CN115685231A - Frequency modulation laser radar system and method for improving coherent detection distance - Google Patents
Frequency modulation laser radar system and method for improving coherent detection distance Download PDFInfo
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Abstract
The invention provides a frequency modulation laser radar system and a method for improving coherent detection distance, which are based on the technology of a multi-frequency continuous wave laser radar of a phase modulation technology, and utilize a mode of generating a plurality of corresponding frequency sidebands by a plurality of microwave frequency adjustment electro-optical modulators to replace frequency, phase or amplitude scanning in any form, carry out linear modulation in specific frequency ranges, modulated signals respectively carry distance and speed information, and obtain the distance and speed information by respectively inverting the phase and frequency changes.
Description
Technical Field
The invention relates to the field of laser sensing and laser radars, in particular to a frequency modulation laser radar system and a frequency modulation laser radar system for improving coherent detection distance.
Background
Visual imaging, radio frequency radar and laser radar are three detection technologies which are currently widely applied to automatic ranging and imaging of ground and aircrafts. The laser radar is an optical version of a radio frequency radar, and point clouds are generated through coded information of light echoes to perform accurate positioning and morphology analysis. The emerging requirements of high-resolution ranging and imaging in the fields of ground measurement and the like have stimulated people to pay attention to the laser radar system. Lidar achieves range measurements by measuring the time of flight of a laser pulse from a laser source to a target and back to a photodetector, or by frequency modulation to produce a radio frequency beat frequency. The reference light and the reflected light from the target are detected by using a continuous laser and coherent detection system. Conventional time-of-flight lidar provides for longer measurement distances by using high peak power laser pulses. The speed information of the object in motion can only be calculated by comparing continuous multiple frames, which is easy to cause large calculation error in practical application due to interference and movement of the object.
An alternative pulse lidar that utilizes coherent detection can achieve simultaneous ranging and velocity measurement by utilizing the doppler effect. Continuous amplitude modulation and frequency modulation laser radar are combined with a coherent detection technology, interference between a back reflection signal and a reference beam is detected by using a linear chirp, frequency scanning or phase scanning mode, radio frequency beat frequency is generated at a photoelectric detector, and the phase or frequency of the beat frequency is used for extracting distance information. While the doppler shift in the mixed frequency produced by the interference simultaneously provides velocity information. However, the maximum measurable distance of a coherent lidar is not only limited by the power of the light source, but also affected by the linewidth of the laser. When the laser radar measures a distance beyond the coherence length of the laser, the signal quality will be degraded due to random phase noise and errors will be generated in the measurement. The use of single frequency narrow linewidth lasers with low phase noise is an ideal solution for coherent detection, but the cost of such lasers is an unavoidable problem facing large-scale use of coherent lidar. Also, fast and linear frequency scanning requires lasers with good stability, while maintaining frequency stability and temporal coherence is another challenge currently facing.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a frequency modulation laser radar system and a frequency modulation laser radar method for improving coherent detection distance.
According to a first aspect of the present invention, there is provided a frequency modulated lidar for improving coherent detection distance, comprising a single-frequency continuous laser, a phase modulator, a fiber amplifier, a fiber circulator and a transceiver unit, a multi-heterodyne detection unit, a comb filter, a data processing unit, and a system clock and a multi-frequency microwave frequency synthesizer, which are connected in sequence by an optical fiber;
the single-frequency continuous laser is used for generating coherent light required by detection, the output of the single-frequency continuous laser is divided into two parts, one part of coherent light is coupled into the phase modulator, and the other part of coherent light enters the multi-heterodyne detection unit;
the phase modulator is used for performing sideband and phase modulation on a part of the coherent light to generate continuous laser with a modulation frequency sideband as a detection light signal;
the optical fiber amplifier is used for modulating and amplifying the detection optical signal;
the optical fiber circulator is used for transmitting a detection optical signal to the target to be detected and receiving an echo signal returned by the target to be detected through the transceiving unit;
the system clock is used for generating a reference clock signal;
the multi-frequency microwave frequency synthesizer is connected with the system clock and used for generating a plurality of frequency signals with stable phases and driving the phase modulator as driving signals;
the multi-heterodyne detection unit is respectively connected with the single-frequency continuous laser and the optical fiber circulator and is used for generating a reference light signal for coherent detection according to the other part of coherent light input by the single-frequency continuous laser, generating a radio frequency mixed signal according to the reference light signal and the echo signal and inputting the radio frequency mixed signal into the dressing filter;
the comb filter is used for filtering the radio frequency mixed signal to respectively obtain a plurality of radio frequency heterodyne signals;
and the data processing unit is used for calculating phase and frequency information in an inversion mode according to the plurality of radio frequency heterodyne signals and calculating distance information and speed information of the target to be measured.
On the basis of the technical scheme, the invention can be improved as follows.
Optionally, the single-frequency continuous laser device is characterized in that the laser output by the single-frequency continuous laser device shows a single longitudinal mode characteristic in a frequency domain, and the single-frequency continuous laser device is a semiconductor laser device, a fiber laser device or a solid laser device.
Optionally, the phase modulator is an optical fiber coupling mach-zehnder interferometric electro-optic modulator or a cascaded electro-optic modulation single waveguide modulator.
Optionally, the optical fiber amplifier is selected according to the wavelength of the detection signal light, and the optical fiber amplifier includes, but is not limited to, an erbium-doped optical fiber amplifier, an erbium-ytterbium co-doped optical fiber amplifier, a thulium-doped optical fiber amplifier, or a raman optical fiber amplifier.
Optionally, the transceiver unit is a fixed-focus collimator or any optical fiber coupling telescope system.
Optionally, the multi-heterodyne detection unit is any form of photodetector, including but not limited to a photomultiplier tube, an avalanche detector, or a balanced detector.
Optionally, the system clock is any voltage controlled oscillator, including but not limited to Wen Buya controlled oscillator, phase locked voltage controlled oscillator, or constant temperature voltage controlled oscillator.
Optionally, the multi-frequency microwave frequency synthesizer includes a voltage-controlled oscillator, a multi-channel DDS, three phase shifters, and a radio frequency power synthesizer;
the voltage-controlled oscillator is a system total clock and is used for providing a reference clock signal of the whole system;
the multichannel DDS is a phase-synchronous direct digital frequency synthesizer with a plurality of signal output ports, and is used for outputting three driving frequency signals according to a reference clock signal and respectively outputting the three driving frequency signals to corresponding phase shifters through the three signal output ports;
each phase shifter is a radio frequency component and is used for providing a tunable phase quantity;
the radio frequency power synthesizer is used for superposing the power of a plurality of phase-adjusted frequency driving signals, does not change the frequency and the phase of each frequency component, and inputs the frequency and the phase into the phase modulator.
According to a second aspect of the present invention, there is provided a coherent detection range improving method based on a frequency-modulated laser radar system, including:
generating a plurality of frequency signals with stable phases through a system clock and a multi-frequency microwave frequency synthesizer, and using the frequency signals as driving signals to drive a phase modulator;
the single-frequency continuous laser generates coherent light required by detection, the output of the coherent light is divided into two parts, one part is coupled into the phase modulator to carry out sideband and phase modulation to generate a detection light signal, and the other part enters the multi-heterodyne detection unit to provide a reference light signal for coherent detection;
the optical fiber amplifiers respectively amplify the detection optical signals, the detection optical signals are transmitted to a target to be detected through the optical fiber circulator, echo signals returned by the target to be detected are received, and the echo signals and the reference optical signals generate radio frequency mixed signals in the multi-heterodyne detection unit;
the radio frequency mixed signal is coupled into a comb filter for filtering, a plurality of radio frequency heterodyne signals are obtained respectively, and distance information and speed information of the target to be measured are obtained through a data processing unit.
The invention provides a frequency modulation laser radar system and a method for improving coherent detection distance, which are based on the technology of multi-frequency continuous wave laser radar of phase modulation technology, and utilize a mode of generating a plurality of corresponding frequency sidebands by a plurality of microwave frequency adjustment electro-optical modulators to replace frequency, phase or amplitude scanning in any form, carry out linear modulation in specific frequency ranges, modulated signals carry distance and speed information respectively, and obtain distance and speed information by respectively inverting the phase and frequency changes.
Drawings
FIG. 1 is a schematic diagram of a frequency modulated lidar system for improving coherent detection range according to the present invention;
FIG. 2 is a schematic diagram of a multi-frequency microwave frequency synthesizer;
fig. 3 is a schematic flow chart of a coherent detection distance improving method based on a frequency-modulated laser radar system according to the present invention.
In the drawings, the names of the components represented by the reference numerals are as follows:
101. a single-frequency continuous laser 102, a phase modulator 103, a fiber amplifier 104, a fiber circulator 105, a transceiver 106, a multi-heterodyne detection unit 107, a system clock 108, a multi-frequency microwave frequency synthesizer 109, a comb filter 110 and a data processing unit;
201. a voltage controlled oscillator, 202, a multi-channel DDS,203, a first phase shifter, 204, a second phase shifter, 205, a third phase shifter, 206, a radio frequency power combiner.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided in the present invention may be arbitrarily combined with each other to form a feasible technical solution, and the combination is not limited by the sequence of steps and/or the structural composition mode, but must be based on the realization of the capability of a person skilled in the art, and when the technical solution combination is contradictory or cannot be realized, the technical solution combination should be considered to be absent and not to be within the protection scope of the present invention.
In order to eliminate the limit of the noise term and the coherence length of the laser, the invention provides a multi-frequency continuous wave laser radar technology based on a phase modulation technology, which utilizes a plurality of microwave frequency adjustment electro-optical modulators to generate a plurality of corresponding frequency sidebands to replace any form of frequency, phase or amplitude scanning and perform linear modulation in specific frequency ranges. Then, multi-heterodyne beat frequency detection is carried out by utilizing the laser which is then modulated with unmodulated laser, phase variation quantity of each specific frequency is inverted, although the absolute value of the phase difference between the reference signal and the echo signal is interfered because the absolute value exceeds the coherence length of the laser, and distance and speed information cannot be directly reflected, based on the phase difference of a plurality of modulation sidebands, the target distance can be effectively calculated by inverting the phase of each sideband by avoiding direct crosstalk of radio frequency, and meanwhile, the target speed can be further obtained by calculating Doppler frequency shift through the variation of the modulation sidebands.
Fig. 1 shows a fm lidar system for increasing coherent detection distance, which includes a single-frequency continuous laser 101, a phase modulator 102, a fiber amplifier 103, a fiber circulator 104, a transceiver 105, a multi-heterodyne detection unit 106, a comb filter 109, a data processing unit 110, a system clock 107, and a multi-frequency microwave frequency synthesizer 108, which are sequentially connected by an optical fiber.
The single-frequency continuous laser 101 is used for generating coherent light required for detection, and an output of the single-frequency continuous laser is divided into two parts, one part of the coherent light is coupled into the phase modulator 102, and the other part of the coherent light enters the multi-heterodyne detection unit 106. The single-frequency continuous laser 101 is characterized in that laser output by the single-frequency continuous laser 101 shows a single longitudinal mode characteristic in a frequency domain, and the single-frequency continuous laser 101 is a semiconductor laser, a fiber laser or a solid laser.
A phase modulator 102 for performing sideband and phase modulation on a portion of the incoming coherent light to generate continuous laser light having a modulation frequency sideband as the probe light signal. The phase modulator 102 is an optical fiber coupling Mach-Zehnder interferometric electro-optic modulator or a cascaded electro-optic modulation single waveguide modulator.
And the optical fiber amplifier 103 is used for modulating and amplifying the detection optical signal. The appropriate fiber amplifier 103 is selected according to the wavelength of the detection signal light, and the fiber amplifier 103 includes, but is not limited to, an erbium-doped fiber amplifier, an erbium-ytterbium co-doped fiber amplifier, a thulium-doped fiber amplifier, or a raman fiber amplifier.
And the optical fiber circulator 104 is configured to transmit a probe optical signal to the target to be measured and receive an echo signal returned by the target to be measured through the transceiver unit 105. The transceiver unit 105 is a fixed focus collimator or any fiber coupled telescope system.
A system clock 107 for generating a reference clock signal. The system clock 107 is any form of voltage controlled oscillator 201 including, but not limited to, a Wen Buya controlled oscillator, a phase locked voltage controlled oscillator, or a constant temperature voltage controlled oscillator.
A multifrequency microwave frequency synthesizer 108 connected to the system clock 107 for generating a plurality of phase-stable frequency signals as driving signals for driving the phase modulator 102.
And a multi-heterodyne detection unit 106, connected to the single-frequency continuous laser 101 and the fiber circulator 104, respectively, and configured to generate a reference light signal for coherent detection according to another part of coherent light input by the single-frequency continuous laser 101, and generate a radio frequency mixed signal according to the reference light signal and the echo signal, and input the radio frequency mixed signal to the comb filter 109. Multi-heterodyne detection unit 106 is any form of photodetector including, but not limited to, a photomultiplier tube, an avalanche detector, or a balanced detector, among others.
And the comb filter 109 is configured to filter the radio frequency mixed signal to obtain a plurality of radio frequency heterodyne signals, respectively.
And the data processing unit 110 is configured to calculate phase and frequency information in an inversion manner according to the plurality of radio frequency heterodyne signals, and calculate distance information and speed information of the target to be measured.
The system clock 107 and the multifrequency microwave frequency synthesizer 108 of the present invention are one of the core components of the overall system, and their main function is to generate multiple frequency signals that are phase-stable, thereby driving the phase modulator 102 for the purpose of modulating multiple optical frequency sidebands. The present invention therefore describes in detail the principles of operation of system clock 107 and multifrequency microwave frequency synthesizer 108 to more clearly convey the concepts of the present invention. As shown in fig. 2, fig. 2 is a schematic diagram of a system clock 107 and a multifrequency microwave frequency synthesizer 108, which includes:
100MHz voltage controlled oscillator 201, multichannel DDS202, three phase control units: a first phase shifter 203, a second phase shifter 204, and a third phase shifter 205, and a radio frequency power combiner 206, wherein:
a 100MHz voltage controlled oscillator 201 serves as the system overall clock to provide reference time and frequency signals for a multi-channel DDS 202.
The multi-channel DDS202 is a phase-synchronized direct digital frequency synthesizer with multiple outputs,
a phase shifter is used to provide a tunable phase amount for the rf components, and an rf power combiner 206 is used to power-add the multiple phase-adjusted frequency signals without changing the frequency and phase of each frequency component to drive the phase modulator 102.
The comb filter has the filtering channel number consistent with the DDS output number, and can independently filter the frequency information of a single frequency channel; the data processing unit 110 has the capability of calculating phase and frequency information in an inversion manner, and can calculate distance information and speed information of the target to be measured through the phase and frequency values.
As shown in fig. 2, the 100MHz voltage-controlled oscillator 201 is a system total clock, and is used to provide a reference electrical signal of the whole system, and the stability of the system total clock affects the accuracy and precision of distance measurement and speed measurement; the output of the 100MHz voltage-controlled oscillator 201 is provided to the multichannel DDS202 as a reference clock, the multichannel DDS202 outputs three driving frequencies of 700MHz, 750MHz and 800MHz, three signal output ports are respectively connected with the first phase shifter 203, the second phase shifter 204 and the third phase shifter 205, and independent phase scanning function can be realized by accurately controlling the phase offset of each phase shifter. Finally, the three driving frequencies are coupled into the rf power combiner 206 to achieve power combining, and the phase modulator 102 is driven to generate multi-frequency sidebands.
It can be understood that the working principle of the frequency-modulated laser radar system for improving the coherent detection distance provided by the invention is as follows: the single-frequency continuous laser 101 is used for generating coherent light required by detection; the output of the multi-heterodyne optical phase modulator is divided into two parts, one part is coupled into the phase modulator 102 to perform sideband and phase modulation, and the other part enters the multi-heterodyne detection unit 106 to provide a reference optical signal for coherent detection; the phase modulator 102 and the optical fiber amplifier 103 respectively modulate and amplify optical signals; the fiber circulator 104 is used for transmitting and receiving echo signals returned by the target to be measured. The echo signal and the reference signal produce a radio frequency hybrid signal in multi-heterodyne detection unit 106.
The voltage-controlled oscillator 201 is used as the total system clock, the output of the voltage-controlled oscillator is provided to the multichannel DDS202 as the reference clock, and the voltage-controlled oscillator outputs three driving frequenciesf 1 ，f 2 ，f 3 The three signal output ports are respectively connected with three phase shifters which are connected in parallel, and the independent phase scanning function can be realized by accurately controlling the phase offset of each phase shifter. The output of multi-frequency microwave frequency synthesizer 108 is used as a drive signal to drive phase modulator 102; the rf signals received by the multi-heterodyne detection unit 106 are coupled into a comb filter for filtering, a plurality of rf heterodyne signals are obtained respectively, the distance information and the speed information of the target to be detected are obtained through the data processing unit 110, and finally, the three driving frequencies are coupled into the rf power synthesizer 206 to realize power synthesis, and the electro-optic modulator is driven to generate a multi-frequency sideband.
In fig. 1 of the present invention, a frequency-modulated lidar system for improving coherent detection distance is provided, and in fig. 2, the operation method and connection method of the system clock and the multi-frequency microwave frequency synthesizer are introduced, and the operation mode and control sequence of the above components have very important influence on the technical method for implementing the present invention, solving the technical problems involved in the present invention and obtaining the expected effect of the present invention. Therefore, the workflow of the above components is explained in detail in fig. 3. Fig. 3 is a flowchart illustrating steps of a method for improving coherent detection range of a frequency modulated laser radar according to the present invention. The method can be realized by the frequency modulation laser radar system, and because the method steps and the principle of using the system are similar, the method steps are simply explained by times, and the method comprises the following steps:
step 1, generating a plurality of frequency signals with stable phases through a system clock and a multi-frequency microwave frequency synthesizer, and using the frequency signals as driving signals to drive a phase modulator;
step 2, a single-frequency continuous laser generates coherent light required for detection, the output of the coherent light is divided into two parts, one part of the coherent light is coupled into a phase modulator to carry out sideband and phase modulation to generate a detection light signal, and the other part of the coherent light enters a multi-heterodyne detection unit to provide a reference light signal for coherent detection;
step 3, the optical fiber amplifiers respectively amplify the detection optical signals, the detection optical signals are transmitted to the target to be detected through the optical fiber circulator, echo signals returned by the target to be detected are received, and the echo signals and the reference optical signals generate radio frequency mixed signals in the multi-heterodyne detection unit;
and 4, coupling the radio frequency mixed signal into a comb filter for filtering, respectively obtaining a plurality of radio frequency heterodyne signals, and obtaining distance information and speed information of the target to be measured through a data processing unit.
The invention provides a frequency modulation laser radar system and a method for improving coherent detection distance, which are based on the technology of multi-frequency continuous wave laser radar of phase modulation technology, and utilize a mode of generating a plurality of corresponding frequency sidebands by a plurality of microwave frequency adjustment electro-optical modulators to replace frequency, phase or amplitude scanning in any form, carry out linear modulation in specific frequency ranges, modulated signals carry distance and speed information respectively, and obtain distance and speed information by respectively inverting the phase and frequency changes.
It should be noted that, in the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to relevant descriptions of other embodiments for parts that are not described in detail in a certain embodiment.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (9)
1. A frequency modulation laser radar system for improving coherent detection distance is characterized by comprising a single-frequency continuous laser, a phase modulator, an optical fiber amplifier, an optical fiber circulator, a receiving and transmitting unit, a multi-heterodyne detection unit, a dressing filter, a data processing unit, a system clock and a multi-frequency microwave frequency synthesizer which are sequentially connected through an optical fiber;
the single-frequency continuous laser is used for generating coherent light required by detection, the output of the single-frequency continuous laser is divided into two parts, one part of coherent light is coupled into the phase modulator, and the other part of coherent light enters the multi-heterodyne detection unit;
the phase modulator is used for performing sideband and phase modulation on a part of the coherent light to generate continuous laser with a modulation frequency sideband as a detection light signal;
the optical fiber amplifier is used for modulating and amplifying the detection optical signal;
the optical fiber circulator is used for transmitting a detection optical signal to the target to be detected and receiving an echo signal returned by the target to be detected through the transceiving unit;
the system clock is used for generating a reference clock signal;
the multi-frequency microwave frequency synthesizer is connected with the system clock and used for generating a plurality of frequency signals with stable phases and driving the phase modulator as driving signals;
the multi-heterodyne detection unit is respectively connected with the single-frequency continuous laser and the optical fiber circulator and is used for generating a reference light signal for coherent detection according to the other part of coherent light input by the single-frequency continuous laser, generating a radio frequency mixed signal according to the reference light signal and the echo signal and inputting the radio frequency mixed signal into the dressing filter;
the dressing filter is used for filtering the radio frequency mixed signal to respectively obtain a plurality of radio frequency heterodyne signals;
and the data processing unit is used for calculating phase and frequency information in an inversion mode according to the radio frequency heterodyne signals and calculating distance information and speed information of the target to be measured.
2. A frequency-modulated lidar system according to claim 1, wherein the single-frequency continuum laser is characterized by an output exhibiting single longitudinal mode behavior in the frequency domain, and wherein the single-frequency continuum laser is a semiconductor laser, a fiber laser, or a solid state laser.
3. The FM lidar system of claim 1, wherein the phase modulator is a fiber coupled Mach-Zehnder interferometric electro-optic modulator or a cascaded electro-optic modulated single waveguide modulator.
4. A frequency modulated lidar system as defined in claim 1 wherein the fiber amplifier is selected based on the wavelength of the probe signal light, and the fiber amplifier includes but is not limited to an erbium doped fiber amplifier, an erbium ytterbium co-doped fiber amplifier, a thulium doped fiber amplifier, or a raman fiber amplifier.
5. A frequency-modulated lidar system according to claim 1, wherein the transceiver unit is a fixed-focus collimator or any fiber-coupled telescope system.
6. A frequency-modulated lidar system according to claim 1, wherein the multi-heterodyne detection unit is any type of photodetector including but not limited to a photomultiplier tube, an avalanche detector, or a balanced detector.
7. A frequency modulated lidar system as claimed in claim 1, wherein the system clock is any form of voltage controlled oscillator including but not limited to Wen Buya controlled oscillator, phase locked voltage controlled oscillator, or constant temperature voltage controlled oscillator.
8. The frequency-modulated lidar system of claim 1, wherein the multifrequency microwave frequency synthesizer comprises a voltage controlled oscillator, a multichannel DDS, three phase shifters, and a radio frequency power synthesizer;
the voltage-controlled oscillator is a system total clock and is used for providing a reference clock signal of the whole system;
the multichannel DDS is a phase-synchronous direct digital frequency synthesizer with a plurality of signal output ports, and is used for outputting three driving frequency signals according to a reference clock signal and respectively outputting the three driving frequency signals to corresponding phase shifters through the three signal output ports;
each phase shifter is a radio frequency component and is used for providing a tunable phase quantity;
the radio frequency power synthesizer is used for superposing the power of a plurality of phase-adjusted frequency driving signals, does not change the frequency and the phase of each frequency component, and inputs the frequency and the phase into the phase modulator.
9. A method for improving coherent detection range of a frequency modulated lidar system according to claim 1, comprising:
generating a plurality of frequency signals with stable phases through a system clock and a multi-frequency microwave frequency synthesizer, and using the frequency signals as driving signals to drive a phase modulator;
the single-frequency continuous laser generates coherent light required by detection, the output of the coherent light is divided into two parts, one part of the coherent light is coupled into the phase modulator to carry out sideband and phase modulation to generate a detection light signal, and the other part of the coherent light enters the multi-heterodyne detection unit to provide a reference light signal for coherent detection;
the optical fiber amplifiers respectively amplify the detection optical signals, the detection optical signals are transmitted to a target to be detected through the optical fiber circulator, echo signals returned by the target to be detected are received, and the echo signals and the reference optical signals generate radio frequency mixed signals in the multi-heterodyne detection unit;
the radio frequency mixed signal is coupled into a comb filter for filtering, a plurality of radio frequency heterodyne signals are obtained respectively, and distance information and speed information of the target to be measured are obtained through a data processing unit.
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