WO2019145242A1 - Dispositif et procédé de détermination de la distance d'un objet en mouvement - Google Patents

Dispositif et procédé de détermination de la distance d'un objet en mouvement Download PDF

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Publication number
WO2019145242A1
WO2019145242A1 PCT/EP2019/051320 EP2019051320W WO2019145242A1 WO 2019145242 A1 WO2019145242 A1 WO 2019145242A1 EP 2019051320 W EP2019051320 W EP 2019051320W WO 2019145242 A1 WO2019145242 A1 WO 2019145242A1
Authority
WO
WIPO (PCT)
Prior art keywords
wgm resonator
frequency
laser
signal
free spectral
Prior art date
Application number
PCT/EP2019/051320
Other languages
German (de)
English (en)
Inventor
Vladimir Davydenko
Original Assignee
Carl Zeiss Smt Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Carl Zeiss Smt Gmbh filed Critical Carl Zeiss Smt Gmbh
Publication of WO2019145242A1 publication Critical patent/WO2019145242A1/fr

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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
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/50—Systems of measurement based on relative movement of target
    • G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • 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
    • G01S7/491—Details of non-pulse systems
    • G01S7/4912—Receivers
    • G01S7/4917—Receivers superposing optical signals in a photodetector, e.g. optical heterodyne detection

Definitions

  • the invention relates to a device and a method for determining a distance of a moving object, as well as a light source for emitting an optical signal with a time-varying frequency, in particular for use in such a device.
  • LIDAR optical distance measurement of objects u.a.
  • a measurement principle also known as LIDAR in which an optical signal, which is temporally changed in its frequency, is emitted towards the object in question and evaluated after back reflection on the object.
  • Fig. 1 a shows only a schematic representation of a known per se basic structure in which a signal emitted by a light source 110 with time-varying frequency (also referred to as "chirp") in two Partial signals is split, this splitting is done for example via a partially transparent mirror, not shown.
  • the two sub-signals are coupled via a signal coupler 150 and superimposed on one another at a detector 160, wherein the first sub-signal 111 reaches the signal coupler 150 and the detector 160 as reference signal without reflection at the object labeled "140".
  • the second partial signal 121 which arrives at the signal coupler 150 or at the detector 160, on the other hand, passes to the object 140 via an optical circulator 130, is reflected back by the latter and thus arrives at the signal coupler with a time delay and a correspondingly changed frequency in comparison to the first partial signal 111 150 and the detector 160.
  • the measuring signal supplied by the detector 160 is evaluated relative to the measuring device or the light source 110 via an evaluation device (not shown), wherein the difference frequency 131 between the sub-signals 111, 121 detected at a specific instant in the diagram of FIG is characteristic of the distance of the object 140 from the measuring device or the light source 110.
  • the time-dependent frequency profile of the signal emitted by the light source 110 can also be such that two sections are present. in which the time derivative of the frequency generated by the light source 110 is opposite to each other.
  • WGMR "whispering gallery mode resonator
  • this frequency sweep of the light source in the case of the structure shown in FIG. by applying to the WGM resonator 510 (made of electro-optical crystal material) with electrical voltage.
  • the tunable frequency range (“sweep ranks”) is limited by the maximum permissible electrical voltage as well as the dimensions of the WGM resonator 510.
  • the low free spectral range (FSR) of the WGM resonator 510 in turn requires a correspondingly strong limitation of the amplification bandwidth of the laser 501, because to ensure a one-mode operation, the free spectral range (FSR) of the WGM resonator 510 must be greater than the gain bandwidth For this reason, in the structure of Fig. 5, as the laser 501, a DFB ("distributed feedback laser") laser with a low spectral amplification bandwidth is typically used.
  • An apparatus according to the invention for determining a distance of a moving object has:
  • a light source for emitting an optical signal having a time-varying frequency
  • the light source comprises a laser, a first WGM resonator which is optically coupled to the laser, and a second WGM resonator, which is optically coupled to the laser, having;
  • a detector for generating a detector signal from a superimposition of a first partial signal and a second partial signal, wherein the first partial signal and the second partial signal have arisen by decomposing the optical signal emitted by the light source, wherein the first partial signal without prior reflection on the object the second sub-signal passes to the detector after reflection at the object, wherein the detector signal for the difference frequency between the frequency of the second sub-signal and the frequency of the first sub-signal is characteristic;
  • the invention is based on the concept that in a tunable light source for use in a device for distance measurement, two WGM resonators with free spectral ranges (FSR) that can be set independently of one another (in particular to slightly, eg by 10% mutually different values) operate. In this way, as described in more detail below, in comparison to the concept described at the outset with reference to FIG.
  • the provision according to the invention of two WGM resonators achieves, in particular, that by changing the free spectral range (FSR) of one of the WGM resonators or both WGM resonators (ie setting different FSR combinations), shifts of the frequencies coinciding in the frequency spectrum Modes of the two WGM resonators and thus the frequency of the emitted light across the entire amplification bandwidth of the laser medium can be realized with the result that in comparison to the use of a single WGM resonator considerably enlarged tuning range is realized.
  • FSR free spectral range
  • the use according to the invention of two WGM resonators in the tunable light source further achieves the requirement described at the beginning of the conventional concept described with reference to FIG. 5 of limiting the gain bandwidth of the laser (eg by using a DFB Laser) deleted. While in the conventional approach using only a single WGM resonator, the circumstance of the comparatively small free spectral range (FSR) of this WGM resonator must be taken into account by correspondingly limiting the amplification bandwidth of the laser must, this limitation can be avoided by the inventive use of two WGM resonators.
  • FSR free spectral range
  • the free spectral range of the first WGM resonator and / or the free spectral range of the second WGM resonator can be varied in order to vary the frequency of the transmitted optical signal.
  • this variation of the free spectral range (FSR) of the first WGM resonator and / or the free spectral range (FSR) of the second WGM resonator is a frequency at which modes of the first WGM resonator and the second WGM resonator coincide over the entire gain bandwidth of the laser displaceable.
  • the laser has an optical semiconductor amplifier. This advantageously makes it possible to take advantage of the fact that the use of two WGM resonators according to the invention eliminates the need for limiting the gain bandwidth of the laser (for example by using a DFB laser).
  • the light source has a tuning range which comprises at least the wavelength range from 20 nm to 100 nm, in particular at least the wavelength range from 5 nm to 150 nm.
  • the optical coupling of the first WGM resonator and / or the second WGM resonator to the laser is realized via at least one prism.
  • the optical coupling of the first WGM resonator and / or the second WGM resonator to the laser is realized via at least one optical waveguide.
  • the invention also relates to a method for determining a distance of a moving object, the method comprising the following steps:
  • the free spectral range (FSR) of the first WGM resonator and / or the free spectral range (FSR) of the second WGM resonator are varied to vary the frequency of the optical signal emitted by the light source.
  • the free spectral range (FSR) of the first WGM resonator and / or the free spectral range (FSR) of the second WGM resonator may be at least temporarily increased by at least 5%, in particular at least 10%, in each case based on the greater value, different values can be set.
  • the invention further relates to a light source for emitting an optical signal with a time-varying frequency, in particular for use in a device for determining a distance of a moving object, with • a laser;
  • a first WGM resonator which is optically coupled to the laser
  • a second WGM resonator which is optically coupled to the laser
  • the free spectral range of the first WGM resonator and / or the free spectral range of the second WGM resonator is variable;
  • objects measured in the context of the distance may be only examples (and without the invention being limited thereto) of objects that are relevant in the road traffic or automobile sector (eg foreign vehicles), but also robot components such as robot arms.
  • robot arms on the one hand, a distance measurement for the purpose of position tracking (“tracking") can take place.
  • robot arms can themselves also be designed for the three-dimensional scanning of components (in a 3D scanner) and for this purpose be equipped with a light source according to the invention.
  • the light source according to the invention or the tuning of the WGM resonators can also be used in telecommunications for rapid switching to another frequency range or in optical coherence tomography (OCT). Further embodiments of the invention are described in the description and the dependent claims.
  • Figure 1a-b is a schematic representation ( Figure 1 a) and a diagram
  • Figure 2a-b are schematic representations for explaining the basic possible structure of a light source according to the invention in exemplary embodiments
  • Figure 3-4 are schematic diagrams for explaining the operation of a light source according to the invention.
  • Figure 5 is a schematic representation for explaining the structure and operation of a conventional light source in a device for distance measurement.
  • FIG. 2a shows a merely schematic illustration for explaining the possible structure of a light source according to the invention.
  • the light source has a laser 201, a first WGM resonator 210, which is optically coupled to the laser 201, and a second WGM resonator 220, which is likewise optically coupled to the laser 201.
  • the optical coupling takes place (without the invention being restricted thereto) according to FIG. 2 a via a respective prism 215 or 225.
  • the optical coupling may also be done in any other suitable manner (e.g., via optical fibers).
  • Fig. 2b shows a schematic representation of an exemplary embodiment thereof.
  • both WGM resonators 260, 270 are arranged on one and the same side of the laser 251 (possibly in an advantageous manner under production aspects).
  • the respective free spectral ranges of the two WGM resonators 210, 220 can be adjusted in a targeted manner by modifying the respective physical parameters of the respective electro-optical material, such as the refractive index or the geometric dimensions (corresponding to FIG "Tuning" of the WGM resonators 210, 220), wherein this modification of the physical parameters in turn can be done by applying an electrical voltage, by pressure and / or heat or in any other suitable manner.
  • the laser 201 emits photons, which cause resonance excitation of both the first WGM resonator 210 and the second WGM resonator 220.
  • the frequency at which the modes of the two WGM resonators 210, 220 coincide and at which the laser 201 emits can thus be determined over the entire amplification bandwidth of the laser 201 be moved.
  • the effect achieved by varying the free spectral range (FSR) of the WGM resonators 210, 220 is illustrated in the diagrams of FIGS. 3 and 4.
  • FIG. 3 shows the corresponding modes for a first setting or combination of the two free spectral ranges (FSR) of the WGM resonators 210, 220 for the two WGM resonators 210, 220 used in the light source according to the invention
  • Fig. 3 shows a portion of the (in arbitrary units) applied frequencies is enlarged accordingly.
  • the frequency of the light emitted by the laser 201 corresponds to the frequency at which the modes of the two WGM resonators 210, 220 coincide, as shown in FIG. 3 at the frequency of slightly less than 16 (arbitrary) frequency units highlighted by the drawn circle Case is.
  • a tuning of the frequency over the entire gain bandwidth of the laser 201 can be achieved, thus using the light source in the arrangement of FIG correspondingly large tuning range, which can comprise, for example, at least the wavelength range from 20 nm to 100 nm, preferably from 5 nm to 150 nm.

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

Abstract

L'invention concerne un dispositif et un procédé permettant de déterminer la distance d'un objet en mouvement, ainsi qu'une source de lumière destinée à émettre un signal optique à fréquence variable dans le temps, destiné en particulier à être utilisée dans un tel dispositif. Un dispositif selon l'invention comprend : une source de lumière (110) destinée à émettre un signal optique ayant une fréquence variable dans le temps, la source de lumière comprenant un laser (201, 251), un premier résonateur WGM (210, 260) couplé optiquement au laser, et un deuxième résonateur WGM (220, 270) couplé optiquement au laser, un détecteur (160) destiné à générer un signal de détecteur à partir d'une superposition d'un premier sous-signal (111) et d'un deuxième sous-signal (121). Le premier sous-signal et le deuxième signal partiel sont générés par décomposition du signal optique émis par la source de lumière (110). Le premier signal partiel parvient au détecteur sans réflexion préalable sur l'objet et le deuxième signal partiel atteint au détecteur (160) après réflexion sur l'objet. Le signal de détecteur est caractéristique de la différence de fréquence entre la fréquence du deuxième sous-signal et la fréquence du premier sous-signal. L'invention concerne en outre un moyen d'évaluation destiné à déterminer la distance de l'objet en fonction de cette différence de fréquence.
PCT/EP2019/051320 2018-01-29 2019-01-21 Dispositif et procédé de détermination de la distance d'un objet en mouvement WO2019145242A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102018201318.7A DE102018201318A1 (de) 2018-01-29 2018-01-29 Lichtquelle zum Aussenden eines optischen Signals mit zeitlich variierender Frequenz, insbesondere zur Verwendung in einer Vorrichtung zum Ermitteln eines Abstandes eines bewegten Objekts
DE102018201318.7 2018-01-29

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WO2019145242A1 true WO2019145242A1 (fr) 2019-08-01

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140321485A1 (en) * 2013-04-25 2014-10-30 Oewaves, Inc. Resonator Based External Cavity Laser
US20160156149A1 (en) * 2014-11-28 2016-06-02 Fujitsu Limited Tunable laser and tunable laser module
US20160299228A1 (en) 2015-04-07 2016-10-13 Oewaves, Inc. Compact LIDAR System

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140321485A1 (en) * 2013-04-25 2014-10-30 Oewaves, Inc. Resonator Based External Cavity Laser
US20160156149A1 (en) * 2014-11-28 2016-06-02 Fujitsu Limited Tunable laser and tunable laser module
US20160299228A1 (en) 2015-04-07 2016-10-13 Oewaves, Inc. Compact LIDAR System

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