Multi-direction echo phase parallel mediation laser radar ranging system and method

Abstract

The present application relates to the technical field of laser radar, and more particularly to a multi-direction echo phase parallel mediation laser radar ranging system and method. The system comprises: a laser transmitter emits a laser beam, which is divided into a local oscillator beam and a probe beam by a beam splitter; a signal generator controls a phase modulator to generate a phase modulation signal to phase modulate the probe beam; an optical frequency comb generation unit generates an optical wave signal of an optical frequency comb for the probe beam, and inputs the optical wave signal into an optical circulator, which is then transmitted to a dispersion unit and receives a reflected echo beam from a target to be ranged; an optical fiber coupler mixes the local oscillator beam with the echo beam, converts the mixed beam into an electrical signal by a photodetector, and inputs the electrical signal into a filter unit to filter a specific frequency band wave signal and shield other frequency band wave signals; and a digital signal processing unit processes and analyzes the retained frequency band wave signal to calculate distance information between the system and the target to be ranged. The advantage is to improve the system detection speed.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a laser radar ranging system and method with multi-directional echo phase parallel modulation. Background Art

[0002] To address the limitations of phase-modulated continuous wave (PhMCW) coherent ranging methods in point cloud imaging, particularly in terms of frame rate and imaging speed, researchers and engineers are exploring multi-directional parallel detection technologies. While existing PhMCW lidar ranging systems can accurately measure distances at a single angle (direction), achieving three-dimensional imaging requires scanning multiple detection angles one by one. This process is time-consuming, as ranging in each direction can take 10 microseconds, while a complete 3D point cloud image may require measurements in tens of thousands of different directions. This results in a point cloud image generation time of hundreds of milliseconds, far exceeding the 50 milliseconds (20 frames per second) required for real-time 3D imaging. An intuitive solution is to replicate the PhMCW laser ranging system multiple times, with each system operating at a specific detection angle, thereby enabling simultaneous distance measurement in multiple directions. This approach can theoretically increase imaging speed by a factor of N, where N is the number of replicated systems. However, this approach has obvious disadvantages. It not only increases the complexity of the system, making it more difficult to operate, but also leads to a significant increase in system size, cost, weight and power consumption, because each set requires its own laser and detector. This increase is unacceptable for practical distance measurement applications.

[0003] Although this parallel system approach can accelerate the acquisition of 3D point cloud images, it is not easy to implement in practical applications due to the aforementioned issues, especially in situations that require compactness, cost-effectiveness, and low energy consumption. Therefore, although PhMCW technology performs well in distance measurement, in order to meet the requirements of real-time 3D imaging, there is still an urgent need to develop more efficient multi-directional parallel detection technology. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a laser radar ranging system and method with multi-directional echo phase parallel modulation.

[0005] The first object of the present invention is to provide a laser radar ranging system with parallel modulation of multi-directional echo phases, comprising a laser transmitter, a beam splitter, a phase modulator, a signal generator, an optical frequency comb generating unit, an optical circulator, a dispersion unit, an optical fiber coupler, a photodetector, a filtering unit, and a digital signal processing unit;

[0006] The laser emitter is used to emit a laser beam;

[0007] The beam splitter is used to split the laser beam into a local oscillator beam and a detection beam;

[0008] The phase modulator is used to perform phase modulation on the detection beam so that the phase of the laser signal changes regularly;

[0009] The signal generator is used to control the phase modulator to generate a phase modulation signal and output a preset phase;

[0010] The optical frequency comb generating unit is configured to generate a light wave signal of an optical frequency comb from the probe light beam modulated by the phase modulator, and input the light wave signal into the optical circulator;

[0011] The optical circulator is used to transmit the optical wave signal to the dispersion unit and receive the echo light beam reflected from the target to be measured;

[0012] The dispersion unit is used to split the light wave signal, which is incident on the target to be measured and then reflected to become the echo light beam, and then returns to the optical circulator;

[0013] The optical fiber coupler is used to mix the local oscillator light beam with the echo light beam to obtain an intermediate frequency signal;

[0014] The photoelectric detector is used to convert the intermediate frequency signal into an electrical signal and input the electrical signal into the filtering unit;

[0015] The filtering unit includes N independent filters for filtering wave signals of a specific frequency band and shielding wave signals of other frequency bands;

[0016] The digital signal processing unit is used to perform data processing and analysis on the reserved frequency band wave signal passing through the filtering unit, and calculate the distance information between the laser radar ranging system with parallel modulation of multi-directional echo phases and the target to be measured.

[0017] Preferably, the filter is a bandpass filter or a low-pass filter.

[0018] Preferably, the optical frequency comb generating unit is any one of a silicon nitride micro-ring optical comb, a phase modulation optical comb, or a cyclic frequency shift optical comb including an acousto-optic modulator and a gain medium.

[0019] Preferably, the optical frequency comb generating unit includes an acousto-optic modulator, a gain medium and two couplers; the gain medium is a fiber amplifier; the light passing through the acousto-optic modulator generates light with a frequency shift of Δω, a coupler couples part of the energy into the fiber amplifier for optical power amplification, and couples it back to the acousto-optic modulator again through another coupler to generate light with a frequency shift of 2Δω; the modulation is repeated to finally generate a light wave signal of an optical frequency comb with a frequency shift of Δω, 2Δω, 3Δω, ..., nΔω.

[0020] Preferably, the light field expression of the light wave signal of the optical frequency comb is:

[0021]

[0022] Where A n is the amplitude of each beam of the amplified light wave signal, ω0 is the initial frequency, Δω is the specific frequency output generated by the acousto-optic modulator, and t is the transmission time of the light wave signal. is the function of the modulation phase changing with time (i.e., the phase of the nth wavelength changing with time), A n and are all known constants.

[0023] Preferably, the local oscillator light beam and the echo light beam generate a local oscillator signal LO and an echo signal R respectively;

[0024] The light field expression of the local oscillator signal LO is:

[0025]

[0026] The light field expression of the echo signal R is:

[0027]

[0028] Where B n is the amplitude of each beam of the echo signal, ω0 is the initial frequency, is the initial phase, Δω is the specific frequency output generated by the acousto-optic modulator, t is the transmission time of the light wave signal, τ n is the time interval, The light wave signal of the nth wavelength exists at the time interval τ n The changing phase of n is the light wave signal with the nth wavelength.

[0029] Preferably, the light field expression of the intermediate frequency signal is:

[0030]

[0031] Where Δω is the specific frequency output generated by the acousto-optic modulator, t is the transmission time of the light wave signal, and τ n is the time interval, The light wave signal of the nth wavelength exists at the time interval τ n The changing phase of n is the light wave signal with the nth wavelength.

[0032] Preferably, the method further comprises a collimator arranged between the optical circulator and the dispersion unit, for collimating the light wave signal and the echo light beam.

[0033] Preferably, the beam splitter is any one of a beam splitter, a silicon photonic chip or a fiber beam splitter with a splitting ratio of 90:10; the phase modulator is a lithium niobate electro-optic phase modulator or a silicon waveguide thermo-optic phase modulator; and the dispersion unit is a beam splitter grating or a prism.

[0034] A second object of the present invention is to provide a laser radar ranging method with multi-directional echo phase parallel modulation, wherein the method uses a laser radar ranging system with multi-directional echo phase parallel modulation for measurement, comprising the following steps:

[0035] S1. The laser transmitter emits a laser beam, which is then split into a local oscillator beam and a detection beam by a beam splitter.

[0036] S2. The phase modulator performs phase modulation on the probe beam so that the phase of the laser signal changes regularly;

[0037] S3. The probe beam modulated by the phase modulator passes through the optical frequency comb generating unit to generate an optical frequency comb lightwave signal, and inputs the lightwave signal to port one of the optical circulator;

[0038] S4. The lightwave signal is output from the second port of the optical circulator and is split by the dispersion unit, then incident on the target to be measured and reflected as an echo beam, and then input from the second port of the optical circulator;

[0039] S5. The echo beam is output from port three of the optical circulator and mixed with the local oscillator beam in the fiber coupler to obtain an intermediate frequency signal;

[0040] S6. The intermediate frequency signal is converted into an electrical signal by a photodetector and input into the filtering unit;

[0041] S7. Filter the specific frequency band wave signal and shield other frequency band wave signals through the N-way independent filter in the filtering unit, and retain the frequency band wave signal to be transmitted to the digital signal processing unit;

[0042] S8. The digital signal processing unit performs data processing and analysis on the reserved frequency band wave signal to calculate the time interval τ n ; Then solve to obtain the distance d between the target object to be measured in each direction and the laser radar ranging system with parallel modulation of the multi-directional intermediate frequency pulse n ; The solution formula is as follows:

[0043]

[0044] Where, τ n is the time interval, and c is the speed of light.

[0045] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0046] This invention proposes a LiDAR ranging system that uses only a single laser and detector for multi-directional echo phase parallel modulation, enabling simultaneous (parallel) measurement at multiple angles. By adding only the optical frequency comb (OFC) generator, a dispersion unit, and a digital signal processing unit, this system achieves parallel detection without significantly increasing the system's size, cost, weight, or power consumption. This makes the system simpler and easier to operate without significantly increasing costs, facilitating wider application. Based on PhMCW, the proposed parallel detection scheme increases the frame rate (or detection speed), overcoming the prior art's drawback of requiring N measurements to measure N points N times. This invention achieves the beneficial effect of measuring N points in a single pass. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural schematic diagram of the laser radar ranging system with multi-directional echo phase parallel adjustment according to the present invention.

[0048] Figure 2 2 is a schematic structural diagram of a laser radar ranging system with multi-directional echo phase parallel modulation provided according to an embodiment of the present invention.

[0049] Figure 3 3 is a schematic diagram of a spectrum of an intermediate frequency signal IF and a bandpass filter provided according to an embodiment of the present invention.

[0050] Figure 4 2 is a schematic structural diagram of a laser radar ranging system with multi-directional echo phase parallel modulation provided according to an embodiment of the present invention.

[0051] Figure 5 2 is a schematic diagram of a spectrum of a multiplier output signal and a low-pass filter according to an embodiment of the present invention.

[0052] Reference numerals:

[0053] 1. Laser transmitter;

[0054] 2. Beam splitter;

[0055] 3. Phase modulator;

[0056] 4. Signal generator;

[0057] 5. Optical frequency comb generation unit;

[0058] 501, coupler; 502, acousto-optic modulator; 503, erbium-doped fiber amplifier;

[0059] 6. Optical circulator;

[0060] 7. Spectroscopic grating;

[0061] 8. Fiber optic coupler;

[0062] 9. Photodetector;

[0063] 10. Filter unit;

[0064] 1001, N-channel low-pass filter; 1002, phase-locked loop;

[0065] 11. Digital signal processing unit;

[0066] 12. Collimator. DETAILED DESCRIPTION

[0067] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, identical modules are denoted by identical reference numerals. In the case of identical reference numerals, their names and functions are also identical. Therefore, their detailed description will not be repeated.

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0069] The present invention provides a laser radar ranging system with multi-directional echo phase parallel modulation, comprising:

[0070] A laser transmitter, for emitting a laser beam;

[0071] A beam splitter is used to split the laser beam into two paths: one path is used as a local oscillator beam (generating a local oscillator signal LO), and the other path is a detection beam that is modulated and emitted into space for distance detection (hereinafter referred to as the "transmitted signal"). The type and splitting ratio of the beam splitter are not limited and can be selected according to system requirements. For example, a fiber optic beam splitter with a splitting ratio of 90:10 can be used. Alternatively, beam splitters, silicon photonic chips, etc. can be used for beam splitting.

[0072] The local oscillator signal LO, the initial frequency is ω0, the initial phase is Then the light field expression of the local oscillator signal LO is:

[0073]

[0074] Where ω0 is the initial frequency, is the initial phase.

[0075] The phase modulator is used to modulate the phase of the laser beam so that the phase of the transmitted laser signal changes regularly. The transmitted signal passes through the phase modulator to perform phase modulation on the transmitted signal. The modulation waveform is a square wave with a certain duty cycle, and its modulation period is T m ;

[0076] Furthermore, the square wave is specifically a square wave with a duty cycle of 50% and a period of 10 μs; the material and structure of the phase modulator are not limited, such as a lithium niobate electro-optical phase modulator, a silicon waveguide thermo-optical phase modulator, etc.;

[0077] A signal generator is used to control the phase modulator to generate a phase modulation signal and output a preset phase;

[0078] The local oscillator signal LO is modulated and amplified by the phase modulator and the acousto-optic modulator to obtain the light wave signal T. At this time, the light field expression of the light wave signal T is:

[0079]

[0080] Where A n is the amplitude of each beam of the amplified light wave signal, ω0 is the initial frequency, Δω is the specific frequency output generated by the acousto-optic modulator, and t is the transmission time of the light wave signal. is the function of the modulation phase changing with time (i.e., the phase of the nth wavelength changing with time), A n and are all known constants;

[0081] An optical frequency comb generating unit, configured to generate equally spaced discrete spectra in the frequency domain, so that the probe beam modulated by the phase modulator generates a light wave signal of the optical frequency comb, and input the light wave signal into the optical circulator;

[0082] An optical circulator, used to transmit the modulated laser signal to the dispersion unit and receive the echo beam reflected from the target to be measured;

[0083] A dispersion unit for splitting composite light containing different wavelengths; the type of dispersion unit is not limited, including but not limited to a spectroscopic grating, a prism, etc.;

[0084] Fiber coupler: The local oscillator beam is incident on the fiber coupler. The detection beam is incident on the target to be measured and then reflected to become an echo beam. The echo beam is also incident on the fiber coupler. The fiber coupler mixes the local oscillator beam (local oscillator signal LO) and the echo beam (echo signal R).

[0085] A photodetector, used to convert the intermediate frequency signal obtained by mixing into an electrical signal;

[0086] The filtering unit is used to filter specific frequency bands and shield wave signals of other frequency bands;

[0087] The digital signal processing unit is used to process and analyze the reserved frequency band wave signal, and then calculate the distance information between the laser radar ranging system with parallel modulation of multi-directional echo phases and the target object being measured.

[0088] Part of the structure of the laser radar ranging system with multi-directional echo phase parallel modulation of the present invention can be replaced by other structural methods, for example:

[0089] (1) The principle of phase modulation is not limited. It can be thermo-optical modulation (heating the waveguide, changing the temperature, changing the waveguide refractive index, and changing the optical phase) or electro-optical modulation (doping the waveguide with P-type and N-type, adjusting the PN junction voltage, adjusting the number of carriers in the waveguide, adjusting the refractive index, and adjusting the phase).

[0090] (2) There is no limit to the method of generating the optical frequency comb, including silicon nitride micro-ring optical comb, cyclic frequency-shifted optical comb containing an acousto-optic modulator and a gain medium, phase-modulated optical comb, etc.; in the cyclic frequency-shifted optical comb of an acousto-optic modulator + gain medium, the type of gain medium is not limited, including semiconductor optical amplifiers, erbium-doped fiber amplifiers, etc.

[0091] (3) Types of digital signal processing units and calculation of τ n There is no limitation on the method, for example: using a TDC (time-to-digital converter, a chip that can measure pulse width) for direct timing; or using an ADC (analog-to-digital converter, oscilloscope, which acquires pulse waveforms and then analyzes them) to collect phase-modulated signals and IF signals for counting / timing; or using an ADC to sample phase-modulated signals and IF signals, calculating the correlation coefficient between the two, and finding the time delay with the largest correlation coefficient; all of the above methods can be used to analyze the data and obtain τ n That's it.

[0092] Furthermore, the system further comprises: a collimator arranged between the optical circulator and the beam splitter grating, for collimating the detection light beam and the echo light beam.

[0093] Furthermore, the optical frequency comb generation unit (OFC) includes a frequency-shifting loop consisting of an acousto-optic modulator (AOM), an erbium-doped fiber amplifier (EDFA), and a coupler. Its operating principle is as follows: light passing through the AOM produces a certain frequency shift Δω. The coupler couples part of the energy into the EDFA, and the remaining energy is transmitted to port one of the optical circulator. The light with a frequency shift of Δω is amplified by the erbium-doped fiber amplifier to compensate for the energy loss caused by the coupler and transmission loss. It is then coupled back to the AOM through the coupler to produce light with a frequency shift of 2Δω. By repeating the above process, the optical frequency comb generation unit will produce frequency combs with frequency shifts of Δω, 2Δω, 3Δω, and so on.

[0094] The lightwave signal E entering port 1 of the optical circulator T The light field expression is:

[0095]

[0096] Where, Indicates the phase of the nth wavelength changing with time, where n are equal, the same as the square wave modulation signal waveform.

[0097] Light wave signal E T The light enters the optical circulator port 1 and exits from the optical circulator port 2, is collimated by the collimator, and then is incident on the dispersion unit.

[0098] Different frequencies indicate that the wavelengths of the light waves are different. After being reflected by the dispersion unit, they are emitted at different diffraction angles, causing the light beam to be dispersed and hit the object under test in different directions. After encountering the object under test, the light wave is reflected. Due to the reversible principle of the optical path, the echo signal R reflected in each direction returns to the optical circulator after passing through the dispersion unit and collimator. Then, using the characteristics of the optical circulator (light entering from Port 2 will be emitted from Port 3), the echo signal R is transmitted to the fiber coupler through the optical circulator. The local oscillator signal LO (that is, the laser beam emitted by the laser transmitter) is used as a reference signal to mix with the echo signal R to obtain the intermediate frequency signal IF. The echo signal R has a flight time interval τ. n , and a delay is generated relative to the local oscillator signal LO. The light field expressions of the echo signal R and the intermediate frequency signal IF are:

[0099]

[0100]

[0101] Where B n is the amplitude of each beam of the echo signal, ω0 is the initial frequency, is the initial phase, Δω is the specific frequency output generated by the acousto-optic modulator, t is the transmission time of the light wave signal, τ n is (time interval), is the light wave signal of the nth wavelength with the time interval τ n The phase change), n is (the light wave signal of the nth wavelength); due to ω0τ n 、nΔωτ n and The three terms are constants, which are useless for distance measurement and do not carry any information. For the sake of convenience, they are discarded. So they are expressed as:

[0102]

[0103] The intermediate frequency signal is the sum of a series of cosine terms; note that Δω is usually on the order of tens of MHz. The bandwidth is only a few MHz, which can be obtained by expanding the Bessel function: The term is a narrowband signal with a center frequency of nΔω and a bandwidth of several MHz. The IF signal is the sum of a series of narrowband signals with a center frequency of nΔω and a bandwidth of several MHz. These narrowband signals have no frequency band overlap (such as Figure 3 As shown), each narrowband signal corresponds to one direction.

[0104] Therefore, by inputting the IF signal into the bandpass filter of different frequency bands, the IF signal in each direction can be filtered out, that is, each item is After finding arccos, we get Subtracting the term nΔωt, we can get That is, the flight time τ in each direction n The phase expression of the delay. Through the analysis and calculation processing of the digital signal processing unit, the original phase modulation signal and We can analyze τ n ; or use TDC (time-to-digital converter) to phase modulate the signal and The time interval τ can be obtained by directly measuring the time interval n (The time required for the light wave to be transmitted to the obstacle and scattered back to the radar). According to the formula (c is the speed of light) and the distance information between the target object and the lidar in each direction can be obtained.

[0105] Specifically, a lightwave signal T passes through an optical circulator, is collimated by a collimator, and then hits a dispersion unit. Since a lightwave contains a series of light beams with different and increasing frequencies, and the relationship between lightwave wavelength and frequency c = υλ, where c is the speed of light, it can be seen that lightwave wavelength and frequency are inversely proportional. Therefore, after being reflected by the dispersion unit, the lightwave signal T is emitted at different diffraction angles. Each lightwave encounters a target object in a different direction and is reflected back. After being reflected by the dispersion unit, it enters the optical circulator again and outputs an echo signal R from port 3. Due to the time interval of flight τ, the echo signal R n , and a delay is generated relative to the local oscillator signal LO, and its light field expression is:

[0106]

[0107] The echo signal R is transmitted to the fiber coupler through the optical circulator. The local oscillator signal LO (i.e., the laser beam emitted by the laser transmitter) is used as a reference signal to mix with the echo signal R to obtain the intermediate frequency signal IF. The local oscillator signal LO and the echo signal R are coherently superimposed to generate a new light field. The light field expression is:

[0108]

[0109] Since the light intensity is proportional to the square of the light field, and the light intensity is proportional to the power, then the power P∝It =E 2 (t) t ,symbol t It means taking the average over time, then the power P is:

[0110]

[0111] because and I R It is the DC component of the local oscillator signal LO and the echo signal R that can be detected by the photodetector. It contains no information and has no effect on the ranging and can be ignored. So it can be simplified to

[0112]

[0113] Define the intermediate frequency signal IF:

[0114]

[0115] Where ω0 is the initial frequency, is the initial phase, Δω is the specific frequency output generated by the acousto-optic modulator, Bn, n and τ n is a constant term, which does not carry any information and has no effect on the distance measurement. To simplify the formula, ω0τ is ignored. n 、nΔωτ n and Three items, so it can be expressed as:

[0116]

[0117] Example 1

[0118] like Figure 1-Figure 3 As shown, this embodiment provides a laser radar ranging system with multi-directional echo phase parallel modulation, including:

[0119] A laser transmitter 1, configured to transmit a laser beam;

[0120] Beam splitter 2 is used to split the laser beam into two paths, one of which is used as a local oscillator beam (generating a local oscillator signal LO), and the other is used as a detection beam, which is modulated and emitted into space for distance detection (hereinafter referred to as "transmitted signal");

[0121] Phase modulator 3, used to perform phase modulation on the laser beam so that the phase of the emitted laser signal changes regularly;

[0122] Signal generator 4, used to control the phase modulator to generate a phase modulation signal and output a preset phase;

[0123] An optical frequency comb generating unit 5, comprising a coupler 501, an acousto-optic modulator 502 (AOM), an erbium-doped fiber amplifier 503 (EDFA), and a frequency shift loop formed by the coupler 501;

[0124] An optical circulator 6 is used to transmit the modulated laser signal to the grating and receive the echo signal;

[0125] a collimator 12 for collimating the probe beam and the echo beam;

[0126] The beam splitter grating 7 is used to split the composite light containing different wavelengths;

[0127] Fiber coupler 8, the local oscillator beam is incident on the fiber coupler, the detection beam is incident on the target to be measured and is reflected to become an echo beam, the echo beam is incident on the fiber coupler, and the fiber coupler mixes the local oscillator signal LO and the echo signal R;

[0128] The photodetector 9 is used to convert the intermediate frequency signal obtained by mixing into an electrical signal;

[0129] The filter unit 10 is used to filter a specific frequency band and shield the wave signals of other frequency bands;

[0130] The filtering unit 10 includes N bandpass filters. Since the intermediate frequency signal is the sum of a series of non-overlapping narrowband signals in the frequency domain, the bandpass filter directly filters out each narrowband signal, so a filter with a high Q value is required.

[0131] The intermediate frequency signal IF is the sum of a series of cosine terms; note that Δω is usually in the order of tens of megahertz (MHz). The bandwidth is only a few megahertz (MHz), which can be obtained by expanding the Bessel function: The term is a narrowband signal with a center frequency of nΔω and a bandwidth of several MHz. The intermediate frequency signal IF is the sum of a series of narrowband signals with a center frequency of nΔω and a bandwidth of several MHz. These narrowband signals have no frequency band overlap (such as Figure 3 As shown), each narrowband signal corresponds to one direction.

[0132] Therefore, by inputting the intermediate frequency signal IF into the bandpass filter of different frequency bands, the IF signal in each direction can be filtered out, that is, each item is The inverse trigonometric function is calculated by the digital processing unit, and arccos is obtained. Subtracting the term nΔωt, we can get That is, the flight time τ in each direction n Phase expression for the delay.

[0133] The digital signal processing unit 11 is used to process and analyze the reserved frequency band wave signal, and then calculate the distance information between the laser radar ranging system with multi-directional echo phase parallel modulation and the measured target object; specifically, through the analysis and calculation processing of the digital signal processing unit 11, the high-speed sampling oscilloscope is used to sample the original phase modulation signal and the phase expression after the flight time delay in each direction. We can analyze τ n ; or use TDC (time-to-digital converter) to phase modulate the signal and The time interval τ can be obtained by directly measuring the time interval n According to the formula (c is the speed of light) and the distance information between the target object and the lidar in each direction can be obtained.

[0134] Example 2

[0135] like Figure 4-Figure 5 As shown, this embodiment provides a laser radar ranging system with multi-directional echo phase parallel modulation, including:

[0136] A laser transmitter 1, configured to transmit a laser beam;

[0137] Beam splitter 2 is used to split the laser beam into two paths, one of which is used as a local oscillator beam (generating a local oscillator signal LO), and the other is used as a detection beam, which is modulated and emitted into space for distance detection (hereinafter referred to as "transmitted signal");

[0138] Phase modulator 3, used to perform phase modulation on the laser beam so that the phase of the emitted laser signal changes regularly;

[0139] Signal generator 4, used to control the phase modulator to generate a phase modulation signal and output a preset phase;

[0140] An optical frequency comb generation unit, comprising a coupler 501, an acousto-optic modulator 502 (AOM), an erbium-doped fiber amplifier 503 (EDFA), and a frequency shift loop formed by the coupler 501;

[0141] An optical circulator 6 is used to transmit the modulated laser signal to the grating and receive the echo signal;

[0142] a collimator 12 for collimating the probe beam and the echo beam;

[0143] The beam splitter grating 7 is used to split the composite light containing different wavelengths;

[0144] Fiber coupler 8, the local oscillator beam is incident on the fiber coupler, the detection beam is incident on the target to be measured and is reflected to become an echo beam, the echo beam is incident on the fiber coupler, and the fiber coupler mixes the local oscillator signal LO and the echo signal R;

[0145] The photodetector 9 is used to convert the intermediate frequency signal obtained by mixing into an electrical signal;

[0146] The filtering unit 10 includes a multiplier and N low-pass filters 1001; specifically, the multiplier is a phase-locked loop 1002; since the intermediate frequency signal is the sum of a series of non-overlapping narrowband signals in the frequency domain, the multiplier moves a narrowband signal to the baseband and then uses a low-pass filter to filter out other signals, making it easier to manufacture a low-pass filter with a high Q value.

[0147] The intermediate frequency signal IF is converted into an electrical signal by a photodetector. At this time, the signal generator drives the acousto-optic modulator with a signal of frequency Δω. At the same time, the signal of frequency Δω is also applied to the phase-locked loop, causing the phase-locked loop to generate a series of signals with integer multiples of Δω. The intermediate frequency signal IF is multiplied by this series of signals. Taking the signal of frequency Δω as an example, the intermediate frequency signal IF is multiplied by it, and the result of the operation is the multiplication output signal:

[0148]

[0149] The multiplication output signal is the sum of a series of cosine terms; Δω is usually on the order of tens of MHz. The bandwidth is only a few MHz, which can be obtained by expanding the Bessel function: The term is a low-frequency narrowband signal with a bandwidth of several MHz. The term is a high-frequency narrowband signal with a center frequency of nΔω and a bandwidth of several MHz (as shown in the figure below). Therefore, the mixed signal is the sum of a low-frequency signal with a bandwidth of several MHz and a series of narrowband signals with a center frequency of nΔω and a bandwidth of several MHz. These narrowband signals have no frequency band overlap (such as Figure 5 As shown). The cutoff frequency of the low-pass filter is set to a value much smaller than Δω. When the above mixed signal passes through the low-pass filter 1001, the first term The signal will be filtered out, and after calculating arccos, we get Similarly, the intermediate frequency signal IF is multiplied by a series of absolute Δω integer multiple signals, and the mixed signals are passed through N low-pass filters to obtain That is, the flight time τ in each direction n Phase expression for the delay.

[0150] The digital signal processing unit 11 is used to process and analyze the reserved frequency band wave signal, and then calculate the distance information between the laser radar ranging system with multi-directional echo phase parallel modulation and the measured target object; specifically, through the analysis and calculation processing of the digital signal processing unit 11, the original phase modulation signal and the We can analyze τ n ; or use TDC (time-to-digital converter) to phase modulate the signal and The time interval τ can be obtained by directly measuring the time interval n According to the formula (c is the speed of light) and the distance information between the target object and the lidar in each direction can be obtained.

[0151] Example 3

[0152] A laser radar ranging method with multi-directional echo phase parallel modulation includes the following steps:

[0153] S1. The laser transmitter emits a laser beam, which is then split into a local oscillator beam and a detection beam by a beam splitter.

[0154] S2. The phase modulator modulates the phase of the probe beam so that the phase of the laser signal changes regularly.

[0155] S3. The probe beam modulated by the phase modulator passes through the optical frequency comb generating unit to generate an optical frequency comb lightwave signal, and the lightwave signal is input to port one of the optical circulator;

[0156] S4. The lightwave signal is output from the second port of the optical circulator and is split by the dispersion unit, then incident on the target to be measured and reflected as an echo beam, and then input from the second port of the optical circulator;

[0157] S5. The echo beam is output from port 3 of the optical circulator and mixed with the local oscillator beam in a fiber coupler to generate an intermediate frequency signal.

[0158] S6. The intermediate frequency signal is converted into an electrical signal by a photodetector and input into a filtering unit;

[0159] S7. Filtering a specific frequency band wave signal and shielding other frequency band wave signals through N independent filters in the filtering unit, and transmitting the retained frequency band wave signal to the digital signal processing unit;

[0160] S8. The digital signal processing unit processes and analyzes the reserved frequency band wave signal and calculates the time interval τ. n ; Then solve the distance d between the target object to be measured in each direction and the laser radar ranging system with multi-directional intermediate frequency pulse parallel modulation n ; The solution formula is as follows:

[0161]

[0162] wherein τ is a time interval, and c is the speed of light. n

[0163] It should be understood that the various forms of flow illustrated above can be re-ordered, steps added or removed. For example, the steps recited in the present disclosure can be performed in parallel, in series, in a different order, or any combination thereof, so long as the desired results of the present disclosure are achieved, which is not limited herein.

[0164] The specific embodiments described above are not intended to be limiting, and any modifications, combinations, sub-combinations and alternatives are intended to be included herein. Thus, while the application has been described in connection with specific embodiments thereof, it will be understood that it is carried out in sub-combinations of these particular embodiments and in combinations of further embodiments waiting to be made. It is intended to embrace all available alternatives, modifications and variances.​

Claims

1. A multi-directional echo phase parallel modulation laser radar ranging system, characterized by: It includes a laser transmitter, a beam splitter, a phase modulator, a signal generator, an optical frequency comb generation unit, an optical circulator, a dispersion unit, a fiber coupler, a photodetector, a filtering unit and a digital signal processing unit; The laser emitter is used to emit a laser beam; The beam splitter is used to split the laser beam into a local oscillator beam and a detection beam; The phase modulator is used to perform phase modulation on the detection beam so that the phase of the laser signal changes regularly; The signal generator is used to control the phase modulator to generate a phase modulation signal and output a preset phase; The optical frequency comb generating unit includes an acousto-optic modulator, a gain medium and two couplers; the gain medium is a fiber amplifier; the light passing through the acousto-optic modulator generates a frequency shift of A coupler couples part of the energy into the fiber amplifier for optical power amplification, and couples it back to the acousto-optic modulator through another coupler, generating a frequency shift of 2 Light; Repeated modulation eventually produces a frequency shift of , 2 , 3 、……、n The optical frequency comb generating unit is configured to generate a light wave signal of an optical frequency comb from the probe light beam modulated by the phase modulator, and input the light wave signal into the optical circulator; The optical circulator is used to transmit the optical wave signal to the dispersion unit and receive the echo light beam reflected from the target to be measured; The dispersion unit is used to split the light wave signal, which is incident on the target to be measured and then reflected to become the echo light beam, and then returns to the optical circulator; The optical fiber coupler is used to mix the local oscillator light beam with the echo light beam to obtain an intermediate frequency signal; The photoelectric detector is used to convert the intermediate frequency signal into an electrical signal and input the electrical signal into the filtering unit; The filtering unit includes N independent filters for filtering wave signals of a specific frequency band and shielding wave signals of other frequency bands; The digital signal processing unit is used to perform data processing and analysis on the reserved frequency band wave signal passing through the filtering unit, and calculate the distance information between the laser radar ranging system with parallel modulation of multi-directional echo phases and the target to be measured.

2. The multi-directional echo phase parallel modulation laser radar ranging system according to claim 1, characterized in that: The filter is a band-pass filter or a low-pass filter.

3. The multi-directional echo phase parallel modulation laser radar ranging system according to claim 2, characterized in that: The optical frequency comb generating unit is any one of a silicon nitride micro-ring optical comb, a phase modulation optical comb, or a cyclic frequency shift optical comb including an acousto-optic modulator and a gain medium.

4. The multi-directional echo phase parallel modulation laser radar ranging system according to claim 1, characterized in that: The light field expression of the light wave signal of the optical frequency comb is: ； Where A n is the amplitude of each beam of the amplified light wave signal, is the initial frequency, The acousto-optic modulator generates a specific frequency output, t is the transmission time of the light wave signal, is a function of the modulation phase changing with time, which means the phase of the nth wavelength changes with time. and are all known constants.

5. The multi-directional echo phase parallel modulation laser radar ranging system according to claim 4, characterized in that: The local oscillator light beam and the echo light beam generate a local oscillator signal LO and an echo signal R respectively; The light field expression of the local oscillator signal LO is: ； The light field expression of the echo signal R is: ； Where, is the amplitude of each beam of the echo signal, is the initial frequency, is the initial phase, The acousto-optic modulator generates a specific frequency output, t is the transmission time of the light wave signal, is the time interval, The light wave signal of the nth wavelength exists at the time interval The changing phase of n is the light wave signal with the nth wavelength.

6. The multi-directional echo phase parallel modulation laser radar ranging system according to claim 5, characterized in that: The light field expression of the intermediate frequency signal is: ； Where, The acousto-optic modulator generates a specific frequency output, t is the transmission time of the light wave signal, is the time interval, The light wave signal of the nth wavelength exists at the time interval The changing phase of n is the light wave signal with the nth wavelength.

7. The laser radar ranging system with multi-directional echo phase parallel modulation according to any one of claims 1 to 6, characterized in that: It also includes a collimator arranged between the optical circulator and the dispersion unit, for collimating the light wave signal and the echo light beam.

8. The laser radar ranging system with multi-directional echo phase parallel adjustment according to claim 7, characterized in that: The beam splitter is any one of a beam splitter, a silicon photonic chip or a fiber beam splitter with a splitting ratio of 90:10; the phase modulator is a lithium niobate electro-optical phase modulator or a silicon waveguide thermo-optical phase modulator; and the dispersion unit is a beam splitter grating or a prism.

9. A multi-directional echo phase parallel modulation laser radar ranging method, using the multi-directional echo phase parallel modulation laser radar ranging system according to any one of claims 1 to 8 for measurement, characterized in that: The steps include: S1. The laser transmitter emits a laser beam, which is then split into a local oscillator beam and a detection beam by a beam splitter. S2. The phase modulator performs phase modulation on the probe beam so that the phase of the laser signal changes regularly; S3. The probe beam modulated by the phase modulator passes through the optical frequency comb generating unit to generate an optical frequency comb lightwave signal, and inputs the lightwave signal to port one of the optical circulator; S4. The lightwave signal is output from the second port of the optical circulator and is split by the dispersion unit, then incident on the target to be measured and reflected as an echo beam, and then input from the second port of the optical circulator; S5. The echo beam is output from port three of the optical circulator and mixed with the local oscillator beam in the fiber coupler to obtain an intermediate frequency signal; S6. The intermediate frequency signal is converted into an electrical signal by a photodetector and input into the filtering unit; S7. Filter the specific frequency band wave signal and shield other frequency band wave signals through the N-way independent filter in the filtering unit, and retain the frequency band wave signal to be transmitted to the digital signal processing unit; S8. The digital signal processing unit performs data processing and analysis on the reserved frequency band wave signal to calculate the time interval ; Then solve to obtain the distance d between the target object to be measured in each direction and the laser radar ranging system with parallel adjustment of the multi-directional echo phase n ; The solution formula is as follows: ； Where, is the time interval, and c is the speed of light.

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