WO2023205881A1 - Appareil de commande de polarisation dans un système lidar - Google Patents

Appareil de commande de polarisation dans un système lidar Download PDF

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Publication number
WO2023205881A1
WO2023205881A1 PCT/CA2023/050530 CA2023050530W WO2023205881A1 WO 2023205881 A1 WO2023205881 A1 WO 2023205881A1 CA 2023050530 W CA2023050530 W CA 2023050530W WO 2023205881 A1 WO2023205881 A1 WO 2023205881A1
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WIPO (PCT)
Prior art keywords
beams
polarization
receive
dbsd
fov
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PCT/CA2023/050530
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English (en)
Inventor
Robert Baribault
Artashes YAVRIAN
Alexander Greiner
Siegwart Bogatscher
Nico Heussner
Stéphane TURCOTTE
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Leddartech Inc.
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Publication of WO2023205881A1 publication Critical patent/WO2023205881A1/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
    • 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
    • G01S7/499—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using polarisation effects

Definitions

  • the present disclosure relates generally to light detection and ranging (LIDAR.) systems and, more particularly, to apparatus for controlling the polarization of beams emitted by lasers in such systems.
  • LIDAR light detection and ranging
  • LIDAR systems are widely used in various applications that have high- resolution demands, for example including autonomous vehicles, agriculture, archaeology, geology, etc. Taking automotive and mobility applications as an example, LIDAR systems enable obstacle detection, avoidance, and safe navigation to be achieved with high accuracy and sufficient resolutions.
  • the LIDAR system can image an angle within a field of view (FOV) and locate objects within the FOV.
  • FOV field of view
  • the FOV an angle covered by the LIDAR system or an angle in which beams are emitted by the LIDAR system, is the maximum area of a sample that the LIDAR system can image.
  • the FOV is determined by a focal length of a lens of the LIDAR system and a sensor size of the LIDAR system.
  • ultrawide FOV is in demand.
  • a dense forest canopy needs a ultrawide FOV to obtain returns from the ground.
  • having a single LIDAR device with an ultrawide FOV can reduce the total number of LIDAR devices required, thereby lowering the sensor costs of the vehicle.
  • a plurality e.g., 16-32
  • stacked lasers are utilized to offer the ultrawide FOV, which may be complex and expensive as many lasers are integrated within the LIDAR system. Therefore, it would be beneficial to provide a LIDAR, system with less hardware cost and an ultrawide FOV (e.g., 180°).
  • Beam-steering devices are employed for beam steering in the LIDAR system. Beam steering refers to changing directions of beams (also referred to as laser pulses) emitted by an emitter of the LIDAR system.
  • a digital beam steering device is a type of beam-steering device which applies a non-mechanical beam steering mechanism to steer beams of the LIDAR system.
  • US 20220026576 Al the contents of which are hereby incorporated by reference, describes that the DBSD includes at least one liquid crystal polarization grating to steer beams at a propagation angle.
  • one or more LIDAR emitters such as an edge-emitting laser (also called in-plane laser) are deployed within a LIDAR system as LIDAR sources to provide incident beams to the DBSD of the LIDAR system.
  • the edgeemitting lasers propagate beams in a direction parallel to a wafer surface of a chip of the edge-emitting laser.
  • the edge-emitting lasers produce high power beams, reliability of the edge-emitting lasers may be reduced significantly because the edge-emitting lasers suffer from catastrophic optical damage (COD).
  • COD catastrophic optical damage
  • one or more surface-emitting lasers such as vertical-cavity surface-emitting lasers (VCSELs)
  • VCSELs vertical-cavity surface-emitting lasers
  • the VCSELs have small drifts in wavelengths as temperature varies.
  • reliability, power, and efficiency offered by the VCSELs are improved compared to the edgeemitting laser.
  • the VCSELs provide unpredictable polarization of beams because of cylindrically symmetric cavity design of the VCSELs.
  • the polarization of beams is unstable.
  • the polarization of a certain mode can turn abruptly with varying bias current, and different transverse modes have different polarizations.
  • the present disclosure describes an apparatus for use in a LIDAR, system which incorporates a laser, such as surface-emitting laser, emitting a plurality of beams with unstable polarizations, at least one optical device converting the plurality of beams with stable polarizations, and a beam-steering device steering the plurality of beams in different respective directions.
  • the at least one optical device may enable the surface-emitting laser to be integrated with the beam-steering device without causing too many changes to the LIDAR system.
  • Efficiency, accuracy, and reliability of the LIDAR system may be improved because spectral shift over temperature is reduced by employing the surface-emitting laser.
  • the apparatus for use in the LIDAR system comprises a plurality of beam-steering devices, for example including nonmechanical beam steering devices, in a transmitting path to achieve an ultrawide field of view (FOV), such as 180 degrees.
  • the FOV may include a first FOV and a second FOV.
  • suitable changes are also made in a receiving path of the LIDAR system to enable reflected beams from the first FOV and the second FOV to be received accurately.
  • the apparatus comprises a laser configured to emit a plurality of beams including a first set of beams each of which has a first polarization and a second set of beams each of which has a second polarization, wherein the first polarization is different from the second polarization; a first optical device configured to receive the plurality of emitted beams and to generate a plurality of beams each of which has a polarization that is identical for each of the generated beams; and a beam-steering device configured to receive the plurality of generated beams each having the polarization and to steer each of the plurality of generated beams to a respective direction.
  • the first polarization is perpendicular with respect to the second polarization.
  • the first optical device further comprises a first polarizing beam splitter (PBS) configured to receive the plurality of emitted beams and to split the first set of beams each of which has the first polarization and the second set of beams each of which has the second polarization; a mirror configured to receive the second set of beams from the PBS and to reflect the second set of beams; a first half-wave plate (HWP) configured to receive the second set of reflected beams and to shift the polarization of each of the second set of reflected beams from the second polarization into the first polarization; and the beam-steering device is configured to receive the plurality of beams each having the first polarization and to steer each of the plurality of beams to a respective direction including: the beam-steering device being configured to receive the first set of split beams with the first polarization from the PBS and to steer each of the first set of split beams to the respective direction in a field of view (PBS)
  • PBS polarizing beam splitter
  • the first optical device is a diffuser that is configured to change a cardinality of the first set of beams and a cardinality of the second set of beams and to generate a third set of beams with the first polarization and a fourth set of beams with the second polarization, wherein a cardinality of the third set is identical to a cardinality of the fourth set.
  • the apparatus further comprises at least one dual brightness enhancement films (DBEFs) each of which is configured to reflect the fourth set of beams and pass the third set of beams.
  • DBEFs dual brightness enhancement films
  • the apparatus further comprises at least one brightness enhancement films (BEFs) each of which is configured to reorient directions of the third and fourth set of beams generated from the diffuser.
  • BEFs brightness enhancement films
  • the apparatus further comprises a second optical device which is configured to collimate the third set of beams.
  • the beam-steering device is configured to receive the plurality of beams each having the first polarization and to steer each of the plurality of beams to a respective direction comprising: the beam-steering device configured to receive the third set of beams with the first polarization and to steer the third set of beams to the respective directions.
  • the first optical device includes: a first digital beam steering device (DBSD) that is configured to receive the plurality of emitted beams and to generate the first set of beams each of which has the first polarization and the second set of beams each of which has the second polarization; a second DBSD configured to receive the second set of beams with the second polarization and to convert the second polarization to the first polarization; a third DBSD configured to receive the first set of beams with the first polarization and to convert the polarization of the first set of beams from the first polarization to the second polarization; and a second HWP configured to receive the first set of beams with the second polarization from the third DBSD and to convert the polarizations of the received set of beams from the second polarization to the first polarizations such that the beam-steering device is configured to receive the first and second set of beams with the first polarization.
  • DBSD digital beam steering device
  • the first optical device includes: a fourth DBSD that is configured to receive the plurality of emitted beams and to generate the first set of beams each of which has the first polarization and the second set of beams each of which has the second polarization; a fifth DBSD configured to receive the second set of beams with the second polarization and to convert the polarization of the received set of beams from the second polarization to the first polarization; a sixth DBSD configured to receive the first set of beams with the first polarization and to convert the polarization of the received set of beams from the first polarization to the second polarization in a first half of a desired steering angle; and a seventh DBSD configured to receive the first set of beams with the second polarization from the sixth DBSD and to convert the polarization of the received first set of beams from the second polarization to the first polarization in a second half of the desired steering angle such that the beam-
  • the first optical device comprises a first depolarizer configured to change a cardinality of the first set of beams with the first polarization and/or a cardinality of the second set of beams with the second polarization such that the changed cardinality of the first set of beams is identical to the changed cardinality of the second set of beams; and a polarization filter configured to filter out the first set of beams with the changed cardinality.
  • the laser includes a surface-emitting laser.
  • the beamsteering device includes a DBSD.
  • the first set of beams include at least one beam with the first polarization
  • the second set of beams includes at least one beam with the second polarization
  • the apparatus comprises a laser configured to emit a plurality of beams including a first set of beams each of which has a first polarization and a second set of beams each of which has a second polarization; a first optical device configured to receive the plurality of emitted beams and to generate a third set of beams each of which has the first polarization and a fourth set of beams each of which has the second polarization, a cardinality of the third set is identical to a cardinality of the fourth set; and a second optical device configured to receive the third set of beams and the fourth set of beams and to separate the third set of beams with the first polarization and the fourth set of beams with the second polarization.
  • the first optical device includes a depolarizer that is configured to change the cardinality of first set of beams with the first polarization and/or the cardinality of the second set of beams with the second polarization and to generate the third set of beams with the first polarization and the fourth set of beams with the second polarization such that the cardinality of the third set is identical to the cardinality of the fourth set.
  • the second optical device includes a digital beam steering device (DBSD).
  • DBSD digital beam steering device
  • the second optical device includes a polarizing beam splitter (PBS).
  • PBS polarizing beam splitter
  • the depolarizer is stacked as a first layer of the second optical device.
  • the depolarizer is a liquid crystal depolarizer.
  • the depolarizer is a quartz wedge achromatic depolarizer.
  • the depolarizer includes at least one of polymer-on-glass diffuser, ground glass diffuser, opal diffuser, or light shaping micro-optics based diffuser.
  • the LIDAR, system further comprises an optical lens that is configured to collimate the plurality of emitted beams.
  • the apparatus further comprises: a first DBSD configured to receive the third set of beams with the first polarization from the second optical device and to steer the third set of beams to different respective directions within a first field of view (FOV); and a second DBSD configured to receive the fourth set of beams with the second polarization from the second optical device and to steer the fourth set of beams to different respective directions within a second FOV.
  • a first DBSD configured to receive the third set of beams with the first polarization from the second optical device and to steer the third set of beams to different respective directions within a first field of view (FOV)
  • FOV field of view
  • the LIDAR further comprising a first and second receiving path.
  • the first receiving path includes a third DBSD configured to receive a first set of backscattered beams each with the first polarization in the first FOV.
  • the second receiving path includes a fourth DBSD configured to receive a second set of backscattered beams each with the second polarization in the second FOV.
  • the apparatus further comprises a receiver configured to receive the first set of backscattered beams with the first polarization and the second set of backscattered beams with the second polarization.
  • the apparatus further comprises a fifth DBSD configured to combine the first set of backscattered beams with the first polarization and the second set of backscattered beams with the second polarization; and a receiver configured to receive the combined first and second set of backscattered beams.
  • the laser includes a surface-emitting laser.
  • the apparatus comprises a transmitting path including a laser configured to emit a plurality of beams; an optical device configured to receive the plurality of emitted beams and to generate a first set of beams each with a first polarization and a second set of beams each with a second polarization; a first beam-steering device configured to steer the first set of beams to different respective directions in a first field of view (FOV); and a second beam-steering device configured to steer the second set of beams to different respective directions in a second FOV.
  • a transmitting path including a laser configured to emit a plurality of beams; an optical device configured to receive the plurality of emitted beams and to generate a first set of beams each with a first polarization and a second set of beams each with a second polarization; a first beam-steering device configured to steer the first set of beams to different respective directions in a first field of view (FOV); and a second beam-steering device configured to steer
  • the optical device includes a digital beam steering device (DBSD).
  • DBSD digital beam steering device
  • the apparatus further comprises: a first receiving path including a third beam-steering device configured to receive a first set of backscattered beams from the first FOV, wherein each of the first set of backscattered beams have the first polarization; a second receiving path including a fourth beam-steering device configured to receive a second set of backscattered beams from the second FOV, wherein each of the second set of backscattered beams have the second polarization.
  • the apparatus further comprises a fifth beam-steering device configured to combine the first set of backscattered beams with the first polarization from the first receiving path and the second set of backscattered beams with the second polarization from the second receiving path; and a receiver configured to receive the combined beams.
  • the first receiving path further comprises a first receiver configured to receive the first set of backscattered beams from the third beam-steering device; and the second receiving path further comprises a second receiver configured to receive the second set of backscattered beams.
  • the optical device includes a polarizing beam splitter (PBS) that is configured to split the first set of beams with the first polarization and the second set of beams with the second polarization.
  • PBS polarizing beam splitter
  • Apparatus for use in a LIDAR system comprises a laser configured to emit a plurality of beams including a first set of beams each of which has a first polarization and a second set of beams each of which has a second polarization; at least one polarization switch configured to selectively switch one of the first set of beams with the first polarization and the second set of beams with the second polarization to the first set of beams with the second polarization or the second set of beams with the respective second polarizations; at least one polarizing beam splitter (PBS) configured to selectively split the plurality of beams with the first polarization and the plurality of beams with the second polarization.
  • PBS polarizing beam splitter
  • the apparatus further comprises a first digital beam steering device (DBSD) configured to steer the plurality of beams with the first polarization to different respective directions in a first field of view (FOV); or a second DBSD configured to steer the plurality of beams with the second polarization to different respective directions in a second FOV.
  • DBSD digital beam steering device
  • the apparatus further comprises a first receiving path including a third DBSD configured to receive a first set of backscattered beams with the first polarization within the first FOV; a second receiving path including a fourth DBSD configured to receive a second set of backscattered beams with the second polarization with the second FOV; and a second PBS configured to split the first or second set of backscattered beams; a receiver configured to respectively receive the first set of backscattered beams and the second set of backscattered beams.
  • the apparatus further comprises an optical device configured to collimate the first set of backscattered beams or the second set of backscattered beams from the second PBS.
  • FIG. 1 is a schematic diagram of an example LIDAR system
  • FIG.2A is a schematic diagram illustrating an example transmitting (Tx) path of the LIDAR system of FIG.l;
  • FIG.2B is a schematic diagram illustrating an alternative Tx path of the LIDAR system of FIG.l;
  • FIG.2C is a top view of a vertical-cavity surface-emitting laser (VCSEL) array that is used as an example laser of the LIDAR system of FIG.l;
  • VCSEL vertical-cavity surface-emitting laser
  • FIG.2D is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l;
  • FIG.3A is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG. 1;
  • FIG.3B is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l;
  • FIG.4A is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l;
  • FIG.4B is a schematic diagram illustrating another alternative receiving (Rx) path of the LIDAR, system of FIG.l;
  • FIG.5A is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l;
  • FIG.5B is a schematic diagram illustrating another alternative Rx path of the LIDAR system of FIG.l;
  • FIG.5C is a schematic diagram illustrating another alternative Rx path of the LIDAR system of FIG.l;
  • FIG.6A is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l;
  • FIG.6B is a schematic diagram illustrating another alternative Rx path of the LIDAR system of FIG.l;
  • FIG.7A is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l in accordance with further example embodiments;
  • FIG.7B is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l in accordance with further example embodiments;
  • FIG.8A is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l;
  • FIG.8B is a schematic diagram illustrating another alternative Tx path of the LIDAR system of FIG.l;
  • FIG. 1 illustrates an example LIDAR system 100 in accordance with an example embodiment.
  • the LIDAR system 100 includes a transmitting (Tx) path 101, a receiving (Rx) path 103, and a controller 108.
  • the transmitting path 101 comprises a transmitting stage 102 and at least one beam-steering device 106(1).
  • the receiving path 103 includes a receiving stage 104 and at least one beamsteering device 106(2).
  • the receiving stage 104 of the receiving path 103 includes an optical receiver 1042 (also referred to as a detector), which may include an avalanche photodiode (AD).
  • AD avalanche photodiode
  • the transmitting stage 102 includes a laser 1022, which simultaneously emits a plurality of beams (also called laser pulses or optical light pulses) each of which has a duration (e.g., typically in the nanosecond (ns) range).
  • the beam-steering devices 106(1) receives the emitted beams (also referred to incident lights or incident beams) from the laser 1022 and then steers the beams to scan objects in a FOV.
  • the beams travel to the objects and are reflected back or backscattered.
  • the reflected beams are received by the receiving path 103 where the beam-steering device 106(2) receives the backscattered or reflected beams and the optical receiver 1042 detects the reflected beams.
  • the optical receiver 1042 may perform signal processing to convert the reflected beams that are optical signals into digital signals.
  • the signal processing within the receiving stage 104 may include removing parasitic background beams from the reflected beams, and then converting the reflected beams to a plurality of digital signals at a sample rate.
  • the controller 108 may control respective operations of the transmitting path 101 and the receiving path 103 of the LIDAR, system by software or hardware or a combination of software and hardware.
  • the controller 108 controls emitting operations of the transmitting stage 102 (e.g., generate a trigger signal, determine time duration of each beam, synchronize emission of each beam with an identical start time, etc.).
  • the controller 108 may control a respective sampling rate of the generated digital signals.
  • the controller 108 may control steering operations of the beamsteering stage 106.
  • the two beam-steering devices 106(1), 106(2) are used in the Tx and Rx paths 101 and 103, in some examples, a common beam- steering device may be used in the two paths 101, 103.
  • the two beam-steering devices 106(1) and 106(2) may be identical or different in accordance with any suitable configurations.
  • the beam-steering devices 106(1), 106(2) may include non-mechanical beam steering devices, such as digital beam steering devices (DBSDs).
  • DBSDs digital beam steering devices
  • the beamsteering devices 106(1), 106(2) may be any suitable beam steering devices.
  • the laser 1022 may include at least one edgeemitting laser or at least one surface-emitting laser.
  • the edge-emitting lasers offer higher power than surface-emitting lasers, whereas a lot of advantages of overall stability, reliability, and efficiency may be achieved by using the surface-emitting lasers.
  • VCSEL is a type of surface-emitting laser, which generates no fixed or predictable polarizations. Furthermore, as grown on [1 0 0] oriented GaAs substrates, VCSELs usually show polarization along the [0 1 1] or [0 -1 1] crystal axes.
  • the polarizations of the beams generated by the VCSEL are unstable because the polarization of a certain mode may turn abruptly with varying bias current and different transverse modes have different polarizations. Because the polarizations of the beams traveling to objects are unstable, energy power of beams of different types of polarizations (e.g., linear s-polarization or linear p-polarization) are unstable. For examples, energy power of beams of the linear s-polarization is variable overtime, and energy power of beams of the linear p-polarization is variable overtime as well. The overall energy power of beams of the linear s- polarization and the linear p-polarization is not constant, which may cause the performance at the receiving stage to be degraded significantly.
  • the VCSELs within the LIDAR, system to improve the performance (e.g., accuracy, efficiency, and/or reliability) of the LIDAR system.
  • the present disclosure will discuss solutions to address the instability of the polarizations of beams emitted by the laser.
  • stable polarizations is meant that a polarization of each beam is variable over time, the beams include more than one polarizations (i.e., mixed polarizations, mix of linear s-polarization and p- polarization), or percentages or respective cardinalities of beams of two polarizations are different such that energy power of a first set of beams of one type of polarization is not identical to energy power of s second set of beams of the other type of polarization, which may cause reflected beams to be received by the LDIAR system with great uncertainty.
  • the performance of the LIDAR system is degraded significantly.
  • the beams with unstable polarizations discussed in the present disclosure are emitted by a laser concurrently (i.e., at one time), rather than generated in a sequence
  • FIG. 2A illustrates an example Tx path 101 of the LIDAR system 100 which generates beams with stable polarizations, in accordance with certain embodiments.
  • the Tx path 101 includes the laser 1022, a polarizing beam splitter (PBS) 202, a mirror 204, a half-wave plate (HWP) 206, and a digital beam steering device (DBSD) 208.
  • the laser 1022 simultaneously emits a plurality of beams.
  • polarizations of the plurality of beams are unstable.
  • the instability of polarizations is caused by including mixing two perpendicular polarizations (e.g., mixing linear s-polarization and linear p- polarization) in the plurality of beams.
  • the plurality of beams comprises a first set of beams each of which has a first polarization (e.g., linear s-polarization) and a second set of beams each of which has a second polarization (e.g., linear p-polarization).
  • the number (i.e., cardinality) of the first set being different from that of the second set results in instability of polarizations.
  • the cardinality of the first set may be equal to or greater than one.
  • the cardinality of the second set may be equal to or greater than one.
  • the polarizing beam splitter (PBS) 202, the mirror 204, and the HWP 206 jointly enable polarizations of output beams of the transmitting stage 102 to be identical with respect to each other (i.e., to be the same polarization).
  • the PBS 202 splits out the first set of beams and the second set of beams.
  • the mirror 204 receives the second set of split beams each of which has a p-polarization and reflects the second set of split beams with 90 degrees.
  • the HWP 206 further shifts each p-polarization to s-polarization.
  • the polarization of beams output from the transmitting stage 102 is s-polarization, and thus the polarization of each of these beams is identical with respect to one another (i.e., it is the same polarization).
  • the DBSD 208 receives the first set of beams with s-polarization from the PBS 202 and steers the first set of beams in a first field of view (FOV), which may cover an area 1 as shown in FIG. 2A in a short distance. Furthermore, the DBSD 208 receives the second set of beams with s-polarization from HWP 206, and then steers the second set of beams in a second field of view (FOV), which may cover an area 2 as shown in FIG. 2A in the short distance.
  • FOV first field of view
  • the LIDAR, system may capture images in a long distance with larger FOV by combining the first and second FOV.
  • the energy power of the beams with the identical polarizations is a constant, which enables the polarizations of the beams input to the beam-steering devices 106(1) to be stable.
  • the stable polarizations of beams enable the LIDAD system 100 to receive reflected beams in the receiving path stably, which may help to improve accuracy of imaging objects at different distances.
  • FIG. 2B illustrates an alternative example Tx path 101 of the LIDAR system 100 which generates beams with stable polarizations, in accordance with alternative embodiments.
  • the Tx path 101 includes the transmitting stage 102 and the steer-beaming device 106(1).
  • the transmitting stage 102 encompasses the laser 1022, a diffuser 212, at least one dual brightness enhancement film (DBEF) 214, and an optional optical device 216.
  • the laser 1022 simultaneously emits a plurality of beams.
  • DBEF dual brightness enhancement film
  • the plurality of beams may include a first set of beams each of which has a first polarization (e.g., linear s-polarization) and a second set of beams each of which has a second polarization (e.g., linear p- polarization).
  • the first polarization may be perpendicular to the second polarization.
  • the diffuser 212 e.g., a holographic diffuser
  • the diffuser 212 evens a cardinality of the second set of beams with the linear p-polarization and a cardinality of the first set of beams with the linear s-polarization, for example by randomizing the linear s-polarization and the linear p-polarization.
  • the diffuser 212 generates a third set of beams with the linear s-polarization and a fourth set of beams with the linear p-polarization.
  • a cardinality of the third set of beams is identical to that of the fourth set of beams.
  • the at least one DBEF 214 passes the third set of beams through and reflect the fourth set of beams, which may help to improve polarization ratio of the linear s-polarization.
  • the diffuser 212 and DBEF 214 offer the possibility to increase the ratio of one desired polarization, enhancement of the desired polarization is achieved.
  • the DBEF 214 may help to provide effect on divergences of the beams.
  • the transmitting stage 102 may further comprise at least one brightness enhancement film (BEF), which may be stacked between the diffuser 212 and the DBEF 214.
  • BEF brightness enhancement film
  • the at least one BEF may help to adjust angles of the fourth set of beams that are reflected from the DBEF 214 if the fourth set of reflected beams are backscattered with too wide angles with respect to an optical axis of the LIDAR, system.
  • the BEFs may help to reorient divergences or respective directions of the third and fourth set of beams with a narrower cone.
  • the optional optical device 206 collimates the first set of passed beams to ensure the first set of passed beams to be in parallel. The collimation may help to facilitate eye safe operation or reduce the number of DBSDs used in the beam-steering device 106(1).
  • output beams of the transmitting stage 102 include only one single polarizations (e.g., linear s-polarization), which enables beams input to the beam-steering device 106(1) to be stable because the input beams have an identical polarization.
  • a DBSD 218 is used to steer the input beams with the identical linear p-polarization in different respective desired directions.
  • a plurality of DBSD stages may be used to steer the input beams in a FOV. Because combination of diffuser 212 and DBEF 214 enable angular of the beams output from the transmitting stage 102 to be spread, the number of DBSD stages may be reduced significantly for a given FOV.
  • At least one DBEF is used to manage desired polarization of beams.
  • at least one a multilayer, reflective polarizer may be used to improve polarization ratio of the output beams of the diffuser 212.
  • the the DBEF is a film, which can be stacked on the diffuser 212 or integrated on the diffuser 212.
  • the DBEF 214 may include a 3MTM DBEF, which is stacked or integrated on the diffuser 212.
  • the at least one BEF may be utilized to be stack between the diffuser 212 and the DBEF 214.
  • the at least one BEF may include a 3MTM BEF.
  • FIGs. 2A-2B illustrate examples of generating beams with stable s-polarization from Tx path 101
  • beams output from the Tx path 101 may have stable p-polarization or any other suitable type of polarization.
  • the first and second polarization may be linear polarizations, e.g., linear s-polarization and linear p- polarization, or vice versa.
  • the first and second polarizations need not be linear, and thus, while in some embodiments, beams input to the beam-steering device have linear polarizations, in other examples, the beams provided to the beam-steering device may have circular or elliptical polarizations.
  • FIG. 2C presents an example laser 1022 in accordance with example embodiments.
  • the laser 1022 is a VCSEL array to simultaneously emit the plurality of beams with unstable polarizations, which may be linear.
  • the VCSEL may help to reduce spectral shift over temperature.
  • the laser 1022 may be a VCSEL.
  • the laser 1022 may be any other suitable surface-emitting laser or any suitable laser with different configurations.
  • the transmitting stage 102 encompasses a laser 1022, a depolarizer 222, and a polarization filter 224.
  • the laser 1022 e.g., VCSEL array
  • the plurality of beams may include a first set of beams each of which has a first polarization (e.g., linear s-polarization) and a second set of beams each of which has a second polarization (e.g., linear p-polarization).
  • the cardinality of the first set is different from the cardinality of the second set.
  • the depolarizer 222 receives the plurality of beams with different cardinalities of the two perpendicular polarizations and then changes one of the cardinalities of the first set and/or the cardinality of the second set to the other one, in order to ensure that the changed cardinality of the first set equals to the changed cardinality of the second set.
  • the depolarizer 222 outputs the changed cardinality of the first set and the changed cardinality of the second set.
  • a cardinality of the plurality of beams is a constant
  • the changed cardinalities of the first and second set in total equals to the constant.
  • each of the changed first set and the changed second set is 50% of the plurality of beams overall.
  • the polarization filter 224 selectively filters the first set with the changed cardinality (i.e., 50% of the plurality of beams overall) or the second set with the changed cardinality (i.e., 50% of the plurality of beams overall).
  • the beam-steering device 106(1) can receive stable beams to perform subsequent steering operations.
  • the beam-steering device 106(1) includes a DBSD 226 which steers each of the filtered beams with a respective identical polarization to different respective directions.
  • non-mechanical beam steering devices e.g., DBSDs
  • DBSDs non-mechanical beam steering devices
  • the beam steering device 106 may include any other suitable beam steering devices and may have different configurations.
  • FIG. 3A uses a plurality of DBSDs to enable each beam output from the Tx path 101 to have the same polarization.
  • the transmitting stage 102 incorporates the laser 1022, which may be the VCSEL array as shown in FIG. 2C.
  • the beam-steering device 106(1) comprises a first, second, third DBSD 302, 304, 306, and a half-wave plate (Z/2) (HWP) 308.
  • the first DBSD 302 converts the linear polarization to a circular polarization (e.g., right-handed or left-handed polarization).
  • a circular polarization e.g., right-handed or left-handed polarization
  • the second DBSD 304 receives a first set of beams with right-handed polarization from the first DBSD 302 and further converts the right-handed polarization of the first set of beams to left- handed polarization.
  • the third DBSD 306 has function similar to the second DBSD 304 for the polarization conversion.
  • the third DBSD 306 converts a second set of received beams with the left-handed polarization from the first DBSD 302 and generates the second set of beams with the right-handed polarization.
  • the HWP 308 further shifts the right-handed polarization to left-handed polarization.
  • FIG. 3B shows an alternative configuration in the Tx path 101 to enable the polarization output from the Tx path 101 to be stable, in accordance with example embodiments.
  • the functionalities of the DBSDs 312, 314, 316 are similar to those of the DBSDs 302, 304, 306 of FIG. 3A, except that given that the DBSD 306 steers each of the second set of beams in a desired angle, the DBSD 316 steers each of the second set of beams in half of the desired angle.
  • the DBSD 318 performs operations similar to the HWP 308 of FIG. 3A except the DBSD 318 further steers each of the second set of beams in half of the desired angle.
  • the plurality of DBSDs in the Tx path 101 enable polarizations of beams output from the Tx path 101 to be identical with respect to each other without affecting the respective angles steered by each of the plurality of DBSDs. Efficiency and reliability of the LIDAR system 100 may be ensured without causing too much hardware cost to the LDAIR system 100.
  • FIG. 3B illustrates that two DBSD 316, 318 each steers each of the second of beams in half of a desired angle, it is not intended for limiting.
  • more than two (i.e., n>2) DBSDs may be used to steer the second set of beams in a desired angle, without affecting polarization of beams output from the more than two DBSDs.
  • each of n DBSDs is used to steer 1/n of the desired angle such that the steered angles crossing the n DBSDs equal to the desired angle.
  • FIGs. 2A-3B propose different kinds of solutions to solve a problem of integrating a laser that emits unstable polarizations (e.g., mixed polarizations, alternating polarizations over time, or a cardinality of beams with one type of polarization being the different that of beams with the other type of polarization) into a LIDAR, system without reducing efficiency, reliability, and accuracy of the LDIAR system.
  • unstable polarizations e.g., mixed polarizations, alternating polarizations over time, or a cardinality of beams with one type of polarization being the different that of beams with the other type of polarization
  • FIGs. 2A-3B employ a PBS, a diffuser, combination of depolarizer and polarization filter, or a plurality of DBSDs as discussed above to enable polarizations output from the Tx path 101 to be identical with respect to each other, which may ensure that the polarizations of the beams output from the Tx path 101 are stable. Regardless reasons of instability of the polarizations generated by the laser, identical polarizations are generated from the Tx path 101. Thus, the embodiments of FIGs. 2A-3B are applicable to any suitable lasers in the LIDAR system.
  • FIG. 4A illustrates an alternative example Tx path 101 which generates a same number of beams for a respective polarization, in accordance with example embodiments.
  • the transmitting stage 102 in the Tx path 101 includes the laser 1022, an optional optical device 402, and a depolarizer 404.
  • the laser 1022 may any laser as discussed with reference to FIG. 30.
  • the optical device 402 collimates the plurality of emitted beams in parallel.
  • the depolarizer 404 adjusts a cardinality of the first set of beams with a first polarization and a cardinality of the second set of beams with a second polarization, and generates a third set of beams with the first polarization and a fourth set of beams with the second polarization.
  • a cardinality of the third set of beams is identical to that of the fourth set of beams.
  • a cardinality of the plurality of beams overall is a constant, a percentage of the third set of beams equals a percentage of the fourth set of beams, which is 50%.
  • the cardinality of the third set equals to the cardinality of the fourth set such that energy power of the third set of beams is identical to that of the fourth set of beams.
  • the DBSD 406 receives the third set of beams each with a first polarization (e.g., linear s-polarization) and convert the linear s-polarization to circular polarization, such as the right-handed polarization.
  • a first polarization e.g., linear s-polarization
  • the DBSD 406 receives the fourth set of beams each with a second polarization (e.g., linear p- polarization) and convert the linear p-polarization to circular polarization, such as the left-handed polarization.
  • a second polarization e.g., linear p- polarization
  • the cardinality of beams with the right-handed polarization is also identical to that of the left-handed polarization.
  • the optional DBSD 408 then steers the third set of beams with the right-handed polarization to different respective directions in a first FOV (e.g., FOV1 as shown in FIG. 4B).
  • the optional DBSD 410 then steers the fourth set of beams with the left-handed polarization to different respective directions in a second FOV (e.g., FOV2 as shown in FIG. 4B).
  • Angles of the first FOV and the second FOV may equal to 108 degrees, which may help to achieve an ultrawide FOV.
  • the depolarizer can change the cardinalities of beams with different respective polarizations, the energy power of two types of polarizations is ensured to be identical when the beams output from the transmitting stage 102. Therefore, stable beams are generated from the LIDAR, system with efficiency and reliability.
  • the two optional DBSDs 408 and 410 may help to enlarge angles of overall FOV of the LDAIR system.
  • the ultrawide FOV (e.g., 180 degrees) may be achieved by the LIDAR system.
  • the depolarizer 404 may include a liquid crystal depolarizer or a quartz wedge achromatic depolarizer. With respect to the liquid crystal depolarizer, it is a collection of half-wave plates with optic axes randomly distributed. After passing through such the depolarizer, the linearly polarized light is converted to a mixture of various polarized components; thus, the degree of polarization (DOP) drastically decreases.
  • the liquid crystal depolarizer a diameter of which may be designed as small as 0.5mm, randomizes linear polarizations.
  • the liquid crystal depolarizer is effective for both monochromatic and broadband light sources.
  • Ranges of thickness of anti-reflection (AR) coating may include 350-700 nm, 650- 1050 nm, or 1050-1700 nm.
  • the quartz wedge achromatic depolarizer converts a polarized beam of light into a pseudo-random polarized beam.
  • the depolarizer 404 can be made in the form of a film or a thin slab, the depolarizer 404 may be integrated to stack with the DBSD 406 as one layer.
  • the depolarizer 404 may be a diffuser, for example including a polymer-on-glass diffuser, ground glass diffuser, opal diffuser or light shaping micro-optics-based diffuser.
  • the depolarizer 404 placed after the laser 1022 depolarizes the beams by adjusting polarizations of the beams the beams are sent in a tailored light cone.
  • the depolarizer 404 may help to increase angular spread of the beams prior to sending the beams to the beamsteering devices 106(1).
  • the number of DBSD stages may be reduced significantly with an ultrawide FOV.
  • FIG. 4B is an example Rx path 103 to receive reflected or backscattered beams which are transmitted from the Tx path 101 of FIG. 4A.
  • the Rx path 103 comprises a first and second receiving path Rxl 113(1), Rx2 113(2).
  • a receiving stage 104 of the Rxl 113(1) includes a receiver 1042(1) and an optional optical device 412(1).
  • the DBSD 414 (1) of the beam-steering device 106(2) receives the reflected beams from the objects within the first FOV and sends the beams to the optical device 412(1).
  • the optical device 412(1) collimates the beams sent from the DBSD 414 in parallel.
  • the receiver 1042(1) then convert the beams which are optical signals to digital signals.
  • Components of the Rx2 113(2) are similar to those of the Rxl 113(1) except that polarizations (e.g., right-handed polarization) of the beams received by the DBSD 414(1) are different from those (e.g., left-handed polarization) of the beams received by the DBSD 414(2).
  • polarizations e.g., right-handed polarization
  • left-handed polarization e.g., left-handed polarization
  • FIG. 5A presents an example Tx path 101 which may help to enlarge FOV, in accordance with embodiments.
  • the laser 1022 of the transmitting stage 102 simultaneously generates a plurality of beams which may be stable.
  • the plurality of beams may have 0 degree of polarization or have two different polarizations each with an identical percentage. That is, the plurality of beams may include a first set of beams each of which has a first polarization (e.g., linear s-polarization) and a second set of beams each of which has a second polarization (e.g., linear p-polarization).
  • a cardinality of the first set is identical to a cardinality of second set.
  • the beam-steering device 106(1) includes a plurality of DBSD 502, 504, 506 to enlarge angles of an overall FOV.
  • the DBSD 502 converts the first polarization (e.g., linear s-polarization) to a first circular polarization (e.g., right-handed circular polarization), and then converts the second polarization (e.g., linear p-polarization) to a second circular polarization (e.g., left-handed circular polarization).
  • the DBSD 504 steers the first set of beams with the first circular polarization in different respective directions in a first FOV.
  • the DBSD 506 steers the second set of beams with the second circular polarization in different respective directions in a second FOV.
  • the overall FOV including the first and second FOV can be 180 degrees. Thus, scanning range of the LIDAR, system may be increased significantly.
  • FIGs. 5B-5C show two alternative example Rx paths 103 to receive reflected beams that are generated by the Tx path 101 of FIG. 5A.
  • the DBSDs 514 and 516 receive reflected beams with two different polarizations respectively, and then send to the DBSD 512. Since a first set of reflected beams received by the DBSD 514 have a FOV different from a second set of reflected beams received by the DBSD 516, the DBSD 512 is used to collect the reflected beams from the first and second FOVs.
  • the DBSD 512 is used to collect the beams from two different respective FOVs, only one single receiver 1042 is needed to fit with the DBSD 512 where half of the receiver 1042 receives the reflected beams from the first FOV and the other half of the receiver 1042 receives the reflected beams from the second FOV.
  • the DBSDs 524 and 526 perform operations similar to the DBSDs 514 and 516.
  • two different receivers for example including a first receiver array 522(1) and a second receiver array 522(2), are included within the receiving stage 104 to receive the reflected beams from two different respective FOVs.
  • FIG. 5B which employs a DBSD 512 to collect reflected beams from two different respective FOVs
  • FIG. 5C two receivers are needed to collect and process the reflected beams from two different respective FOVs.
  • using multiple DBSDs may help to reduce hardware cost of receivers. Cost of manufacturing of the LIDAR, system may be reduced significantly.
  • FIG. 6A presents an example Tx path 101 which may help to enlarge FOV, in accordance with alternative embodiments.
  • a plurality of beams generated by the laser 1022 of the transmitting stage 102 may be stable as well.
  • the PBS 602 splits the first set of beams with a first polarization (e.g., linear s-polarization) and the second set of beams with a second polarization (e.g., linear p-polarization).
  • a first polarization e.g., linear s-polarization
  • second polarization e.g., linear p-polarization
  • the DBSD 604 receives the first set of beams with the linear s- polarization, convert the linear s-polarization to a circular polarization (e.g., right- handed circular polarization), and steers the first set of beams into different respective directions in the first FOV.
  • the DBSD 606 receives the second set of beams with the linear p-polarization, convert the linear p-polarization to a circular polarization (e.g., left-handed circular polarization), and steers the second set of beams into different respective directions in the second FOV. Comparing this example with the example of FIG.
  • the DBSD 502 is replaced with the PBS 602
  • the two DBSDs 604, 606 can still perform steering in the first and second FOVs.
  • the overall FOV scanned by the LIDAR 100 can be achieved to be ultrawide (e.g., 180 degrees) as well.
  • FIG. 6B shows an alternative example Rx path 103 to receive reflected beams that are generated by the Tx path 101 of FIG. 6A.
  • the DBSD 614 receives reflected beams in the first FOV
  • the DBSD 616 receives reflected beams in the second FOV.
  • Half of the receiver 1042 receives the reflected beams in the first FOV from the DBSD 614
  • the other half of the receiver 1042 receives the reflected beams in the second FOV from the DBSD 616.
  • one or more optical device may be placed between the DBSD 614 and the receiver 1042 or between the DBSD 616 and the receiver 1042 to collimate the reflected beams in parallel.
  • FIG. 7A presents an example Tx path 101 which may help to enlarge FOV and to integrate a laser emitting unstable beams into the LDIAR, in accordance with alternative embodiments. Components of the Tx path 101 as shown in FIG. 7A are similar to those of the Tx path 101 as presented in FIG.
  • a depolarizer 701 is disposed between the laser 1022 and the DBSD 702.
  • the depolarizer 701 can change percentages of different respective polarizations of beams emitted by the laser. That is, if the plurality of beams emitted by the laser 1022 have two different percentages of polarizations (e.g., linear s-polarization and p-polarization), the depolarizer 701 enables the percentage of the linear s- polarization to be identical to the percentage of the linear p-polarization.
  • the plurality of DBSDs 702, 704, and 706 perform conversions and steering similar to that of DBSDs 502, 504, and 506 as shown in FIG. 5A. Such configurations may not only help to integrate the laser emitting unstable polarization beams into the LIDAR, system without degrading reliability of the LIDAR system, ultrawide FOV is also achieved by utilizing the plurality of DBSDs.
  • FIG. 7B presents an alternative example Tx path 101 which may help to enlarge FOV and to integrate a laser emitting unstable beams into the LDIAR, in accordance with alternative embodiments.
  • Components of the Tx path 101 as shown in FIG. 7B are similar to those of the Tx path 101 as presented in FIG. 7A except that the DBSD 702 disposed between the depolarizer 701 and the DBSDs 704, 706 is replaced with a PBS 712.
  • the PBS 712 splits the beams with two different polarizations out and sends 50% of beams with linear s-polarization to the DBSD 704 and sends 50% of beams with the linear p-polarization to the DBSD 706.
  • the DBSDs 704, 706 may convert different linear polarizations to different respective circular polarizations (e.g., right-handed circular polarization or lefthanded circular polarization).
  • a laser emitting unstable polarizations may be incorporated into the Tx path 101 of the LIDAR system to reduce spectral shift over temperature, which may help to improve efficiency and reliability of the LIDAR system without causing too many changes to the beamsteering devices.
  • two or more DBSDs are used to achieve an ultrawide FOV, for example including 180 degrees, which may help to improve scanning range of the LIDAR, system.
  • FIG. 8A presents an example Tx path 101 which may help to integrate a laser emitting unstable beams into the LDIAR, in accordance with alternative embodiments.
  • the transmitting stage 102 includes a laser 1022, a polarization switch 801, and a PBS 802.
  • any suitable laser may be used as the laser 1022.
  • a plurality of beams including a first set of beams with a first polarization (e.g., linear s-polarization) and a second set of beams with a second polarization are simultaneously generated by the laser 1022.
  • a cardinality of the first set and a cardinality of the second set may be different.
  • the polarization switch 801 switches polarizations of one type to the other type of polarizations. For examples, the second set of beams with the second polarization are switched to the second set of beams with the first polarization by the polarization switch 801.
  • the PBS 802 splits the first and second set of beams with the first polarizations.
  • the DBSD 806 then performs polarization conversion to convert the first polarization to a circular polarization and then steers the first and second set of beams in a first FOV. Alternatively, if the first set of beams with the first polarization are switched to the first set of beams with the second polarization by the polarization switch 801.
  • the PBS 802 splits the first and second set of beams with the second polarizations out.
  • the DBSD 804, rather than the DBSD 806, then performs polarization conversion to convert the second polarization to a circular polarization and then steers the first and second set of beams in a second FOV.
  • scanning in the second FOV is performed consecutively to scanning in the first FOV.
  • more than one polarization switch 801 and more than one PBS 802 may be used, in order to reduce dispersion of the plurality of beams.
  • the plurality of beams generated by the transmitting stage 102 have identical polarizations.
  • the energy power of the plurality of beams is constant and stable, which may help to improve efficiency and reliability of the LIDAR, system.
  • the overall FOV e.g. 180 degrees
  • FIG. 8B shows an alternative example Rx path 103 to receive reflected beams that are generated by the Tx path 101 of FIG. 8A.
  • the DBSDs 814, 816 receives reflected beams.
  • the DBSD 814 receives a plurality of beams from the first FOV and sends the plurality of beams with identical polarizations (e.g., linear s- polarization) to the PBS 812.
  • the PBS 812 splits the plurality of beams with the identical polarizations out.
  • the receiver 1042 then processes the plurality of beam and convert the plurality of beams (i.e., optical signal) into digital signals.
  • the DBSD 816 receives a plurality of beams from the second FOV, and then sends the plurality of beams with identical polarizations (e.g., linear p- polarization) to the PBS 812.
  • the PBS 812 splits the plurality of beams with the identical polarizations out.
  • the receiver 1042 then processes the plurality of beam and convert the plurality of beams (i.e., optical signal) into digital signals.
  • the configuration of adding PBS in the Rx path may help to reduce the number of receivers in the receiving stage 104.
  • the hardware cost in the Rx path is reduced to receive the plurality of beams from the two FOVs, which may enable the accuracy of the LIDAR system to be increased without introducing too many hardware cost.
  • optical device may include an optical lens.
  • a suitable software product may be stored in a pre-recorded storage device or other similar non-volatile or non- transitory computer readable medium, for example.
  • the software product includes instructions tangibly stored thereon that enable a processing device (e.g., a microprocessor) to execute examples of the methods disclosed herein.

Abstract

Un appareil est utilisé dans un système LIDAR. L'appareil comprend un laser, un premier dispositif optique et un dispositif d'orientation de faisceau. Le laser émet une pluralité de faisceaux comprenant un premier ensemble de faisceaux, chacun ayant une première polarisation, et un second ensemble de faisceaux, chacun ayant une seconde polarisation. La première polarisation est différente de la seconde polarisation. Le premier dispositif optique reçoit la pluralité de faisceaux émis et génère une pluralité de faisceaux ayant une polarisation qui est identique pour chacun des faisceaux générés. Le dispositif d'orientation de faisceau reçoit la pluralité de faisceaux générés ayant chacun la polarisation et dirige chaque faisceau de la pluralité de faisceaux générés vers une direction respective.
PCT/CA2023/050530 2022-04-25 2023-04-19 Appareil de commande de polarisation dans un système lidar WO2023205881A1 (fr)

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Citations (4)

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Publication number Priority date Publication date Assignee Title
US8982313B2 (en) * 2009-07-31 2015-03-17 North Carolina State University Beam steering devices including stacked liquid crystal polarization gratings and related methods of operation
US9784840B2 (en) * 2012-03-23 2017-10-10 Windar Photonics A/S Multiple directional LIDAR system
US10960900B1 (en) * 2020-06-30 2021-03-30 Aurora Innovation, Inc. Systems and methods for autonomous vehicle control using depolarization ratio of return signal
US11280970B2 (en) * 2018-06-14 2022-03-22 Ayar Labs, Inc. Beam steering structure with integrated polarization splitter

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8982313B2 (en) * 2009-07-31 2015-03-17 North Carolina State University Beam steering devices including stacked liquid crystal polarization gratings and related methods of operation
US9784840B2 (en) * 2012-03-23 2017-10-10 Windar Photonics A/S Multiple directional LIDAR system
US11280970B2 (en) * 2018-06-14 2022-03-22 Ayar Labs, Inc. Beam steering structure with integrated polarization splitter
US10960900B1 (en) * 2020-06-30 2021-03-30 Aurora Innovation, Inc. Systems and methods for autonomous vehicle control using depolarization ratio of return signal

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