Frequency modulated continuous wave laser radar target information optical domain resolving system

Abstract

The invention provides a frequency-modulated continuous wave laser radar target information optical domain resolving system, which belongs to the technical field of laser radars, and comprises a signal generation unit used for generating a frequency mixing signal containing target distance and speed information; the optical loading unit is used for loading the frequency mixing signal to a first optical carrier to obtain a modulated optical signal; the optical frequency shift loop is used for performing fixed frequency shift and fixed duration delay on the modulated optical signal to obtain an optical pulse sequence; and the signal processing unit is used for detecting the time interval between the carrier wave and the sideband in the optical pulse sequence and resolving the target distance and speed according to the fixed frequency, the fixed time length and the time interval. According to the invention, the frequency mixing signal of the laser radar is processed through the optical Fourier transform technology, so that the calculation of the target distance and speed is realized, the processing delay of an all-optical calculation mode is lower, and the anti-electromagnetic interference capability is higher.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, and in particular to a frequency-modulated continuous wave lidar target information optical domain solution system. Background Technology

[0002] Frequency Modulated Continuous Wave (FMCW) lidar measures target distance and velocity by analyzing the difference frequency signal between the reflected laser and a local oscillator. Traditional methods use digital Fourier transforms (such as Discrete Fourier Transform and Fast Fourier Transform) for spectral analysis of lidar data, which suffers from high processing delays and susceptibility to electromagnetic interference. Summary of the Invention

[0003] This invention provides a frequency modulated continuous wave (FMCW) lidar target information optical domain solution system to solve the technical problems of high delay and susceptibility to electromagnetic interference in target detection of existing FMCW lidar.

[0004] This invention provides a frequency-modulated continuous wave lidar target information optical domain solution system, comprising: The signal generation unit is used to generate a mixed signal containing target distance and velocity information; An optical loading unit is used to load the mixing signal onto a first optical carrier to obtain a modulated optical signal; An optical frequency shifting loop is used to perform fixed frequency shifting and fixed time delay on the modulated optical signal to obtain an optical pulse sequence; The signal processing unit is used to detect the time interval between the carrier and the sideband in the optical pulse sequence, and to calculate the target distance and speed based on the fixed frequency, the fixed duration and the time interval.

[0005] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the signal generation unit comprises: The laser signal generation module is used to generate the FMCW sweep frequency transmitted optical signal and the FMCW sweep reference optical signal; The free-space transceiver module is used to transmit the FMCW swept-frequency transmitted optical signal to the target under test and to receive the reflected optical signal from the target under test. The heterodyne detection receiving module is used to perform heterodyne mixing between the returned optical signal and the FMCW sweep frequency reference optical signal to obtain the mixed signal.

[0006] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the laser signal generation module includes: Pump light source, used to generate the second optical carrier; A linear sweep frequency modulation unit is used to frequency modulate the sidebands of the second optical carrier to obtain an FMCW sweep frequency signal; An optical beam splitter is used to split the FMCW sweep signal into the FMCW sweep transmit optical signal and the FMCW sweep reference optical signal.

[0007] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the optical loading unit comprises: A pump light source is used to generate the first optical carrier; An electro-optic modulator is used to modulate the mixing signal onto the first optical carrier to obtain the modulated optical signal.

[0008] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the optical loading unit further includes: A radio frequency amplifier is used to amplify the mixed signal; The electro-optic modulator is used to modulate the amplified mixing signal onto the first optical carrier.

[0009] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the optical frequency shifting loop comprises, in sequence, the following components in the optical path: An optical 2×2 coupler is used to couple the modulated optical signal into the optical frequency shifting loop, and to couple the frequency-shifted and delayed optical signal into the signal processing unit; The frequency shift module is used to shift the modulated optical signal at a fixed frequency. An optical filter is used to control the optical frequency shift bandwidth of the modulated optical signal within the optical frequency shift loop and to control the number of rotations of the modulated optical signal within the optical frequency shift loop. An optical isolator is used to control the unidirectional transmission of the modulated optical signal; An optical delay line is used to delay the modulated optical signal for a fixed duration.

[0010] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the optical frequency shifting loop further includes: A polarization controller is used to stabilize the polarization state of the modulated optical signal.

[0011] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the optical frequency shifting loop further includes: An optical amplifier is used to compensate for the transmission loss and coupling loss of the modulated optical signal.

[0012] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the optical frequency shifting loop and the signal generation unit satisfy the following: ; For the fixed duration, The optical frequency shift bandwidth is... For the fixed frequency, The frequency sweep period of the signal generation unit.

[0013] According to the present invention, a frequency-modulated continuous wave lidar target information optical domain solution system is provided, wherein the signal processing unit includes: A photodetector is used to perform photoelectric conversion on the optical pulse sequence to obtain a time-domain pulse signal; An electrical ADC sampling module is used to sample the time-domain pulse signal; An electrical signal processing module is used to detect the time interval between the carrier and the sideband in the sampled time-domain pulse signal, and to calculate the target distance and speed based on the fixed frequency, the fixed duration and the time interval.

[0014] The frequency-modulated continuous wave lidar target information optical domain solution system provided by this invention processes the lidar's mixed signal using optical Fourier transform technology. Utilizing the frequency shift and time delay characteristics of the optical frequency shift loop, it directly maps the spectral information of the mixed signal into an optical pulse sequence, thereby achieving the calculation of target distance and velocity. The processing delay only includes the time it takes for the mixed signal to propagate from the optical loading unit to the optical frequency shift loop, the time it takes for the optical pulse sequence output from the optical frequency shift loop to propagate to the signal processing unit, and the time it takes for the signal processing unit to process the optical pulse sequence, resulting in lower processing delay. Furthermore, the all-optical calculation method has stronger anti-electromagnetic interference capabilities. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is one of the structural schematic diagrams of the frequency-modulated continuous wave lidar target information optical domain solution system provided by the present invention.

[0017] Figure 2 This is the second schematic diagram of the optical domain solution system for target information of frequency-modulated continuous wave lidar provided by the present invention.

[0018] Figure 3 This is the third schematic diagram of the structure of the frequency-modulated continuous wave lidar target information optical domain solution system provided by the present invention.

[0019] Figure 4 The graphs provided by this invention show the relationship between the frequency and time of the return optical signal and the FMCW sweep reference optical signal, the relationship between the frequency and time of the mixing signal, and the relationship between the amplitude and time of the mixing signal.

[0020] Figure 5 These are the amplitude-frequency relationship diagram, time relationship diagram, and amplitude-time relationship diagram of the optical pulse sequence provided by this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] The following is combined Figures 1-5 This invention describes the optical domain solution system for target information of frequency-modulated continuous wave lidar.

[0023] Figure 1 This is one of the structural schematic diagrams of the frequency-modulated continuous wave lidar target information optical domain solution system provided by the present invention, such as... Figure 1 As shown, including but not limited to: The signal generation unit is used to generate a mixed signal containing target distance and velocity information; An optical loading unit is used to load the mixing signal onto the first optical carrier to obtain a modulated optical signal; An optical frequency shifting loop is used to shift a modulated optical signal at a fixed frequency and delay it for a fixed duration to obtain an optical pulse sequence. The signal processing unit is used to detect the time interval between the carrier and the sideband in the optical pulse sequence, and to calculate the target distance and speed based on a fixed frequency, a fixed duration and a time interval.

[0024] In one embodiment, such as Figure 2 As shown, the signal generation unit of the present invention may specifically include: The laser signal generation module is used to generate the FMCW sweep frequency transmitted optical signal and the FMCW sweep reference optical signal; The free-space transceiver module is used to transmit FMCW swept-frequency transmitted optical signals to the target under test and to receive the reflected optical signals from the target under test. The heterodyne detection receiving module is used to perform heterodyne mixing between the return optical signal and the FMCW sweep frequency reference optical signal to obtain the mixed signal.

[0025] In one embodiment, such as Figure 2 As shown, the laser signal generating module of the present invention may further include: Pump light source, used to generate the second optical carrier; The linear sweep frequency modulation unit is used to frequency modulate the sideband of the second optical carrier to obtain the FMCW sweep frequency signal; An optical beam splitter is used to split the FMCW sweep signal into an FMCW sweep transmit optical signal and an FMCW sweep reference optical signal.

[0026] Among them, the pump light source is used to generate a frequency of The continuous optical carrier; the linear sweep frequency modulation unit is used to frequency modulate the sideband of the second optical carrier to obtain the FMCW sweep frequency signal, with a sweep frequency bandwidth of B and a sweep frequency period of T; the optical beam splitter is used to split the FMCW sweep frequency signal into two beams: the FMCW sweep frequency transmitted optical signal and the FMCW sweep frequency reference optical signal.

[0027] The FMCW sweep frequency transmitted optical signal is transmitted to the target in space through the free space transceiver module. The reflected optical signal from the target is recoupled into the heterodyne detection receiving module through the free space transceiver module.

[0028] In one embodiment, such as Figure 2 As shown, the laser signal generation module of the present invention may further include: an optical amplifier, located between the linear sweep frequency modulation unit and the optical beam splitter, for amplifying the FMCW sweep frequency signal. The optical amplifier can amplify the sidebands generated after modulation.

[0029] In one embodiment, such as Figure 2 As shown, the heterodyne detection receiving module of the present invention may further include: An optical 180-degree mixer is used to mix the return optical signal and the FMCW sweep reference optical signal by 180 degrees to obtain a mixed optical signal. A balanced photodetector is used to perform heterodyne detection and photoelectric conversion on mixed optical signals to obtain a mixed signal.

[0030] Due to the time-of-flight delay of light (related to distance) and the Doppler effect (related to velocity), there is a difference between the frequency of the returned light signal and the frequency of the FMCW sweep reference light signal. Heterodyne mixing of the returned light signal and the FMCW sweep reference light signal produces a mixed signal, the frequency of which contains crucial information about the target's distance and velocity.

[0031] Let the frequency of the mixing signal during the half-cycle of frequency increase in the FMCW frequency sweep process be . The frequency of the mixing signal during the half-cycle of frequency reduction is Then the distance L and velocity V of the target to be measured are respectively: ; ; C represents the speed of light. The theoretical range resolution of FMCW lidar. .

[0032] In one embodiment, such as Figure 2 As shown, the optical loading unit of the present invention may specifically include: Pump light source, used to generate the first optical carrier; An electro-optic modulator is used to modulate a mixing signal onto a first optical carrier to obtain a modulated optical signal.

[0033] The pump source is used to generate a continuous optical carrier, and the electro-optic modulator is used to generate the modulation sidebands of the mixing signal. Two sidebands of any type need to be generated.

[0034] In one embodiment, such as Figure 2 As shown, the optical loading unit of the present invention may further include: Radio frequency amplifiers are used to amplify mixed signals; An electro-optic modulator is specifically used to modulate the amplified mixed signal onto a first optical carrier.

[0035] The radio frequency amplifier is used to obtain a mixing signal sufficient to drive the electro-optic modulator.

[0036] In one embodiment, such as Figure 2 As shown, the optical frequency shifting loop of the present invention may sequentially include the following components in the optical path: An optical 2×2 coupler is used to couple a modulated optical signal into an optical frequency shifting loop, and to couple a frequency-shifted and delayed optical signal into a signal processing unit. Frequency shifting module, used to shift the modulated optical signal at a fixed frequency; An optical filter is used to control the optical frequency shift bandwidth of the modulated optical signal within the optical frequency shift loop, and to control the number of rotations of the modulated optical signal within the optical frequency shift loop. Optical isolators are used to control the unidirectional transmission of modulated optical signals; Optical delay lines are used to delay modulated optical signals for a fixed duration.

[0037] The modulated optical signal is injected into the optical frequency shifting loop via a 2×2 optical coupler. The optical signal, after frequency shifting and delay in the optical frequency shifting loop, is then injected into the signal processing unit via another 2×2 optical coupler. The frequency shifting module is configured to shift the frequency of the optical signal once per cycle in the optical frequency shifting loop. That is, a fixed frequency is Optical filters are used to control the optical frequency shift bandwidth of optical signals. The frequency shift number of the optical signal (the number of times the optical signal cycles in the optical frequency shifting loop) is then calculated. Optical isolators are used to ensure unidirectional transmission of optical signals in the optical frequency shifting loop; optical delay lines are configured such that the optical signal is delayed once per cycle in the optical frequency shifting loop. That is, a fixed duration of , In this case, the reciprocals of the frequency shift and time delay of the optical frequency shift loop satisfy an integer multiple relationship.

[0038] After multiple cycles, carriers and sidebands of different frequencies will form a series of time-separated optical pulses at the output of the optical frequency shifting loop due to the "frequency-time" mapping relationship, thus obtaining an optical pulse sequence.

[0039] It is understandable that the optical frequency shifting loop is equivalent to the optical Fourier transform.

[0040] In one embodiment, such as Figure 2 As shown, the optical frequency shifting loop of the present invention may further include: A polarization controller is used to stabilize the polarization state of a modulated optical signal.

[0041] A polarization controller is used to keep the polarization state of an optical signal constant and optimize loop performance.

[0042] In one embodiment, such as Figure 2 As shown, the optical frequency shifting loop of the present invention may further include: Optical amplifiers are used to compensate for transmission and coupling losses in modulated optical signals.

[0043] In one embodiment, such as Figure 2 As shown, the signal processing unit of the present invention may specifically include: A photodetector is used to convert optical pulse sequences into photoelectric signals to obtain time-domain pulse signals. An electrical ADC sampling module is used to sample time-domain pulse signals; The electrical signal processing module is used to detect the time interval between the carrier and the sideband in the sampled time-domain pulse signal, and to calculate the target distance and speed based on a fixed frequency, fixed duration and time interval.

[0044] In this invention, based on a single-frequency optical signal, the optical field input to the optical frequency-shifting loop can be expressed as: ; in, The amplitude of the input light field, The frequency of the input optical signal.

[0045] The output optical field of the optical frequency shifting loop can be expressed as: ; When the condition is met When the above formula is simplified, it can be represented as: ; The power of the output optical field of the optical frequency shifting loop can be expressed as: ; Based on the power expression of the output optical field of the optical frequency shifting loop, it can be obtained that when a single-frequency optical signal is input into the optical frequency shifting loop, the output of the optical frequency shifting loop has a period of... Time-domain pulse train, each pulse with a 3-dB linewidth It is inversely proportional to the optical frequency shift bandwidth, specifically written as The frequency phase difference of the input optical frequency shift loop After the optical frequency is processed by the optical loading unit, optical frequency shifting loop, and signal processing unit, the output time-domain waveform time interval is... Therefore, the frequency resolution of the optical domain solution system is Since the output of the optical frequency shifter loop is a periodic time-domain pulse, there exists a frequency range without ambiguity. .

[0046] For positive and negative first-order sidebands and carrier-injected optical frequency shifting loops, the output time-domain waveform of the optical frequency shifting loop is the spectral power distribution of the input modulated optical signal. The timing of the pulses corresponding to the sidebands can be extracted from the output time-domain waveform. The time of the pulse corresponding to the carrier wave The time difference between the carrier and the sideband pulses is then obtained. Then, the frequency of the mixing signal modulated on the electro-optic modulator is calculated. Let the time interval between the modulation sideband and the corresponding carrier pulse in the rising half-cycle of the FMCW sweep period be . The time interval between the modulation sideband and the corresponding carrier pulse in the falling half-cycle of the FMCW sweep period is ,but , Therefore, we can conclude that: ; ; This allows for the calculation of target distance and speed based on fixed frequency, fixed duration, and time intervals.

[0047] The optical calculation process of this invention can be performed synchronously with the FMCW lidar sensing process, without waiting for the complete acquisition of the mixing signal within half a cycle of the FMCW frequency sweep. Therefore, the processing delay of this invention is determined only by the signal transmission link. The processing delay includes the time for the mixing signal to propagate from the optical loading unit to the optical frequency shifting loop, the time for the optical pulse sequence output from the optical frequency shifting loop to propagate to the signal processing unit, and the time for the optical pulse sequence to be processed by the signal processing unit. Specifically, the processing delay includes the time for the mixing signal to be amplified by the RF amplifier, loaded onto the electro-optic modulator, and for the modulated optical signal to propagate to the optical 2×2 coupler; the time for the optical pulse sequence output from the optical frequency shifting loop to propagate to the photodetector to complete the photoelectric conversion; and the time for the time-domain pulse signal after photoelectric conversion to be sampled by the electrical ADC sampling module to complete the ADC. The resulting electrical signal waveform is the processed Fourier transform result. Compared to the traditional method that requires acquiring a complete mixing electrical signal and then performing a Fourier transform through an electronic processor to analyze its spectrum, this invention has a lower processing delay; the all-optical calculation method has stronger resistance to electromagnetic interference.

[0048] As described above, the frequency-modulated continuous wave lidar target information optical domain solution system of the present invention processes the mixed signal of the lidar through optical Fourier transform technology. Utilizing the frequency shift and time delay characteristics of the optical frequency shifting loop, the spectral information of the mixed signal is directly mapped into an optical pulse sequence, thereby realizing the calculation of target distance and velocity. The processing delay only includes the time for the mixed signal to propagate from the optical loading unit to the optical frequency shifting loop, the time for the optical pulse sequence output by the optical frequency shifting loop to propagate to the signal processing unit, and the time for the signal processing unit to process the optical pulse sequence, resulting in lower processing delay. The all-optical calculation method has stronger resistance to electromagnetic interference.

[0049] In one embodiment, the optical frequency shifting loop and signal generation unit of the present invention can satisfy: .

[0050] In this way, the optical Fourier transform calculation can be completed within half a cycle of a single FMCW lidar, and when the equality holds, the frequency resolution of the optical Fourier transform matches the range resolution of the lidar.

[0051] In one embodiment, such as Figure 3 As shown, the linear sweep frequency modulation unit of the present invention may include: A function generator is used to generate periodic triangular wave signals; A voltage-controlled oscillator is used to frequency modulate a triangular wave signal to obtain an FMCW radio frequency signal. Radio frequency amplifier, used to amplify FMCW radio frequency signals; A carrier-suppressed single-sideband modulator is used to optically modulate the second optical carrier and the FMCW radio frequency signal to obtain an FMCW swept frequency signal. An optical filter is used to remove the residual carrier of the FMCW sweep signal to obtain a clean FMCW sweep signal.

[0052] The optical amplifier of the present invention can be an erbium-doped fiber amplifier, and the optical beam splitter can be an optical 1×2 coupler.

[0053] Free space transceiver modules may include: The transmitting collimator is used to transmit the FMCW swept frequency transmitted optical signal onto the target under test; A receiving collimator is used to couple the reflected light signal from the target into an optical 180-degree mixer. The optical 180-degree mixer can be an optical 2×2 coupler.

[0054] The electro-optic modulator can be an electro-optic phase modulator, the electrical ADC sampling module can be a real-time oscilloscope, and the electrical signal processing module can be a computer processing terminal.

[0055] The frequency shift module may include a function generator, an RF amplifier, and an acousto-optic frequency shifter. The acousto-optic frequency shifter, driven by the function generator and the RF amplifier, is used to shift the optical signal in the loop at a fixed frequency. The optical delay line may be a single-mode optical fiber.

[0056] by Figure 3 The invention will be illustrated using an example. The pump source is a C-band continuous-wave laser. The function generator outputs a triangular wave signal with a period of T=25µs, a duty cycle of 50%, and a peak-to-peak value of 3V. This signal drives a voltage-controlled oscillator to generate an FMCW radio frequency signal with a sweep bandwidth of B=4GHz. Therefore, the theoretical range resolution of the FMCW lidar is... The FMCW radio frequency signal is amplified by an RF amplifier and then loaded onto a carrier-suppressed single-sideband modulator to modulate the pump source, generating an FMCW-modulated optical signal. The FMCW-modulated optical signal is then filtered by an optical filter to remove residual carrier signals, yielding a clean FMCW sweep signal. This FMCW sweep signal is amplified by an erbium-doped fiber amplifier and then split into two beams by an optical 1×2 coupler. The component with 99% power is used as the FMCW sweep transmit signal, and the component with 1% power is used as the FMCW sweep reference signal. The FMCW sweep transmit signal is transmitted to the target in space via a transmit collimator. The reflected signal is then coupled into an optical 2×2 coupler via a receive collimator. The frequency-time relationship between the reflected signal and the FMCW sweep reference signal is as follows: Figure 4As shown in Figure a, the return optical signal and the FMCW sweep reference optical signal are mixed 180 degrees through an optical 2×2 coupler. After photoelectric conversion by a balanced photodetector, the mixed signal is obtained. The frequency-time relationship of the mixed signal is shown in the figure below. Figure 4 As shown in b, the relationship between the mixing signal strength and time is as follows: Figure 4 As shown in c. By extracting the frequency of the mixing signal within the half-cycle interval of the FMCW sweep frequency, the distance and velocity of the target under test can be calculated.

[0057] The mixed signal, amplified by the RF amplifier, passes through an electro-optic phase modulator to generate sidebands. The positive and negative first-order sidebands and the carrier wave are selected as the effective sidebands and injected into the optical frequency shifter loop via an optical 2×2 coupler. The optical signal entering the optical frequency shifter loop then passes through an acousto-optic frequency shifter, where its frequency is shifted. The acousto-optic frequency shifter is driven by a sinusoidal signal with a frequency of 80.82MHz generated by a function generator, amplified by an RF amplifier. A polarization controller, erbium-doped fiber amplifier, optical isolator, and single-mode fiber are inserted into the loop to control the polarization state within the loop, compensate for loop transmission loss, ensure unidirectional transmission of the optical signal within the loop, and adjust the loop delay, respectively. Each time the optical signal propagates through the loop, it generates [a certain amount of time / delay]. Spectrum shift and The delay. The number of loops the optical signal travels through within the loop is determined by the bandpass optical filter within the loop, and the frequency shift can be adjusted by flexibly adjusting the bandpass bandwidth.

[0058] Figure 5 a shows the relationship between the spectrum of the modulated optical signal and time, during the rising half-cycle of the FMCW sweep period ( The frequency of the mixing signal is Therefore, the frequency difference between the modulation sideband and the carrier is During the half-cycle of the FMCW sweep frequency period ( The frequency of the mixing signal is Therefore, the frequency difference between the modulation sideband and the carrier is . Figure 5 b shows the time-domain pulse signal waveform output by the optical frequency shift loop: at t=0, the frequency is The modulated optical signal begins to enter the loop. At this time, the loop mainly contains the residual signal from the previous half-cycle. As the modulation frequency in the current half-cycle increases... The signal is continuously injected into the loop, and the output time-domain pulse is gradually established. After the establishment time... Then, the time interval between the modulation sideband and the corresponding carrier pulse is: ,like Figure 5 As shown in c; at t=T / 2, the frequency is The modulated optical signal begins to enter the loop, at which point the loop mainly contains... The residual signal, with the modulation frequency in the current half-cycle being The signal is continuously injected into the loop, and the output time-domain pulse is gradually established. After the establishment time... Then, the time interval between the modulation sideband and the corresponding carrier pulse is: ,like Figure 5 As shown in d.

[0059] To match the parameters of the FMCW lidar, the optical Fourier transform settling time of the optical frequency shifting loop is matched with the half-cycle of the FMCW frequency sweep, i.e. =T / 2=12.5us. This gives the number of frequency shifts. The corresponding optical frequency shift bandwidth is Therefore, the bandwidth of the optical bandpass filter within the optical frequency shift loop is set to 4.5 GHz. Under these parameters, the frequency resolution of the optical Fourier transform in the optical frequency shift loop is... The corresponding FMCW ranging solution distance resolution is This matches the theoretical range resolution of the FMCW lidar. The frequency calculation range of the optical Fourier transform is... The corresponding FMCW ranging range is approximately 2.1m. To achieve a longer ranging range, optimization can be achieved by reducing the delay within the loop.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency-modulated continuous wave lidar target information optical domain solution system, characterized in that, include: The signal generation unit is used to generate a mixed signal containing target distance and velocity information; An optical loading unit is used to load the mixing signal onto a first optical carrier to obtain a modulated optical signal; An optical frequency shifting loop is used to perform fixed frequency shifting and fixed time delay on the modulated optical signal to obtain an optical pulse sequence; The signal processing unit is used to detect the time interval between the carrier and the sideband in the optical pulse sequence, and to calculate the target distance and speed based on the fixed frequency, the fixed duration and the time interval.

2. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 1, characterized in that, The signal generation unit includes: The laser signal generation module is used to generate the FMCW sweep frequency transmitted optical signal and the FMCW sweep reference optical signal; The free-space transceiver module is used to transmit the FMCW swept-frequency transmitted optical signal to the target under test and to receive the reflected optical signal from the target under test. The heterodyne detection receiving module is used to perform heterodyne mixing between the returned optical signal and the FMCW sweep frequency reference optical signal to obtain the mixed signal.

3. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 2, characterized in that, The laser signal generating module includes: Pump light source, used to generate the second optical carrier; A linear sweep frequency modulation unit is used to frequency modulate the sidebands of the second optical carrier to obtain an FMCW sweep frequency signal; An optical beam splitter is used to split the FMCW sweep signal into the FMCW sweep transmit optical signal and the FMCW sweep reference optical signal.

4. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 1, characterized in that, The optical loading unit includes: A pump light source is used to generate the first optical carrier; An electro-optic modulator is used to modulate the mixing signal onto the first optical carrier to obtain the modulated optical signal.

5. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 4, characterized in that, The optical loading unit further includes: A radio frequency amplifier is used to amplify the mixed signal; The electro-optic modulator is used to modulate the amplified mixing signal onto the first optical carrier.

6. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 1, characterized in that, The optical frequency shifting loop includes, in sequence, the following components along the optical path: An optical 2×2 coupler is used to couple the modulated optical signal into the optical frequency shifting loop, and to couple the frequency-shifted and delayed optical signal into the signal processing unit; The frequency shift module is used to shift the modulated optical signal at a fixed frequency. An optical filter is used to control the optical frequency shift bandwidth of the modulated optical signal within the optical frequency shift loop and to control the number of rotations of the modulated optical signal within the optical frequency shift loop. An optical isolator is used to control the unidirectional transmission of the modulated optical signal; An optical delay line is used to delay the modulated optical signal for a fixed duration.

7. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 6, characterized in that, The optical frequency shifting loop also includes: A polarization controller is used to stabilize the polarization state of the modulated optical signal.

8. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 6, characterized in that, The optical frequency shifting loop also includes: An optical amplifier is used to compensate for the transmission loss and coupling loss of the modulated optical signal.

9. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 6, characterized in that, The optical frequency shifting loop and the signal generation unit satisfy the following: ； For the fixed duration, The optical frequency shift bandwidth, For the fixed frequency, The frequency sweep period of the signal generation unit is denoted as .

10. The frequency-modulated continuous wave lidar target information optical domain solution system according to claim 1, characterized in that, The signal processing unit includes: A photodetector is used to perform photoelectric conversion on the optical pulse sequence to obtain a time-domain pulse signal; An electrical ADC sampling module is used to sample the time-domain pulse signal; An electrical signal processing module is used to detect the time interval between the carrier and the sideband in the sampled time-domain pulse signal, and to calculate the target distance and speed based on the fixed frequency, the fixed duration and the time interval.

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