Laser radar system

Abstract

The application provides a laser radar system applied to the technical field of laser technology and comprising a switchable light source for outputting a light signal of low-coherence laser or high-coherence sweep-frequency laser; a first coupler connected with the switchable light source and used for splitting the light signal to obtain a first light signal and a second light signal; a signal path connected with the first coupler and used for obtaining reflected light of a target object according to the first light signal; a reference path connected with the first coupler and used for adjusting the optical time delay of the reference path; a second coupler connected with the signal path and the reference path respectively and used for combining the reflected light and the second light signal to obtain a third light signal; a photoelectric detector connected with the reference path and used for detecting the third light signal and converting the third light signal into an electric signal; and an analog-to-digital converter connected with the photoelectric detector and used for quantizing and storing the electric signal. The switchable light source can be used for coarsely measuring and finely measuring the distance of the target object, so that the spatial distance of the target object can be obtained.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a laser radar system. Background Art

[0002] Among related technologies, lidar provides real-time three-dimensional measurement of the surrounding environment and is widely used in many key areas such as autonomous driving. In principle, lidar is divided into time-of-flight (ToF) radar and frequency-modulated continuous wave (FMCW) radar. ToF radar has the advantage of long detection range, and ToF radar based on random modulated continuous wave (RMCW) also has the advantages of anti-blocking and parallelization. However, ToF radar has low spatial resolution. Meanwhile, FMCW radar has the advantages of high spatial resolution and high sensitivity, but is limited by the detector's bandwidth, making long-range detection difficult. Summary of the Invention

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a laser radar system that aims to achieve long-range detection while having high spatial resolution.

[0004] In a first aspect, an embodiment of the present application provides a laser radar system, comprising:

[0005] A switchable light source for outputting optical signals of low-coherence laser or high-coherence swept-frequency laser;

[0006] a first coupler, connected to the switchable light source, for splitting the optical signal to obtain a first optical signal and a second optical signal;

[0007] a signal path connected to the first coupler, and configured to obtain reflected light from a target object according to the first optical signal;

[0008] a reference path, connected to the first coupler, and used to adjust the optical delay of the reference path;

[0009] a second coupler connected to the signal path and the reference path, respectively, for combining the reflected light and the second optical signal to obtain a third optical signal;

[0010] a photodetector, connected to the reference path, configured to detect the third optical signal and convert the third optical signal into an electrical signal;

[0011] An analog-to-digital converter is connected to the photodetector and is used to quantize and store the electrical signal.

[0012] According to some embodiments of the present application, the signal path includes:

[0013] a circulator, connected to the first coupler, and configured to guide the first optical signal to the lens group;

[0014] The lens group is connected to the circulator and is used to focus the first optical signal onto a target object to obtain the reflected light.

[0015] According to some embodiments of the present application, the lens group is further used to guide the reflected light back to the circulator.

[0016] According to some embodiments of the present application, the circulator is further configured to guide the reflected light to the second coupler.

[0017] According to some embodiments of the present application, the reference path includes:

[0018] The adjustable optical delay is connected to the first coupler and is used to adjust the optical delay of the reference path.

[0019] According to some embodiments of the present application, the laser radar system further includes:

[0020] The optical switch is provided between the second coupler and the photodetector, and is used to connect or disconnect the photodetector.

[0021] According to some embodiments of the present application, the laser radar system further includes:

[0022] The adjustable attenuator is provided between the first coupler and the adjustable optical delay, and is used to adjust the optical power of the reference path to be consistent with the optical power of the signal path.

[0023] According to some embodiments of the present application, the laser radar system further includes:

[0024] A polarization controller is provided between the circulator and the second coupler, and is used to adjust the polarization of the reflected light to match the polarization of the reference path.

[0025] According to some embodiments of the present application, the laser radar system further includes:

[0026] An optical amplifier is provided between the switchable light source and the first coupler, and is used to amplify the optical power of the optical signal output by the switchable light source.

[0027] According to some embodiments of the present application, the laser radar system further includes:

[0028] The electrical amplifier is arranged between the photodetector and the analog-to-digital converter and is used to amplify the electrical signal.

[0029] According to the technical solution of the embodiment of the present application, there are at least the following beneficial effects: the embodiment of the present application proposes a laser radar system, including: a switchable light source for outputting an optical signal of a low-coherence laser or a high-coherence swept-frequency laser; a first coupler, connected to the switchable light source, for splitting the optical signal to obtain a first optical signal and a second optical signal; a signal path, connected to the first coupler, for obtaining the reflected light of the target object according to the first optical signal; a reference path, connected to the first coupler, for adjusting the optical delay of the reference path; a second coupler, respectively connected to the signal path and the reference path, for combining the reflected light and the second optical signal to obtain a third optical signal; a photodetector, connected to the reference path, for detecting the third optical signal and converting the third optical signal into an electrical signal; and an analog-to-digital converter, connected to the photodetector, for quantifying and storing the electrical signal. The embodiment of the present application can realize coarse and fine measurement of the distance of the target object by switching the output optical signals of low-coherence laser and high-coherence swept-frequency laser through a switchable light source, and obtain two electrical signals in the cases of low-coherence laser and high-coherence swept-frequency laser, so as to calculate the actual time delay through the two electrical signals, and then calculate the spatial distance of the target object through the actual time delay. Therefore, the embodiment of the present application can realize long-distance detection while having high spatial resolution.

[0030] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0032] Figure 1 This is a schematic structural diagram of a laser radar system provided by one embodiment of the present application;

[0033] Figure 2 is a structural diagram of a laser radar system provided by another embodiment of the present application;

[0034] Figure 3 This is a flowchart for obtaining the spatial distance of a target object provided by an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0036] In the description of this application, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0037] In the description of this application, "several" means one or more, "many" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The terms "first" and "second" are used solely to distinguish technical features and are not to be construed as indicating or implying relative importance, or as implicitly specifying the number or order of the technical features indicated.

[0038] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0039] In some cases, lidar provides real-time three-dimensional measurement of the surrounding environment and is widely used in many key areas such as autonomous driving. In principle, lidar is divided into time-of-flight (ToF) radar and frequency-modulated continuous wave (FMCW) radar. ToF radar has the advantage of long detection range, and ToF radar based on random modulated continuous wave (RMCW) also has the advantages of anti-blocking and parallel operation. However, ToF radar has low spatial resolution. Meanwhile, FMCW radar has the advantages of high spatial resolution and high sensitivity, but is limited by the detector bandwidth, making long-range detection difficult.

[0040] Based on the above situation, the present application proposes a lidar system, which aims to achieve long-distance detection while having high spatial resolution.

[0041] The various embodiments of the laser radar system of the present application are further described below in conjunction with the accompanying drawings.

[0042] like Figure 1 and Figure 2 As shown, Figure 1 is a schematic structural diagram of a laser radar system provided by an embodiment of the present application. Figure 2 It is a structural diagram of a lidar system provided in another embodiment of the present application.

[0043] In one embodiment, the laser radar system includes a switchable light source 100 , a first coupler 200 , a signal path 300 , a reference path 400 , a second coupler 500 , a photodetector 600 , and an analog-to-digital converter 700 .

[0044] It can be understood that the above-mentioned switchable light source 100 can be a laser light source provided by a hybrid domain lidar, can be a Fourier domain mode-locked laser, can be an ultrafast mode-locked laser, can be an electro-optically modulated continuous wave laser, and is used to output optical signals of low-coherence laser or high-coherence swept-frequency laser. The embodiment of the present application does not specifically limit the specific type of the switchable light source 100.

[0045] It can be understood that the switchable light source 100 of the embodiment of the present application can output optical signals of low-coherence laser or high-coherence swept-frequency laser. When the switchable light source 100 outputs low-coherence laser, the laser radar system can perform rough measurement of the distance to the target object; when the switchable light source 100 outputs high-coherence swept-frequency laser, the laser radar system can perform fine measurement of the distance to the target object.

[0046] It can be understood that the first coupler 200 is used to split the optical signal to obtain the first optical signal and the second optical signal, wherein the splitting ratio is adjusted according to the optical signal power loss caused by the target object.

[0047] It can be understood that the above-mentioned first coupler 200 can be a fiber optic splitter based on a fiber fused cone and waveguide splitting mechanism, or can be a free-space optical splitter. The embodiment of the present application does not specifically limit the specific type of the first coupler 200.

[0048] It can be understood that the signal path 300 is connected to the first coupler 200 and is used to obtain the reflected light of the target object according to the first optical signal.

[0049] It can be understood that the reference path 400 is connected to the first coupler 200 to adjust the optical delay of the reference path 400 .

[0050] It is understandable that the second coupler 500 is connected to the signal path 300 and the reference path 400 respectively, and combines the reflected light and the second optical signal to obtain a third optical signal, wherein the coupling ratio is adjusted according to the optical signal power loss caused by the target object.

[0051] It can be understood that the above-mentioned second coupler 500 can be a fiber optic splitter based on a fiber fused cone and waveguide splitting mechanism, or can be a free-space optical splitter. The embodiment of the present application does not specifically limit the specific type of the second coupler 500.

[0052] It can be understood that the photodetector 600 is connected to the reference path 400 and is used to detect the third optical signal and convert the third optical signal into an electrical signal.

[0053] It is understandable that the above-mentioned photodetector 600 may be a photodiode detector, an avalanche photodiode detector, or a balanced photoelectric amplifier. The embodiment of the present application does not specifically limit the specific type of the photodetector 600.

[0054] It is understood that the analog-to-digital converter 700 is connected to the photodetector 600 for quantifying and storing the electrical signal.

[0055] It is understandable that the above-mentioned analog-to-digital converter 700 may be an oscilloscope or an acquisition card, and the embodiment of the present application does not specifically limit the specific type of the analog-to-digital converter 700.

[0056] In addition, in one embodiment, the signal path 300 includes a circulator 310 and a lens group 320 .

[0057] It can be understood that the circulator 310 is connected to the first coupler 200 to guide the first optical signal to the lens group 320 .

[0058] It can be understood that the circulator 310 has three ports, a first port, a second port, and a third port, and outputs the first optical signal input to the first port from the second port to the lens group 320 .

[0059] It can be understood that the above-mentioned circulator 310 can be a transmissive circulator 310 or a reflective circulator, and the embodiment of the present application does not specifically limit the specific type of the circulator 310.

[0060] It can be understood that the lens group 320 is connected to the circulator 310 to focus the first optical signal onto the target object to obtain reflected light.

[0061] It is understandable that the lens group 320 focuses the light output from the second port of the circulator 310 onto the target object, deflects the light beam on the target object to achieve horizontal scanning of the target, reconstruct its three-dimensional position information, and obtain reflected light.

[0062] It can be understood that the lens group 320 is also used to guide the reflected light back to the second port of the circulator 310, and the circulator 310 is also used to guide the reflected light input from the second port to the second coupler 500 through the third port.

[0063] It is understandable that the lens group 320 mentioned above can be composed of one or more optical elements such as spherical lenses, aspherical lenses or metasurfaces, and the embodiments of the present application do not specifically limit it.

[0064] In addition, in one embodiment, the reference path 400 includes an adjustable optical delay 410 .

[0065] It can be understood that the adjustable optical delay 410 is connected to the first coupler 200 and is used to adjust the optical delay of the reference path 400 .

[0066] It can be understood that the adjustable optical delay 410 adjusts the optical delay of the reference path 400 according to the target position distance of the target object measured by the switchable light source 100 when outputting low-coherence laser light, so that the optical path difference between the signal path 300 and the reference path 400 when the switchable light source 100 outputs high-coherence swept-frequency laser light is less than the measurement range of the frequency modulated continuous wave (FMCW) radar, thereby enabling the FMCW radar.

[0067] It is understandable that the above-mentioned adjustable optical delay 410 can be a manually or electrically adjustable delay line, or an array optical delay system based on a micro-electromechanical system, and the embodiments of the present application do not specifically limit it.

[0068] In addition, in one embodiment, the laser radar system further includes an optical switch 800 .

[0069] It can be understood that the optical switch 800 is disposed between the second coupler 500 and the photodetector 600 to turn the photodetector 600 on or off.

[0070] It can be understood that the above-mentioned optical switch 800 is used to switch the optical signal to enable or disable balance detection. It can be a manual mechanical optical switch, an electrically controlled mechanical optical switch, a micro-electromechanical system optical switch, or an optical switch composed of an adjustable attenuator. The embodiment of the present application does not specifically limit the specific type of the optical switch 800.

[0071] In addition, in one embodiment, the laser radar system also includes an adjustable attenuator 900.

[0072] It can be understood that the adjustable attenuator 900 is disposed between the first coupler 200 and the adjustable optical delay 410 , and is used to adjust the optical power of the reference path 400 to be consistent with the optical power of the signal path 300 .

[0073] It can be understood that the above-mentioned adjustable attenuator 900 can be a manual mechanical attenuator, an electrically controlled mechanical attenuator, an electro-optical modulation attenuator, or an acousto-optical modulation attenuator. The embodiment of the present application does not specifically limit the specific type of the adjustable attenuator 900.

[0074] In addition, in one embodiment, the laser radar system also includes a polarization controller 1000.

[0075] It can be understood that the polarization controller 1000 is disposed between the circulator 310 and the second coupler 500 to adjust the polarization of the reflected light to match the polarization of the reference path 400 .

[0076] It can be understood that the above-mentioned polarization controller 1000 can be an online polarization controller 1000 based on different types of optical fibers such as a three-ring type, a double-ring type, and an extruded type, or a free-space polarization controller 1000 composed of multiple glass slides. The embodiment of the present application does not specifically limit the specific type of the polarization controller 1000.

[0077] In addition, in one embodiment, the laser radar system also includes an optical amplifier 1100.

[0078] It can be understood that the optical amplifier 1100 is disposed between the switchable light source 100 and the first coupler 200 , and is used to amplify the optical power of the optical signal output by the switchable light source 100 .

[0079] It can be understood that the above-mentioned optical amplifier 1100 can be a semiconductor optical amplifier, a doped fiber amplifier, a Raman amplifier, or a parametric amplifier. The embodiment of the present application does not specifically limit the specific type of the optical amplifier 1100.

[0080] In addition, in one embodiment, the lidar system also includes an electrical amplifier 1200.

[0081] It can be understood that the electrical amplifier 1200 is disposed between the photodetector 600 and the analog-to-digital converter 700 for amplifying the electrical signal.

[0082] It can be understood that the above-mentioned electrical amplifier 1200 can be a transimpedance amplifier or a low-noise amplifier, and the embodiment of the present application does not specifically limit the specific type of the electrical amplifier 1200.

[0083] Based on the laser radar systems of the above-mentioned embodiments, the overall embodiments of the laser radar system of the present application are proposed below.

[0084] Example 1:

[0085] like Figure 1 As shown, the laser radar system includes: a switchable light source 100, a first coupler 200, a circulator 310, a lens group 320, an adjustable optical delay 410, a second coupler 500, an optical switch 800, a photodetector 600 and an analog-to-digital converter 700.

[0086] Working principle: A switchable light source 100 is used, whose output optical signal can be switched between low-coherence laser and high-coherence swept-frequency laser. The first coupler 200 is used to split the optical signal into a first optical signal of the signal path 300 of the Michelson interferometer and a second optical signal of the reference path 400. The splitting ratio is selected according to the reflection efficiency of the target. The signal path 300 of the Michelson interferometer starts from the circulator 310, whose function is to guide the first optical signal from the first port to the second port, and to guide the reflected light from the target object from the second port to the third port. The lens group 320 focuses the optical signal emitted from the second port of the circulator onto the target, completes the lateral scanning of the target object to reconstruct its three-dimensional position information, and guides the reflected light of the target back to the second port of the circulator. The reference path 400 of the Michelson interferometer starts from the adjustable optical delay 410, which functions according to the random modulated continuous wave (Random Modulated Continuous Wave). The FMCW (FMCW) radar measures the target distance to adjust the optical delay introduced by the reference path 400, thereby ensuring that the optical path difference between the Michelson interferometer signal path 300 and the reference path 400 is less than the FMCW radar's measurement range, thereby enabling the FMCW radar. The Michelson interferometer signal path 300 and the reference path 400 terminate at a second coupler 500, which combines the optical signals into a third optical signal using the coherent superposition method required by FMCW radar or the additive superposition method required by RMCW radar. An optical switch 800 enables or disables balanced detection. When the lidar operates in FMCW mode, optical switch 800 is enabled, and when it operates in RMCW mode, optical switch 800 is disabled. A balanced photodetector 600 detects the optical signal and converts it into an electrical signal that can be read by an electronic device. An analog-to-digital converter 700 quantizes and stores the electrical signal.

[0087] It is understood that when switchable light source 100 outputs low-coherence laser light, optical switch 800 is closed and the target distance is roughly measured using RMCW radar. The optical delay of reference path 400 is adjusted accordingly to keep the arm length difference within the Michelson interferometer less than the FMCW measurement range. Subsequently, when switchable light source 100 outputs high-coherence swept-frequency laser light, optical switch 800 is opened and the target distance is precisely measured using FMCW radar.

[0088] Example 2:

[0089] like Figure 2 As shown, the lidar system includes: a switchable light source 100, an optical amplifier 1100, a first coupler 200, a circulator 310, a lens group 320, an adjustable attenuator 900, an adjustable optical delay 410, a polarization controller 1000, a second coupler 500, a photodetector 600, an electrical amplifier 1200 and an analog-to-digital converter 700.

[0090] Working principle: A switchable light source 100 is used, and its output optical signal can be switched between low-coherence laser or high-coherence swept-frequency laser; an optical amplifier 1100 is used to amplify the optical power of the optical signal; a first coupler 200 is used to divide the optical signal into a first optical signal of the signal path 300 of the Michelson interferometer and a second optical signal of the reference path 400, and the splitting ratio is selected according to the reflection efficiency of the target; the starting point of the signal path 300 of the Michelson interferometer is a circulator 310, and its function is to guide the first optical signal from the first port to the second port, and to guide the reflected light reflected from the target object from the second port to the third port; the lens group 320 focuses the reflected light emitted from the second port of the circulator onto the target, and completes the lateral scanning of the target object to reconstruct its three-dimensional position information, and guides the reflected light of the target object back to the second port of the circulator; the reflected light reflected from the target object passes through the second port of the circulator and is output from the third port, and is polarized. The controller 1000 adjusts its polarization to match the reference path 400. The starting point of the Michelson interferometer reference path 400 is the adjustable attenuator 900, which is used to adjust the optical power of the reference path 400 to match the signal path 300. The function of the adjustable optical delay 410 is to adjust the optical delay introduced by the reference path 400 according to the target position distance measured by the RMCW radar, so that the optical path difference between the two paths of the Michelson interferometer is less than the measurement range of the FMCW radar, thereby enabling the FMCW radar. The end points of the Michelson interferometer signal path 300 and the reference path 400 are the second coupler 500, which is used to combine the optical signals in the coherent superposition method required for FMCW, or in the additive superposition method required for RMCW. The photodetector 600 is used to detect the optical signal and convert it into an electrical signal that can be read by an electronic device. The electrical amplifier 1200 is used to amplify the photocurrent. The analog-to-digital converter 700 is used to quantize and store the electrical signal.

[0091] It is understood that when the switchable light source 100 outputs low-coherence laser light, the target distance is roughly measured using the RMCW radar. The optical delay of the reference path 400 is adjusted accordingly to keep the arm length difference within the Michelson interferometer less than the FMCW measurement range. Subsequently, when the switchable light source 100 outputs high-coherence swept-frequency laser light, the target distance is precisely measured using the FMCW radar.

[0092] like Figure 3 As shown, Figure 3 This is a flowchart for obtaining the spatial distance of a target object provided by an embodiment of the present application.

[0093] In one embodiment, first, the collected low-coherence laser signal portion is calculated using the RMCW principle and autocorrelation algorithm to obtain a delay-correlation curve, ignoring the peak at the zero delay position and finding the highest peak, and recording its corresponding delay as T; next, the reference path 400 introduces a delay TR that is less than or equal to the delay T through an adjustable optical delay, and T minus TR must be less than the measurable time range of the FMCW radar; then, the collected high-coherence swept-frequency laser portion is calculated using the FMCW radar principle and Fourier transform algorithm to obtain a frequency-amplitude curve, ignoring the peak at the zero frequency position and finding the highest peak, and recording its frequency as F. The delay TF is equal to F divided by the sweep speed of the light source; finally, the actual target delay is TR+TF, and the spatial distance of the target is (TR+TF)*c / 2, where c is the speed of light in the medium.

[0094] The above is a specific description of the preferred implementation of the present application, but the present application is not limited to the above implementation mode. Technical personnel familiar with the art can also make various equivalent modifications or substitutions under the shared conditions that do not violate the spirit of the present application. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A laser radar system, characterized in that: include: A switchable light source for outputting optical signals of low-coherence laser or high-coherence swept-frequency laser; a first coupler, connected to the switchable light source, for splitting the optical signal to obtain a first optical signal and a second optical signal; a signal path connected to the first coupler, and configured to obtain reflected light from a target object according to the first optical signal; a reference path, connected to the first coupler, and used to adjust the optical delay of the reference path; a second coupler connected to the signal path and the reference path, respectively, for combining the reflected light and the second optical signal to obtain a third optical signal; a photodetector, connected to the reference path, configured to detect the third optical signal and convert the third optical signal into an electrical signal; an analog-to-digital converter, connected to the photodetector, for quantifying and storing the electrical signal; The reference path includes an adjustable optical delay, which is connected to the first coupler and is used to adjust the optical delay of the reference path according to the target position distance of the target object measured by the switchable light source when outputting the low-coherence laser.

2. The laser radar system according to claim 1, characterized in that The signal path includes: a circulator, connected to the first coupler, and configured to guide the first optical signal to the lens group; The lens group is connected to the circulator and is used to focus the first optical signal onto a target object to obtain the reflected light.

3. The laser radar system according to claim 2, characterized in that The lens group is further configured to guide the reflected light back to the circulator.

4. The laser radar system according to claim 3, characterized in that The circulator is further configured to guide the reflected light to the second coupler.

5. The laser radar system according to claim 1, wherein: The laser radar system further includes: The optical switch is provided between the second coupler and the photodetector, and is used to connect or disconnect the photodetector.

6. The laser radar system according to claim 1, characterized in that The laser radar system further includes: The adjustable attenuator is provided between the first coupler and the adjustable optical delay, and is used to adjust the optical power of the reference path to be consistent with the optical power of the signal path.

7. The laser radar system according to claim 2, characterized in that The laser radar system further includes: A polarization controller is provided between the circulator and the second coupler, and is used to adjust the polarization of the reflected light to match the polarization of the reference path.

8. The laser radar system according to claim 1, wherein: The laser radar system further includes: An optical amplifier is provided between the switchable light source and the first coupler, and is used to amplify the optical power of the optical signal output by the switchable light source.

9. The laser radar system according to claim 1, wherein: The laser radar system further includes: The electrical amplifier is arranged between the photodetector and the analog-to-digital converter and is used to amplify the electrical signal.

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