WO2024105090A1 - Lidar device, lidar frontend, lidar system and method for carrying out lidar measurements - Google Patents

Lidar device, lidar frontend, lidar system and method for carrying out lidar measurements Download PDF

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Publication number
WO2024105090A1
WO2024105090A1 PCT/EP2023/081870 EP2023081870W WO2024105090A1 WO 2024105090 A1 WO2024105090 A1 WO 2024105090A1 EP 2023081870 W EP2023081870 W EP 2023081870W WO 2024105090 A1 WO2024105090 A1 WO 2024105090A1
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WO
WIPO (PCT)
Prior art keywords
optical
lidar
frontend
detecting section
light generating
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PCT/EP2023/081870
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French (fr)
Inventor
Sarah CWALINA
Christoph KOTTKE
Volker Jungnickel
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Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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Publication of WO2024105090A1 publication Critical patent/WO2024105090A1/en

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Classifications

    • 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
    • G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • 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
    • G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
    • G01S7/4815—Constructional features, e.g. arrangements of optical elements of transmitters alone using multiple transmitters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4818—Constructional features, e.g. arrangements of optical elements using optical fibres
    • 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
    • G01S7/491—Details of non-pulse systems
    • G01S7/4911—Transmitters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/491—Details of non-pulse systems
    • G01S7/4912—Receivers
    • G01S7/4913—Circuits for detection, sampling, integration or read-out
    • G01S7/4914—Circuits for detection, sampling, integration or read-out of detector arrays, e.g. charge-transfer gates

Definitions

  • LIDAR device LIDAR frontend
  • LIDAR system LIDAR system and method for carrying out LIDAR measurements
  • the invention relates to a LIDAR device as claimed in claim 1 , a LIDAR frontend as claimed in claim 11 , a LIDAR system as claimed in claim 13 and a method for carrying out LIDAR measurements according to claim 16.
  • LIDAR systems are used in a plurality of technical areas such as autonomous driving, robotics and end-user devices, e.g., mobile phones.
  • coherent LiDAR systems like frequency modulation continuous wave laser - FMCW LiDAR are increasingly used.
  • a general challenge of LIDAR systems is spatial resolution.
  • coherent scanning LiDAR systems may suffer from an inherent resolution vs. framerate trade-off. More particularly, a higher resolution requires more pixels per frame and each pixel requires a certain measurement time. Therefore, the framerate may be reduced in favor of the resolution - or vice versa. To this day, this remains to be a showstopper for deployment of coherent scanning LiDARs in highly dynamical applications, like advanced driver assistance systems (ADAS).
  • ADAS advanced driver assistance systems
  • a light generating and detecting section configured to generate a plurality of spatially separated optical signals (which are to be transmitted to an object) and to detect a plurality of spatially separated optical signals (which are received from the object);
  • an optical coupler interacting with the light generating and detecting section and configured to be optically coupled to a plurality of optical waveguides communicating the optical signals generated by the light generating and detecting section to an optical LIDAR frontend and communicating optical signals from the optical LIDAR frontend to the light generating and detecting section.
  • the light generating and detecting section of the LIDAR device may comprise a plurality of detectors for detecting the optical signals communicated from the LIDAR frontend via the optical waveguides.
  • the light generating and detecting section of the LIDAR device is formed as a photonic integrated circuit - PIC, i.e., as an integrated device which e.g., comprises the transmitters and/or detectors.
  • the light generating and detecting section may comprise a plurality of sub-sections (e.g., functional blocks), wherein each one of the sub-sections comprises one of the optical transmitters mentioned above and/or one of the detectors.
  • Each one of the sub-sections may comprise further components such as further optical elements, e.g., a circulator.
  • the subsections (including its components such as a transmitter, detector and/or at least one other component such as a circulator) may be formed by a PIC (wherein the PIC may realize all or at least some of the sub-sections).
  • the LIDAR device may further comprise electronic circuitry configured to process (e.g., preequalize) electric signals to be provided to the transmitters of the light generating and detecting section and/or to receive and process electric signals from the detectors of the light generating and detecting section, the electrical signals representing signals (e.g., data) to be optically transmitted and optical signals received by the light generating and detecting section, respectively.
  • the electronic circuitry may comprise a digital signal processing (DSP) unit or processor configured to process electric signals to be provided to the transmitters and/or electric signals received from the detectors, e.g., in such a way that cross talk between the spatially separated optical signals (i.e., between different spatially separated LIDAR channels) is eliminated or at least suppressed.
  • DSP digital signal processing
  • the LIDAR device may be realized by a common module, e.g., comprising the light generating and detecting section and the electron circuitry.
  • the light generating and detecting section which may be formed as a PIC as set out above, and the electron circuitry are arranged in a common housing.
  • the invention in a second aspect, relates to a LIDAR frontend, configured to transmit optical signals generated by a LIDAR device as described above to an object, wherein the LIDAR frontend comprises an optical frontend coupler configured to be optically coupled to a plurality of optical waveguides for communicating the optical signals generated by the LIDAR device and communicating optical signals from the LIDAR frontend (i.e., the object) back to the LIDAR device.
  • the LIDAR frontend may be a passive device.
  • the LIDAR frontend may comprise a scanning mechanism configured to transmit the optical signals received via the optical waveguides and the frontend coupler to the object. Further, the scanning mechanism may be configured to transmit light (optical signals) received from the object, in particular light reflected at the object, to the LIDAR device (via the frontend coupler and the optical waveguides).
  • the frontend coupler may comprise a PIC and/or micro optics (or other beam forming optics) to collimate and/or redirect optical signals received from the plurality of optical waveguides.
  • the scanning mechanism comprises at least one reflective element (e.g., a mirror).
  • the at least one reflective element may be moveable in such a way that it redirects incoming light in a plurality of directions to scan the object.
  • the plurality of optical waveguides may be formed by a plurality of separate optical fibers, i.e. , a fiber bundle. It is also conceivable that both a multicore fiber and a plurality of separate optical fibers are used to realize the plurality of optical waveguides of the LIDAR system.
  • the LIDAR system thus may combine parallelization of a plurality of transmitters and receivers (e.g., the above-mentioned sub-units of the LIDAR device) with space division multiplexing (SDM) through a common scanning unit to increase the capacity of the LIDAR system.
  • SDM space division multiplexing
  • the use of the multicore fiber or a fiber bundle to connect the LIDAR device and the LIDAR frontend may allow a more flexible arrangement of the components of the LIDAR system. This may be beneficial for applications where the LIDAR frontend needs to be lightweight and further away from the nearest power supply, e.g., in vehicle such as a car.
  • the LIDAR device may be arranged in a considerable distance from the LIDAR frontend.
  • all optical signals may be transmitted through one optical fiber component, e.g., a multicore fiber or a fiber bundle, acting as an interface between the (e.g., passive) optical LIDAR frontend and the processing unit (the LIDAR device).
  • adaptive field-of-view (FOV) management of the scanning mechanism may be employed to increase the framerate even further.
  • This may include scanning parts of a scene, which contain relevant information, e.g., moving objects, with higher resolution and less relevant areas more coarsely.
  • relevant information e.g., moving objects
  • intelligent algorithms or deep learning algorithms e.g., convolutional-neural-networks
  • the LIDAR system according to the invention thus may provide at least one of i) framerate and resolution improvement of scanning LiDARs with space division multiplexing, ii) miniaturization and optical integration (e.g., using PICs), multicore fibers or fiber bundles and special optical couplers (e.g., MCF couplers) to allow separation of optical LIDAR frontend from the processing unit (the LIDAR device), and iii) advanced digital signal processing with crosstalk mitigation for FMCW LiDAR and adaptive field-of-view management, e.g. using deep learning algorithms.
  • Applications for the SDM LiDAR system according to the invention may be in highly dynamic sensing scenarios, like advanced driver assistance systems, infrastructure traffic monitoring, industrial robotics or even end-user applications.
  • the invention is also related to a method for carrying out LIDAR measurements, in particular using the LIDAR system described above, the method comprising generating and/or detecting a plurality of spatially separated optical signals; communicating the generated spatially separated optical signals to an object via a plurality of optical waveguides and/or receiving spatially separated optical signals from the object via the plurality of optical waveguides.
  • Fig.1 schematically, a LIDAR system according to an embodiment of the invention.
  • Fig. 2 optical signals produced by a LIDAR system according to the invention.
  • the LIDAR system 100 depicted in Fig. 1 comprises a LIDAR device 10 and a LIDAR frontend 20.
  • the LIDAR device 10 and the LIDAR frontend 20 are optically coupled to one another via an optical multicore fiber - MCF 30, the multiple cores 31 of MCF 30 realizing a plurality of spatially separated optical waveguides.
  • the LIDAR device 10 comprises a light generating and detecting section 1 , which, in turn, has a plurality of sub-sections in the form of LIDAR blocks 11 .
  • Each one of the LIDAR blocks 11 comprises at least one optical transmitter (e.g., an FMCW laser) and at least one detector (e.g., a photodiode).
  • the light generating and detecting section 1 is capable of generating and detecting a plurality of spatially separated optical signals.
  • the separate transmitters of at least some of the different LIDAR blocks may be replaced by a single common transmitter, wherein the output of the single transmitter is divided into a plurality of spatially separate optical signals.
  • a portion of the optical output of the common transmitter may be used as a reference signal supplied to the LIDAR blocks 11.
  • the LIDAR blocks 11 may be formed by a common module 50, e.g., the LIDAR blocks 11 may be arranged on a common substrate.
  • the LIDAR blocks 11 are realized by a photonic integrated circuit (PICs).
  • PICs photonic integrated circuit
  • each one of the LIDAR blocks 11 may comprise additional optical components such as at least one circulator.
  • the LIDAR blocks 11 may provide optical inputs and outputs such that the LIDAR device 10 is equipped with a plurality of separate optical inputs and a plurality of separate optical outputs.
  • the LIDAR device 10 further comprises an optical coupler 2 interacting with the LIDAR blocks 11 and optically coupling them to the MCF 30. More specifically, the optical coupler 2 is configured and coupled to the LIDAR blocks 11 in such a way that the spatially separated optical signals generated by the transmitters of the LIDAR blocks 11 are coupled to the optical waveguides (i.e., the fiber cores 31) of the MCF 30.
  • the LIDAR blocks 11 may be coupled one-to-one to the fiber cores 31 via the optical coupler 2.
  • optical signals generated by the LIDAR blocks 11 are thus conveyed to the LIDAR frontend 20 via the MCF 30.
  • optical signals output by the LIDAR frontend 20 are communicated to the detectors of the LIDAR blocks 11 by means of the MCF 30.
  • a fiber bundle may be used as already set forth above.
  • the LIDAR device 10 may comprise electronic circuitry configured to provide control signals to the transmitters of the LIDAR blocks 11 and/or to receive and process electric signals from the detectors of the LIDAR blocks 11.
  • the electronic circuitry comprises a digital signal processor - DSP 3.
  • the DSP 3 may be configured to process signals to be provided to the transmitters and/or signals received from the detectors in such a way that cross talk between the spatially separated optical signals (i.e., between different spatially separated LIDAR channels) is mitigated.
  • the DSP 3 employs a MIMO scheme, which processes received spatially adjacent optical signals, i.e., from adjacent pixels.
  • the LIDAR device 10 thus may be a processing unit configured to produce and receive spatially separated optical signals and also is capable of electronically processing electrical signals supplied to the transmitters and received from the detectors.
  • the MCF 30 thus acts as an interface between the LIDAR processing unit (the LIDAR device 10) and the (e.g., passive) LIDAR frontend.
  • the optical frontend 20 comprises an optical frontend coupler 21 optically coupled to the MCF 30, e.g., by means of a plurality of optical elements 211 assigned to the fiber cores 31 of the MCF 30.
  • the optical elements 211 are configured to collimate and redirect light received from the fiber cores 31 of the MCF.
  • the optical frontend coupler 21 may be formed as a PIC.
  • the optical frontend 20 comprises a scanning mechanism 22 configured to transmit the optical signals received via the MCF 30 and the frontend coupler 21 to an object to be investigated (not shown).
  • the scanning mechanism 22 may comprise a single moveable mirror or a plurality of moveable mirrors. The light received from the scanned object travels back through the same paths and may passed from circulators of the LIDAR blocks to the corresponding detector. Further, distance information (e.g., pixel distance information) may be obtained by digital signal processing (e.g., implemented by DSP 3).
  • Fig. 2 illustrates an example of an optical output produced by a LIDAR system of the invention.
  • the optical output comprises a plurality of spatially separated optical signals OS which are jointly moved to a plurality of different scanning positions P.
  • the spatially separate optical signals OS are generated by the LIDAR device of the system, e.g., the LIDAR blocks 11 shown in Fig. 1 , and output by the multiple waveguides, e.g., the MCF 30 in Fig. 1.
  • each core of the MCF projects one light spot, i.e., one pixel or sub-pixel.
  • the spatially separate optical signals OS are moved to the plurality of scanning positions P by means of the scanning mechanism of the LIDAR frontend of the system.
  • the optical signals OS reach the different scanning positions P at subsequent points in time.
  • the joint presentation in Fig. 2 is for illustrative purposes only.
  • a (e.g., passive) increase of the resolution by a factor given by the number of optical waveguides between the LI DAR device and the LI DAR frontend, e.g., the number of MCF cores, can be achieved, this increase being independent of the framerate.
  • optical signals OS e.g., light spots, “pixels”, produced by the optical signals
  • the gap may be small or not present at all.
  • the spatial separation of the optical signals produced by the LIDAR device of the LIDAR system thus may also relate to a distance between a center of the optical signals.

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

Abstract

The invention relates to LIDAR device (10), comprising a light generating and detecting section (1) configured to generate a plurality of spatially separated optical signals and to detect a plurality of spatially separated optical signals; and an optical coupler (2) interacting with the light generating and detecting section (1) and configured to be optically coupled to a plurality of optical waveguides (31) communicating the optical signals generated by the light generating and detecting section (1) to an optical LIDAR frontend (20) and communicating optical signals from the optical LIDAR frontend (20) to the light generating and detecting section (1). The invention also relates to a LIDAR frontend, a LIDAR system and a method for carrying out LIDAR measurements.

Description

LIDAR device, LIDAR frontend, LIDAR system and method for carrying out LIDAR measurements
Description
The invention relates to a LIDAR device as claimed in claim 1 , a LIDAR frontend as claimed in claim 11 , a LIDAR system as claimed in claim 13 and a method for carrying out LIDAR measurements according to claim 16.
LIDAR systems are used in a plurality of technical areas such as autonomous driving, robotics and end-user devices, e.g., mobile phones. Especially coherent LiDAR systems like frequency modulation continuous wave laser - FMCW LiDAR are increasingly used. However, a general challenge of LIDAR systems is spatial resolution. For example, coherent scanning LiDAR systems may suffer from an inherent resolution vs. framerate trade-off. More particularly, a higher resolution requires more pixels per frame and each pixel requires a certain measurement time. Therefore, the framerate may be reduced in favor of the resolution - or vice versa. To this day, this remains to be a showstopper for deployment of coherent scanning LiDARs in highly dynamical applications, like advanced driver assistance systems (ADAS).
It is therefore an object of the invention to enhance the performance of LIDAR systems. According to the invention, in a first aspect, a LIDAR device is provided, comprising
- a light generating and detecting section configured to generate a plurality of spatially separated optical signals (which are to be transmitted to an object) and to detect a plurality of spatially separated optical signals (which are received from the object); and
- an optical coupler interacting with the light generating and detecting section and configured to be optically coupled to a plurality of optical waveguides communicating the optical signals generated by the light generating and detecting section to an optical LIDAR frontend and communicating optical signals from the optical LIDAR frontend to the light generating and detecting section.
The LIDAR device may be part of a space division multiplexing LIDAR system comprising - besides the LIDAR device itself - the plurality of optical waveguides and a LIDAR frontend for transmitting optical signals produced by the LIDAR device to a targeted object. For example, the LIDAR frontend comprises a corresponding scanning mechanism as will be discussed further below. More particularly, the LIDAR device may be placed in a distance from the LIDAR frontend while being connected to the LIDAR frontend via the plurality of optical waveguides. The plurality of optical waveguides may be formed by a plurality of separate optical fibers, i.e. , a fiber bundle, and/or at least one multi core fiber.
The optical coupler of the LIDAR device may comprise a plurality of outputs, each one of the outputs being assigned to one of the optical waveguides. More particularly, the outputs of the optical coupler may be assigned (e.g., coupled) to the optical waveguides in a one-to-one relationship, i.e., each one of the outputs is assigned to a different one of the optical fibers. More particularly, the coupler of the LIDAR device is configured to adapt the optical output geometry of the light generating and detecting section to the geometry of the plurality of optical waveguides, e.g., a multicore fiber or a fiber bundle. For example, the coupler of the LIDAR device is a multicore fiber coupler.
According to another embodiment, the light generating and detecting section comprises a single optical transmitter, wherein the light generating and detecting section is configured to generate the spatially separated optical signals using light produced by the single optical transmitter, e.g., using a beam splitter.
However, the light generating and detecting section may comprise a plurality of optical transmitters, wherein the light generating and detecting section is configured to generate each one of the spatially separated optical signals using light produced by one of the optical transmitters. For example, the transmitters are assigned to the optical waveguides in a one- to-one relationship, i.e., each one of the transmitters is assigned to a different one of the optical fibers.
Further, the light generating and detecting section of the LIDAR device may comprise a plurality of detectors for detecting the optical signals communicated from the LIDAR frontend via the optical waveguides.
For example, the light generating and detecting section of the LIDAR device is formed as a photonic integrated circuit - PIC, i.e., as an integrated device which e.g., comprises the transmitters and/or detectors.
Moreover, the light generating and detecting section may comprise a plurality of sub-sections (e.g., functional blocks), wherein each one of the sub-sections comprises one of the optical transmitters mentioned above and/or one of the detectors. Each one of the sub-sections may comprise further components such as further optical elements, e.g., a circulator. The subsections (including its components such as a transmitter, detector and/or at least one other component such as a circulator) may be formed by a PIC (wherein the PIC may realize all or at least some of the sub-sections).
According to another embodiment, the light generating and detecting section is configured to generate and/or detect the optical signals using a coherent optical modulation and/or detection scheme. The coherent optical modulation and/or detection scheme may be based on frequency modulated continuous waves. Accordingly, at least one of the optical transmitters of the light generating and detecting section may be formed by a frequency modulated continuous wave laser.
The LIDAR device may further comprise electronic circuitry configured to process (e.g., preequalize) electric signals to be provided to the transmitters of the light generating and detecting section and/or to receive and process electric signals from the detectors of the light generating and detecting section, the electrical signals representing signals (e.g., data) to be optically transmitted and optical signals received by the light generating and detecting section, respectively. The electronic circuitry may comprise a digital signal processing (DSP) unit or processor configured to process electric signals to be provided to the transmitters and/or electric signals received from the detectors, e.g., in such a way that cross talk between the spatially separated optical signals (i.e., between different spatially separated LIDAR channels) is eliminated or at least suppressed. For example, the electronic circuitry employs a MIMO (multiple input multiple output) scheme for processing the signals to be provided to the transmitters and/or for processing the signals received from the detector. In particular, detector signals originating from received adjacent optical signals (pixels) are jointly processed by means of a MIMO algorithm. The MIMO algorithm e.g., takes into account cross talk components (e.g., all of the possible cross talk components) of the spatially separated optical signals (i.e. , optical channels).
Moreover, the LIDAR device may be realized by a common module, e.g., comprising the light generating and detecting section and the electron circuitry. For example, the light generating and detecting section, which may be formed as a PIC as set out above, and the electron circuitry are arranged in a common housing.
In a second aspect, the invention relates to a LIDAR frontend, configured to transmit optical signals generated by a LIDAR device as described above to an object, wherein the LIDAR frontend comprises an optical frontend coupler configured to be optically coupled to a plurality of optical waveguides for communicating the optical signals generated by the LIDAR device and communicating optical signals from the LIDAR frontend (i.e., the object) back to the LIDAR device. The LIDAR frontend may be a passive device.
The LIDAR frontend may comprise a scanning mechanism configured to transmit the optical signals received via the optical waveguides and the frontend coupler to the object. Further, the scanning mechanism may be configured to transmit light (optical signals) received from the object, in particular light reflected at the object, to the LIDAR device (via the frontend coupler and the optical waveguides).
Moreover, the frontend coupler may comprise a PIC and/or micro optics (or other beam forming optics) to collimate and/or redirect optical signals received from the plurality of optical waveguides. For example, the scanning mechanism comprises at least one reflective element (e.g., a mirror). The at least one reflective element may be moveable in such a way that it redirects incoming light in a plurality of directions to scan the object.
The invention, in a third aspect, relates to a LIDAR system comprising a plurality of optical waveguides and at least one of a LIDAR device and a LIDAR frontend described above, wherein the optical coupler of the LIDAR device is optically coupled to the plurality of optical waveguides (e.g., to one end of the optical fibers) and/or the optical frontend coupler of the LIDAR frontend is optically coupled to the plurality of optical waveguides (e.g., to the other end of the optical fibers). The plurality of optical waveguides may be formed by at least one optical multicore fiber (MCF). In particular, each one of the multiple cores of the MCF forms an optical waveguide in conjunction with a cladding material that at least partially surrounds the cores.
According to another solution, the plurality of optical waveguides may be formed by a plurality of separate optical fibers, i.e. , a fiber bundle. It is also conceivable that both a multicore fiber and a plurality of separate optical fibers are used to realize the plurality of optical waveguides of the LIDAR system.
The LIDAR system thus may combine parallelization of a plurality of transmitters and receivers (e.g., the above-mentioned sub-units of the LIDAR device) with space division multiplexing (SDM) through a common scanning unit to increase the capacity of the LIDAR system. More particularly, the use of the multicore fiber or a fiber bundle to connect the LIDAR device and the LIDAR frontend may allow a more flexible arrangement of the components of the LIDAR system. This may be beneficial for applications where the LIDAR frontend needs to be lightweight and further away from the nearest power supply, e.g., in vehicle such as a car. For example, the LIDAR device may be arranged in a considerable distance from the LIDAR frontend. In particular, all optical signals may be transmitted through one optical fiber component, e.g., a multicore fiber or a fiber bundle, acting as an interface between the (e.g., passive) optical LIDAR frontend and the processing unit (the LIDAR device).
Additionally, adaptive field-of-view (FOV) management of the scanning mechanism may be employed to increase the framerate even further. This may include scanning parts of a scene, which contain relevant information, e.g., moving objects, with higher resolution and less relevant areas more coarsely. To identify those scenes (i.e., areas of interest) intelligent algorithms or deep learning algorithms (e.g., convolutional-neural-networks) may be used.
The LIDAR system according to the invention thus may provide at least one of i) framerate and resolution improvement of scanning LiDARs with space division multiplexing, ii) miniaturization and optical integration (e.g., using PICs), multicore fibers or fiber bundles and special optical couplers (e.g., MCF couplers) to allow separation of optical LIDAR frontend from the processing unit (the LIDAR device), and iii) advanced digital signal processing with crosstalk mitigation for FMCW LiDAR and adaptive field-of-view management, e.g. using deep learning algorithms. Applications for the SDM LiDAR system according to the invention may be in highly dynamic sensing scenarios, like advanced driver assistance systems, infrastructure traffic monitoring, industrial robotics or even end-user applications. The invention is also related to a method for carrying out LIDAR measurements, in particular using the LIDAR system described above, the method comprising generating and/or detecting a plurality of spatially separated optical signals; communicating the generated spatially separated optical signals to an object via a plurality of optical waveguides and/or receiving spatially separated optical signals from the object via the plurality of optical waveguides.
Features of the embodiments described above in conjunction with the LIDAR system can be analogously used to modify the above method.
Embodiments of the invention will be described below with reference to the drawings. The drawings show:
Fig.1 schematically, a LIDAR system according to an embodiment of the invention; and
Fig. 2 optical signals produced by a LIDAR system according to the invention.
The LIDAR system 100 depicted in Fig. 1 comprises a LIDAR device 10 and a LIDAR frontend 20. The LIDAR device 10 and the LIDAR frontend 20 are optically coupled to one another via an optical multicore fiber - MCF 30, the multiple cores 31 of MCF 30 realizing a plurality of spatially separated optical waveguides.
More particularly, the LIDAR device 10 comprises a light generating and detecting section 1 , which, in turn, has a plurality of sub-sections in the form of LIDAR blocks 11 . Each one of the LIDAR blocks 11 comprises at least one optical transmitter (e.g., an FMCW laser) and at least one detector (e.g., a photodiode). By means of the transmitters and detectors of the different LIDAR blocks 11 , the light generating and detecting section 1 is capable of generating and detecting a plurality of spatially separated optical signals. As an alternative, the separate transmitters of at least some of the different LIDAR blocks may be replaced by a single common transmitter, wherein the output of the single transmitter is divided into a plurality of spatially separate optical signals. Further, in case coherent detection is employed, a portion of the optical output of the common transmitter may be used as a reference signal supplied to the LIDAR blocks 11. The LIDAR blocks 11 may be formed by a common module 50, e.g., the LIDAR blocks 11 may be arranged on a common substrate. For example, at least some of the LIDAR blocks 11 are realized by a photonic integrated circuit (PICs). Moreover, each one of the LIDAR blocks 11 may comprise additional optical components such as at least one circulator. Further, the LIDAR blocks 11 may provide optical inputs and outputs such that the LIDAR device 10 is equipped with a plurality of separate optical inputs and a plurality of separate optical outputs.
The LIDAR device 10 further comprises an optical coupler 2 interacting with the LIDAR blocks 11 and optically coupling them to the MCF 30. More specifically, the optical coupler 2 is configured and coupled to the LIDAR blocks 11 in such a way that the spatially separated optical signals generated by the transmitters of the LIDAR blocks 11 are coupled to the optical waveguides (i.e., the fiber cores 31) of the MCF 30. The LIDAR blocks 11 may be coupled one-to-one to the fiber cores 31 via the optical coupler 2.
The spatially separated optical signals generated by the LIDAR blocks 11 are thus conveyed to the LIDAR frontend 20 via the MCF 30. Conversely, optical signals output by the LIDAR frontend 20 are communicated to the detectors of the LIDAR blocks 11 by means of the MCF 30. It should be noted that instead of a multicore fiber a fiber bundle may be used as already set forth above.
Moreover, the LIDAR device 10 may comprise electronic circuitry configured to provide control signals to the transmitters of the LIDAR blocks 11 and/or to receive and process electric signals from the detectors of the LIDAR blocks 11. For example, the electronic circuitry comprises a digital signal processor - DSP 3. The DSP 3 may be configured to process signals to be provided to the transmitters and/or signals received from the detectors in such a way that cross talk between the spatially separated optical signals (i.e., between different spatially separated LIDAR channels) is mitigated. For example, the DSP 3 employs a MIMO scheme, which processes received spatially adjacent optical signals, i.e., from adjacent pixels. The LIDAR device 10 thus may be a processing unit configured to produce and receive spatially separated optical signals and also is capable of electronically processing electrical signals supplied to the transmitters and received from the detectors. The MCF 30 thus acts as an interface between the LIDAR processing unit (the LIDAR device 10) and the (e.g., passive) LIDAR frontend.
The optical frontend 20 comprises an optical frontend coupler 21 optically coupled to the MCF 30, e.g., by means of a plurality of optical elements 211 assigned to the fiber cores 31 of the MCF 30. The optical elements 211 are configured to collimate and redirect light received from the fiber cores 31 of the MCF. The optical frontend coupler 21 may be formed as a PIC.
Moreover, the optical frontend 20 comprises a scanning mechanism 22 configured to transmit the optical signals received via the MCF 30 and the frontend coupler 21 to an object to be investigated (not shown). The scanning mechanism 22 may comprise a single moveable mirror or a plurality of moveable mirrors. The light received from the scanned object travels back through the same paths and may passed from circulators of the LIDAR blocks to the corresponding detector. Further, distance information (e.g., pixel distance information) may be obtained by digital signal processing (e.g., implemented by DSP 3).
Fig. 2 illustrates an example of an optical output produced by a LIDAR system of the invention. The optical output comprises a plurality of spatially separated optical signals OS which are jointly moved to a plurality of different scanning positions P. The spatially separate optical signals OS are generated by the LIDAR device of the system, e.g., the LIDAR blocks 11 shown in Fig. 1 , and output by the multiple waveguides, e.g., the MCF 30 in Fig. 1. For example, each core of the MCF projects one light spot, i.e., one pixel or sub-pixel. The spatially separate optical signals OS are moved to the plurality of scanning positions P by means of the scanning mechanism of the LIDAR frontend of the system. Thus, the optical signals OS reach the different scanning positions P at subsequent points in time. The joint presentation in Fig. 2 is for illustrative purposes only. Hence, a (e.g., passive) increase of the resolution by a factor given by the number of optical waveguides between the LI DAR device and the LI DAR frontend, e.g., the number of MCF cores, can be achieved, this increase being independent of the framerate.
It should be noted that there might be a gap between the optical signals OS (e.g., light spots, “pixels”, produced by the optical signals). The gap, however, may be small or not present at all. The spatial separation of the optical signals produced by the LIDAR device of the LIDAR system thus may also relate to a distance between a center of the optical signals.

Claims

Claims
1. LIDAR device (10), comprising a light generating and detecting section (1) configured to generate a plurality of spatially separated optical signals and to detect a plurality of spatially separated optical signals; and an optical coupler (2) interacting with the light generating and detecting section (1) and configured to be optically coupled to a plurality of optical waveguides (31) communicating the optical signals generated by the light generating and detecting section (1) to an optical LIDAR frontend (20) and communicating optical signals from the optical LIDAR frontend (20) to the light generating and detecting section (1).
2. LIDAR device as claimed in claim 1 , wherein the optical coupler (2) comprises a plurality of outputs, each one of the outputs to be assigned to one of the optical waveguides (31).
3. LIDAR device as claimed in claim 1 or 2, wherein the light generating and detecting section (1) comprises a single optical transmitter and is configured to generate the spatially separated optical signals using light produced by the single optical transmitter.
4. LIDAR device as claimed in claim 1 or 2, wherein the light generating and detecting section (1) comprises a plurality of optical transmitters and is configured to generate each one of the spatially separated optical signals using light produced by one of the optical transmitters.
5. LIDAR device as claimed in any of the preceding claims, wherein the light generating and detecting section (1) comprises a plurality of detectors for detecting the optical signals communicated from the LIDAR frontend (20) via the optical waveguides (31).
6. LIDAR device as claimed in claimed in claim 4 or 5, wherein the light generating and detecting section (1) comprises a plurality of sub-sections (11), wherein each one of the sub-sections (11) comprises one of the optical transmitters and/or one of the detectors.
7. The LIDAR device as claimed in any of the preceding claims, wherein the light generating and detecting section (1) is formed at least partially by a photonic integrated circuit.
8. The LIDAR device as claimed in any of the preceding claims, wherein the light generating and detecting section (1) is configured to generate and/or detect the optical signals using a coherent optical modulation and/or detection scheme. The LIDAR device as claimed in any of the preceding claims, wherein the light generating and detecting section (1) comprises at least one frequency modulated continuous wave laser. The LIDAR device as claimed in any of the preceding claims, further comprising electronic circuitry configured to process electric signals to be provided to the transmitters of the light generating and detecting section and/or to receive and process electric signals from the detectors of the light generating and detecting section, wherein the electronic circuitry employs a Ml MO scheme for processing the signals to be provided to the transmitters and/or for processing the signals received from the detectors. LIDAR frontend (20), configured to transmit and receive optical signals generated by a LIDAR device (10) as claimed in any of claims 1 to 10 to an object, wherein the LIDAR frontend (20) comprises an optical frontend coupler (21) configured to be optically coupled to a plurality of optical waveguides (31) for communicating the optical signals generated by the LIDAR device (10) and communicating optical signals from the LIDAR frontend (20) to the LIDAR device (10). The LIDAR frontend as claimed in claim 11 , comprising a scanning mechanism (22) configured to transmit the optical signals received via the optical waveguides (31) and the optical frontend coupler (21) to the object. LIDAR system (100) comprising a plurality of optical waveguides (31) and at least one of a LIDAR device (10) as claimed in any of claims 1 to 10 and a LIDAR frontend (20) as claimed claim 11 or 12, wherein the optical coupler (2) of the LIDAR device (10) is optically coupled to the plurality of optical waveguides (31) and/or the optical frontend coupler (21) of the LIDAR frontend (20) is optically coupled to the plurality of optical waveguides (31). The LIDAR system as claimed in claim 13, wherein the plurality of optical waveguides (31) is formed by at least one optical multicore fiber (30). The LIDAR system as claimed in claim 13, wherein the plurality of optical waveguides is formed by a plurality of separate optical fibers. Method for carrying out LIDAR measurements, in particular using the LIDAR system (100) as claimed in any of claims 13 to 15, comprising generating and/or detecting a plurality of spatially separated optical signals - communicating the generated spatially separated optical signals to an object via a plurality of optical waveguides (31) and/or receiving spatially separated optical signals from the object via the plurality of optical waveguides (31).
PCT/EP2023/081870 2022-11-16 2023-11-15 Lidar device, lidar frontend, lidar system and method for carrying out lidar measurements WO2024105090A1 (en)

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