CN113721226A - Frequency modulation continuous wave laser radar - Google Patents
Frequency modulation continuous wave laser radar Download PDFInfo
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- CN113721226A CN113721226A CN202111015637.4A CN202111015637A CN113721226A CN 113721226 A CN113721226 A CN 113721226A CN 202111015637 A CN202111015637 A CN 202111015637A CN 113721226 A CN113721226 A CN 113721226A
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- 230000003287 optical effect Effects 0.000 claims abstract description 264
- 230000008054 signal transmission Effects 0.000 claims abstract description 58
- 238000005070 sampling Methods 0.000 claims abstract description 30
- 230000000712 assembly Effects 0.000 claims abstract description 15
- 238000000429 assembly Methods 0.000 claims abstract description 15
- 230000035559 beat frequency Effects 0.000 claims abstract description 12
- 239000013307 optical fiber Substances 0.000 claims description 33
- 239000000835 fiber Substances 0.000 claims description 8
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 230000003321 amplification Effects 0.000 claims description 2
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 13
- 238000000034 method Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000005684 electric field Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/491—Details of non-pulse systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
Abstract
The embodiment of the invention discloses a frequency modulation continuous wave laser radar which comprises N laser emission assemblies, N optical signal transmission modules, a signal processing module and a laser scanning module, wherein the N laser emission assemblies respectively emit laser with different wavelengths; the optical signal transmission module is used for transmitting the laser emitted by the laser emitting component and the reflected laser of the laser scanning module to carry out beat frequency processing and transmitting the beat frequency processing to the signal processing module; the laser scanning module receives laser from the optical signal transmission module for emission and transmits reflected laser to the optical signal transmission module; the signal processing module carries out signal processing by collecting beat frequency signals of the optical signal transmission module, and the laser scanning module is controlled by the signal processing module; by emitting laser beams with different wavelengths, the sampling rate of the laser point cloud is improved under the condition that the emitting frequency of the whole laser emitting assembly is unchanged.
Description
Technical Field
The invention relates to the field of radar structures, in particular to a frequency modulation continuous wave laser radar.
Background
The radar system of the laser radar for emitting laser beams to detect characteristic quantities such as the position, the speed and the like of a target is widely applied to the field of automatic driving. The working principle is that a detection signal (laser beam) is transmitted to a target, then a received signal (target echo) reflected from the target is compared with the transmitted signal, and after appropriate processing, relevant information of the target, such as target distance, direction, height, speed, attitude, even shape and other parameters, can be obtained, so that the target is detected, tracked and identified.
In the process of implementing the invention, the inventor finds that the prior art has at least the following problems: when the laser radar is applied to laser point cloud sampling, the sampling is more and more accurate, but the sampling rate is limited by the frequency of a carrier signal, so that the existing requirement cannot be met.
Thus, there is a need for a better solution to the problems of the prior art.
Disclosure of Invention
In view of this, the invention provides a frequency modulated continuous wave lidar which increases the sampling rate of laser point cloud by emitting laser beams with different wavelengths under the condition that the emitting frequency of the whole laser emitting assembly is not changed.
Specifically, the present invention proposes the following specific examples:
the embodiment of the invention provides a frequency modulation continuous wave laser radar which comprises N laser emission assemblies, N optical signal transmission modules, a signal processing module and a laser scanning module, wherein N is an integer greater than 1;
the N laser emission assemblies respectively emit laser with different wavelengths;
the optical signal transmission module is used for transmitting the laser emitted by the laser emitting component and the reflected laser of the laser scanning module to carry out beat frequency processing and transmitting the beat frequency processing to the signal processing module;
the laser scanning module receives laser from the optical signal transmission module for emission and transmits reflected laser to the optical signal transmission module;
the signal processing module carries out signal processing by collecting beat frequency signals of the optical signal transmission module, and the laser scanning module is controlled by the signal processing module;
the N laser emission assemblies are respectively connected with the N optical signal transmission modules;
the N optical signal transmission modules are respectively connected with the laser scanning module;
and the N optical signal transmission modules are respectively connected with the signal processing module.
In consideration of the fact that the number of the laser cloud points cannot be increased without limit by increasing the carrier frequency, the laser cloud points can be simultaneously emitted by a plurality of laser emitting components in the scheme, and the number of the laser cloud points is increased under the condition that the carrier frequency is not increased.
In a specific embodiment, each laser emitting assembly consists of a driver and a laser; wherein the driver is connected to the laser to modulate the output frequency of the laser.
In a specific embodiment, each optical signal transmission module comprises a first optical splitter, a first optical coupler, an optical transceiver and a photoelectric detector;
the first optical splitter is used for splitting one input optical signal into two output optical signals, and the input end of the first optical splitter is connected with the output end of the laser emission component;
the first output end of the first optical splitter outputs a transmitting light wave, and the first output end of the first optical splitter is connected with one end of the optical transceiver;
the other end of the optical transceiver is connected with the input end of the laser scanning module;
the second output end of the first optical splitter outputs a local oscillator light wave, and the second output end of the first optical splitter is connected with the first input end of the first optical coupler;
the first optical coupler is used for combining two paths of input optical signals into one path of output optical signal, and a second input end of the first optical coupler is connected with one end of the optical transceiver;
the output end of the first optical coupler is connected with the input end of the photoelectric detector;
and the output end of the photoelectric detector is connected with the input end of the signal processing module.
In a particular embodiment, the optical transceiver includes a collimator therein that converts the transmitted light within the optical fiber into collimated light.
In a specific embodiment, each of the optical signal transmission modules includes: the optical transceiver comprises a first optical splitter, an optical fiber circulator, a first optical coupler, an optical transceiver and a photoelectric detector;
the input end of the first optical splitter is connected with the output end of the laser emission component; the first output end of the first optical splitter is connected with the first end of the optical fiber circulator; the second end of the optical fiber circulator is connected with one end of the optical transceiver; the third end of the optical fiber circulator is connected with the second input end of the first optical coupler;
the other end of the optical transceiver is connected with the input end of the laser scanning module; the second output end of the first optical splitter is connected with the first input end of the first optical coupler;
the output end of the first optical coupler is connected with the input end of the photoelectric detector; and the output end of the photoelectric detector is connected with the input end of the signal processing module.
In a specific embodiment, each optical signal transmission module further includes a second optical splitter and a third optical splitter, the number of the optical fiber circulators of the optical signal transmission module is M, the number of the optical transceivers of the optical signal transmission module is M, the number of the first optical couplers of the optical signal transmission module is M, the number of the photodetectors of the optical signal transmission module is M, and M is an integer greater than 1;
the second optical splitter is used for splitting one path of input optical signals into M paths of output optical signals, and the input end of the second optical splitter is connected with the first output end of the first optical splitter;
the M output ends of the second optical splitter are respectively connected with the first ends of the M optical fiber circulators;
the second ends of the M optical fiber circulators are respectively connected with one ends of M optical transceivers;
the other ends of the M optical transceivers are respectively connected with the input end of the laser scanning module;
the third ends of the M optical fiber circulators are respectively connected with the second input ends of the M first optical couplers;
the third optical splitter is used for splitting one input optical signal into M output optical signals, and the input end of the third optical splitter is connected with the second output end of the first optical splitter;
the M output ends of the third optical splitter are respectively connected with the first input ends of the M first optical couplers;
the output ends of the M first optical couplers are respectively connected with the input ends of the M photoelectric detectors;
and the output ends of the M photoelectric detectors are respectively connected with the input end of the signal processing module.
Specifically, since the number of laser cloud points cannot be increased without limit by increasing the carrier frequency (and the cost for increasing the carrier frequency is high), in the scheme, multi-path light splitting can be formed for each laser emitting component through the optical splitter, and the number of laser cloud points is increased without increasing the carrier frequency. In combination with the above plurality of laser emitting assemblies, a multiple integration effect can be achieved.
In a specific embodiment, each optical signal transmission module further comprises an optical fiber amplifier, an input end of the optical fiber amplifier is connected with the first output end of the first optical splitter; and the output end of the optical fiber amplifier is connected with the input end of the second optical splitter.
In a specific embodiment, the laser scanning module comprises at least two laser emitters, and the laser emitting directions of the at least two laser emitters are different;
a polygon mirror including a first rotation axis extending in a first direction and a plurality of mirror facets surrounding the first rotation axis;
a swing mirror including a second rotation axis extending in a second direction and a reflection surface parallel to the second rotation axis;
wherein the second direction intersects the first direction; the laser transmitter and the swing mirror are respectively arranged on the light incident side and the light emergent side of the prism surface of the polygon prism;
the polygon prism rotates around the first rotating shaft, so that the prism surface reflects laser beams emitted by at least two laser emitters onto the reflecting surface; the oscillating mirror oscillates around the second rotating shaft, so that laser beams emitted by at least two laser emitters are emitted in different directions.
In a specific embodiment, the photodetector includes P receivers, P amplifying units and P sampling units, where P is a positive integer;
the receivers are used for receiving the reflected laser and converting optical signals into electric signals, and the output ends of the P receivers are respectively connected with the input ends of the P amplifying units;
the amplifying units are used for amplifying the electric signals, and the output ends of the P amplifying units are respectively connected with the input end of the sampling unit;
the sampling unit is used for sampling the amplified signals output by the amplifying unit, sampling data are transmitted to the signal processing module, and the P sampling units are respectively connected with the input end of the signal processing module.
In a specific embodiment, the signal processing module includes: the device comprises an amplifier, a low-pass filter, an analog-to-digital conversion module and a processor;
the photoelectric detector, the amplifier, the low-pass filter and the analog-to-digital conversion module in each optical signal transmission module are sequentially connected with the processor.
Therefore, the technical problem that the sampling rate of the laser point cloud cannot be increased rapidly is solved by the technical means of emitting the laser beams with different wavelengths, and the technical effect of improving the sampling rate of the laser point cloud under the condition of not greatly improving the carrier frequency is achieved.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings required to be used in the embodiments will be briefly described below, and it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope of the present invention. Like components are numbered similarly in the various figures.
Fig. 1 shows a schematic structural diagram of a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 2 is a schematic diagram illustrating a second structure of a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 3 shows a third schematic structural diagram of a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating a fourth structure of a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 5 shows a fifth structural diagram of a frequency modulated continuous wave lidar according to an embodiment of the invention;
fig. 6 is a schematic diagram illustrating a laser signal generated by a laser emitting component in a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 7 is a schematic diagram illustrating a relationship between a laser output frequency and a laser driving current when modulation is performed in a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 8 is a schematic diagram illustrating a relationship between laser output power and driving current when modulation is performed in a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 9 is a schematic diagram illustrating a waveform of a signal inputted from a fourth coupler in a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 10 is a schematic diagram illustrating a waveform of a signal output by a photodetector in a frequency modulated continuous wave lidar according to an embodiment of the present invention;
fig. 11 shows a schematic structural diagram of a laser scanning module in a frequency modulated continuous wave lidar according to an embodiment of the present invention.
Illustration of the drawings:
100-a laser emitting assembly;
200-an optical signal transmission module; 201-a first optical splitter; 202-a first optical coupler; 203-an optical transceiver; 204-a photodetector; 205-fiber optic circulator; 206-a second optical splitter; 207-third optical splitter; 208-a fiber amplifier;
300-a laser scanning module; 400-a signal processing module;
210-a laser emitter; 220-a polygon prism; 230-a swing mirror; 21-a first direction; 22-a second direction;
2100-a first axis of rotation; 2200-a second rotation axis; 221-prism facets; 231-reflecting surface.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
Hereinafter, the terms "including", "having", and their derivatives, which may be used in various embodiments of the present invention, are only intended to indicate specific features, numbers, steps, operations, elements, components, or combinations of the foregoing, and should not be construed as first excluding the existence of, or adding to, one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present invention belong. The terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning that is consistent with their contextual meaning in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in various embodiments of the present invention.
Example 1
It should be noted that the number N of laser emitting components provided in this embodiment is an integer greater than 1. In practical operation, the value of N is not limited.
In a specific embodiment, as shown in fig. 2, each optical signal transmission module 200 includes a first optical splitter 201, a first optical coupler 202, an optical transceiver 203, and a photodetector 204, where the first optical splitter 201 is configured to split one input optical signal into two output optical signals, and an input end of the first optical splitter 201 is connected to an output end of the laser emission component 100; the first output end of the first optical splitter 201 outputs a transmitting optical wave, and the first output end of the first optical splitter 201 is connected with one end of the optical transceiver 203; the other end of the optical transceiver 203 is connected with the input end of the laser scanning module 300; the second output end of the first optical splitter 201 outputs a local oscillator optical wave, and the second output end of the first optical splitter 201 is connected with the first input end of the first optical coupler 202; the first optical coupler 202 is configured to combine two input optical signals into one output optical signal, and a second input end of the first optical coupler 202 is connected to one end of the optical transceiver 203; the output end of the first optical coupler 202 is connected with the input end of the photodetector 204; the output end of the photodetector 204 is connected with the input end of the signal processing module 400.
It should be noted that, the first optical splitter 201 provided in this embodiment only needs to have a function of splitting one input optical signal into two output optical signals, and other optical splitters having two or more controlled outputs can also meet the above requirements. In practical operation, there is no limitation on the type, size and kind of the first optical splitter 201.
Specifically, the first optical splitter 201 outputs local laser light, the optical transceiver 203 outputs reflected laser light, and both perform beat processing and output beat signals.
It should be noted that the first optical coupler 202 provided in this embodiment only needs to have a function of combining two input optical signals into one output optical signal, and other optical couplers having more than two control inputs can also meet the above requirements. In actual practice, there is no limitation on the type, size, and kind of the first optical coupler 202.
Specifically, the optical transceiver 203 includes a collimator therein, which converts the transmission light in the optical fiber into collimated light. In addition, in order to couple light into a required device with maximum efficiency and realize maximum efficiency reception of a received light signal, the optical transceiver 203 includes a collimator, and transmission of the light signal is better realized through the arrangement of the collimator.
Specifically, as shown in fig. 3, each optical signal transmission module 200 includes: a first optical splitter 201, a fiber circulator 205, a first optical coupler 202, an optical transceiver 203, and a photodetector 204; the input end of the first optical splitter 201 is connected with the output end of the laser emitting component 100; the first output end of the first optical splitter 201 is connected with the first end of the optical fiber circulator 205; the second end of the fiber optic circulator 205 is connected to one end of the optical transceiver 203; the third end of the optical fiber circulator 205 is connected with the second input end of the first optical coupler 202; the other end of the optical transceiver 203 is connected with the input end of the laser scanning module 300; the second output end of the first optical splitter 201 is connected with the first input end of the first optical coupler 202; the output end of the first optical coupler 202 is connected with the input end of the photodetector 204; the output end of the photodetector 204 is connected with the input end of the signal processing module 400. Isolation of the input and output signals is achieved by the provision of the fiber optic circulator 205.
Specifically, as shown in fig. 4, each optical signal transmission module 200 further includes a second optical splitter 206 and a third optical splitter 207, the number of the optical fiber circulators 205 of the optical signal transmission module 200 is M, the number of the optical transceivers 203 of the optical signal transmission module 200 is M, the number of the first optical couplers 202 of the optical signal transmission module 200 is M, the number of the photodetectors 204 of the optical signal transmission module 200 is M, the number of the optical fiber circulators 205 of the optical signal transmission module 200 is M, and M is an integer greater than 1; the second optical splitter 206 is configured to split one input optical signal into M output optical signals, and an input end of the second optical splitter 206 is connected to the first output end of the first optical splitter 201; the M output ends of the second optical splitter 206 are respectively connected with the first ends of the M optical fiber circulators 205; second ends of the M optical fiber circulators 205 are respectively connected to one ends of the M optical transceivers 203; the other ends of the M optical transceivers 203 are respectively connected with the input end of the laser scanning module 300; the third ends of the M optical fiber circulators 205 are respectively connected to the second input ends of the M first optical couplers 202; the third optical splitter 207 is configured to split one input optical signal into M output optical signals, and an input end of the third optical splitter 207 is connected to the second output end of the first optical splitter 201; the M output ends of the third optical splitter 207 are respectively connected with the first input ends of the M first optical couplers 202; the output ends of the M first optical couplers 202 are respectively connected with the input ends of the M photodetectors 204; the output ends of the M photodetectors 204 are respectively connected with the input end of the signal processing module 400.
Specifically, since the number of laser cloud points cannot be increased without limitation by increasing the carrier frequency (and the cost for increasing the carrier frequency is high), in the scheme, multiple paths of light splitting can be formed for each laser emitting component through a plurality of optical splitters, and the number of laser cloud points is increased without increasing the carrier frequency. In combination with the above plurality of laser emitting assemblies, a multiple integration effect can be achieved. On the basis, M times of the sampling rate of the laser point cloud can be increased by corresponding M transceivers to each laser emission component, so that the sampling rate of the laser point cloud is further increased.
It should be noted that the number M of the laser emitting assemblies 100 provided in the present embodiment is an integer greater than 1. In practical operation, the value of M is not limited.
It should be noted that, the second optical splitter 206 and the third optical splitter 207 provided in this embodiment only need to have a function of splitting one input optical signal into M output optical signals, and other optical splitters having M or more control outputs may also meet the above requirements. In practical operation, there is no limitation on the type, size and kind of the second optical splitter 206 and the third optical splitter 207.
In addition, as shown in fig. 5, each optical signal transmission module 200 further includes an optical fiber amplifier 208, and an input end of the optical fiber amplifier 208 is connected to the first output end of the first optical splitter 201; the output of the fiber amplifier 208 is connected to the input of the second optical splitter 206.
The fiber amplifier 208 is used for intensity amplification and noise suppression of the acquired light waves.
Specifically, the frequency modulation continuous wave laser radar in the scheme can measure distance and speed. The laser emitting assembly 100 consists of a driver and a laser; wherein the driver is connected to the laser to modulate the output frequency of the laser.
Further, the laser is a laser emitting module which generates a continuous wave laser beam with adjustable wavelength.
In practical operation, a 1550nm laser is preferably selected to generate a 1550nm narrow-linewidth wavelength-tunable continuous wave laser beam; lasers with other wavelengths can be selected to generate laser beams with other wavelengths; as for the driver, it is used to generate a current in the shape of a linear triangular wave for modulating the output frequency of the laser.
The laser is a narrow linewidth linear frequency modulation continuous wave laser light source, the generated output light beam is continuous coherent laser with linearly modulated frequency, symmetrical triangular wave linear modulation is adopted, the frequency of a modulation signal changes in a symmetrical triangular shape along with time, in a period, the front half part is in positive frequency modulation, and the rear half part is in negative frequency modulation; the light field of the output beam is represented as:
wherein T is time, E0 is amplitude, T is frequency modulation period, f0 is frequency modulation initial frequency and is frequency modulation rate, B is frequency modulation bandwidth, φ up (n) is initial phase of rising section of nth output beam frequency modulation pulse, φ down (n) is initial phase of falling section of nth output beam frequency modulation pulse, exp is exponential function with natural constant E as base,
the signal waveform of the laser output under the drive of the driver is shown in fig. 6.
Further, the driver includes: a laser diode modulator, or a laser electric field amplitude external modulator, or a phase modulator. Thus, the corresponding modulation mode can be laser diode direct modulation, laser electric field amplitude external modulation or optical external modulation implemented by a phase modulator.
When the laser diode is selected for direct modulation, if the steady-state operating point of the laser diode is 300mA, and a steady current (the stability RMS is 10 μ a) of 300mA is superimposed with a triangular wave current with the amplitude of 500 μ a, triangular wave frequency modulation can be realized. In this case, the relationship between the laser output frequency and the drive current is as shown in fig. 7.
When the laser electric field amplitude external modulation is selected, the emitted laser and the local oscillator laser are subjected to completely consistent intensity modulation, and the relationship between the obtained laser output light power and the laser diode driving current is shown in fig. 8.
When the phase modulator is selected for modulation, external light modulation can be carried out on the basis of the phase modulator, specifically, the lithium niobate electro-optic phase modulator can be selected for phase modulation of single-frequency laser; the frequency modulation is realized through optical phase modulation, and the frequency is extended along with time to obtain triangular wave linear frequency modulation.
After the optical fiber amplifier 208 amplifies the intensity of the transmitting light wave output by the first optical splitter 201 and suppresses noise, the transmitting light wave corresponding to each wavelength is divided into N transmitting light waves by the second optical splitter, and assuming that the frequency of the modulating signal output by the 1550nm laser is 500Khz, the wavelengths are λ 1, λ 2, λ 3, and N is 2, the laser point cloud sampling rate of the fm cw lidar is 500Khz × 3 × 2 — 3 Mhz. Therefore, under the condition that the sampling rate of the laser point cloud is constant, the more the number of the first optical branches and the second optical branches is, the less the number of the 1550nm lasers with different wavelengths is, and the lower the emission frequency of the 1550nm lasers is. Other wavelengths are similar and will not be described in detail herein.
The waveform of the signal input specifically to the first coupler is shown in fig. 9.
Specifically, for better photodetection, the photodetector 204 includes P receivers, P amplifying units and P sampling units, where P is a positive integer;
the receivers are used for receiving the reflected laser and converting optical signals into electric signals, and the output ends of the P receivers are respectively connected with the input ends of the P amplifying units;
the amplifying units are used for amplifying the electric signals, and the output ends of the P amplifying units are respectively connected with the input end of the sampling unit;
the sampling unit is used for sampling the amplified signal output by the amplifying unit, the sampled data are transmitted to the signal processing module 400, and the P sampling units are respectively connected with the input end of the signal processing module 400.
As for the photodetector 204, it is used to convert the acquired optical signal into a current signal. The waveform of the signal output by the photodetector 204 is a sine wave, as shown in fig. 10.
Specifically, the laser scanning module 300 includes at least two laser emitters 210, and the laser emitting directions of the at least two laser emitters 210 are different; as shown in fig. 11, the method further includes:
a polygon mirror 220 including a first rotation axis 2100 extending in the first direction 21 and a plurality of mirror facets 221 surrounding the first rotation axis 2100;
the oscillating mirror 230 includes a second rotation axis 2200 extending in the second direction 22 and a reflection surface 231 parallel to the second rotation axis 2200.
Wherein the second direction 22 and the first direction 21 intersect; the laser transmitter 210 and the swing mirror 230 are respectively arranged on the light-in side and the light-out side of the prism surface 221 of the polygon prism 220;
the polygon 220 rotates around the first rotation axis 2100, so that the prism surface 221 reflects the laser beams emitted from the at least two laser emitters 210 onto the reflection surface 231; the oscillating mirror 230 oscillates around the second rotation axis 2200 to make the laser beams emitted from the at least two laser emitters 210 emit in different directions.
Specifically, two laser transmitters 210 may be adopted in the present solution, so that after laser beams emitted by the two laser transmitters 210 are reflected by the polygon mirror 220 and the swing mirror 230 in sequence, at least two laser scanning areas corresponding in number may be formed in space, and at this time, the detection resolution of the laser radar in space may increase along with the increase of the number of the laser transmitters 210. Meanwhile, because the laser beam is scanned in space by the rotation of the polygon mirror 220 and the swing of the swing mirror 230, the precision requirement on the emission angle of each laser emitter 210 is lower from the angle of the emission angle debugging work of the laser emitters 210, the emission angle debugging is easier to perform compared with the scheme that the existing laser emitters need consistent emission angles, and the debugging work is simpler and more convenient; from overall structure, the requirement on the placement position of the laser emitter is low, and compared with the scheme that the existing laser emitters need to be arranged at certain intervals, the space interval can be properly reduced, the placement accuracy is reduced, and the structural layout is relatively simpler.
In addition, by providing the polygon mirror 220 and the swing mirror 230, wherein the polygon mirror 220 includes a first rotating shaft 2100 extending along the first direction 21 and a plurality of prism faces 221 surrounding the first rotating shaft 2100, and the swing mirror 230 includes a second rotating shaft 2200 extending along the second direction 22 and a reflecting face 231 parallel to the second rotating shaft 2200, at this time, by rotating the polygon mirror 220 around the first rotating shaft 2100 and swinging the swing mirror 230 around the second rotating shaft 2200, the laser beams emitted by at least two laser transmitters 210 can be scanned in two dimensions perpendicular to the first direction 21 and perpendicular to the second direction 22, i.e. a space, simultaneously, the increase of the resolution of the laser radar is realized, and simultaneously, the precision requirements of the laser radar on the emitting angle and the placing position of the laser transmitter 210 can be properly reduced, which is beneficial for reducing the cost and simplifying the debugging work.
Further, the polygon mirror 220 rotates around the first rotation axis 2100, so that the prism surface 221 reflects the laser beams emitted from at least two of the laser emitters 210 onto the reflection surface 231; the oscillating mirror 230 oscillates around the second rotation axis 2200, so that the laser beams emitted from at least two of the laser emitters 210 are emitted in different directions. Interference can be effectively avoided.
In a specific embodiment, the signal processing module 400 includes: the device comprises an amplifier, a low-pass filter, an analog-to-digital conversion module and a processor;
the photodetector 204, the amplifier, the low-pass filter, and the analog-to-digital conversion module in each optical signal transmission module 200 are sequentially connected to the processor. The processor is also connected to all of the laser emitting assemblies 100 and the laser scanner. The signal processing module 400 amplifies, filters, controls gain, acquires AD, and processes each path of electrical signal of the optoelectronic module; and at the same time, for accomplishing data communication, as well as control of the driver, control of the laser scanner, and the like.
In conclusion, the scheme can realize sufficient point cloud sampling rate, can ensure sufficient precision and has an interference resistance function.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus may be implemented in other manners. The above-described apparatus embodiments are merely illustrative, and it should also be noted that, in alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams, and combinations of blocks in the block diagrams, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition, each functional module or unit in each embodiment of the present invention may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention.
Claims (10)
1. A frequency modulation continuous wave laser radar is characterized by comprising N laser emission assemblies, N optical signal transmission modules, a signal processing module and a laser scanning module, wherein N is an integer greater than 1;
the N laser emission assemblies respectively emit laser with different wavelengths;
the optical signal transmission module is used for transmitting the laser emitted by the laser emitting component and the reflected laser of the laser scanning module to carry out beat frequency processing and transmitting the beat frequency processing to the signal processing module;
the laser scanning module receives laser from the optical signal transmission module for emission and transmits reflected laser to the optical signal transmission module;
the signal processing module carries out signal processing by collecting beat frequency signals of the optical signal transmission module, and the laser scanning module is controlled by the signal processing module;
the N laser emission assemblies are respectively connected with the N optical signal transmission modules;
the N optical signal transmission modules are respectively connected with the laser scanning module;
and the N optical signal transmission modules are respectively connected with the signal processing module.
2. A frequency modulated continuous wave lidar as defined in claim 1 wherein each lasing assembly is comprised of a driver and a laser; wherein the driver is connected to the laser to modulate the output frequency of the laser.
3. A frequency modulated continuous wave lidar according to claim 1 or 2, wherein each optical signal transmission module comprises a first optical splitter, a first optical coupler, an optical transceiver, and a photodetector,
the first optical splitter is used for splitting one input optical signal into two output optical signals, and the input end of the first optical splitter is connected with the output end of the laser emission component;
the first output end of the first optical splitter outputs a transmitting light wave, and the first output end of the first optical splitter is connected with one end of the optical transceiver;
the other end of the optical transceiver is connected with the input end of the laser scanning module;
the second output end of the first optical splitter outputs a local oscillator light wave, and the second output end of the first optical splitter is connected with the first input end of the first optical coupler;
the first optical coupler is used for combining two paths of input optical signals into one path of output optical signal, and a second input end of the first optical coupler is connected with one end of the optical transceiver;
the output end of the first optical coupler is connected with the input end of the photoelectric detector;
and the output end of the photoelectric detector is connected with the input end of the signal processing module.
4. A frequency modulated continuous wave lidar in accordance with claim 3, comprising a collimator in the optical transceiver that converts the transmitted light in the optical fiber to collimated light.
5. A frequency modulated continuous wave lidar as defined in claim 1 wherein each optical signal transmission module comprises: the optical transceiver comprises a first optical splitter, an optical fiber circulator, a first optical coupler, an optical transceiver and a photoelectric detector;
the input end of the first optical splitter is connected with the output end of the laser emission component; the first output end of the first optical splitter is connected with the first end of the optical fiber circulator; the second end of the optical fiber circulator is connected with one end of the optical transceiver; the third end of the optical fiber circulator is connected with the second input end of the first optical coupler;
the other end of the optical transceiver is connected with the input end of the laser scanning module; the second output end of the first optical splitter is connected with the first input end of the first optical coupler;
the output end of the first optical coupler is connected with the input end of the photoelectric detector; and the output end of the photoelectric detector is connected with the input end of the signal processing module.
6. A frequency modulated continuous wave lidar according to claim 5, wherein each optical signal transmission module further comprises a second optical splitter, a third optical splitter, the number of optical fiber circulators of the optical signal transmission module is M, the number of optical transceivers of the optical signal transmission module is M, the number of first optical couplers of the optical signal transmission module is M, the number of photodetectors of the optical signal transmission module is M, and M is an integer greater than 1;
the second optical splitter is used for splitting one path of input optical signals into M paths of output optical signals, and the input end of the second optical splitter is connected with the first output end of the first optical splitter;
the M output ends of the second optical splitter are respectively connected with the first ends of the M optical fiber circulators;
the second ends of the M optical fiber circulators are respectively connected with one ends of M optical transceivers;
the other ends of the M optical transceivers are respectively connected with the input end of the laser scanning module;
the third ends of the M optical fiber circulators are respectively connected with the second input ends of the M first optical couplers;
the third optical splitter is used for splitting one input optical signal into M output optical signals, and the input end of the third optical splitter is connected with the second output end of the first optical splitter;
the M output ends of the third optical splitter are respectively connected with the first input ends of the M first optical couplers;
the output ends of the M first optical couplers are respectively connected with the input ends of the M photoelectric detectors;
and the output ends of the M photoelectric detectors are respectively connected with the input end of the signal processing module.
7. A frequency modulated continuous wave lidar according to claim 6, wherein each optical signal transmission module further comprises a fiber amplifier having an input connected to the first output of the first optical splitter; and the output end of the optical fiber amplifier is connected with the input end of the second optical splitter.
8. A frequency modulated continuous wave lidar according to claim 1, 2, 4, 6, or 7, wherein the laser scanning module comprises at least two laser emitters, at least two of the laser emitters having different lasing directions;
a polygon mirror including a first rotation axis extending in a first direction and a plurality of mirror facets surrounding the first rotation axis;
a swing mirror including a second rotation axis extending in a second direction and a reflection surface parallel to the second rotation axis;
wherein the second direction intersects the first direction; the laser transmitter and the swing mirror are respectively arranged on the light incident side and the light emergent side of the prism surface of the polygon prism;
the polygon prism rotates around the first rotating shaft, so that the prism surface reflects laser beams emitted by at least two laser emitters onto the reflecting surface; the oscillating mirror oscillates around the second rotating shaft, so that laser beams emitted by at least two laser emitters are emitted in different directions.
9. A frequency modulated continuous wave lidar according to claim 4, 6 or 7, wherein the photodetector comprises P receivers, P amplification units and P sampling units, wherein P is a positive integer;
the receivers are used for receiving the reflected laser and converting optical signals into electric signals, and the output ends of the P receivers are respectively connected with the input ends of the P amplifying units;
the amplifying units are used for amplifying the electric signals, and the output ends of the P amplifying units are respectively connected with the input end of the sampling unit;
the sampling unit is used for sampling the amplified signals output by the amplifying unit, sampling data are transmitted to the signal processing module, and the P sampling units are respectively connected with the input end of the signal processing module.
10. A frequency modulated continuous wave lidar according to claim 4, 6 or 7, wherein the signal processing module comprises: the device comprises an amplifier, a low-pass filter, an analog-to-digital conversion module and a processor;
the photoelectric detector, the amplifier, the low-pass filter and the analog-to-digital conversion module in each optical signal transmission module are sequentially connected with the processor.
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