and the detection unit substantially perpendicularly after being focused, so as to achieve the purpose of suppressing the angle drift;
  • the telecentric The optical path is designed so that the probe light perpendicular to the focal plane is collimated and exits through the diaphragm, which can effectively ensure the light extraction efficiency.
  • the receiving optical assembly includes: a positive-negative lens group to lengthen the focal length.
  • the positive-negative lens group realizes a compact long focal length receiving lens group, which can effectively reduce the instantaneous field of view of the laser radar, effectively reduce the reception of ambient light, and help improve the signal-to-noise ratio.
  • Fig. 1 is a functional block diagram of an embodiment of the laser radar of the present invention
  • Fig. 2 is a schematic structural diagram of a narrow linewidth light source in the lidar embodiment shown in Fig. 1;
  • Fig. 3 shows a schematic diagram of the optical path structure of the lidar embodiment shown in Fig. 1;
  • Fig. 4 is a schematic structural diagram of a narrow linewidth light source in another embodiment of the laser radar of the present invention.
  • Fig. 5 is a structural schematic diagram of a narrow linewidth light source in another embodiment of the laser radar of the present invention.
  • FIG. 6 is a schematic diagram of the optical path structure of another embodiment of the laser radar of the present invention.
  • FIG. 7 is a schematic diagram of the optical path structure of another embodiment of the laser radar of the present invention.
  • Fig. 8 is a schematic diagram of the principle of the optical system in the embodiment of Fig. 7;
  • FIG. 9 is a schematic diagram of the optical path structure of another embodiment of the laser radar of the present invention.
  • Fig. 10 is a schematic diagram of the optical path structure of another embodiment of the laser radar of the present invention.
  • One approach is to achieve the smallest possible single-pixel instantaneous field of view.
  • the amount of ambient light received by the detector is proportional to the square of the instantaneous field of view, so reducing the instantaneous field of view of a single pixel as much as possible can effectively reduce the impact of ambient light.
  • a small instantaneous field of view means a longer focal length or a smaller pixel size, which poses considerable challenges to both the optical system and the detection device.
  • Optical filters can effectively remove light in wavelength bands other than the bandwidth, so the use of narrow-band optical filters corresponding to the emission wavelength can effectively suppress ambient light other than the emission wavelength.
  • the emission wavelength must be within the bandwidth of the filter, so factors such as the bandwidth of the laser in the light source in the lidar, the spectral temperature drift of the laser, and the spectral temperature drift of the filter are all related to the bandwidth of the filter.
  • Existing laser radars often use semiconductor lasers as light sources, but the excessive spectral bandwidth and spectral temperature drift of semiconductor lasers limit the space for bandwidth compression of the filter, which affects the further compression of the bandwidth of the filter, making it difficult to achieve the ambient light suppression effect Ideal level.
  • the emission unit includes: a narrow linewidth light source, the emission unit is suitable for generating detection light; the detection light emitted to the three-dimensional space is reflected to form echo light; an optical filter and a detection unit, the optical filter
  • the detection unit and the detection unit are sequentially located on the optical path of the echo light, the detection unit includes: a single photon detector, and the detection unit is suitable for receiving the echo light transmitted through the optical filter.
  • the emitting unit includes a narrow linewidth light source
  • the detecting unit includes a single photon detector.
  • the detection light width generated by the narrow-linewidth light source is very small and the wavelength is stable, which can provide enough space for the compression of the filter bandwidth, that is, the filter can be set as a filter with a relatively small bandwidth, which can effectively suppress the environment
  • Light, combined with the single photon detector in the detection unit, can effectively improve the signal-to-noise ratio; and the single-photon detector has lower circuit noise and dark noise, which can further improve the signal-to-noise ratio.
  • FIG. 1 shows a functional block diagram of an embodiment of the laser radar of the present invention.
  • the lidar includes:
  • the emitting unit 110 includes: a narrow linewidth light source 111, the emitting unit 110 is suitable for generating a probe light 112; the probe light 112 emitted to a three-dimensional space is reflected to form an echo light 132; an optical filter 120 and The detection unit 130, the filter 120 and the detection unit 130 are sequentially located on the optical path of the echo light 132, the detection unit 130 includes: a single photon detector 131, the detection unit 130 is suitable for receiving the transmitted light The echo light of the filter 120.
  • the emitting unit 110 adopts a narrow linewidth light source 111, and the generated probe light 112 has a very small linewidth and stable wavelength, which can provide enough space for the compression of the filtering bandwidth; therefore, the optical filter can be set to a bandwidth of A fairly small filter, so as to achieve the purpose of greatly suppressing ambient light noise, combined with the low circuit noise characteristics of the single photon detector in the detection unit, can effectively control the overall noise, improve the signal-to-noise ratio, and improve the performance of the distance measurement .
  • the emission unit 110 is suitable for generating probe light 112 .
  • the emitting unit 110 includes a narrow linewidth light source 111 , that is, the narrow linewidth light source 111 is suitable for generating a narrow linewidth probe light 112 .
  • the linewidth of the narrow linewidth light source 111 is within 1 nm. In this way, the compression space of the bandwidth of the optical filter can be effectively expanded, which is beneficial to the further improvement of the ambient light suppression effect.
  • the narrow linewidth light source 111 may be a narrow linewidth laser module. But narrow linewidth laser modules are just one example. In other embodiments of the present invention, the narrow linewidth light source may also be a narrow linewidth laser.
  • FIG. 2 a schematic structural diagram of the narrow linewidth light source in the lidar embodiment shown in FIG. 1 is shown.
  • the narrow linewidth laser module includes: at least one semiconductor laser 113 and an external cavity feedback device 114 located on the light emitting path of the semiconductor laser 113 .
  • the semiconductor laser 113 and the external cavity feedback device 114 can be used to form a narrow linewidth laser module, the existing conventional semiconductor laser 113 can be used to realize the formation of narrow linewidth probe light, and the cost can be effectively controlled.
  • the narrow linewidth light source in the lidar embodiment shown in FIG. 2 includes multiple semiconductor lasers. In other embodiments of the present invention, the narrow linewidth light source may also only include one semiconductor laser.
  • the reason for the spectral temperature drift of the semiconductor laser 113 is that the change in the operating temperature causes a change in the band gap of the semiconductor, and the change in the band gap of the semiconductor will cause a change in the distribution of inversion particles, so that the most The wavelength that is easy to oscillate changes.
  • the change of the wavelength that is most likely to start vibration does not mean that there is no distribution of inversion particles at the energy level corresponding to the target wavelength, but that part of the energy is extracted by the wavelength that starts vibration first.
  • the external cavity feedback device 114 provides feedback for the resonant cavity of the semiconductor laser 113 to reflect photons of the target wavelength, then the longitudinal mode corresponding to the target wavelength can start to vibrate and extract energy, So as to achieve the purpose of locking wavelength and mode selection.
  • the external cavity feedback device 114 can lock the wavelength of the semiconductor laser 113, thereby reducing the spectral bandwidth and spectral temperature drift of the semiconductor laser 113, thereby providing space for the bandwidth compression of the optical filter, and enhancing the suppression ability of ambient light , thereby improving the signal-to-noise ratio and improving the radar ranging capability.
  • the semiconductor laser 113 is an Edge-Emitting Laser (EEL).
  • EEL Edge-Emitting Laser
  • the narrow linewidth light source includes a plurality of semiconductor lasers 113 , each of which generates a line of laser light, and the plurality of semiconductor lasers 113 are arranged in an array.
  • the semiconductor laser may also include a plurality of light emitting units arranged in an array, capable of simultaneously generating multi-line laser light.
  • the external cavity feedback device 114 includes: gratings, such as at least one of volume Bragg gratings (Volume Bragg Gratings, VBG) and volume fiber gratings.
  • gratings such as at least one of volume Bragg gratings (Volume Bragg Gratings, VBG) and volume fiber gratings.
  • the light beam generated by the semiconductor laser 113 is vertically incident on the external cavity feedback device 114 . Since the wavelength of light reflected by the external cavity feedback device 114 is related to the optical path length of its internal light transmission, making the light incident vertically can effectively improve the accuracy of the wavelength of photons reflected by the external cavity feedback device 114, which is conducive to further improving The accuracy of locking the wavelength further improves the suppression effect of spectral temperature drift.
  • the incident surface of the external cavity feedback device 114 is perpendicular to the optical axis of the light beam generated by the semiconductor laser 113, so that as many light rays generated by the semiconductor laser 113 as possible can be vertically incident into the external cavity feedback device 114 .
  • the narrow linewidth laser module further includes: a collimating device 115, the collimating device 115 is located on the optical path between the semiconductor laser 113 and the external cavity feedback device 114 to compress the beam divergence.
  • the compression of the divergence angle of the beam can make the light generated by the semiconductor laser 113 incident into the external cavity feedback device 114 at an angle as vertical as possible, which is beneficial to reduce light energy loss and improve luminous efficiency.
  • the divergence angle of the light beam incident on the external cavity feedback device 114 is less than 10°. Compressing the divergence angle of the beam to less than 10° minimizes the divergence of the beam and makes the beam incident perpendicular to the external cavity feedback device 114 as much as possible.
  • the semiconductor laser 113 is an edge-emitting laser, so the collimator 115 is a fast-axis collimator lens (Fast-Axis Collimators, FAC). Therefore, the light generated by the semiconductor laser 113 undergoes fast-axis compression through the fast-axis collimating lens, and then achieves wavelength locking through the external cavity feedback device 114, that is, Volume Bragg gratings (Volume Bragg gratings, VBG), thereby realizing Narrow spectral linewidth, and stable spectral output within a certain temperature range.
  • FAC fast-axis collimator lens
  • the reflectivity of the cavity surface before the light exit of the semiconductor laser 113 is smaller than a preset value so that the light reflected by the external cavity feedback device 114 is projected into the semiconductor laser 113 again.
  • the front cavity surface of the semiconductor laser 113 refers to the laser surface facing the external cavity feedback device 114 in the light emitting direction of the semiconductor laser 113 . Controlling the reflectivity of the cavity surface before the light exit of the semiconductor laser 113 can make the light reflected by the external cavity feedback device 114 re-enter the semiconductor laser 113 as much as possible to cause oscillation and suppress energy loss.
  • the reflectivity of the light-exiting front cavity surface of the semiconductor laser 113 is within 5%.
  • the distance between the semiconductor laser 113 and the external cavity feedback device 114 is smaller than a preset value to improve the feedback efficiency of the external cavity feedback device 114 . Controlling the distance between the semiconductor laser 113 and the external cavity feedback device 114 can make the relationship generated by the semiconductor laser 113 incident on the external cavity feedback device 114 as much as possible to provide feedback, thereby effectively Provide feedback on efficiency. Specifically, the distance between the semiconductor laser 113 and the external cavity feedback device 114 is less than 5mm.
  • the external cavity feedback device is a volume Bragg grating
  • the thickness of the volume Bragg grating is smaller than a preset value to improve the feedback efficiency of the external cavity feedback device 114 .
  • the greater the thickness of the volume Bragg grating the longer the optical path of the light transmitted inside it, and the greater the divergence of the light. Therefore, controlling the overall thickness of the volume Bragg grating can make as much light as possible provide feedback to improve Feedback efficiency.
  • the thickness of the volume Bragg grating is within 5mm.
  • the emission unit further includes: a uniform light device 116 to further form a desired line light source or dot matrix light source according to system requirements.
  • the homogenizing device 116 may include at least one of a micro-lens array (micro-lens array, MLA) and a diffractive optical element (Diffractive Optical Element, DOE).
  • the probe light 112 generated by the transmitting unit 110 is reflected in a three-dimensional space to form an echo light 132 .
  • the detection unit 130 is suitable for collecting the echo light 132 .
  • the detection unit 130 includes a single photon detector 131, and the optical filter 120 is located on the optical path of the echo light 132, and the optical filter 120 is suitable for removing ambient light and non-detection light in the echo light 132. 112-band infrared light to suppress noise.
  • the probing light 112 is generated by the narrow linewidth light source 111 in the reflection unit 110, that is, the probing light 112 has a narrow linewidth and a stable wavelength; therefore, the signal light wavelength linewidth in the echo light 132 is relatively narrow ; and the optical filter 120 can make the light in the bandwidth range pass through, and block the light outside the bandwidth range, so the bandwidth of the optical filter 120 only needs the part corresponding to the detection light width in the echo light 132, that is, Yes, that is, the optical filter 120 can choose an optical filter with a small bandwidth, so that as much ambient light as possible is filtered by the optical filter, that is, the narrow linewidth laser 111 in the emitting unit 110 Adopt, provide enough space for the compression of filter bandwidth.
  • the ambient light is largely filtered out by the filter 120, which can effectively improve the detection effect of the single photon detector in the detection unit 130; and the single photon detector has lower circuit noise and dark noise, which can further improve the signal noise ratio.
  • the bandwidth of the filter 110 is determined based on the wavelength of the probe light 112 generated by the emitting unit 110 to suppress ambient light, so the generation of the probe light 112 with narrow line width and stable wavelength is the key to the The compression of the bandwidth of the optical filter 120 provides enough space, which can effectively improve the ambient light filtering effect.
  • the optical filter is an ultra-narrow-band optical filter.
  • the bandwidth of the optical filter 110 is within 10 nm. Due to the adoption of the narrow linewidth light source, the bandwidth of the generated probe light 112 is narrower, the wavelength is stable (for example, the bandwidth can be less than 1nm), and the spectral temperature drift is low, so the ultra-narrowband filter, the bandwidth of the filter 110 Restricted within 10nm, not only has limited influence on signal strength, but also can effectively suppress environmental noise and improve system signal-to-noise ratio.
  • the echo light is vertically incident on the filter 120 (incident angle is 0°).
  • incident angle is 0°
  • the transmission wavelength changes, which is called the angle drift of the filter. Controlling the incident angle of echo light can effectively compress the variation range of the transmitted wavelength, which is conducive to suppressing environmental noise and improving the system signal-to-noise ratio.
  • the single photon detector 131 includes: at least one of a SiPM detector and a SPAD detector, that is, the single photon detector includes: a silicon photomultiplier (Silicon photomultiplier, SiPM) detector and at least one of Single Photon Avalanche Diodes (SPAD) detectors.
  • SiPM detectors and SPAD detectors Compared with detectors such as APD detectors (that is, avalanche photodetectors), SiPM detectors and SPAD detectors have more sensitive photon response capabilities, and have lower circuit noise and dark noise. Therefore, the adoption of SiPM detectors and SPAD detectors can effectively improve the signal-to-noise ratio of the system.
  • FIG. 3 shows a schematic diagram of an optical path structure of the lidar embodiment shown in FIG. 1 .
  • the lidar further includes: an outgoing transmission unit 140 and a receiving transmission unit 150, the outgoing transmission unit 140 is located on the optical path of the detection light 112, and the receiving transmission unit 150 is located on the return transmission unit 150.
  • the light path of Wavelight 132 The light path of Wavelight 132.
  • the outgoing transmission unit 140 is located on the optical path of the detection light 112, so the detection light 112 is transmitted to the three-dimensional space after being transmitted by the outgoing transmission unit 140, and the outgoing transmission unit 140 is suitable for detecting the detection light 112 Perform operations such as collimation and shaping.
  • the receiving and transmitting unit 150 is located on the optical path of the echo light 132, so the echo light 132 formed by reflection is received and transmitted by the receiving and transmitting unit 150 to be projected to the detection unit 130, and the receiving and transmitting unit 150 is suitable for Convergence, shaping and other operations are performed on the received echo light 132 .
  • At least one of the receiving transmission unit 150 and the outgoing transmission unit 140 has a telecentric design, that is to say, in the receiving transmission unit 150 and the outgoing transmission unit 140, the apertures are located at At the front focal plane, the image-space chief ray is perpendicular to the focal plane.
  • the exit transmission unit 140 includes an exit diaphragm 142 and an exit optical assembly 141; superior.
  • the telecentric optical path can make the probe light generated by the transmitting unit 110 perpendicular to the focal plane be collimated by the exit optical component 141 and then exit through the exit diaphragm 142 , so as to improve the light extraction efficiency.
  • the receiving and transmitting unit 150 includes a receiving aperture 152 and a receiving optical assembly 151 , and the receiving aperture 152 is located on a focal plane of the receiving optical assembly 151 away from the detecting unit 130 .
  • a receiving and transmitting unit 150 with a telecentric optical path the echoed light is incident on the optical filter 120 and the detection unit 130 at a substantially vertical angle after being focused by the receiving optical assembly 151, so that the light transmitted through the optical filter 120
  • the echo light basically has no angle drift, and the transmission wavelength drift of the filter caused by the incident angle of the echo light on the filter deviates from 0° is suppressed, so as to achieve the purpose of ensuring the narrow bandwidth of the filter.
  • the lidar embodiment adopts an optical path scheme based on a paraxial optical path.
  • the practice of adopting the paraxial solution is only an example.
  • the laser radar of the present invention may also adopt a coaxial optical path solution.
  • the lidar is a solid-state lidar, that is, the transmitting unit 110 and the detecting unit 130 both adopt an area array structure, such as an EEL array or a SPAD area array, and the interior of the lidar There are absolutely no moving parts.
  • the laser radar can also be a mechanically rotating laser radar, for example, the transmitting unit and the detection unit are arranged on the rotor, so as to realize rotational scanning, such as a 360° scanning laser radar.
  • the semiconductor laser 113 is an edge-emitting laser (Edge-Emitting Laser, EEL). Its spectral bandwidth is about 10nm, the manufacturing error of the center wavelength reaches ⁇ 5nm, and the spectral temperature drift coefficient reaches 0.28nm/K. When considering the operating temperature range of 100K of the laser radar, if the light generated by the semiconductor laser 113 is directly used as the detection light, the spectral bandwidth of the filter will be at least 48nm.
  • EEL edge-emitting Laser
  • the spectral bandwidth of the narrow linewidth laser module is compressed to within 1nm, and the spectral temperature drift coefficient can be reduced to less than 0.07nm/K; Considering factors such as manufacturing errors of the optical filter 120 itself, the bandwidth of the optical filter 120 can be reduced to within 10 nm. Therefore, purely from the perspective of ambient light noise, the optical signal-to-noise ratio of this solution is increased by nearly 5 times.
  • the circuit noise (mainly from the amplifier) of the analog signal circuit of the avalanche photodetector (APD) is higher than that of the single photon detector circuit (such as SiPM/SPAD circuit), and the dark noise of the APD device is also much higher than that of the single photon detector (such as SiPM/SPAD). Therefore, the circuit noise and dark noise of single-photon detectors (such as SiPM/SPAD) can also be controlled at extremely low levels compared with traditional avalanche photodetector (APD) devices, and the overall detection signal-to-noise ratio of the system will be larger. The amplitude is increased, and correspondingly, the lidar system can achieve farther detection performance.
  • FIG. 4 shows a schematic structural diagram of a narrow linewidth light source in another embodiment of the lidar of the present invention.
  • this embodiment is a narrow-linewidth laser module solution based on a vertical-cavity surface-emitting laser, that is, in some embodiments of the present invention, the semiconductor laser 213 is a vertical-cavity surface-emitting laser (Vertical-cavity surface-emitting laser) surface-emitting laser, VCSEL).
  • VCSEL Vertical-cavity surface-emitting laser
  • the collimating device 215 is a microlens array
  • the external cavity feedback device 214 is a volume Bragg grating.
  • the semiconductor laser 213 includes a plurality of light-emitting units, the light generated by the light-emitting units is collimated through the microlens array, and the wavelength is locked through the volume Bragg grating to compress the spectral bandwidth.
  • the collimating device 215 can also be other collimating devices such as a diffractive lens
  • the external cavity feedback device 214 can also be other external cavity feedback devices such as a fiber grating.
  • the microlens corresponds to the light emitting unit of the semiconductor laser 213 one by one, and each microlens can collimate the laser light emitted by the light emitting unit.
  • the microlens and the light-emitting unit of the semiconductor laser 213 can be in other correspondences, such as the semiconductor laser 213 and the microlens are set in one-to-one correspondence, and the light emitted by a plurality of light-emitting units of the semiconductor laser 213 is collimated by a microlens. straight.
  • FIG. 5 shows a schematic structural diagram of a narrow linewidth light source in another embodiment of the lidar of the present invention.
  • the narrow linewidth light source is a narrow linewidth laser 311 .
  • the narrow linewidth light source may include a plurality of narrow linewidth lasers 331 .
  • the narrow linewidth laser 311 includes: at least one of a distributed feedback laser (Distributed Feedback Laser, DFB) and a photonic crystal surface emitting laser.
  • DFB distributed Feedback Laser
  • the linewidth of the light beam formed by the narrow linewidth laser 311 is relatively narrow, and the narrow linewidth laser 311 is directly used as the light source, which can realize the integrated setting of the light source, which is beneficial to the improvement of the integration degree of the laser radar.
  • the narrow linewidth laser 311 is a distributed feedback laser. Bragg gratings are arranged inside the distributed feedback laser, which can directly output narrow linewidth spectrum.
  • the downstream of the optical path of the narrow linewidth laser can also be provided with uniform light such as a micro-lens array (micro-lens array, MLA) or a diffractive optical element (Diffractive Optical Element, DOE). device.
  • MLA micro-lens array
  • DOE diffractive Optical Element
  • FIG. 6 shows a schematic diagram of the optical path structure of another embodiment of the laser radar of the present invention.
  • This embodiment is the same as the previous embodiment, and the present invention will not repeat them here.
  • the difference between the foregoing embodiments is that this embodiment adopts an optical path scheme based on rotating mirror scanning.
  • the emitting unit 410 and the detecting unit 430 are respectively located on both sides of the rotating mirror 460, that is, the rotating mirror 160 is located between the emitting unit 410 and the detecting unit 430, and the different surfaces of the rotating mirror 460 are respectively The probe light and the echo light are reflected.
  • the outgoing transmission unit 440 is located between the transmitting unit 410 and the rotating mirror 460; the receiving transmission unit 450 is located between the detecting unit 430 and the rotating mirror 460; in addition, the receiving transmission unit 450
  • the optical filter 420 between the detecting unit 430 is suitable for filtering ambient light and infrared light in the non-detecting light band, so as to improve the signal-to-noise ratio of the system.
  • the lidar shown in Figure 6 is a hybrid solid-state lidar, that is to say, the lidar rotates around the rotation axis through the rotating mirror 460 to deflect the detection light to different angles; other structural components Fixed setting.
  • the rotating mirror can also be other scanning devices.
  • FIG. 7 shows a schematic diagram of an optical path structure of another embodiment of the lidar of the present invention.
  • the emission unit 510 has a narrow linewidth light source
  • the detection unit 530 has a high-sensitivity single-photon detector (such as a SiPM detector, a SPAD detector), and is also provided with a filter 520 (such as ultra-narrow-band filter).
  • the receiving optical assembly includes: a positive-negative lens group to lengthen the focal length, that is, as shown in FIG. 7, the receiving optical assembly includes a positive lens 551 and a negative lens 552, and the positive-negative lens group
  • a compact long focal length receiving lens group is realized in the form of a long focal length optical path, which has a compact structure and can elongate the focal length.
  • each unit has a smaller instantaneous field of view, that is, receives less ambient light, which can also improve the system signal-to-noise ratio.
  • the narrow-linewidth polarized detection light generated by the emission unit 510 is reflected by the polarization beam splitter 561, and after being collimated by the positive lens 551, it is reflected by the mirror 571 to the scanning mirror 572; the detection light is reflected by the scanning device 572 An outgoing scan is formed to illuminate the target under test.
  • the echo light reflected by the target to be measured returns along the original optical path, and after being reflected by the scanning device 572 and the mirror 571, is projected onto the 1/4 wave plate 562, and is polarized after being transmitted through the 1/4 wave plate 562 After being converged by the positive lens 551, the echo light with a changed polarization state can pass through the polarization beam splitter 561, and then expand the beam through the negative lens to lengthen the focal length of the optical system at the receiving end. The echo light finally passes through the The light filtered by the filter 520 is received by the detection unit 530 .
  • FIG. 8 it shows a schematic diagram of the principle of the optical system in the embodiment of the present invention.
  • the optical system in FIG. 8 can be applied to the receiving end of the lidar optical path structure shown in FIG. 7 .
  • the optical system includes a combination of a positive lens 551 and a negative lens 552 .
  • the focal length of the positive lens 551 is f1
  • the convergence angle is ⁇
  • the focal point is A.
  • the converging angle of the negative lens 402 is ⁇ .
  • the light through the positive lens 551 should converge at point A, but after the negative lens 552 is set between the main plane of the positive lens 551 and the focal point A of the positive lens 551, due to the dilation effect of the negative lens 552 on the light, the convergent point of the light is Move far from A to point B, and the convergence angle becomes ⁇ , ⁇ is smaller than ⁇ .
  • the positive lens 551 and the negative lens 552 are combined to form an equivalent lens, the distance between the main plane and the converging point B is f, that is, the focal length of the equivalent lens is f.
  • f is extended compared to f1.
  • the distance between the positive lens 551 and the negative lens 552 is constant (for example, the distance between the main planes of the two is smaller than the focal length of the positive lens 551), the combination of the positive lens 551 and the negative lens 552 can increase the focal length of the optical system.
  • the distance L between the main plane of positive lens 551 and the focal plane where point B is located is the physical length of this optical system, and f is greater than L, which shows that etc.
  • the equivalent focal length f of the effective lens also exceeds the limitation of the physical size of the optical system.
  • a negative lens 552 or a lens group that realizes the function of the negative lens 552 can be set between the positive lens (group) and the detection unit, so that the focal length of the receiving end can be greatly extended, so that when a larger-sized photodetector (such as SiPM, Compared with APD, the photosensitive surface of SiPM is more than double), according to f can be increased with the increase of L, thereby limiting the convergence angle ⁇ to suppress the interference of ambient light, thereby further improving the signal-to-noise ratio of the system.
  • a larger-sized photodetector such as SiPM, Compared with APD, the photosensitive surface of SiPM is more than double
  • the scanning device may be a two-dimensional scanning vibrating mirror, a MEMS vibrating mirror, or a one-dimensional scanning rotating mirror, a vibrating mirror, or the like.
  • the present invention is not limited thereto.
  • the positive lens and negative lens in the illustration are just simplified representations, and may be equivalent representations of lens groups in practical applications, and are not limited to the illustration.
  • FIG. 9 shows a schematic diagram of an optical path structure of another embodiment of the lidar of the present invention.
  • This embodiment is the same as the previous embodiment, and the present invention will not repeat them here.
  • the difference of the above-mentioned embodiments is that this embodiment uses a small reflector to realize the light splitting of the coaxial light path.
  • the probe light produced by the transmitting unit 610 is reflected from the small reflector 660 to the positive lens 651, collimated and reflected by the scanning mirror 670; After being converged, it is transmitted through the edge area of the small mirror 660 , transmitted through the negative lens 652 and the filter 620 , and then received by the detection unit 630 .
  • FIG. 10 shows a schematic diagram of the optical path structure of another embodiment of the lidar of the present invention.
  • the probe light generated by the transmitting unit 710 passes through the small hole of the small mirror 760, is collimated by the positive lens 751, reflected by the mirror 771 and the scanning mirror 772, and then exits; the echo light is transmitted by the scanning mirror 772 and the mirror 771 reflection, the positive lens 751 converges and is reflected to the negative lens 752 by the reflective surface other than the aperture of the small mirror 760 , and is received by the detection unit 730 after being filtered by a filter (not shown in the figure).
  • the emitting unit includes a narrow linewidth light source
  • the detecting unit includes a single photon detector.
  • the detection light width generated by the narrow-linewidth light source is very small and the wavelength is stable, which can provide enough space for the compression of the filter bandwidth, that is, the filter can be set as a filter with a relatively small bandwidth, which can effectively suppress the environment
  • Light, combined with the single photon detector in the detection unit, can effectively improve the signal-to-noise ratio; and the single-photon detector has lower circuit noise and dark noise, which can further improve the signal-to-noise ratio.
  • the incident surface of the external cavity feedback device is perpendicular to the optical axis of the light beam produced by the semiconductor laser; the divergence angle of the light beam produced by the semiconductor laser is compressed by the collimation device; the light beam produced by the semiconductor laser is as vertical as possible
  • the method is incident on the external cavity feedback device, so as to ensure the accuracy of the wavelength locked by the external cavity feedback device, and effectively ensure the compression effect of the spectral bandwidth of the detection light, thereby achieving the purpose of improving the signal-to-noise ratio.
  • the distance between the external cavity feedback device and the semiconductor laser and the length of the optical path of the probe light inside the external cavity feedback device are specially designed to meet their respective preset values, so as to effectively ensure that the external cavity The feedback efficiency of the feedback device.
  • the narrow linewidth light source may also be a narrow linewidth laser, such as at least one of a distributed feedback laser or a photonic crystal surface emitting laser.
  • the linewidth of the beam formed by the narrow-linewidth laser is relatively narrow. Directly using the narrow-linewidth laser as the light source can realize the integrated setting of the light source, which is conducive to the improvement of the integration of the laser radar.
  • the lidar also includes: an ultra-narrow-band filter. Since the emission unit includes a narrow-linewidth light source, its spectral bandwidth is extremely small, for example, less than 1 nm, and has a lower spectral temperature drift, so the bandwidth of the ultra-narrow-band filter is extremely small, for example, less than 10 nm, which can Effectively suppress ambient light noise, thereby achieving the purpose of improving the signal-to-noise ratio.
  • the echo light is vertically incident on the ultra-narrow-band filter to prevent the transmission wavelength change of the echo light when it is transmitted through the ultra-narrow-band filter, effectively suppressing the angle drift of the echo light received by the detection unit, thereby ensuring the The bandwidth of the ultra-narrow-band filter described above is stable.
  • At least one of the receiving transmission unit and the outgoing transmission unit has a telecentric design.
  • the optical path of the telecentric design can make the echo light incident on the ultra-narrow-band filter and the detection unit substantially perpendicularly after being focused, so as to achieve the purpose of suppressing the angle drift;
  • the telecentric The optical path is designed so that the probe light perpendicular to the focal plane is collimated and exits through the diaphragm, which can effectively ensure the light extraction efficiency.
  • the receiving optical assembly includes: a positive-negative lens group to lengthen the focal length.
  • the positive-negative lens group realizes a compact long focal length receiving lens group, which can effectively reduce the instantaneous field of view of the laser radar, effectively reduce the reception of ambient light, and help improve the signal-to-noise ratio.

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Abstract

一种激光雷达，包括：发射单元，所述发射单元包括：窄线宽光源，所述发射单元适宜于产生探测光；出射至三维空间的探测光被反射后形成回波光；滤光片和探测单元，所述滤光片和所述探测单元依次位于所述回波光的光路上，所述探测单元包括：单光子探测器，所述探测单元适宜于接收透射所述滤光片的回波光。窄线宽光源、滤光片和单光子探测器的配合能够有效提高信噪比。

Description

激光雷达
本申请要求2021年11月5日提交中国专利局、申请号为2021113090203、发明名称为“激光雷达”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及激光探测，特别涉及一种激光雷达。
背景技术
激光雷达是一种常用的测距传感器，具有探测距离远、分辨率高、受环境干扰小等特点，广泛应用于智能机器人、无人机、无人驾驶等领域。激光雷达的工作原理是利用激光往返于雷达和目标之间所用的时间，或者调频连续光在雷达和目标之间往返所产生的频移来评估目标的距离或速度等信息。
测远性能是激光雷达的一项重要技术指标。激光雷达的测远性能主要取决于系统的信噪比水平。而环境光作为一项重要噪声来源，抑制环境光一直是激光雷达设计中的一项重要目标。
随着SiPM、SPAD等单光子探测器件引入激光雷达，由于其更强的光子探测能力、更高的灵敏度、更低的电子噪声，使得环境光成为了最主要的噪声信号来源。因此在具有单光子探测器件的激光雷达中，抑制环境光变得尤为重要。
但是现有激光雷达设计往往难以这种满足需求，从而影响了激光雷达的整体性能。
发明内容
本发明解决的问题是如何抑制环境光噪声，从而提高激光雷达的信噪比、提高测远性能。
为解决上述问题，本发明提供一种激光雷达，包括：
发射单元，所述发射单元包括：窄线宽光源，所述发射单元适宜于产生探测光；出射至三维空间的探测光被反射后形成回波光；滤光片和探测单元，所述滤光片和所述探测单元依次位于所述回波光的光路上，所述探测单元包括：单光子探测器，所述探测单元适宜于接收透射所述滤光片的回波光。
可选的，所述窄线宽光源的线宽在1nm以内。
可选的，所述窄线宽光源包括：窄线宽激光器模组和窄线宽激光器中的至少一种。
可选的，所述窄线宽激光器模组包括：至少一个半导体激光器和位于所述半导体激光器发光光路上的外腔反馈器件。
可选的，所述半导体激光器包括：边发射激光器和垂直腔面发射激光器中的至少一种。
可选的，所述外腔反馈器件包括：光栅。
可选的，所述光栅包括：体布拉格光栅和体光纤光栅中的至少一种。
可选的，所述外腔反馈器件的入射面垂直于所述半导体激光器所产生的光束的光轴。
可选的，所述窄线宽激光器模组还包括：准直器件，所述准直器件位于所述半导体激光器和所述外腔反馈器件之间的光路上以压缩光束发散角。
可选的，入射至所述外腔反馈器件的光束的发散角小于10°。
可选的，所述半导体激光器所产生的光束垂直入射至所述外腔反馈器件。
可选的，所述半导体激光器的出光前腔面的反射率小于预设值以 使所述外腔反馈器件所反射的光线再次投射入所述半导体激光器。
可选的，所述半导体激光器的出光前腔面的反射率在5％以内。
可选的，所述半导体激光器和所述外腔反馈器件之间的距离小于预设值以提高所述外腔反馈器件的反馈效率。
可选的，所述半导体激光器和所述外腔反馈器件之间的距离小于5mm。
可选的，所述外腔反馈器件为体布拉格光栅，所述体布拉格光栅的厚度小于预设值以提高所述外腔反馈器件的反馈效率。
可选的，所述体布拉格光栅的厚度在5mm以内。
可选的，所述窄线宽激光器包括：分布式反馈激光器和光子晶体表面发射激光器中的至少一种。
可选的，所述滤光片的带宽基于所述发射单元所产生探测光的波长确定以抑制环境光。
可选的，所述滤光片为超窄带滤光片。
可选的，所述滤光片的带宽在10nm以内。
可选的，还包括：出射传输单元和接收传输单元，所述出射传输单元位于所述探测光的光路上，所述接收传输单元位于所述回波光的光路上；所述接收传输单元和所述出射传输单元中至少一个具有远心设计。
可选的，所述接收传输单元包括接收光阑和接收光学组件，所述接收光阑位于所述接收光学组件远离所述探测单元一侧的焦平面上；和/或，所述出射传输单元包括出射光阑和出射光学组件；所述出射光阑位于所述发射光学组件远离所述发射单元一侧的焦平面上。
可选的，所述接收光学组件包括：正-负透镜组以拉长焦距。
可选的，所述回波光垂直入射至所述滤光片。
可选的，所述单光子探测器包括：SiPM探测器和SPAD探测器中的至少一种。
与现有技术相比，本发明的技术方案具有以下优点：
本发明技术方案中，所述发射单元包括窄线宽光源，所述探测单元包括单光子探测器。所述窄线宽光源所产生探测光线宽很小、波长稳定，能够为滤光带宽的压缩提供足够的空间，即所述滤光片能够设置为带宽相当小的滤光片，能够有效抑制环境光，配合探测单元中的单光子探测器，能够有效提高信噪比；而且单光子探测器具有更低的电路噪声和暗噪声，从而能够进一步改善信噪比。
本发明可选方案中，所述外腔反馈器件的入射面垂直于所述半导体激光器所产生光束的光轴；通过准直器件压缩半导体激光器所产生光束的发散角；使得半导体激光器所产生的光束以尽可能垂直的方式入射至所述外腔反馈器件，从而以保证外腔反馈器件所锁定波长的精度，有效保证探测光光谱带宽的压缩效果，进而达到改善信噪比的目的。
本发明可选方案中，所述外腔反馈器件和所述半导体激光器之间的距离和所述探测光在所述外腔反馈器件内部光程的长度通过特别设计以满足各自的预设值，以有效保证外腔反馈器件的反馈效率。
本发明可选方案中，所述窄线宽光源还可以是窄线宽激光器，例如分布式反馈激光器或者光子晶体表面发射激光器中的至少一种。窄线宽激光器所形成光束的线宽较窄，直接采用窄线宽激光器作为光源，能够实现光源的集成式设置，有利于激光雷达集成度的提高。
本发明可选方案中，所述激光雷达还包括：超窄带滤光片。由于所述发射单元包括窄线宽光源，其光谱带宽极小，例如可以小于1nm，而且具有较低的光谱温漂，因此所述超窄带滤光片的带宽极小，例如可以小于10nm，能够有效抑制环境光噪声，进而达到改善信噪比的目的。
本发明可选方案中，回波光垂直入射至所述超窄带滤光片，防止滤光片在回波光偏离垂直入射时出现透射波长变化，从而保证所述超窄带滤光片的带宽稳定，有效抑制滤光片角度漂移导致的回波光损失。
本发明可选方案中，所述接收传输单元和所述出射传输单元中至少一个具有远心设计。对于接收传输单元而言，远心设计的光路能够使回波光聚焦后基本垂直入射至所述超窄带滤光片和探测单元，从而达到抑制角度漂移的目的；对于出射传输单元而言，远心设计的光路，使垂直于焦平面的探测光都准直后经光阑出射，能有效保证出光效率。
本发明可选方案中，所述接收光学组件包括：正-负透镜组以拉长焦距。正-负透镜组的形式实现紧凑型长焦距接收镜头组，能有效减小所述激光雷达的瞬时视场角，能有效减少环境光的接收，有利于改善信噪比。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本发明激光雷达一实施例的功能框图；
图2是图1所示激光雷达实施例中窄线宽光源的结构示意图；
图3示出了图1所示激光雷达实施例的光路结构示意图；
图4是本发明激光雷达另一实施例中窄线宽光源的结构示意图；
图5是本发明激光雷达再一实施例中窄线宽光源的结构示意图；
图6是本发明激光雷达又一实施例的光路结构示意图；
图7是本发明激光雷达又一实施例的光路结构示意图；
图8是图7实施例中光学系统的原理示意图；
图9是本发明激光雷达又一实施例的光路结构示意图；
图10是本发明激光雷达又一实施例的光路结构示意图。
具体实施方式
由背景技术可知，现有技术中激光雷达的设计抑制环境光的能力难以满足使用单光子探测器的要求。现结合当前激光雷达设计抑制环境光的途径分析其难以满足需求的原因：
现有激光雷达光学系统的设计中，环境光抑制的途径主要有两个：
一个途径是实现尽可能小的单像素瞬时视场角。探测器接收的环境光量与瞬时视场角呈平方正比关系，因此尽可能减小单个像素的瞬时视场角，能够有效减小环境光的影响。但是小的瞬时视场角意味着更长的焦距或更小的像素尺寸，这对光学系统和探测器件来说均具有相当的挑战。
另一个途径是减小滤光片带宽。滤光片可有效去除带宽以外波段光线，因此采用发射波长相对应的窄带滤光片能够有效抑制发射波长以外的环境光。但是发射波长必须位于滤光片的带宽范围内，因此激光雷达内光源中激光器的带宽、激光器的光谱温漂、滤光片的光谱温漂等因素均与滤光片的带宽相关。现有激光雷达往往采用半导体激光器作为光源，而半导体激光器过大的光谱带宽和光谱温漂使滤光片带宽压缩的空间有限，影响了滤光片带宽的进一步压缩，导致环境光抑制效果难以达到理想水平。
为解决所述技术问题，本发明提供一种激光雷达，包括：
发射单元，所述发射单元包括：窄线宽光源，所述发射单元适宜于产生探测光；出射至三维空间的探测光被反射后形成回波光；滤光片和探测单元，所述滤光片和所述探测单元依次位于所述回波光的光 路上，所述探测单元包括：单光子探测器，所述探测单元适宜于接收透射所述滤光片的回波光。
本发明技术方案中，所述发射单元包括窄线宽光源，所述探测单元包括单光子探测器。所述窄线宽光源所产生探测光线宽很小、波长稳定，能够为滤光带宽的压缩提供足够的空间，即所述滤光片能够设置为带宽相当小的滤光片，能够有效抑制环境光，配合探测单元中的单光子探测器，能够有效提高信噪比；而且单光子探测器具有更低的电路噪声和暗噪声，从而能够进一步改善信噪比。
为使本发明的上述目的、特征和优点能够更为明显易懂，下面结合附图对本发明的具体实施例做详细的说明。
参考图1，示出了本发明激光雷达一实施例的功能框图。
所述激光雷达包括：
发射单元110，所述发射单元110包括：窄线宽光源111，所述发射单元110适宜于产生探测光112；出射至三维空间的探测光112被反射后形成回波光132；滤光片120和探测单元130，所述滤光片120和所述探测单元130依次位于所述回波光132的光路上，所述探测单元130包括：单光子探测器131，所述探测单元130适宜于接收透射所述滤光片120的回波光。
其中，所述发射单元110采用窄线宽光源111，所产生的探测光112线宽很小、波长稳定，能够为滤光带宽的压缩提供足够的空间；因此所述滤光片能够设置为带宽相当小的滤光片，从而达到大幅度抑制环境光噪声的目的，配合探测单元中单光子探测器低电路噪声的特性，能够达到有效控制总体噪声，提高信噪比，提升测远性能的目的。
下面结合附图详细说明本发明激光雷达实施例的技术方案。
所述发射单元110适宜于产生探测光112。所述发射单元110包括窄线宽光源111，即所述窄线宽光源111适宜于产生窄线宽的探测光112。
本发明一些实施例中，所述窄线宽光源111的线宽在1nm以内。这样能够有效扩大滤光片带宽的压缩空间，有利于环境光抑制效果的进一步提升。
本发明一些实施例中，所述窄线宽光源111可以为窄线宽激光器模组。但是窄线宽激光器模组仅为一示例。本发明另一些实施例中，所述窄线宽光源也可以为窄线宽激光器。
结合参考图2，示出了图1所示激光雷达实施例中窄线宽光源的结构示意图。
本发明一些实施例中，所述窄线宽激光器模组包括：至少一个半导体激光器113和位于所述半导体激光器113发光光路上的外腔反馈器件114。利用所述半导体激光器113和所述外腔反馈器件114构成窄线宽激光器模组的做法，能够利用现有常规半导体激光器113实现窄线宽探测光的形成，能够有效控制成本。
需要说明的是，图2所示激光雷达实施例中窄线宽光源包括多个半导体激光器。本发明另一些实施例中，所述窄线宽光源也可以仅包括1个半导体激光器。
所述半导体激光器113的光谱温漂产生的原因是：工作温度变化引起了半导体禁带宽度发生了变化，而半导体禁带宽度的变化会导致反转粒子的分布发生变化，使该工作温度下最容易起振的波长发生变化。但是最容易起振波长的变化并不表示目标波长相对应的能级上没有反转粒子的分布，只是该部分能量被最先起振的波长提取了。因此在振荡尚未开始的荧光阶段，所述外腔反馈器件114为所述半导体激光器113的谐振腔提供反馈，反射目标波长的光子，那么目标波长所对应的纵模既能够起振，提取能量，从而达到锁定波长、模式选择的目的。
所述外腔反馈器件114能够锁定所述半导体激光器113的波长，从而能够减小所述半导体激光器113的光谱带宽和光谱温漂，进而为 滤光片带宽压缩提供空间，增强环境光的抑制能力，进而提升信噪比，提高雷达测远能力。
本发明一些实施例中，所述半导体激光器113为边发射激光器(Edge-Emitting Laser，EEL)。如图2所示，所述窄线宽光源包括多个所述半导体激光器113，每个所述半导体激光器113产生一线激光，多个所述半导体激光器113呈阵列排布。本发明另一些实施例中，所述半导体激光器也可以包括多个呈阵列排布的发光单元，能够同时产生多线激光。
本发明一些实施例中，所述外腔反馈器件114包括：光栅，例如体布拉格光栅(Volume Bragg Gratings，VBG)和体光纤光栅中的至少一种。
本发明一些实施例中，所述半导体激光器113所产生的光束垂直入射至所述外腔反馈器件114。由于所述外腔反馈器件114所反射光线的波长与其内部光线传输的光程长度相关，因此使光线垂直入射，能够有效提高所述外腔反馈器件114所反射光子波长的精度，有利于进一步提高锁定波长的精度，进一步提高光谱温漂的抑制效果。
本发明一些实施例中，所述外腔反馈器件114的入射面垂直于所述半导体激光器113所产生的光束的光轴，从而使所述半导体激光器113所产生的光线尽可能多的能够垂直入射至所述外腔反馈器件114内。
此外，本发明一些实施例中，所述窄线宽激光器模组还包括：准直器件115，所述准直器件115位于所述半导体激光器113和所述外腔反馈器件114之间的光路上以压缩光束发散角。光束发散角的压缩，能够使所述半导体激光器113所产生的光线以尽可能垂直的角度入射至所述外腔反馈器件114内，有利于降低光能损耗，有利于发光效率的提高。
具体的，本发明一些实施例中，入射至所述外腔反馈器件114的 光束的发散角小于10°。将光束发散角压缩至10°以下，尽量减小光束的发散，能够使光束尽可能的垂直于所述外腔反馈器件114入射。
如图2所示实施例中，所述半导体激光器113为边发射激光器，因此所述准直器件115为快轴准直透镜(Fast-Axis Collimators，FAC)。所以，所述半导体激光器113所产生的光线经快轴准直透镜进行快轴压缩，再通过所述外腔反馈器件114，即体布拉格光栅(Volume Bragg gratings，VBG)实现波长锁定，从而可以实现窄光谱线宽，并在一定温度范围内光谱稳定输出。
另外，本发明一些实施例中，所述半导体激光器113的出光前腔面的反射率小于预设值以使所述外腔反馈器件114所反射的光线再次投射入所述半导体激光器113。其中，所述半导体激光器113的出光前腔面是指所述半导体激光器113出光方向上、朝向所述外腔反馈器件114的激光器表面。控制所述半导体激光器113的出光前腔面的反射率，能够使所述外腔反馈器件114反射回的光尽可能多的再次进入所述半导体激光器113以引起振荡，抑制能量损耗。具体的，所述半导体激光器113的出光前腔面的反射率在5％以内。
而且，本发明一些实施例中，所述半导体激光器113和所述外腔反馈器114件之间的距离小于预设值以提高所述外腔反馈器件114的反馈效率。控制所述半导体激光器113和所述外腔反馈器件114之间的距离，能够使所述半导体激光器113所产生的关系尽可能多的入射至所述外腔反馈器件114以提供反馈，从而能够有效提供反馈效率。具体的，所述半导体激光器113和所述外腔反馈器件114之间的距离小于5mm。
如图2所示，本发明一些实施例中，所述外腔反馈器件为体布拉格光栅，所述体布拉格光栅的厚度小于预设值以提高所述外腔反馈器件114的反馈效率。所述体布拉格光栅的厚度的越大，光线在其内部传输的光程越长，光线发散程度越大，因此控制所述体布拉格光栅的整体厚度，能够使尽可能多的光线提供反馈以提高反馈效率。具体的， 所述体布拉格光栅的厚度在5mm以内。
需要说明的是，如图2所示，本发明一些实施例中，所述发射单元还包括：匀光器件116，以进一步根据系统需要形成期望的线光源或点阵光源等。具体的，所述匀光器件116可以包括微透镜阵列(micro-lens array，MLA)和衍射光学元件(Diffractive Optical Element，DOE)中的至少一种。
继续参考图1，所述发射单元110所产生的探测光112在三维空间被反射后形成回波光132。所述探测单元130适宜于采集所述回波光132。所述探测单元130包括单光子探测器131，而且所述滤光片120位于所述回波光132的光路上，所述滤光片120适宜于去除所述回波光132中的环境光以及非探测光112波段的红外光以抑制噪声。
由于所述探测光112由所述反射单元110中的窄线宽光源111产生，即所述探测光112的线宽较窄、波长稳定；因此所述回波光132中的信号光波长线宽较窄；而所述滤光片120能够使带宽范围内的光线透过，阻挡带宽范围以外光线，所以所述滤光片120的带宽仅需要所述回波光132中与探测光线宽相对应的部分即可，即所述滤光片120可以选择带宽很小的滤光片，从而使尽可能多的环境光被滤光片滤除，也就是说，所述发射单元110中窄线宽激光器111的采用，为滤光片带宽的压缩提供足够的空间。
进一步，环境光被所述滤光片120大量滤除，能够有效提高探测单元130中单光子探测器的探测效果；而且单光子探测器具有更低的电路噪声和暗噪声，从而能够进一步改善信噪比。
本发明一些实施例中，所述滤光片110的带宽基于所述发射单元110所产生探测光112的波长确定以抑制环境光，因此线宽窄、波长稳定的探测光112的产生，为所述滤光片120带宽的压缩提供了足够的空间，能够有效提高环境光滤除效果。
本发明一些实施例中，所述滤光片为超窄带滤光片。具体的，本 发明一些实施例中，所述滤光片110的带宽在10nm以内。由于窄线宽光源的采用，所产生探测光112的带宽较窄、波长稳定(例如，带宽可以小于1nm)，而且光谱温漂较低，因此超窄带滤光片、将滤光片110的带宽限制在10nm以内，不仅对信号强度影响有限，而且能够有效抑制环境噪声，提高系统信噪比。
本发明一些实施例中，所述回波光垂直入射至所述滤光片120(入射角度为0°)。光线在滤光片的入射角度在偏离0°时，出现透射波长变化的现象，被称之为滤光片的角度漂移。控制回波光入射角度，能够有效压缩透射波长的变化范围，有利于抑制环境噪声，提高系统信噪比。
本发明一些实施例中，所述单光子探测器131包括：SiPM探测器和SPAD探测器中的至少一种，即所述单光子探测器包括：硅光电倍增管(Silicon photomultiplier，SiPM)探测器和单光子雪崩二极管(Single Photon Avalanche Diodes，SPAD)探测器中的至少一种。SiPM探测器和SPAD探测器相较于APD探测器(即雪崩光电探测器)等探测器具有更灵敏的光子响应能力，同时具有更低的电路噪声和暗噪声。因此SiPM探测器和SPAD探测器的采用，能够有效提高系统信噪比。
结合参考图1和图3，其中图3示出了图1所示激光雷达实施例的光路结构示意图。
本发明一些实施例中，所述激光雷达还包括：出射传输单元140和接收传输单元150，所述出射传输单元140位于所述探测光112的光路上，所述接收传输单元150位于所述回波光132的光路上。
所述出射传输单元140位于所述探测光112的光路上，因此所述探测光112经所述出射传输单元140传输后向三维空间出射，所述出射传输单元140适宜于对所述探测光112进行准直、整形等操作。
所述接收传输单元150位于所述回波光132的光路上，因此反射 所形成的回波光132经所述接收传输单元150接收并传输以投射至所述探测单元130，所述接收传输单元150适宜于对所接收的回波光132进行会聚、整形等操作。
如图3所示，所述接收传输单元150和所述出射传输单元140中至少一个具有远心设计，也就是说，所述接收传输单元150和所述出射传输单元140中，光阑均位于前焦面，像方主光线垂直于焦平面。
具体的，如图3所示，所述出射传输单元140包括出射光阑142和出射光学组件141；所述出射光阑142位于所述发射光学组件141远离所述发射单元110一侧的焦平面上。远心光路能够使所述发射单元110所产生的垂直于焦平面的探测光均经出射光学组件141准直后经所述出射光阑142出射，从而达到提高出光效率的目的。
类似的，所述接收传输单元150包括接收光阑152和接收光学组件151，所述接收光阑152位于所述接收光学组件151远离所述探测单元130一侧的焦平面上。具有远心光路的接收传输单元150，所述回波光经接收光学组件151聚焦后以基本垂直的角度入射至所述滤光片120和所述探测单元130，从而使得透射所述滤光片120的回波光基本没有角度漂移，抑制回波光在滤光片的入射角度偏离0°造成的滤光片透射波长漂移，以达到保证滤光片窄带宽的目的。
需要说明的是，如图3所示，所述激光雷达实施例采用的是一种基于旁轴光路的光路方案。但是采用旁轴方案的做法仅为一示例，本发明另一些实施例中，本发明的激光雷达也可以采用同轴光路的光路方案。
此外，如图1至图3所示，所述激光雷达为固态激光雷达，即所述发射单元110和所述探测单元130均采用面阵结构，例如EEL阵列、SPAD面阵，且激光雷达内部完全无运动部件。本发明其他实施例中，所述激光雷达也可以是机械旋转的激光雷达，例如将所述发射单元和所述探测单元设置于转子上，从而实现旋转扫描，例如360°扫描激光雷达。
具体的，所述半导体激光器113为边发射激光器(Edge-Emitting Laser，EEL)。其光谱带宽约10nm，中心波长制造误差达±5nm，光谱温漂系数达0.28nm/K。当考虑激光雷达100K工作温度范围时，直接以半导体激光器113所产生的光学作为探测光的话，所述滤光片光谱带宽将至少达48nm。
当设置所述外腔反馈器件以构成窄线宽激光器模组时，所述窄线宽激光器模组的光谱带宽被压缩至1nm以内，且光谱温漂系数可以降低至小于0.07nm/K；再考虑所述滤光片120自身的制造误差等因素，所述滤光片120带宽可减小至10nm以内。因此，单纯从环境光噪声角度，本方案的光学信噪比提升近5倍。
此外，雪崩光电探测器(APD)模拟信号电路的电路噪声(主要来源于放大器)高于单光子探测器电路(例如SiPM/SPAD电路)，APD器件的暗噪声也远高于单光子探测器(例如SiPM/SPAD)。因此，单光子探测器(例如SiPM/SPAD)的电路噪声和暗噪声相较于传统的雪崩光电探测器(APD)器件也可以控制在极低的水平，系统的整体探测信噪比水平将大幅度提升，相应的，激光雷达系统也就可以实现更远的探测性能。
参考图4，示出了本发明激光雷达另一实施例中窄线宽光源的结构示意图。
本实施例与前述实施例相同之处本发明在此不再赘述。前述实施例不同之处在于，本实施例为基于垂直腔面发射激光器的窄线宽激光器模组方案，即本发明一些实施例中，所述半导体激光器213为垂直腔面发射激光器(Vertical-cavity surface-emitting laser，VCSEL)。
此外，本实施例中，所述准直器件215为微透镜阵列，所述外腔反馈器件214为体布拉格光栅。所述半导体激光器213包括多个发光单元，所述发光单元所产生的光学经过所述微透镜阵列准直，在经过体布拉格光栅实现波长锁定以压缩光谱带宽。其中，所述准直器件215还可以为衍射透镜等其他准直器件，所述外腔反馈器件214也还 可以为光纤光栅等其他外腔反馈器件。
需要说明的是，本实施例中，微透镜与半导体激光器213的发光单元一一对应，每个微透镜可以将发光单元发出的激光进行准直。本发明另一些实施例中，微透镜与半导体激光器213的发光单元可以为其他对应关系，如半导体激光器213与微透镜一一对应设置，半导体激光器213多个发光单元发出的光线被一个微透镜准直。
参考图5，示出了本发明激光雷达再一实施例中窄线宽光源的结构示意图。
本实施例与前述实施例相同之处本发明在此不再赘述。前述实施例不同之处在于，本实施例中，所述窄线宽光源为窄线宽激光器311。如图5所示，所述窄线宽光源可以包括多个窄线宽激光器331。
本发明一些实施例中，所述窄线宽激光器311包括：分布式反馈激光器(Distributed Feedback Laser，DFB)和光子晶体表面发射激光器中的至少一种。窄线宽激光器311所形成光束的线宽较窄，直接采用窄线宽激光器311作为光源，能够实现光源的集成式设置，有利于激光雷达集成度的提高。具体的，如图5所示，所述窄线宽激光器311为分布式反馈激光器。分布式反馈激光器内部布置有布拉格光栅，可直接输出窄线宽光谱。
需要说明的是，本发明另一些实施例中，所述窄线宽激光器的光路下游也可以设置微透镜阵列(micro-lens array，MLA)或衍射光学元件(Diffractive Optical Element，DOE)等匀光器件。
参考图6，示出了本发明激光雷达又一实施例的光路结构示意图。
本实施例与前述实施例相同之处本发明在此不再赘述。前述实施例不同之处在于，本实施例采用的是基于转镜扫描的光路方案。
所述发射单元410和所述探测单元430分别位于转镜460的两侧，即所述转镜160位于所述发射单元410和所述探测单元430之间，所述转镜460的不同表面分别反射所述探测光和所述回波光。
所述出射传输单元440位于所述发射单元410和所述转镜460之间；所述接收传输单元450位于所述探测单元430和所述转镜460之间；此外，所述接收传输单元450和所述探测单元430之间的滤光片420适于滤除环境光和非探测光波段的红外光，以提高系统信噪比。
需要说明的是，图6所示的激光雷达为混合固态激光雷达，也就是说，所述激光雷达中经所述转镜460绕旋转轴转动，将探测光向不同的角度偏转；其他结构部件固定设置。在其他实施例中，所述转镜也可以是其他扫描装置。
参考图7，示出了本发明激光雷达又一实施例的光路结构示意图。
本实施例与前述实施例相同之处本发明在此不再赘述。前述实施例不同之处在于，本实施例采用的是基于同轴光路的方案。其中，所述发射单元510中具有窄线宽光源，所述探测单元530中具有高灵敏度的的单光子探测器(例如SiPM探测器、SPAD探测器)，而且还设置有滤光片520(例如超窄带滤光片)。
本发明一些实施例中，所述接收光学组件包括：正-负透镜组以拉长焦距，即如图7所示，所述接收光学组件包括正透镜551和负透镜552，正-负透镜组的形式实现紧凑型长焦距接收镜头组，这种长焦距光路，结构紧凑，能够拉长焦距。对于所述探测单元530来说，每个单元具有更小的瞬时视场角，即接收到更少的环境光，同样能够提高系统信噪比。
所述发射单元510产生的窄线宽的偏振探测光经偏振分光器561反射，透射正透镜551准直后，被反射镜571反射至扫描镜572；所述探测光经所述扫描装置572反射形成出射扫描以照明待测目标。待测目标反射的回波光沿原光路返回，先后经所述扫描装置572和所述反射镜571反射后，投射至1/4波片562上，在透射所述1/4波片562后偏振态改变，被所述正透镜551会聚后，偏振态改变的回波光能够透射所述偏振分光器561，再经负透镜扩束，以拉长接收端光学系统的焦距，回波光最终经所述滤光片520滤光后由探测单元530接收。
如图8所示，展示本发明实施例中光学系统的原理示意图。图8中的光学系统可应用于图7所示激光雷达光路结构的接收端。具体的，所述光学系统包括正透镜551和负透镜552的组合。其中，正透镜551的焦距为f1，会聚角为α，焦点为A。负透镜402会聚角为γ。经正透镜551的光线本应会聚于A点，但在正透镜551的主平面和正透镜551的焦点A之间设置负透镜552之后，由于负透镜552对光线的扩张作用，使得光线的会聚点从A远移至B点，且会聚角变为γ，γ小于α。正透镜551和负透镜552组合形成等效透镜的主平面和会聚点B之间的间距为f，即等效透镜的焦距为f。
可以发现，f相比于f1得到了延长。在正透镜551和负透镜552之间间距一定时(比如两者的主平面间距小于正透镜551的焦距)，由正透镜551和负透镜552组合可以增大光学系统的焦距。
而且，如果探测单元设置在B点所在的焦平面，则正透镜551的主平面和B点所在焦平面之间的间距L，即为此光学系统的物理长度，而f大于L，说明了等效透镜的等效焦距f还超出了光学系统物理尺寸的限制。
因此，在正透镜(组)和探测单元之间设置负透镜552或实现负透镜552功能的透镜组，就能实现接收端的焦距大幅延长，从而当采用较大尺寸的光探测器(如SiPM，相比于APD，SiPM的感光面大一倍多)，根据
Figure PCTCN2022097824-appb-000001
f可以随L增大而增大，从而限制会聚角γ，来抑制环境光的干扰，从而进一步提高系统的信噪比。
需要说明的是，图7所示实施例中，所述扫描装置可以是二维扫描振镜、MEMS振镜，也可以是一维扫描转镜、振镜等。本发明对此并不限定。图示中的正透镜、负透镜只是简化的表述，在实际应用中可以是透镜组的等效表示，并非以图示为限。
参考图9，示出了本发明激光雷达又一实施例的光路结构示意图。
本实施例与前述实施例相同之处本发明在此不再赘述。前述实施 例不同之处在于，本实施例采用小反射镜实现同轴光路的分光。
如图9所示，所述发射单元610所产生的探测光从小反射镜660反射至正透镜651、经准直和扫描镜670反射后出射；回波光被所述扫描镜670反射、正透镜651会聚后，从小反射镜660边缘区域透射，经负透镜652和滤光片620透射后被探测单元630接收。
参考图10，示出了本发明激光雷达又一实施例的光路结构示意图。
本实施例与前述实施例相同之处本发明在此不再赘述。前述实施例不同之处在于，本实施例中小反射镜为小孔反射镜。
所述发射单元710所产生的探测光从所述小反射镜760的小孔透过，经正透镜751准直、反射镜771和扫描镜772反射后出射；回波光被扫描镜772和反射镜771反射、正透镜751会聚后被小反射镜760小孔以外的反射面反射到负透镜752，经滤光片(图中未示出)滤光后被探测单元730接收。
综上，本发明技术方案中，所述发射单元包括窄线宽光源，所述探测单元包括单光子探测器。所述窄线宽光源所产生探测光线宽很小、波长稳定，能够为滤光带宽的压缩提供足够的空间，即所述滤光片能够设置为带宽相当小的滤光片，能够有效抑制环境光，配合探测单元中的单光子探测器，能够有效提高信噪比；而且单光子探测器具有更低的电路噪声和暗噪声，从而能够进一步改善信噪比。
而且，所述外腔反馈器件的入射面垂直于所述半导体激光器所产生光束的光轴；通过准直器件压缩半导体激光器所产生光束的发散角；使得半导体激光器所产生的光束以尽可能垂直的方式入射至所述外腔反馈器件，从而以保证外腔反馈器件所锁定波长的精度，有效保证探测光光谱带宽的压缩效果，进而达到改善信噪比的目的。
另外，所述外腔反馈器件和所述半导体激光器之间的距离和所述探测光在所述外腔反馈器件内部光程的长度通过特别设计以满足各 自的预设值，以有效保证外腔反馈器件的反馈效率。
此外，所述窄线宽光源还可以是窄线宽激光器，例如分布式反馈激光器或者光子晶体表面发射激光器中的至少一种。窄线宽激光器所形成光束的线宽较窄，直接采用窄线宽激光器作为光源，能够实现光源的集成式设置，有利于激光雷达集成度的提高。
进一步，所述激光雷达还包括：超窄带滤光片。由于所述发射单元包括窄线宽光源，其光谱带宽极小，例如可以小于1nm，而且具有较低的光谱温漂，因此所述超窄带滤光片的带宽极小，例如可以小于10nm，能够有效抑制环境光噪声，进而达到改善信噪比的目的。
另外，回波光垂直入射至所述超窄带滤光片，防止回波光在透射所述超窄带滤光片时出现透射波长变化，有效抑制所述探测单元所接受回波光的角度漂移，从而保证所述超窄带滤光片的带宽稳定。
所述接收传输单元和所述出射传输单元中至少一个具有远心设计。对于接收传输单元而言，远心设计的光路能够使回波光聚焦后基本垂直入射至所述超窄带滤光片和探测单元，从而达到抑制角度漂移的目的；对于出射传输单元而言，远心设计的光路，使垂直于焦平面的探测光都准直后经光阑出射，能有效保证出光效率。
本发明可选方案中，所述接收光学组件包括：正-负透镜组以拉长焦距。正-负透镜组的形式实现紧凑型长焦距接收镜头组，能有效减小所述激光雷达的瞬时视场角，能有效减少环境光的接收，有利于改善信噪比。
虽然本发明披露如上，但本发明并非限定于此。任何本领域技术人员，在不脱离本发明的精神和范围内，均可作各种更动与修改，因此本发明的保护范围应当以权利要求所限定的范围为准。

Claims (26)

  1. 一种激光雷达，其特征在于，包括：
    发射单元，所述发射单元包括：窄线宽光源，所述发射单元适宜于产生探测光；
    出射至三维空间的探测光被反射后形成回波光；
    滤光片和探测单元，所述滤光片和所述探测单元依次位于所述回波光的光路上，所述探测单元包括：单光子探测器，所述探测单元适宜于接收透射所述滤光片的回波光。
  2. 如权利要求1所述的激光雷达，其特征在于，所述窄线宽光源的线宽在1nm以内。
  3. 如权利要求1所述的激光雷达，其特征在于，所述窄线宽光源包括：窄线宽激光器模组和窄线宽激光器中的至少一种。
  4. 如权利要求3所述的激光雷达，其特征在于，所述窄线宽激光器模组包括：至少一个半导体激光器和位于所述半导体激光器发光光路上的外腔反馈器件。
  5. 如权利要求4所述的激光雷达，其特征在于，所述半导体激光器包括：边发射激光器和垂直腔面发射激光器中的至少一种。
  6. 如权利要求4所述的激光雷达，其特征在于，所述外腔反馈器件包括：光栅。
  7. 如权利要求6所述的激光雷达，其特征在于，所述光栅包括：体布拉格光栅和体光纤光栅中的至少一种。
  8. 如权利要求4所述的激光雷达，其特征在于，所述外腔反馈器件的入射面垂直于所述半导体激光器所产生的光束的光轴。
  9. 如权利要求4所述的激光雷达，其特征在于，所述窄线宽激光器模组还包括：准直器件，所述准直器件位于所述半导体激光器和所述外腔反馈器件之间的光路上以压缩光束发散角。
  10. 如权利要求4所述的激光雷达，其特征在于，入射至所述外腔反馈器件的光束的发散角小于10°。
  11. 如权利要求4、8～10中任一项所述的激光雷达，其特征在于，所述半导体激光器所产生的光束垂直入射至所述外腔反馈器件。
  12. 如权利要求4所述的激光雷达，其特征在于，所述半导体激光器的出光前腔面的反射率小于预设值以使所述外腔反馈器件所反射的光线再次投射入所述半导体激光器。
  13. 如权利要求4或12所述的激光雷达，其特征在于，所述半导体激光器的出光前腔面的反射率在5％以内。
  14. 如权利要求4所述的激光雷达，其特征在于，所述半导体激光器和所述外腔反馈器件之间的距离小于预设值以提高所述外腔反馈器件的反馈效率。
  15. 如权利要求4或14所述的激光雷达，其特征在于，所述半导体激光器和所述外腔反馈器件之间的距离小于5mm。
  16. 如权利要求4所述的激光雷达，其特征在于，所述外腔反馈器件为体布拉格光栅，所述体布拉格光栅的厚度小于预设值以提高所述外腔反馈器件的反馈效率。
  17. 如权利要求16所述的激光雷达，其特征在于，所述体布拉格光栅的厚度在5mm以内。
  18. 如权利要求3所述的激光雷达，其特征在于，所述窄线宽激光器包括：分布式反馈激光器和光子晶体表面发射激光器中的至少一种。
  19. 如权利要求1所述的激光雷达，其特征在于，所述滤光片的带宽基于所述发射单元所产生探测光的波长确定以抑制环境光。
  20. 如权利要求1所述的激光雷达，其特征在于，所述滤光片为超窄带滤光片。
  21. 如权利要求1所述的激光雷达，其特征在于，所述滤光片的带宽在10nm以内。
  22. 如权利要求1所述的激光雷达，其特征在于，还包括：出射传输单元和接收传输单元，所述出射传输单元位于所述探测光的光路上，所述接收传输单元位于所述回波光的光路上；
    所述接收传输单元和所述出射传输单元中至少一个具有远心设计。
  23. 如权利要求22所述的激光雷达，其特征在于，所述接收传输单元包括接收光阑和接收光学组件，所述接收光阑位于所述接收光学组件远离所述探测单元一侧的焦平面上；
    和/或，
    所述出射传输单元包括出射光阑和出射光学组件；所述出射光阑位于所述发射光学组件远离所述发射单元一侧的焦平面上。
  24. 如权利要求23所述的激光雷达，其特征在于，所述接收光学组件包括：正-负透镜组以拉长焦距。
  25. 如权利要求1所述的激光雷达，其特征在于，所述回波光垂直入射至所述滤光片。
  26. 如权利要求1所述的激光雷达，其特征在于，所述单光子探测器包括：SiPM探测器和SPAD探测器中的至少一种。
PCT/CN2022/097824 2021-11-05 2022-06-09 激光雷达 WO2023077801A1 (zh)

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WO2020118173A1 (en) * 2018-12-07 2020-06-11 Michigan Aerospace Corporation Feedback control for lidar using principles of direct atomic vapor absorption
CN111856508A (zh) * 2019-04-18 2020-10-30 昆山星谕传感科技有限公司 一种窄线宽滤波激光雷达
CN113093222A (zh) * 2021-03-11 2021-07-09 武汉大学 一种基于体布拉格光栅的单支谱测温激光雷达系统

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Publication number Priority date Publication date Assignee Title
WO2020118173A1 (en) * 2018-12-07 2020-06-11 Michigan Aerospace Corporation Feedback control for lidar using principles of direct atomic vapor absorption
CN210119572U (zh) * 2019-04-18 2020-02-28 苏州镭智传感科技有限公司 一种窄线宽滤波激光雷达
CN111856508A (zh) * 2019-04-18 2020-10-30 昆山星谕传感科技有限公司 一种窄线宽滤波激光雷达
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