Coherent calibration apparatus, detection apparatus, and terminal device

Abstract

A coherent calibration apparatus, a detection apparatus, and a terminal device, which relate to the technical field of detection, and are used for realizing coherence of dual-light-source frequency modulation. The coherent calibration apparatus comprises a first calibration path, a second calibration path, and a first phase-locked loop, wherein the first phase-locked loop is configured to acquire a first intermediate-frequency signal from the first calibration path and a second intermediate-frequency signal from the second calibration path, and output a first feedback signal to a light source module in the second calibration path; the first feedback signal is configured to calibrate a second frequency-modulated optical signal output by the light source module in the second calibration path, such that the second frequency-modulated optical signal and a first frequency-modulated optical signal output by a light source module in the first calibration path have opposite frequency modulation slopes and a constant phase difference; and the first frequency-modulated optical signal and the second frequency-modulated optical signal are configured to jointly detect a target. The solution enables frequency-modulated optical signals output by two light source modules to have consistent frequency modulation slopes, opposite modulation directions, and a locked phase difference, thereby improving the accuracy of velocity measurement and ranging.

Description

A coherent calibration device, detection device and terminal equipment Technical Field

[0001] This application relates to the field of detection technology, and in particular to a coherent calibration device, a detection device, and a terminal device. Background Technology

[0002] Frequency-modulated continuous wave (FMCW) lidar (light detection and ranging) is currently a mainstream type of LiDAR, which uses changes in the frequency of the laser emission source to detect distance and velocity. To obtain more accurate distance and velocity information, FMCW LiDAR can employ a dual-source FMCW architecture. The frequency modulation mode of the beams emitted by the two sources is shown in Figure 1a. Ideally, the frequency modulation periods of the beams emitted by the two sources are the same, the modulation directions are opposite, the absolute values ​​of the slopes are identical, and the start time, inflection point, and end time are completely identical.

[0003] However, during frequency modulation, due to the influence of the internal physical mechanisms of the laser (such as imperfections in manufacturing processes and thermal effects), the modulation slopes of the two light sources may become misaligned, as shown in Figure 1b. This phenomenon affects the measurement accuracy of FMCW LiDAR, therefore, the frequency modulation process of the two light sources needs to be calibrated. However, current mainstream calibration schemes can only achieve approximate consistency in the modulation slopes of the two light sources, but cannot maintain consistency in the start time, inflection point, and end time. In other words, they cannot achieve coherence in the frequency modulation of the two light sources. This results in poor performance of the phase noise compensation algorithm for dual-light source FMCW LiDAR, reduced modulation bandwidth, and decreased accuracy in velocity and distance measurement.

[0004] In summary, how to achieve coherence in frequency modulation of dual light sources is a technical problem that urgently needs to be solved in the field of dual-light source FMCW LiDAR.

[0005] Summary of the Invention

[0006] This application provides a coherent calibration device, a detection device, and a terminal device for achieving coherence of dual-source frequency modulation.

[0007] In a first aspect, this application provides a coherent calibration device, including a first calibration path, a second calibration path, and a first phase-locked loop (PLL). Each calibration path includes a light source module, a delay-frequency discrimination optical path, and a photodetector. The light source module in each calibration path outputs a frequency-modulated (FM) optical signal, which is converted into an intermediate frequency (IF) signal after passing through the delay-frequency discrimination optical path and the photodetector in each calibration path. The first PLL is used to acquire the first IF signal output by the photodetector in the first calibration path and the second IF signal output by the photodetector in the second calibration path, and outputs a first feedback signal to the light source module in the second calibration path. The first feedback signal is used to calibrate the second FM optical signal output by the light source module in the second calibration path, so that the second FM optical signal and the first FM optical signal output by the light source module in the first calibration path have opposite modulation slopes and a constant phase difference. The first FM optical signal and the second FM optical signal are used to jointly detect a target.

[0008] Based on the coherent calibration device described above, two intermediate frequency (IF) signals generated after the frequency-modulated (FM) optical signals output from two light source modules pass through a delayed frequency discrimination optical path and a photodetector can be used to modulate the FM optical signal output from one of the light source modules. This allows the modulation slope and phase of the FM optical signal output from the first light source module to track the modulation slope and phase of the FM optical signal output from the second light source module. This achieves consistent modulation slopes, opposite modulation directions, and phase difference locking between the FM optical signals output from the two light source modules, thus realizing the coherence of the frequency modulation of the two light source modules. The two coherent FM optical signals will have opposite phase noise. The two IF signals obtained by jointly detecting the target using the two FM optical signals will also have opposite phase noise. The phase noise of these two IF signals can cancel each other out, thereby optimizing the benefits of the phase noise compensation algorithm, increasing the usable modulation bandwidth, and improving the accuracy of speed and distance measurement.

[0009] In one possible design, the frequency-modulated optical signal output by the light source module in each calibration path is split into a local oscillator signal, a signal to be delayed, and a detection signal. The detection signal is used to detect the target. The signal to be delayed is processed by the delay-discrimination optical path in each calibration path and mixed with the local oscillator signal to obtain an intermediate frequency signal. The intermediate frequency signal is detected and output by the photodetector in each calibration path. The detection signal in the first calibration path and the detection signal in the second calibration path are used to merge and detect the target.

[0010] Based on the above design, the frequency-modulated light signal output by the light source module can be split into the detection path and the calibration path. The light signal split into the calibration path can be used to calibrate the frequency-modulated light signal output by the light source module. The calibrated frequency-modulated light signal is then split into a detection signal to more accurately detect the target and improve the detection effect.

[0011] In one possible design, the coherent calibration device further includes a third calibration path and a second phase-locked loop. The second phase-locked loop is used to acquire the second intermediate frequency signal output by the photodetector in the second calibration path and the third intermediate frequency signal output by the photodetector in the third calibration path, and outputs a second feedback signal to the light source module in the third calibration path. The second feedback signal is used to calibrate the third frequency-modulated optical signal output by the light source module in the third calibration path, so that the third frequency-modulated optical signal and the second frequency-modulated optical signal have opposite frequency modulation slopes and a constant phase difference.

[0012] Based on the above design, the frequency modulation slopes of the two frequency-modulated optical signals in the third calibration path and the second calibration path can be opposite and the phase difference locked. That is, the frequency modulation slopes of the two frequency-modulated optical signals in the third calibration path and the first calibration path can be the same and the phase difference locked. In this way, the in-phase modulation of the two light sources in the third calibration path and the first calibration path can be achieved, which can meet the needs of multi-light source detection scenarios that require in-phase modulation and improve the flexibility and versatility of light source modulation.

[0013] In a further possible design, the coherent calibration device also includes a fourth calibration path and a third phase-locked loop (PLL). The third PLL is used to acquire the first intermediate frequency (IF) signal output by the photodetector in the first calibration path and the fourth IF signal output by the photodetector in the fourth calibration path, and outputs a third feedback signal to the light source module in the fourth calibration path. The third feedback signal is used to calibrate the fourth frequency-modulated (FM) optical signal output by the light source module in the fourth calibration path, so that the fourth FM optical signal and the first FM optical signal have opposite modulation slopes and a constant phase difference. The first FM optical signal, the second FM optical signal, the third FM optical signal, and the fourth FM optical signal are used to jointly detect the target. The first FM optical signal and the second FM optical signal correspond to one detection channel, and the third FM optical signal and the fourth FM optical signal correspond to another detection channel.

[0014] Based on the above design, four frequency-modulated optical signals output from four light sources can be used to jointly detect the target on two detection channels. In this way, the coherent calibration device can obtain the detection range of both detection channels with each detection, increasing the detection range and improving detection efficiency. Furthermore, since the two frequency-modulated optical signals in each detection channel are inversely modulated, the phase noise in the intermediate frequency signals obtained from the two frequency-modulated optical signals on each detection channel can cancel each other out, resulting in good velocity and distance measurement accuracy for each detection channel.

[0015] In one possible design, the first phase-locked loop includes a frequency and phase detector and a low-pass filter. The frequency and phase detector is used to determine the error signal between the first intermediate frequency signal and the second intermediate frequency signal based on the complex form of the first intermediate frequency signal and the second intermediate frequency signal. The low-pass filter is used to determine a first feedback signal based on the error signal. The first feedback signal is positively correlated with the error signal.

[0016] Based on the above design, the phase difference information of the two intermediate frequency signals can be obtained by using the complex form of the two intermediate frequency signals, thereby achieving phase locking of the two intermediate frequency signals and realizing the coherence of frequency modulation of the two light sources corresponding to the two intermediate frequency signals.

[0017] In further possible designs, the error signal satisfies the following condition: The first feedback signal satisfies the following condition: P ∝ -(k1τ1+k2τ2)t+Δφ1(t)+Δφ2(t). Among them, S err Let P be the error signal, R1 and R2 be the responsivity of the photodetectors in the first and second calibration paths, E1 and E2 be the light field intensities of the first and second frequency-modulated optical signals, k1 and k2 be the frequency modulation slopes of the first and second frequency-modulated optical signals, τ1 and τ2 be the delay durations of the delay-discriminator optical paths in the first and second calibration paths, and t be the detection time. These are the phase noises generated by the first and second frequency-modulated optical signals after passing through the delayed frequency-discriminating optical path, respectively.

[0018] Based on the above design, the implementation forms of the error signal and the first feedback signal are given. The first feedback signal is positively correlated with the error signal. More specifically, it is positively correlated with the sum of the frequency modulation slopes k1+k2 of the two frequency-modulated optical signals and the sum of the phase noise. They are positively correlated; under phase-locked loop (PLL) conditions, the sum of the frequency modulation slopes k1+k2 and the sum of the phase noise are... Both are 0. The former can achieve opposite frequency modulation slopes for two frequency-modulated optical signals, while the latter can achieve opposite sums of phase noise for two frequency-modulated optical signals, which is phase difference locking, and can accurately achieve phase locking for two frequency-modulated optical signals.

[0019] In a further possible design, the phase detector includes a first phase detector and a second phase detector, and the low-pass filter includes a first filter and a second filter. In this case, the first phase-locked loop also includes an adder. When the first phase-locked loop is operating, the first phase detector calculates the error signal of the in-phase component based on the in-phase components of the first and second intermediate frequency (IF) signals. The first filter determines the in-phase feedback signal based on the error signal of the in-phase component, which is positively correlated with the error signal of the in-phase component. The second phase detector calculates the error signal of the quadrature component based on the quadrature components of the first and second IF signals. The second filter determines the quadrature feedback signal based on the error signal of the quadrature component, which is positively correlated with the error signal of the quadrature component. The adder superimposes the in-phase feedback signal and the quadrature feedback signal to obtain the first feedback signal.

[0020] Based on the above design, the first phase-locked loop can be designed as an analog phase-locked loop. The analog phase-locked loop includes two sets of phase detectors and filters. The two sets of phase detectors and filters calculate the error signal and feedback signal for the in-phase part and quadrature component of the intermediate frequency signal, respectively. Then, they are superimposed by an adder, which can reduce the calculation difficulty of directly using the complex form of the intermediate frequency signal and improve the phase-locking efficiency.

[0021] In one possible design, in any calibration path, the complex form of the intermediate frequency signal can be obtained through various structures, such as:

[0022] Structure 1: The delay-discriminating optical path in the calibration circuit includes a beam splitter, an optical delay line, and a 90° optical mixer. The calibration circuit also includes processing components. During operation, the beam splitter splits the frequency-modulated optical signal output from the light source module to obtain the signal to be delayed and the local oscillator signal. The local oscillator signal is output to the 90° optical mixer, and the signal to be delayed is output to the optical delay line. The optical delay line delays the signal to be delayed to obtain the delayed signal, which is then output to the 90° optical mixer. The 90° optical mixer is used to... The delayed signal and the local oscillator signal are mixed to obtain mixed signals with phases of 0°, 90°, 180°, and 270°. A photodetector is used to determine the in-phase component of the intermediate frequency (IF) signal based on the mixed signals with phases of 0° and 180°, and the quadrature component based on the mixed signals with phases of 90° and 270°. The in-phase and quadrature components of the IF signal are then output to the processing element. The processing element generates a complex form of the IF signal based on the in-phase and quadrature components and sends it to the first phase-locked loop. Structure 1 utilizes a 90° optical mixer to separate the in-phase and quadrature components of the IF signal, thereby obtaining the complex form of the IF signal. This structure is simple and has a low cost.

[0023] Structure 2: The delay-frequency discriminator optical path in the calibration circuit includes a beam splitter and an optical delay line. The calibration circuit also includes a power divider, a 90° phase shifter, and processing components. During operation, the beam splitter splits the frequency-modulated optical signal output from the light source module to obtain the signal to be delayed and the local oscillator signal. The local oscillator signal is output to the photodetector, and the signal to be delayed is output to the optical delay line. The optical delay line delays the signal to be delayed to obtain the delayed signal, and then outputs the delayed signal to the photodetector. The photodetector... The first structure uses a photodetector to generate a real-valued intermediate frequency (IF) signal based on the delayed signal and the local oscillator signal. The power divider splits the real-valued IF signal to obtain the in-phase component and the signal to be phase-shifted. It outputs the in-phase component to the processing element and the signal to be phase-shifted to a 90° phase shifter. The 90° phase shifter performs phase shifting on the signal to be phase-shifted to obtain the quadrature component of the IF signal. The processing element generates a complex-valued IF signal based on the in-phase and quadrature components and sends it to the first phase-locked loop. The second structure first uses a photodetector to obtain the real-valued IF signal, then uses a 90° phase shifter to convert it from real to complex form. This structure is relatively simple and has a lower cost.

[0024] In further possible designs, the photodetector is a detector array, or includes one or more balanced photodiodes (BPDs). Based on this, the coherent calibration device can support a variety of photodetectors, offering good flexibility and versatility.

[0025] In further possible designs, the optical delay line can be a fiber optic delay line or an on-chip waveguide delay line. Based on this, the coherent calibration device can support various optical delay lines, offering good flexibility and versatility.

[0026] In a further possible design, when the optical delay line is an on-chip waveguide delay line, the optical delay line and other components (such as a 90° optical mixer) can be integrated on the same waveguide to improve the integration of the coherent calibration device.

[0027] In a further possible design, the first calibration path and the second calibration path share the same optical delay line. For example, the coherent calibration device may also include a beam combiner and a beam splitter. The signals to be delayed in the two calibration paths are combined into one beam by the beam combiner and then input into the same optical delay line for delay processing. The delayed signals are then split into the corresponding delayed signals for the two calibration paths by the beam splitter and output to their respective subsequent components.

[0028] Based on the above design, the number of optical delay lines required in the coherent calibration device can be reduced, the space occupied by the optical delay lines can be reduced, the hardware cost can be reduced, and the coherent calibration device can be designed in a very simple way.

[0029] In one possible design, the first calibration path further includes a first processing element, which is used to acquire the first intermediate frequency signal output by the photodetector in the first calibration path and output a first pre-distortion signal to the light source module in the first calibration path. The first pre-distortion signal is used to drive the light source module in the first calibration path to output a first frequency-modulated light signal whose frequency changes linearly with time.

[0030] Based on the above design, the first pre-distortion signal can drive the light source module in the first calibration path to output a first frequency-modulated optical signal whose frequency and time follow a linear variation law. After the first frequency-modulated optical signal is split into a detection signal, it is used for target measurement, which can improve the detection accuracy of target measurement. At the same time, the first frequency-modulated signal can also be used as a reference to calibrate the second frequency-modulated optical signal output by the light source module in the second calibration path, so that the frequency and time of the second frequency-modulated optical signal also follow a linear variation law.

[0031] In a further possible design, the light source module in the first calibration path includes a first signal generator and a first light source. The first signal generator is connected between the first processing element and the first light source. The first signal generator is used to acquire a first pre-distortion signal output by the first processing element and output a first modulation signal to the first light source. The first pre-distortion signal is used to calibrate the linearity between the first modulation signal output by the first signal generator and the first frequency-modulated optical signal output by the first light source.

[0032] Based on the above design, a signal generator can be used to drive the light source to output a frequency-modulated light signal that conforms to a set rule, such as a triangular wave signal whose frequency changes linearly with time, in order to meet the needs of practical application scenarios.

[0033] In one possible design, the light source module in the second calibration path includes a second signal generator and a second light source. The second signal generator is used to acquire a first feedback signal and output a second modulation signal to the second light source. The second modulation signal is used to calibrate the coherence between the second frequency-modulated optical signal output by the second light source and the first frequency-modulated optical signal output by the first light source.

[0034] Based on the above design, pre-distortion processing can be performed only on the frequency-modulated optical signal in the first calibration path, while the frequency-modulated optical signal in the second calibration path is not subject to pre-distortion processing. This reduces the number of components in the coherent calibration device and simplifies the structural design. Because pre-distortion processing is performed in the first calibration path, the frequency-modulated optical signal in the second calibration path has an opposite modulation slope to that in the first calibration path. Therefore, the frequency-modulated optical signal in the second calibration path can also maintain a basically linear relationship between frequency and time.

[0035] In one possible design, the second calibration path further includes a second processing element. The second processing element is used to determine a second predistortion signal based on the second intermediate frequency signal output by the photodetector in the second calibration path, superimpose the second predistortion signal with the first feedback signal output by the first phase-locked loop, and send the superimposed signal to the light source module in the second calibration path. The superimposed signal is used to drive the light source module in the second calibration path to output a second frequency-modulated optical signal. The frequency of the second frequency-modulated optical signal changes linearly with time and has an opposite frequency modulation slope and a constant phase difference to the first frequency-modulated optical signal.

[0036] Based on the above design, the second predistortion signal can drive the light source module in the second calibration path to output a second frequency-modulated optical signal whose frequency and time change linearly. The first feedback signal can ensure that the second frequency-modulated optical signal and the first frequency-modulated optical signal have opposite modulation slopes and phase difference lock. Therefore, the superposition of the second predistortion signal and the first feedback signal can achieve frequency modulation coherence of the two light sources while ensuring that the phase-locked light source outputs a frequency-modulated optical signal whose modulation frequency and time change linearly.

[0037] In a further possible design, the light source module in the second calibration path includes a second signal generator and a second light source. The second signal generator is used to acquire the superimposed signal output by the second processing element and output a second modulation signal to the second light source. The second modulation signal is used to calibrate the linearity between the second modulation signal output by the second signal generator and the second frequency-modulated optical signal output by the second light source, as well as to calibrate the opposite frequency modulation slope and constant phase difference between the second frequency-modulated optical signal output by the second light source and the first frequency-modulated optical signal output by the first light source.

[0038] Based on the above design, a signal generator can be used to drive the light source to output a second frequency-modulated optical signal that conforms to a set rule, such as a triangular wave signal whose frequency changes linearly with time and follows the opposite direction of the first frequency-modulated optical signal, in order to meet the needs of practical application scenarios.

[0039] In one possible design, the first phase-locked loop is either a digital phase-locked loop or an analog phase-locked loop.

[0040] Based on the above design, it can support various phase-locked loop structural designs, improving the versatility of coherent calibration devices.

[0041] Secondly, this application provides a coherent calibration method applicable to a coherent calibration device, and more specifically, applicable to the first phase-locked loop in the coherent calibration device provided in the first aspect above. The method includes the following steps: acquiring a first intermediate frequency (IF) signal and a second IF signal, and determining a first feedback signal based on the first IF signal and the second IF signal; wherein the first IF signal is an IF signal generated after the first frequency-modulated optical signal output by the light source module in the first calibration path passes through the delay frequency discrimination optical path and the photodetector in the first calibration path, and the second IF signal is an IF signal generated after the first frequency-modulated optical signal output by the light source module in the second calibration path passes through the delay frequency discrimination optical path and the photodetector in the second calibration path, and the first feedback signal is used to calibrate the second frequency-modulated optical signal so that the frequency modulation slope of the second frequency-modulated optical signal is opposite to that of the first frequency-modulated optical signal and the phase difference is constant.

[0042] In one possible design, the method further includes: acquiring a first echo signal and a second echo signal, and measuring the distance and / or velocity of a target in the detection space based on the first echo signal and the second echo signal, wherein the first echo signal is the echo signal obtained by detecting a target after the detection signal of the first frequency-modulated light signal emitted by the light source module in the first calibration path is split, and the second echo signal is the echo signal obtained by detecting a target after the detection signal of the second frequency-modulated light signal emitted by the light source module in the second calibration path is split.

[0043] Based on the above design, the detection signals after the frequency-modulated optical signals in the two calibration paths are split can be used to jointly detect the target. Since the frequency modulation slopes of the two frequency-modulated optical signals are opposite and the phase difference is constant, the echo signals corresponding to the two frequency-modulated optical signals have opposite phase noise. The phase noise of the two echo signals after merging cancels each other out, resulting in high accuracy of speed measurement and / or distance measurement.

[0044] In one possible design, the method further includes: acquiring a third intermediate frequency signal and determining a second feedback signal based on the second and third intermediate frequency signals, wherein the third intermediate frequency signal is the intermediate frequency signal generated after the third frequency-modulated optical signal emitted by the light source module in the third calibration path passes through the delayed frequency discrimination optical path and photodetector in the third calibration path, and the second feedback signal is used to calibrate the third frequency-modulated optical signal so that the frequency modulation slope of the third frequency-modulated optical signal is opposite to that of the second frequency-modulated optical signal and the phase difference is constant.

[0045] Based on the above design, the second calibration path can be phase-locked onto the first calibration path, and the third calibration path can be phase-locked onto the second calibration path. Through two phase-locking operations, the effect of in-phase modulation of the two light sources in the third calibration path and the first calibration path can be achieved.

[0046] In a further possible design, the method further includes: acquiring a fourth intermediate frequency (IF) signal, and determining a third feedback signal based on the first IF signal and the fourth IF signal. The fourth IF signal is the IF signal generated after the fourth frequency-modulated optical signal emitted by the light source module in the fourth calibration path passes through the delayed frequency discrimination optical path and photodetector in the fourth calibration path. The third feedback signal is used to calibrate the fourth IF signal so that the modulation slope of the fourth IF signal is opposite to that of the first IF signal and the phase difference is constant. The detection signals after the first, second, third, and fourth IF signals are split are used to jointly detect the target. The two detection signals after the first and second IF signals are split correspond to one detection channel, and the two detection signals after the third and fourth IF signals are split correspond to another detection channel.

[0047] In one possible design, the first feedback signal is determined based on the first intermediate frequency signal and the second intermediate frequency signal. Specifically, this can be achieved by determining the error signal between the first and second intermediate frequency signals based on their complex forms, extracting the phase information from the error signal, and determining the first feedback signal based on the phase signal. The first feedback signal is positively correlated with the phase information.

[0048] In further possible designs, the error signal satisfies the following condition: The first feedback signal satisfies the following condition: P ∝- (k1τ1+k2τ2)t+Δφ1(t)+Δφ2(t). Among them, S err Let P be the error signal, R1 and R2 be the responsivity of the photodetectors in the first and second calibration paths, E1 and E2 be the light field intensities of the first and second frequency-modulated optical signals, k1 and k2 be the frequency modulation slopes of the first and second frequency-modulated optical signals, τ1 and τ2 be the delay durations of the delay-discriminator optical paths in the first and second calibration paths, and t be the detection time. These are the phase noises generated by the first and second frequency-modulated optical signals after passing through the delayed frequency-discriminating optical path, respectively.

[0049] In one possible design, the method further includes: determining a first predistortion signal based on a first intermediate frequency signal using a predistortion algorithm, the first predistortion signal being used to drive the light source module in the first calibration path to output a first frequency-modulated optical signal whose frequency varies linearly with time.

[0050] In one possible design, the method further includes: determining a second predistortion signal using a predistortion algorithm based on the second intermediate frequency signal; obtaining a superimposed signal based on the second predistortion signal and the first feedback signal; the superimposed signal is used to drive the light source module in the second calibration path to output a second frequency-modulated optical signal whose frequency changes linearly with time and whose frequency modulation slope is opposite to that of the first frequency-modulated optical signal and whose phase difference is constant.

[0051] Thirdly, this application provides a coherent calibration apparatus, including units and / or modules for implementing the coherent calibration method in any of the designs in the second aspect above. For example, in one example, it includes an acquisition unit and a determination unit. The acquisition unit is used to acquire a first intermediate frequency (IF) signal and a second IF signal, and the determination unit is used to determine a first feedback signal based on the first IF signal and the second IF signal. The first IF signal is an IF signal generated after the first frequency-modulated optical signal output from the light source module in the first calibration path passes through the delayed frequency discrimination optical path and the photodetector in the first calibration path. The second IF signal is an IF signal generated after the first frequency-modulated optical signal output from the light source module in the second calibration path passes through the delayed frequency discrimination optical path and the photodetector in the second calibration path. The first feedback signal is used to calibrate the second frequency-modulated optical signal, such that the second frequency-modulated optical signal has an opposite modulation slope to the first frequency-modulated optical signal and a constant phase difference.

[0052] Fourthly, this application provides a coherent calibration apparatus, including a processor coupled to a memory, the processor being configured to execute a computer program or instructions stored in the memory, such that the coherent calibration apparatus performs a coherent calibration method as described in the second aspect above or any of the designs in the second aspect above.

[0053] Fifthly, this application provides a detection device, including the coherent calibration device in the first aspect or any of the designs in the first aspect, or including the coherent calibration device in the third or fourth aspect.

[0054] In one possible design, the detection device can be a device or system with multiple frequency-modulated continuous wave light sources, such as FMCW LiDAR, or optical frequency domain reflectometry (OFDR) systems, optical coherence tomography (OCT) systems, etc.

[0055] In a sixth aspect, this application provides a terminal device that includes the coherent calibration device in the first aspect or any of the designs in the first aspect, or includes the coherent calibration device in the third or fourth aspect, or includes the detection device in the fifth aspect.

[0056] The technical effects that can be achieved in the second to sixth aspects mentioned above can be referred to the description of the beneficial effects in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0057] Figure 1a illustrates an ideal frequency modulation mode for dual-source optical signal emission.

[0058] Figure 1b illustrates an example of a practical frequency modulation mode for a dual-source emitted optical signal;

[0059] Figure 2 illustrates a possible application scenario to which this application applies;

[0060] Figure 3a illustrates an exemplary architecture diagram of a mainstream dual-source FMCW LiDAR;

[0061] Figure 3b illustrates a comparative diagram of two intermediate frequency signals generated by the currently mainstream dual-source FMCW LiDAR.

[0062] Figure 3c illustrates a schematic diagram of a dual-light source FMCW LiDAR provided in the industry.

[0063] Figure 3d illustrates an exemplary structural diagram of a reference calibration path provided in the industry.

[0064] Figure 3e illustrates, for example, a schematic diagram of the nonlinear relationship between the light emitted by a light source and the modulation signal;

[0065] Figure 3f illustrates an exemplary schematic diagram of a phase-locked structure for single-source frequency modulation provided by the industry;

[0066] Figure 3g illustrates a possible structural schematic diagram for achieving phase locking in dual-source frequency modulation;

[0067] Figure 4 illustrates a schematic diagram of the structure of a coherent calibration device provided in this application;

[0068] Figure 5 illustrates a schematic diagram of the structure of a first phase-locked loop provided in this application;

[0069] Figure 6a illustrates an exemplary implementation of a first phase-locked loop provided in this application;

[0070] Figure 6b illustrates an exemplary implementation of another first phase-locked loop provided in this application;

[0071] Figure 6c illustrates an exemplary implementation of another first phase-locked loop provided in this application;

[0072] Figure 6d illustrates an exemplary implementation of another first phase-locked loop provided in this application;

[0073] Figure 7 illustrates a schematic diagram of a calibration path provided in Implementation Method 1;

[0074] Figure 8 illustrates an exemplary structural diagram of another calibration path provided by Implementation Method 1;

[0075] Figure 9a illustrates a schematic diagram of another calibration path provided by Implementation Method 1;

[0076] Figure 9b exemplarily illustrates a structural schematic diagram of another calibration path provided by Implementation Method 1;

[0077] Figure 10 illustrates a schematic diagram of a calibration path provided in implementation method two;

[0078] Figure 11 illustrates an exemplary structural diagram of another calibration path provided by implementation method two;

[0079] Figure 12a illustrates a schematic diagram of a coherent calibration device provided in Embodiment 1;

[0080] Figure 12b illustrates a waveform diagram of a triangular wave linear frequency modulation provided in Implementation Scheme 1;

[0081] Figure 13 illustrates a schematic diagram of another coherent calibration device provided in Implementation Scheme 1.

[0082] Figure 14 illustrates a schematic diagram of a coherent calibration device provided in Embodiment 2;

[0083] Figure 15 illustrates a schematic diagram of a coherent calibration device provided in Embodiment 3;

[0084] Figure 16a illustrates a schematic diagram of a coherent calibration device provided in Embodiment 4;

[0085] Figure 16b illustrates, by way of example, a waveform diagram of a triangular wave linear frequency modulation provided in Implementation Scheme 4;

[0086] Figure 17a illustrates an exemplary application architecture diagram of a coherent calibration device provided in this application in an FMCW LiDAR;

[0087] Figure 17b exemplarily illustrates a comparison diagram of intermediate frequency signals using and without a coherent calibration device provided in this application;

[0088] Figure 18 illustrates a schematic flowchart of a coherent calibration method provided in this application;

[0089] Figure 19 illustrates a schematic diagram of the structure of a coherent calibration device provided in this application;

[0090] Figure 20 illustrates a schematic diagram of another coherent calibration device provided in this application;

[0091] Figure 21 illustrates a schematic diagram of the structure of a detection device provided in this application;

[0092] Figure 22 illustrates a schematic diagram of the structure of a terminal device provided in this application. Detailed Implementation

[0093] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0094] The following provides explanations for some of the terms used in this application. It should be noted that these explanations are for the convenience of those skilled in the art and do not constitute a limitation on the scope of protection claimed in this application.

[0095] I. Complex signals.

[0096] Complex signals are signals represented in complex form. An exponential signal can typically be represented in complex form as shown in formula (1.1): e x =cos(x)+jsin(x)……(1.1)

[0097] Among them, e x Let cos(x) + j sin(x) be the real form of the exponential signal, and let cos(x) + j sin(x) be the complex form of the exponential signal; cos(x) is the real part of the complex form, also known as the in-phase component; sin(x) is the imaginary part of the complex form, also known as the quadrature component; j is the imaginary unit. 2 =-1.

[0098] II. Light Field

[0099] The light field refers to the amount of light passing through each point in every direction. For a light source, including but not limited to point light sources, line light sources, area light sources, or array light sources, its light field signal (referred to as the light signal) can be expressed as the following formula (1.2):

[0100] Where R is the optical signal, j is the imaginary unit, w is the instantaneous frequency of the optical signal, and t is the emission time. Let be the phase noise of the optical signal at time t.

[0101] III. Coherence

[0102] Also known as coherent, it refers to a signal with continuous phase and constant phase difference, such as a phase difference of 0 or an unchanged phase difference.

[0103] IV. Responsivity of Photodetectors

[0104] Also known as the sensitivity of a photodetector, it can be expressed as the ratio of the output signal voltage of the photodetector to the incident light power. The larger the output signal voltage and the smaller the incident light power, the greater the responsivity of the photodetector, the more sensitive the photodetector is to small signal changes, and the higher the detection accuracy.

[0105] V. Frequency mixing.

[0106] Frequency mixing, also known as coherent demodulation, refers to the difference between the frequencies and phases of two signals. In FMCW LiDAR, the probe signal is typically a linear frequency modulated (LFM) signal. After this LFM signal interacts with the target object, the reflected echo signal (i.e., the received signal) will also have the same frequency variation characteristics. However, depending on the distance to the target, the echo signal will have a certain phase and frequency difference relative to the probe signal. Therefore, after receiving the echo signal, the echo signal and the probe signal can be mixed, that is, the frequency and phase of the probe signal and the echo signal are differed to obtain a low-frequency beat signal, also known as a beat frequency signal or intermediate frequency signal. The beat frequency signal contains information about the frequency difference between the two signals, which is proportional to the target distance. It also contains information about the Doppler effect caused by the target's movement, based on which the target's velocity can be calculated.

[0107] The preceding text introduced some of the terms used in this application. The following text introduces the possible application scenarios of this application.

[0108] In one possible implementation, the coherent calibration device provided in this application can be integrated into a detection device, which can be installed on a vehicle, including but not limited to: vehicles, ships, airplanes, drones, trains, subways, automated guided vehicles (AGVs), or unmanned vehicles. For example, please refer to Figure 2, which illustrates a possible application scenario of this application. In this scenario, the detection device is installed on the front bumper of a vehicle. This detection device can serve as an information source for path planning, assisting the driver in achieving or automatically achieving safe driving. It is understood that the detection device can also be installed in other locations on the vehicle, such as around the headlights, around the rearview mirrors, near the doors, on the rear bumper, behind the windshield, or on the roof, to capture information about the vehicle's surrounding environment. When the detection device is installed behind the windshield, the requirement for no gravel collision risk is lower, and it does not affect the vehicle's appearance. Furthermore, the windshield itself has window heating and defogging functions as well as wiper cleaning functions.

[0109] It should be understood that the above application scenarios are merely examples, and the detection device provided in this application can also be applied to other possible scenarios, not limited to those listed above. For example, the detection device can also be installed in a roadside unit (RSU) as a roadside traffic detection device to realize intelligent vehicle-road cooperative communication. For example, the detection device can also be installed in the cabin of a vehicle as a liveness detection device to detect and alert the user to children or pets left behind in the cabin. Furthermore, the detection device can also be applied to terminal devices or components of terminal devices, such as smartphones, smart home devices, smart manufacturing equipment, medical devices, industrial equipment, and robots. These will not be listed exhaustively here. Moreover, the detection device can also be applied to…

[0110] It should be noted that the application scenarios described in this application are for the purpose of more clearly illustrating the technical solutions of this application, and do not constitute a limitation on the technical solutions provided in this application.

[0111] In addition, the above-mentioned application scenarios can be applied to fields such as autonomous driving, assisted driving, intelligent driving, autonomous driving, connected vehicles, optical communication, security monitoring, biomedicine, surveying and mapping (such as 3D mapping and remote sensing mapping), meteorological research, biomass and vegetation research, air quality monitoring, and aviation and aerospace applications.

[0112] The detection devices mentioned above may include, but are not limited to, LiDAR, such as dual-source FMCW LiDAR. Before introducing the specific solution provided in this application, the relevant content of dual-source FMCW LiDAR will be introduced below.

[0113] Figure 3a shows a schematic diagram of a mainstream dual-source FMCW LiDAR architecture. This architecture includes two light sources (referred to as source 1 and source 2), two beam splitters, two circulators, two detectors, a mirror, a semi-transparent mirror, and a collimating lens. The semi-transparent mirror can also be other types of lenses, such as a polarization beam splitter (PBS), without limitation. Source 1 and source 2 are both continuously frequency modulated laser sources. Source 1 outputs a frequency-modulated optical signal R1, and source 2 outputs a frequency-modulated optical signal R2. These two frequency-modulated optical signals R1 and R2 are split by their respective beam splitters to produce the detector signal R. 13 R 23 Then, they are transmitted to the detection space via their respective circulators, one of which is the detection signal R. 13 The signal is reflected by the reflector to the semi-transparent mirror and then mixed with another detection signal R. 23The beams are combined into a single beam, then collimated by a collimating lens before being directed toward the target object. The echo signal reflected back from the target object passes through the collimating lens, then through a semi-transparent mirror, a reflecting mirror, and their respective circulators. Locally, it interferes with the calibration signal from the detector path, which has been split by its respective beam-splitting element, to obtain the intermediate frequency signal S on the detector path. 01 and S 02 Two intermediate frequency signals S 01 and S 02 After superposition, a Fourier transform is performed to complete the speed and distance measurement.

[0114] Based on the dual-source FMCW LiDAR shown in Figure 3a, the frequency-modulated optical signals R1 and R2 output from the two sources are split into a detection signal R. 13 R 23 The light path traversed during emission and reflection, as well as the effects experienced upon striking the target object's surface, are all identical. Therefore, in order to make the two intermediate frequency signals S... 01 S 02 The noise in the two light sources can cancel each other out. The frequency modulation modes of the output light signals from the two light sources can be configured as shown in Figure 1a above. That is, the frequency modulation periods of the two light sources are the same, the modulation directions are opposite, and the absolute values ​​of the slopes are identical. For example, if the frequency modulation direction of the output light signal from light source 1 is that the frequency first increases and then decreases, then the frequency modulation direction of the output light signal from light source 2 is that the frequency first decreases and then increases. The absolute values ​​of the slopes of the two changes are the same, and the starting time, inflection point time, and modulation period are all completely identical. Thus, the frequency modulations of the output light signals from light source 1 and light source 2 are completely opposite, and the resulting modulation noise is also opposite. After the two beams with opposite modulation noises are split and combined into one beam and hit the target object, the noise in the generated echo signal is also opposite. The noise in the intermediate frequency signal generated based on the echo signal with opposite noise is also opposite. After the two intermediate frequency signals are superimposed, the opposite noises cancel each other out, resulting in a good noise suppression effect.

[0115] However, as described in the background section, the frequency modulation method shown in Figure 1a represents an ideal state. Since the two light sources originate from different independent devices, their respective frequency modulation processes are also independent. Therefore, the modulation noise of the frequency-modulated optical signals R1 and R2 output by the two light sources is uncorrelated. In other words, the modulation slopes of the two frequency-modulated optical signals R1 and R2 cannot be guaranteed to be strictly consistent or phase-independent, as shown in Figure 1b. For a dual-light source FMCW LiDAR where the modulation slope cannot be guaranteed to be strictly consistent and the phase-independent, the obtained intermediate frequency signal S... 01 S 02 As shown in Figure 3b, the detection problems it brings can be summarized into the following three points:

[0116] Question 1: The absolute values ​​of the frequency modulation slopes of the two frequency-modulated optical signals R1 and R2 are inconsistent, resulting in a different detection signal R after the two frequency-modulated optical signals R1 and R2 are split. 13 R 23 The absolute values ​​of the slopes are inconsistent, which leads to the two detection signals R 13 R 23 The two intermediate frequency signals S obtained from the target detection 01 S 02 Since they cannot be aligned in frequency, two intermediate frequency signals S are superimposed. 01 S 02 The obtained detection results are inaccurate, resulting in low accuracy in ranging and velocity measurement;

[0117] Question 2: The phase difference between the frequency modulation slopes of the two frequency-modulated optical signals R1 and R2 is random, causing the two intermediate frequency signals S... 01 S 02 The phase difference is also random, resulting in poor performance of the phase noise compensation algorithm, and the superposition of two intermediate frequency signals S 01 S 02 It cannot effectively eliminate signal noise on the detection path, resulting in a low signal-to-noise ratio, large spectral broadening, reduced maximum detection performance, and decreased accuracy in speed and distance measurement.

[0118] Question 3: The start and end times and inflection points of the frequency modulation cycles of the two frequency-modulated optical signals R1 and R2 are inconsistent, resulting in a reduction in the usable modulation bandwidth within the frequency modulation cycle, a smaller region of interest (ROI), and an impact on minimum distance resolution. For example, referring to Figures 1a and 1b above, within one frequency modulation cycle, the overlapping portion of the modulation frequencies of the two light sources is the ROI. The greater the deviation in the inflection points of the modulation frequencies of the two light sources, the greater the misalignment between the two frequency modulation curves, the shorter the overlapping straight line portion of the two frequency modulation curves becomes, the fewer the usable modulation frequencies, and the smaller the ROI.

[0119] To address the aforementioned issues with dual-source FMCW LiDARs, and to achieve relatively consistent frequency modulation slopes between the two sources, as shown in Figure 3c, the industry has implemented a reference calibration path between each source and its corresponding beam splitter. For example, reference calibration path 1 is set between source 1 and its corresponding beam splitter, and reference calibration path 2 is set between source 2 and its corresponding beam splitter. The beam splitter corresponding to each source splits the frequency-modulated light signal output by the source into a detection path signal and a calibration path signal. The detection path signal is used to detect the target, while the calibration path signal enters the reference calibration path. The reference calibration path, based on predistortion technology, inputs a pre-learned driving waveform to the connected source to drive the connected source to output a beam whose frequency changes linearly with time.

[0120] For example, taking reference calibration path 1 as an example (see Figure 3d), reference calibration path 1 may include a driving circuit, a time-delayed frequency discrimination optical path, a photodetector, and processing elements. Taking linear frequency modulation as an example, the driving circuit can generate a modulation signal L1 whose frequency changes linearly with time, and input the modulation signal L1 to the light source 1. The modulation signal L1 is used to drive the light source 1 to emit a frequency-modulated optical signal R1 whose frequency changes linearly with time. The beam splitter splits the frequency-modulated optical signal R1 into a probe signal and a calibration signal. The probe signal is output to the circulator for target measurement, and the calibration signal is output to reference calibration path 1 for linear frequency modulation. The calibration path signal includes a local oscillator signal and a signal to be delayed. The local oscillator signal is output to the photodetector, while the signal to be delayed is processed by the delay frequency discrimination optical path and then enters the photodetector. After delay, the signal is mixed with the local oscillator signal to generate an intermediate frequency (IF) signal S1 on the calibration path. This IF signal S1 is detected by the photodetector and output to the processing element. The processing element calls the predistortion algorithm based on the IF signal S1 to generate a predistortion signal P1 and outputs the predistortion signal P1 to the driving circuit. This predistortion signal P1 is used to calibrate the modulation signal L1 output by the driving circuit to the light source 1, so that the frequency change of the frequency-modulated optical signal R1 emitted by the light source 1 is linear with the modulation signal L1 input to the light source 1. As shown in Figure 3e, since the frequency of the modulation signal L1 is linearly related to time, this linear relationship will be linearly reflected in the frequency of the frequency-modulated optical signal R1 output by the light source 1, so that the frequency change of the frequency-modulated optical signal R1 is also linearly related to time.

[0121] Based on the structure shown in Figure 3d, since the reference calibration path corresponding to each light source can use a predistortion algorithm to calibrate the frequency-modulated optical signal output by each light source, making the frequency of the frequency-modulated optical signal output by each light source change linearly with time, by configuring the predistortion algorithm of the two reference calibration paths, the frequency consistency of the frequency-modulated optical signals R1 and R12 output by the two light sources can be roughly achieved, that is, the absolute value of the frequency modulation slope of the two frequency-modulated optical signals R1 and R12 is roughly the same. However, since the two reference calibration paths operate independently and their phase responses are not consistent, this scheme cannot guarantee the absolute consistency of the frequency modulation start position, end position, and inflection point position of the two frequency-modulated optical signals R1 and R12. In other words, this scheme can only solve the first problem mentioned above, but cannot solve the second and third problems mentioned above. This scheme cannot achieve phase locking of dual-light source frequency modulation.

[0122] Optionally, to achieve phase locking of the frequency modulation of the light source, some schemes also input an external reference signal into the processing element of the reference calibration path, as shown in Figure 3f. Figure 3f still uses reference calibration path 1 as an example. In this case, "S1" on the left side of the processing element is the intermediate frequency signal generated after the frequency-modulated optical signal R1 emitted by the light source 1 passes through the delay frequency discrimination optical path and photodetector. "F1" on the right side is the external reference signal. Both signals enter the processing element together. The processing element is equipped with a phase-locked loop (PLL) module. The two signals are closed-loop phase-locked in the PLL module to generate a feedback signal P1. The feedback signal P1 is used to control the output modulation signal L1 of the drive circuit. This modulation signal L1 can not only control the output frequency-modulated optical signal R1 of the light source 1 to be linear with time, but also lock the phase of the frequency-modulated optical signal R1 with the phase of the external reference signal F1, that is, phase-locking. Based on this phase-locked loop, the modulation slope and phase noise of the frequency-modulated optical signal R1 output by the light source 1 are both related to the external reference signal F1. In this way, the linearity of the frequency-modulated optical signal R1 output by the light source 1 can be improved and the noise can be suppressed.

[0123] However, the above scheme can only perform phase locking for a single light source and does not help with slope tracking and phase locking for dual-source frequency modulation. If this scheme is to be applied to the dual-source FMCW LiDAR shown in Figure 3d, phase-locked loop (PLL) modules need to be set in the processing elements of reference calibration path 1 and reference calibration path 2 respectively. Each PLL module in the processing element is used to individually control the frequency-modulated optical signal output by the light source on its respective optical path based on the external reference signal. For example, as shown in Figure 3g, in reference calibration path 1, the PLL module in the processing element generates a feedback signal P1 based on the input external reference signal F1 and its own intermediate frequency (IF) signal S1. This feedback signal P1 is used to control the drive circuit to send a drive signal L1 to light source 1, driving light source 1 to output a frequency-modulated optical signal R1 whose frequency changes linearly with time and whose phase is locked with the external reference signal F1. Similarly, in the reference calibration path 2, the phase-locked loop module in the processing element generates a feedback signal P2 based on the input external reference signal F2 and its own intermediate frequency signal S2. The feedback signal P2 is used to control the drive circuit to send a drive signal L2 to the light source 2, so as to drive the light source 2 to output a frequency-modulated light signal R2 whose frequency changes linearly with time and whose phase is locked with the external reference signal F2.

[0124] According to the above design, the two reference calibration paths can improve the linearity of the two light sources respectively, making the modulation slope of the two light sources related to the frequency of the external reference signal, and the phase locked with the phase of the external reference signal. However, this modulation method is still for individual modulation of a single light source, and does not directly link the modulation information of the two light sources. There will be some differences in the modulation process of different light sources. Therefore, even if the external reference signals F1 and F2 are set to be the same, the modulation slopes of the two light sources cannot be strictly aligned at all times, the slope switching point (i.e., the inflection point) cannot be guaranteed to be consistent, and the phases of the modulation slopes of the two light sources are not directly related, that is, they are not coherent.

[0125] In view of this, this application provides a coherent calibration scheme. This scheme utilizes two intermediate frequency (IF) signals generated after the frequency-modulated (FM) optical signals output from two light sources pass through a delayed frequency discrimination optical path and a photodetector to generate a feedback signal. The feedback signal is then used to modulate the FM optical signal output from one of the light sources, ensuring that the FM optical signal from that source maintains the same modulation slope, opposite modulation direction, and phase difference lock with the FM optical signal from the other source. This solves the problems of inconsistent modulation slopes and random phase differences in reverse-modulated continuous wave light sources. Using the two FM optical signals modulated by this coherent calibration scheme to jointly detect a target can improve the signal-to-noise ratio of the detected IF signal, thereby improving the accuracy of ranging and velocity measurement.

[0126] The coherent calibration scheme proposed in this application will be described in detail below with reference to Figures 4 to 22.

[0127] Please refer to Figure 4, which shows a schematic diagram of a coherent calibration device provided in this application. The coherent calibration device includes a first calibration path 110, a second calibration path 120, and a first phase-locked loop 210. Each calibration path 110 and 120 includes a light source module, a delay-frequency discrimination optical path, and a photodetector. The light source module in each calibration path outputs a frequency-modulated optical signal, which is converted into an intermediate frequency (IF) signal after passing through the delay-frequency discrimination optical path and photodetector in each calibration path. For example, the first calibration path 110 includes a light source module 111, a delay-frequency discrimination optical path 112, and a photodetector 113. The light source module 111 outputs a first frequency-modulated optical signal R1, which is converted into a first IF signal S1 after passing through the delay-frequency discrimination optical path 112 and photodetector 113. The second calibration path 120 includes a light source module 121, a time-delayed frequency discrimination optical path 122, and a photodetector 123. The light source module 121 outputs a second frequency-modulated optical signal R2. After passing through the time-delayed frequency discrimination optical path 122 and the photodetector 123, the second frequency-modulated optical signal R2 becomes a second intermediate frequency signal S2.

[0128] As shown in Figure 4, the first phase-locked loop 210 is connected between photodetector 113, photodetector 123, and light source module 121. When the coherent calibration device is working, the first phase-locked loop 210 is used to acquire the first intermediate frequency signal S1 output by photodetector 113 and the second intermediate frequency signal S2 output by photodetector 123, and outputs a first feedback signal P to the light source module 121. 21 The first feedback signal P 21 The second frequency-modulated light signal R2 output by the light source module 121 is used to calibrate the second frequency-modulated light signal R2, so that the slope of the second frequency-modulated light signal R2 is opposite to that of the first frequency-modulated light signal R1 output by the light source module 111 and the phase difference is constant. The first frequency-modulated light signal R1 and the second frequency-modulated light signal R2 are used to jointly detect the target.

[0129] Based on the above structure, the first phase-locked loop 210 can be used to ensure that the absolute values ​​of the modulation slopes of the two frequency-modulated optical signals R1 and R2 output from the light source modules in the two calibration paths are the same but opposite in sign, and that the phase difference is constant. Thus, the modulation slopes of the two frequency-modulated optical signals R1 and R2 are consistent, their modulation directions are opposite, and the start, inflection, and end times of their modulation cycles are all consistent. The consistent modulation slopes of the two frequency-modulated optical signals R1 and R2 ensure that the corresponding two intermediate frequency signals S1 and S2 are aligned in frequency, improving the accuracy of ranging and velocity measurement, thus solving the first problem mentioned above. The constant phase difference between the two frequency-modulated optical signals R1 and R2 allows the phase noise of the two intermediate frequency signals S1 and S2 obtained when the two frequency-modulated optical signals R1 and R2 jointly detect the target to cancel each other out. This results in better phase noise compensation algorithm performance, higher signal-to-noise ratio of the detected signal, greater spectral broadening, and improved maximum detection performance, thus solving the second problem mentioned above. The fact that the start and end times and inflection points of the frequency modulation cycles of the two frequency-modulated optical signals R1 and R2 are consistent can increase the available modulation bandwidth within the frequency modulation cycle, increase the ROI, improve the minimum distance resolution, and solve the above-mentioned problem three.

[0130] To further illustrate the scheme, the components in the coherent calibration device will be described below to provide an exemplary implementation scheme.

[0131] First phase-locked loop

[0132] Optionally, the first phase-locked loop 210 can be a digital phase-locked loop or an analog phase-locked loop. If it is a digital phase-locked loop, the first phase-locked loop 210 can be considered as a software module, or a software algorithm unit or logic unit, located on the processing chip, which can implement the functions of the first phase-locked loop 210 described above. If it is a hardware module, the first phase-locked loop 210 can be a processor, hardware circuit, chip, or chip system, which has the necessary hardware units set up, and the various hardware units work together to implement the functions of the first phase-locked loop 210 described above.

[0133] Taking a simulated phase-locked loop as an example, please refer to Figure 5, which shows a possible structural schematic diagram of a first phase-locked loop 210 provided in this application. The first phase-locked loop 210 includes a phase frequency detector (PFD) 211 and a low-pass filter 212. Referring to Figure 5 and Figure 4 above, the PFD 211 has two input terminals and one output terminal. The two input terminals are respectively connected to photodetector 113 and photodetector 123, and the output terminal is connected to the input terminal of the low-pass filter 212. The output terminal of the low-pass filter 212 is connected to the light source module 121. Based on this structure and connection relationship, the PFD 211 can acquire the first intermediate frequency signal S1 output by photodetector 113 and the second intermediate frequency signal S2 output by photodetector 123. According to the complex form of the first intermediate frequency signal S1 and the second intermediate frequency signal S2, the error signal S between the first intermediate frequency signal S1 and the second intermediate frequency signal S2 is determined. err and the error signal S err The output is sent to low-pass filter 212. Low-pass filter 212 can adjust the output based on the error signal S. err Determine the first feedback signal P 21 and the first feedback signal P 21 The output is sent to the light source module 121, wherein the first feedback signal P 21 With error signal S err They show a positive correlation.

[0134] For example, combining the light field signal formula shown in formula (1.2) above, the first frequency-modulated light signal R1 output by the light source module 111 and the second frequency-modulated light signal R2 output by the light source module 121 can be expressed as the following expression (2.1):

[0135] Where t is the detection time, and w1 and w2 are the instantaneous frequencies of the first frequency-modulated optical signal R1 and the second frequency-modulated optical signal R2 at time t, respectively. are the phase noises of the first frequency-modulated optical signal R1 and the second frequency-modulated optical signal R2, respectively, where j is the imaginary unit.

[0136] Alternatively, if linear frequency modulation is used, and each light source uses the same frequency modulation slope in the modulation cycle, then the instantaneous frequency w1 of the first frequency-modulated optical signal R1 and the instantaneous frequency w2 of the second frequency-modulated optical signal R2 can be expressed as the following expression (2.2):

[0137] Where k1 and k2 are the modulation slopes of the first frequency-modulated optical signal R1 and the second frequency-modulated optical signal R2, respectively, and Ω1 and Ω2 are the carrier frequencies of the first frequency-modulated optical signal R1 and the second frequency-modulated optical signal R2, respectively. It can be understood that if the light source module 111 and the light source module 121 are frequency-modulated in opposite directions, then the modulation slopes of the two frequency-modulated optical signals are opposite numbers, that is, k1 = -k2.

[0138] Based on the above expressions (2.1) and (2.2), the complex form of the first intermediate frequency signal S1 generated after the first frequency-modulated optical signal R1 passes through the delayed frequency-discriminating optical path 112 and the photodetector 113 can be expressed as:

[0139] Wherein, I1 is the real part of the complex form of the first intermediate frequency signal S1, which is the in-phase component of the first intermediate frequency signal S1; Q1 is the imaginary part of the complex form of the first intermediate frequency signal S1, which is the quadrature component of the first intermediate frequency signal S1; T1 is the responsivity of the photodetector 113; E1 is the light field intensity of the first frequency-modulated light signal R1; and τ1 is the delay duration of the delay-delayed frequency discrimination optical path 112. The phase noise generated by the first frequency-modulated optical signal R1 after passing through the delayed frequency-discriminating optical path 112. This refers to the phase noise of the first frequency-modulated optical signal R1 before it passes through the delayed frequency-discriminating optical path 112. This is the phase noise of the first frequency-modulated optical signal R1 after passing through the delayed frequency-discriminating optical path 112.

[0140] Similarly, after the second frequency-modulated optical signal R2 passes through the delayed frequency-discriminating optical path 122 and the photodetector 123, the complex form of the generated second intermediate frequency signal S2 can be expressed as:

[0141] Wherein, I2 is the real part of the complex form of the second intermediate frequency signal S2, that is, the in-phase component of the second intermediate frequency signal S2; Q2 is the imaginary part of the complex form of the second intermediate frequency signal S2, that is, the quadrature component of the second intermediate frequency signal S2; T2 is the responsivity of the photodetector 123; E2 is the optical field intensity of the second frequency-modulated optical signal R2; and τ2 is the delay duration of the delay-discriminator optical path 122. The phase noise generated by the second frequency-modulated optical signal R2 after passing through the delayed frequency-discriminating optical path 122. This refers to the phase noise of the second frequency-modulated optical signal R2 before it passes through the delayed frequency-discriminating optical path 122. This is the phase noise of the second frequency-modulated optical signal R2 after passing through the delayed frequency-discriminating optical path 122.

[0142] Based on the complex forms of the first intermediate frequency signal S1 and the second intermediate frequency signal S2, the error signal S err It satisfies the following expression (2.3):

[0143] The above error signal S err In the given information, T1, T2, E1, E2, k1, k2, τ1, and τ2 are all constant coefficients. Therefore, All coefficients are constant; based on this, the first feedback signal P 21 With error signal S err They exhibit a positive correlation, which can be expressed as the following expression (2.4): P 21 ∝-(k1τ1+k2τ2)t+Δφ1(t)+Δφ2(t)……(2.4)

[0144] In the above expression (2.4), -(k1τ1+k2τ2) is related to the frequency modulation slope k1 of the first frequency-modulated optical signal R1 and the frequency modulation slope k2 of the second frequency-modulated optical signal R2. Phase noise with the first frequency-modulated optical signal R1 Phase noise with the second frequency-modulated optical signal R2 Related. Assuming the delay durations of the two delay-discriminating optical paths 112 and 122 are the same, i.e., τ1 = τ2, then, in the reverse frequency modulation scenario, it is expected that the frequency modulation slope k1 of the first frequency-modulated optical signal R1 and the frequency modulation slope k2 of the second frequency-modulated optical signal R2 are opposite, and the phase noise of the first frequency-modulated optical signal R1 is... Phase noise with the second frequency-modulated optical signal R2 To cancel each other out, that is, to expect k1 = -k2, and Based on this, the above expression (2.5) actually indicates: the first feedback signal P 21 The sum of the frequency modulation slopes k1+k2 of the two frequency-modulated optical signals R1 and R2, and the sum of the phase noise. They show a positive correlation.

[0145] Optionally, the first feedback signal P 21 It can be a voltage signal, and the value of this voltage signal can be either positive or negative. For example:

[0146] When the error signal S err A larger value means a larger sum of slopes (k1 + k2) of the two frequency-modulated optical signals R1 and R2 (e.g., a larger positive value) and a larger sum of phase noise. The larger the value (e.g., a large positive value), the larger the voltage signal value will be (e.g., a large positive value) based on the positive correlation. This larger value is used to instruct the light source module 121 to reduce the frequency modulation slope k2 and phase noise of the second frequency-modulated optical signal R2. This reduces the sum of the reduced frequency modulation slope k2 and the frequency modulation slope k1 of the first frequency-modulated optical signal R1 to approximately 0, thus reducing the phase noise. Phase noise with the first frequency-modulated optical signal R1 The sum of these two signals also approaches 0, thus achieving a second frequency-modulated optical signal R2 with opposite frequency modulation slopes and a constant phase difference with the first frequency-modulated optical signal R1.

[0147] Conversely, when the error signal S err The smaller the value, the smaller the sum of the frequency modulation slopes k1+k2 of the two frequency-modulated optical signals R1 and R2 (e.g., a smaller negative value), and the smaller the sum of the phase noise. The smaller the value (e.g., a smaller negative value), the smaller the voltage signal value will be (e.g., a smaller negative value) based on the positive correlation. This smaller value is used to indicate to the light source module 121 to increase the frequency modulation slope k2 and phase noise of the second frequency-modulated optical signal R2. This ensures that the sum of the increased frequency modulation slope k2 and the frequency modulation slope k1 of the first frequency-modulated optical signal R1 approaches 0, thus reducing the phase noise. Phase noise with the first frequency-modulated optical signal R1 The sum of these two signals also approaches 0, thus achieving a second frequency-modulated optical signal R2 with opposite frequency modulation slopes and a constant phase difference with the first frequency-modulated optical signal R1.

[0148] Furthermore, when the error signal S err Approaching the set constant value When this happens, it means that the sum of the slopes of the frequency modulation slopes of the two frequency-modulated optical signals R1 and R2, k1+k2, approaches 0, and the sum of the phase noise... It also approaches 0. The second frequency-modulated optical signal R2 and the first frequency-modulated optical signal R1 have opposite frequency modulation slopes and constant phase difference. In this case, the voltage signal value can be configured to 0 or set to a constant value.

[0149] Based on the above positive correlation, the first feedback signal P 21 The light source module 121 can be driven to modulate the frequency and phase of its output second frequency-modulated optical signal R2, so as to achieve the effect that the frequency modulation slope of the second frequency-modulated optical signal R2 is opposite to that of the first frequency-modulated optical signal R1 output by the light source module 111 and the phase is locked, thereby realizing coherent calibration of dual light source frequency modulation and improving the accuracy of distance and speed measurement.

[0150] Optionally, referring to Figure 5 above, the first phase-locked loop 210 determines the first feedback signal P 21 When using the complex form of the first intermediate frequency signal S1 and the second intermediate frequency signal S2, there are several possible implementations. For example:

[0151] In implementation form one, the first intermediate frequency (IF) signal S1 and the second IF signal S2 input to the first phase-locked loop (PLL) 210 are themselves complex numbers. In this case, as shown in Figure 6a, the first PLL 210 can consist of only a PFD and a filter. The complex IF signals S1 and S2 are directly input to the PFD, which calculates the error signal S of the complex IF signals S1 and S2. err And send it to the filter, the filter based on the first feedback signal P 21 With the error signal S in complex form err The positive correlation was used to determine the first feedback signal P. 21 And output;

[0152] In the second implementation, the first intermediate frequency (IF) signal S1 and the second IF signal S2 input to the first phase-locked loop (PLL) 210 are complex in-phase and quadrature components, respectively. In this case, as shown in Figure 6b, the first PLL 210 may include two PFDs and two filters, as well as an adder. One PFD is used to receive the in-phase component I of the first IF signal S1. S1 The in-phase component I of the second intermediate frequency signal S2 S2 And calculate the error signal S of the in-phase component. erri =I S1 ×I S2 Then it is sent to the connected filter, which calculates the error signal S based on the in-phase component. erri The in-phase feedback signal P was determined. 21i And output to the adder, in-phase feedback signal P 21i Error signal S of in-phase component erri They are positively correlated. Similarly, another PFD is used to receive the quadrature component Q of the first intermediate frequency signal S1. S1 The quadrature component Q of the second intermediate frequency signal S2 S2 And calculate the error signal S of the orthogonal components. errq =Q S1 ×Q S2 Then it is sent to the connected filter, which calculates the error signal S based on the quadrature component. errq Determine the orthogonal feedback signal P 21q And output to the adder, quadrature feedback signal P 21q Error signal S with orthogonal components errq They are positively correlated. The adder is used to superimpose the in-phase feedback signal P. 21i and orthogonal feedback signal P 21q Obtain the first feedback signal P 21 And output;

[0153] In implementation form three, the first intermediate frequency (IF) signal S1 and the second IF signal S2 input to the first phase-locked loop (PLL) 210 are in real-valued form. In this case, as shown in Figure 6c, the first PLL 210 may include two PFDs and two filters. In addition, it includes two beam splitters, two 90° phase shifters, and an adder. One beam splitter receives the real-valued first IF signal S1 and divides it into two sub-signals of equal power. One of the two sub-signals serves as the in-phase component I of the first IF signal S1. S1 The input is directly fed into the first PDF (the PDF shown above in the diagram), while the other is phase-shifted by a 90° phase shifter and becomes the quadrature component Q of the first intermediate frequency signal S1. S1 Input to the second PDF (PDF shown below). Similarly, another beam splitter is used to receive the real-form second intermediate frequency signal S2 and split the second intermediate frequency signal S2 into two sub-signals of equal power, one of which is I. S2 The in-phase component of the second intermediate frequency signal S2 is directly input to the first PDF, while the other component is phase-shifted by a 90° phase shifter and becomes the quadrature component Q of the second intermediate frequency signal S2. S2 Input to the second PDF. The first PDF is based on the in-phase component I of the first intermediate frequency signal S1. S1 The in-phase component I of the second intermediate frequency signal S2 S2 Calculate the error signal S of the in-phase component erri It is then sent to the connected filter, which, based on the error signal S of the in-phase component,... erri Determine the in-phase feedback signal P 21q The output is then sent to an adder, and the second PDF is based on the quadrature component Q of the first intermediate frequency signal S1. S1 The quadrature component Q of the second intermediate frequency signal S2 S2 Calculate the error signal S of the orthogonal components errq It is then sent to the connected filter, which, based on the error signal S of the quadrature component. errq Determine the orthogonal feedback signal P 21q The signal is then output to an adder, which superimposes the in-phase feedback signal P. 21i and orthogonal feedback signal P 21q Obtain the first feedback signal P 21 And output it.

[0154] Understandably, other implementation forms are also possible. For example, combining implementation form three and implementation form one, implementation form four can be obtained, as shown in Figure 6d. In this implementation form, the first intermediate frequency signal S1 and the second intermediate frequency signal S2 input to the first phase-locked loop 210 are in real number form. The first phase-locked loop 210 includes a PFD and a filter, as well as two beam splitters, two 90° phase shifters, and two adders. The real number form of the first intermediate frequency signal S1 and the second intermediate frequency signal S2 first pass through the two beam splitters and the two 90° phase shifters to become the in-phase component I of the first intermediate frequency signal S1. S1 and orthogonal components Q S1 The in-phase component I of the second intermediate frequency signal S2 S2 and orthogonal components Q S2 Then the in-phase component I of the first intermediate frequency signal S1 S1 and orthogonal components Q S1 The first intermediate frequency signal S1, which is superimposed into a complex form by an adder, and the in-phase component I of the second intermediate frequency signal S2 are... S2 and orthogonal components Q S2 The signals are then superimposed by another adder to form a complex second intermediate frequency signal S2. The complex first intermediate frequency signal S1 and the complex second intermediate frequency signal S2 are then passed through a PFD and a filter to generate a first feedback signal P. 21 .

[0155] Alternatively, the first intermediate frequency signal S1 input to the first phase-locked loop 210 may be in real form and the second intermediate frequency signal S2 may be in complex form; or, the first intermediate frequency signal S1 input to the first phase-locked loop 210 may be in complex form and the second intermediate frequency signal S2 may be in real form; or, the first intermediate frequency signal S1 input to the first phase-locked loop 210 may be in-phase and quadrature components in complex form and the second intermediate frequency signal S2 may be in real form, and so on. These scenarios can all be obtained by combining the above implementation forms one to four, and this application will not list them one by one.

[0156] It should be noted that the above description uses an analog phase-locked loop (PLL) 210 as an example. When the PLL 210 is a digital PLL, the low-pass filter described above can be replaced with a software module that has a proportional-integral-derivative (PID) algorithm. This software module can implement the low-pass filtering function based on the PID algorithm. Alternatively, the low-pass filter can be replaced with a proportional-integral (PI) and a differentiator (DE), or a PI can be used for low-pass filtering first, followed by filtering with another filter, etc. The specific implementation is not limited.

[0157] Calibration path

[0158] Optionally, in each calibration path, the frequency-modulated optical signal output by the light source module is split into a local oscillator signal, a signal to be delayed, and a detection signal. The detection signal is used to detect the target, while the signal to be delayed is processed by the delay frequency discrimination optical path in each calibration path and mixed with the local oscillator signal to obtain an intermediate frequency signal. The intermediate frequency signal is detected and output by the photodetector in each calibration path.

[0159] Optionally, the intermediate frequency (IF) signal output by the photodetector in each calibration path can be in real form, complex form, or a complex form of in-phase and quadrature components. Each calibration path has multiple possible implementation structures. For ease of understanding, the following example uses the output of a complex IF signal, illustrating two possible implementation structures through implementation methods one and two.

[0160] Implementation Method 1

[0161] Please refer to Figure 7, which shows a schematic diagram of a calibration path provided in Implementation Method 1. In this example, the calibration path includes a light source module, a time-delayed frequency discrimination optical path, a photodetector, and an adder (⊕). The time-delayed frequency discrimination optical path includes a beam splitter and an optical delay line. The input terminal of the 90° optical mixer and the beam splitter are connected to the light source module. One output terminal is connected to one input terminal of the 90° optical mixer, and the other output terminal is connected to one end of the optical delay line. The other end of the optical delay line is connected to the other input terminal of the 90° optical mixer. The output terminal of the 90° optical mixer is connected to the input terminal of the photodetector. The output terminal of the photodetector is connected to the input terminal of the adder. The output terminal of the adder is connected to the first phase-locked loop 210 shown in Figure 4.

[0162] Based on this structure and connection, the frequency-modulated light signal R output by the light source module enters the beam splitter, which performs beam splitting on the frequency-modulated light signal R to obtain the signal to be delayed, R0. 01 and calibration path local oscillator signal R 02 The beam splitter outputs the calibration path local oscillator signal R through an output terminal. 02 The output is sent to a 90° optical mixer, and the signal R to be delayed is then sent to another output terminal. 01 Output to the optical delay line. Delayed signal R 01 After being delayed by the optical delay line, the signal becomes the delayed signal, which then enters the 90° optical mixer. The 90° optical mixer processes the delayed signal and the calibration path local oscillator signal R. 02The system performs frequency mixing to obtain mixed signals with phases of 0°, 90°, 180°, and 270°, which are then output to a photodetector. The photodetector determines the in-phase component I of the intermediate frequency (IF) signal based on the mixed signals with phases of 0° and 180°, and the quadrature component Q of the IF signal based on the mixed signals with phases of 90° and 270°. The in-phase component I and the quadrature component Q of the IF signal are then output to an adder. The adder superimposes the in-phase component I and the quadrature component Q of the IF signal to generate a complex IF signal S = I + jQ, which is then sent to the first phase-locked loop 210.

[0163] Optionally, the photodetector can be a detector array, or include one or more balanced photodiodes (BPDs). For example, Figure 7 shows an example including two BPDs, namely BPD1 and BPD2. In this case, the two inputs of BPD1 can be connected to the 0° and 180° signal outputs of the 90° optical mixer, and its output is connected to one input of the adder. The two inputs of BPD2 can be connected to the 90° and 270° signal outputs of the 90° optical mixer, and its output is connected to the other input of the adder. BPD1 is used to acquire the mixed signals with phases of 0° and 180° output from the 0° and 180° signal outputs of the 90° optical mixer, and uses the signal difference between the 0° and 180° mixed signals as the in-phase component I of the intermediate frequency signal, or uses the signal difference between the 180° and 180° mixed signals as the in-phase component I of the intermediate frequency signal. Similarly, BPD2 is used to acquire the 90° and 270° phase mixed signals output from the 90° and 270° signal output terminals of the 90° optical mixer, and uses the signal difference between the 90° phase mixed signal and the 270° phase mixed signal as the quadrature component Q of the intermediate frequency signal, or uses the signal difference between the 270° phase mixed signal and the 90° phase mixed signal as the quadrature component Q of the intermediate frequency signal.

[0164] Understandably, if the photodetector is a detector array, then the detector array can include four detectors (PDs), such as PD11, PD12, PD21, and PD22 shown in Figure 8. PD11, PD12, PD21, and PD22 are connected to the 0°, 180°, 90°, and 270° signal output terminals of the 90° optical mixer, respectively, or to the 180°, 0°, 270°, and 90° signal output terminals, respectively. The output terminals of PD11 and PD12 are combined into one and connected to one input terminal of the adder, and the output terminals of PD21 and PD22 are combined into one and connected to the other input terminal of the adder. The difference between the signals detected by PD11 and PD12 is taken as the in-phase component I of the intermediate frequency signal, and the difference between the signals detected by PD21 and PD22 is taken as the quadrature component Q of the intermediate frequency signal. The in-phase component I and the quadrature component Q are combined in the adder to form a complex intermediate frequency signal S = I + jQ.

[0165] Understandably, photodetectors can also be other components, such as phototubes, photomultiplier tubes, avalanche photodiodes (APDs), single-photon avalanche diodes (SPADs), etc., without limitation.

[0166] Optionally, the optical delay lines described above are components capable of delaying the transmission of optical signals, and may include, but are not limited to, fiber optic delay lines or on-chip waveguide delay lines. For example, Figure 7 illustrates a fiber optic delay line, which utilizes the transmission of optical signals within an optical fiber to achieve signal delay and typically has a relatively long length. Figure 8, for another example, shows an on-chip waveguide delay line. As an example, an on-chip waveguide delay line is a waveguide device fabricated on a semiconductor chip. Its working principle is to achieve signal delay by controlling the propagation path length of electromagnetic waves in a dielectric waveguide, silicon-based waveguide, or other materials. The semiconductor materials used in on-chip waveguide delay lines can be, for example, silicon (Si) or silicon nitride (SiN), and they transmit optical signals internally. On-chip waveguide delay lines have the advantage of easy integration with other circuits. For example, Figure 8 shows the integration of an on-chip waveguide delay line and a 90° optical mixer onto a single waveguide. This increases the waveguide's integration density, resulting in advantages such as good programmability, high delay accuracy, and smaller size.

[0167] Optionally, as shown in Figure 7 or Figure 8, the calibration path may also include a target measurement path, and the beam splitter element also has a third output terminal connected to the target measurement path. Based on this structure and connection relationship, the beam splitter element performs beam splitting processing on the frequency-modulated optical signal R output by the light source module, in addition to obtaining the delay signal R described above. 01 and calibration path local oscillator signal R 02 In addition, the detection signal R can also be obtained. 03 Detection signal R 03 The data is input to the target measurement path for target measurement, such as measuring the distance and velocity of the target. The structure of the target measurement path can be seen in Figure 3a above. For example, if the calibration path belongs to the optical path of light source 1, the target measurement path may include the upper circulator, reflector, semi-transparent mirror, collimating lens and detector. If the calibration path belongs to the optical path of light source 2, the target measurement path may include the lower circulator, semi-transparent mirror, collimating lens and detector, or it may include other components, which will not be described again in this application.

[0168] Optionally, taking Figure 7 as an example, the light source module includes a signal generator and a light source. The output of the signal generator is connected to the input of the light source, and the output of the light source is connected to the input of the beam splitter. The signal generator is used to output a modulation signal L to the light source. This modulation signal L can drive the light source to output a frequency-modulated optical signal R whose frequency-time relationship conforms to a set variation law, such as a frequency-modulated optical signal R whose frequency changes linearly with time, or a frequency-modulated optical signal R whose frequency changes linearly with time in the form of a triangular wave or sawtooth wave. In some scenarios, the signal generator is also called a driver circuit. In some cases, the driver circuit also needs to be responsible for timing control functions, such as controlling the time window for the light source to output the frequency-modulated optical signal R, and synchronizing with the receiving end (i.e., the receiving operation of the target measurement path) to accurately demodulate the information in the echo signal (i.e., the received signal).

[0169] The signal generator can be a device capable of generating arbitrary waveforms, such as an arbitrary waveform generator (AWG). The AWG can output a modulated signal L of arbitrary waveform to the light source, for example, a modulated signal L whose frequency changes linearly with time in the form of a triangular wave. The light source can be a frequency-sweeping light source, such as a distributed feedback (DFB) laser. The DFB laser can perform triangular wave frequency modulation on the modulated signal L output by the AWG, generating a frequency-modulated optical signal R whose frequency changes linearly with time in the form of a triangular wave. The modulated signal L output by the signal generator to the light source and the frequency-modulated optical signal R output by the light source are linearly related.

[0170] However, due to the influence of the internal physical mechanism of the light source (such as imperfections in the manufacturing process, thermal effects, etc.), the frequency-modulated light signal R output by the light source may have a nonlinear relationship with time. In this case, it is necessary to perform nonlinear frequency modulation on the frequency-modulated light signal R output by the light source. That is, it is necessary to calibrate the linearity between the modulation signal L output by the signal generator to the light source and the frequency-modulated light signal R output by the light source.

[0171] Based on this, in one example (see Figure 9a), the calibration path can also include a predistortion unit connected between the output of the adder and the input of the signal generator. That is, the output of the adder is simultaneously connected to the input of both the first phase-locked loop 210 and the predistortion unit. Thus, the complex intermediate frequency signal S = I + jQ obtained by the adder is output to the first phase-locked loop 210 to participate in the phase locking of the two calibration paths, and also output to the predistortion unit. The predistortion unit calculates the predistortion signal based on the intermediate frequency signal S = I + jQ using a predistortion algorithm and outputs the predistortion signal to the signal generator. This predistortion signal is used to calibrate the linearity between the modulation signal L output by the signal generator to the light source and the frequency-modulated light signal R output by the light source, ensuring that the light source can output a frequency-modulated light signal R that conforms to a linear variation law under the action of the modulation signal L. This frequency-modulated light signal R is split into a detection signal and enters the target measurement path, which can improve the detection accuracy of the target measurement path.

[0172] Optionally, the adder and predistortion unit mentioned above can be configured individually or integrated. For example, Figure 9a shows an integrated configuration. In this case, the calibration path can also include a processing element, in which the adder and predistortion unit are integrated. The processing element can be a central processing unit (CPU), a microcontroller unit (MCU), a system on a chip (SOC), or other units or modules with processing or control capabilities.

[0173] In some scenarios, the adder and predistortion unit are hardware modules. In this case, the signals processed by the adder and predistortion unit are both analog signals. As shown in Figure 9a, the in-phase component I and quadrature component Q output by the photodetector are analog signals. These analog signals can be directly input to the adder for superposition. The superimposed intermediate frequency signal S = I + jQ is directly output to the predistortion unit for signal predistortion processing. The generated predistortion signal P is also an analog signal. This analog predistortion signal can be directly input to the signal generator to control the signal generator to output the modulation signal L.

[0174] In other scenarios, the adder and predistortion unit are software modules. In this case, the signals processed by the adder and predistortion unit are both digital signals. The adder can be replaced by an addition algorithm, and the predistortion unit can be replaced by a predistortion algorithm. As shown in Figure 9b, the processing element can also include two analog-to-digital converters (ADCs), namely ADC1 and ADC2, and one digital-to-analog converter (DAC). ADC1 is connected between the in-phase component I output of the photodetector and one input of the processing element; ADC2 is connected between the quadrature component Q output of the photodetector and the other input of the processing element; and the DAC is connected between the output of the processing element and the input of the signal generator. Based on this structure and connection, the in-phase component I and quadrature component Q output by the photodetector are analog signals. ADC1 converts the in-phase component I in the analog domain into a digital signal and outputs it to the processing element, and ADC2 converts the quadrature component Q in the analog domain into a digital signal and also outputs it to the processing element. The processing element uses a summation algorithm to superimpose the two digital signals, obtaining an intermediate frequency (IF) signal S = I + jQ in the digital domain, which is then output to the first phase-locked loop (PLL). The processing element also uses a predistortion algorithm to predistort the IF signal S = I + jQ in the digital domain, obtaining a predistorted signal, which is then output to the DAC. The DAC converts the predistorted signal in the digital domain into an analog signal and outputs it to the signal generator to control the generator to output the modulation signal L.

[0175] Optionally, an amplifier can be provided after the in-phase component I and quadrature component Q output terminals of the photodetector. The amplifier is used to amplify the in-phase component I and quadrature component Q output from the photodetector before outputting them to subsequent devices. For example, taking the structure shown in Figure 9b as an example, as shown in Figure 9b, the calibration circuit can also include amplifier 1 and amplifier 2. Amplifier 1 is connected between the in-phase component I output terminal of the photodetector and the input terminal of ADC1, and is used to amplify the in-phase component I output from the photodetector before inputting it to ADC1. Amplifier 2 is connected between the quadrature component Q output terminal of the photodetector and the input terminal of ADC2, and is used to amplify the in-phase component I output from the photodetector before inputting it to ADC2.

[0176] The amplifier can be a trans-impedance amplifier (TIA), which amplifies the input signal with a certain intensity of low noise. That is, it amplifies the useful signal in the input signal while suppressing the amplification of the noise signal, thereby improving the optical signal-to-noise ratio (OSNR). Alternatively, it can be other types of amplifiers, which are not specifically limited here.

[0177] Based on the structure in the above implementation method one, the calibration path can output a complex intermediate frequency signal S = I + jQ. Therefore, the first phase-locked loop 210 can adopt the structure shown in Figure 6a above. In this case, the structure of the first phase-locked loop 210 is relatively simple, the cost is low, and the complexity of the coherent calibration device is low.

[0178] Implementation Method Two

[0179] Please refer to Figure 10, which shows a schematic diagram of a calibration path provided in Implementation Method Two. In this example, in addition to the light source module, the delay-frequency discriminator optical path, and the photodetector, the calibration path also includes a power divider, a 90° phase shifter, and an adder. The time-delay frequency discrimination optical path includes a beam splitter and an optical delay line. The input of the beam splitter is connected to the light source module. One output is connected to one input of the photodetector. The other output is connected to one end of the optical delay line. The other end of the optical delay line is connected to the other input of the photodetector. The output of the photodetector is connected to the input of the power divider. One output of the power divider is connected to one input of the adder. The other output of the power divider is connected to the input of the 90° phase shifter. The output of the 90° phase shifter is connected to the other input of the adder. The output of the adder is connected to the first phase-locked loop 210 shown in Figure 4.

[0180] Based on this structure and connection, the frequency-modulated light signal R output by the light source module enters the beam splitter, which performs beam splitting on the frequency-modulated light signal R to obtain the signal to be delayed, R0. 01 and calibration path local oscillator signal R 02 The calibration path local oscillator signal R is output through one terminal. 02 The signal R to be delayed is output to a photodetector and then output to another terminal. 01 Output to the optical delay line. Delayed signal R 01After being delayed by the optical delay line, the signal becomes a delayed signal, which then enters the photodetector. The photodetector determines the real-valued intermediate frequency (IF) signal based on the delayed signal and the local oscillator signal from the calibration path, and outputs it to the power divider. The power divider splits the real-valued IF signal to obtain the in-phase component I and the signal to be phase-shifted. The in-phase component I is output to the adder, and the signal to be phase-shifted is output to a 90° phase shifter. After phase-shifting by the 90° phase shifter, the signal becomes the quadrature component Q of the IF signal, which also enters the adder. The adder superimposes the in-phase component I and the quadrature component Q of the IF signal to generate a complex-valued IF signal S = I + jQ, which is then sent to the first phase-locked loop 210.

[0181] Based on the structure in the second implementation method, the calibration path can also output a complex intermediate frequency signal S = I + jQ. The difference between this and the structure in the first implementation method is that the complex form in the first implementation method is achieved by a 90° optical mixer in the delay frequency discrimination optical path, while the delay frequency discrimination optical path in the second implementation method does not have a 90° optical mixer. Instead, a 90° phase shifter is set after the photodetector. The 90° phase shifter realizes the conversion of the intermediate frequency signal from real form to complex form.

[0182] Understandably, all the design elements in Implementation Method 1 above also apply to Implementation Method 2:

[0183] For example, the photodetector in implementation method two can also be a detector array, or include one or more BPDs. Figure 10 shows an example with one BPD, which is connected to the calibration path of the first beam splitter element, specifically the local oscillator signal R. 02 The signal output terminal and the output terminal of the optical delay line are used to output the calibration path local oscillator signal R. 02 The difference between the delayed signal and the intermediate frequency signal is taken as the real number form of the intermediate frequency signal. It is understandable that when the photodetector is a detection array, as shown in Figure 11, it can include two PDs, namely PD1 and PD2. PD1 is used to detect the local oscillator signal R of the calibration path. 02 And output, PD2 is used to detect the delayed signal and output it, PD1 outputs the calibration path local oscillator signal R 02 The delayed signal from PD2 is combined into one signal and then output to the power divider.

[0184] For example, as shown in Figure 10, the light source module in the second implementation method can also include a signal generator and a light source. The signal generator is used to output a modulation signal L to the light source to drive the light source to output a frequency-modulated light signal R whose frequency-time correlation meets the set law.

[0185] For example, as shown in Figure 11, the adder in implementation method two can also be integrated into the processing element. The processing element can also include a predistortion unit (not shown in the figure). The predistortion unit generates a predistortion signal P based on the complex form of the intermediate frequency signal and sends it to the signal generator to calibrate the linearity between the frequency-modulated signal L output by the signal generator to the light source and the frequency-modulated light signal R output by the light source. The adder and predistortion unit can be hardware modules or software modules, without limitation.

[0186] For example, as shown in Figure 11, implementation method two can also include ADC1, ADC2, and DAC, and / or, amplifier 1 and amplifier 2. Taking the simultaneous inclusion of these five components as an example, amplifier 1 is connected between the in-phase signal I output terminal of the power divider and the input terminal of ADC1; amplifier 2 is connected between the output terminal of the 90° phase shifter and the input terminal of ADC2; the output terminals of ADC1 and ADC2 are both connected to the input terminals of the processing element; and the DAC is connected between the output terminal of the processing element and the signal generator. Based on this structure and connection, amplifier 1 amplifies the in-phase component I in the analog domain of the power divider output with low noise and outputs it to ADC1. ADC1 converts it into a digital signal and outputs it to the processing element. Amplifier 2 amplifies the quadrature component Q in the analog domain of the 90° phase shifter output with low noise and outputs it to ADC2. ADC2 converts it into a digital signal and outputs it to the processing element. The processing element determines the complex form S = I + jQ of the intermediate frequency signal in the digital domain based on the in-phase component I and the quadrature component Q in the digital domain and outputs it to the first phase-locked loop 210. It also determines the predistortion signal P in the digital domain based on the intermediate frequency signal and outputs it to the DAC. The DAC converts the predistortion signal P in the digital domain into an analog signal and outputs it to the signal generator.

[0187] For example, the optical delay line in implementation method two can also be an optical fiber delay line or an on-chip waveguide delay line. Figure 10 shows the on-chip waveguide delay line scheme, and Figure 11 shows the optical fiber delay line scheme.

[0188] Of course, the other designs in implementation method one can also be applied to implementation method two, and they will not be listed again here.

[0189] The above implementation methods one and two describe possible structures when the intermediate frequency (IF) signal in complex form is output from the calibration path. Based on these structures, we can deduce the structures when the IF signal in real form is output from the calibration path, as well as the structures when the IF signal in in-phase and quadrature complex form is output. Specifically:

[0190] If the calibration path outputs complex in-phase and quadrature components, then an adder is not required in the calibration path. For example, in implementation method one as shown in Figures 7, 8, 9a, or 9b, the two output terminals of the photodetector (such as the output terminals of BPD1 and BPD2 in Figures 7, 9a, or 9b, or the output terminals of PD11 and PD12 after beam combining and PD21 and PD22 after beam combining in Figure 8) can be directly connected to the first phase-locked loop 210. In this way, the in-phase component I and quadrature component Q output by the photodetector will be directly transmitted to the first phase-locked loop 210. As another example, in implementation method two as shown in Figures 10 or 11, the output terminal of the in-phase component I of the power divider and the output terminal of the 90° phase shifter can be directly connected to the first phase-locked loop 210. In this way, the in-phase component I output by the power divider and the quadrature component Q output by the 90° phase shifter will be directly transmitted to the first phase-locked loop 210. In this case, the structure of the first phase-locked loop 210 can be seen in Figure 6b above;

[0191] If the calibration path outputs a real-valued intermediate frequency (IF) signal, then the 90° optical mixer and 90° phase shifter may not be required in the calibration path. For example, in implementation method one as shown in Figures 7, 8, 9a, or 9b, the 90° optical mixer can be replaced with a 180° optical mixer. The photodetector has one BPD or two PDs. No adder is required in the calibration path. The 180° optical mixer has two outputs, each outputting a mixed signal with a phase difference of 0° and 180°. This mixed signal is detected by one or two BPDs as a real-valued IF signal and then directly transmitted to the first phase-locked loop 210. Alternatively, in implementation method two as shown in Figures 10 or 11, the power divider, 90° phase shifter, and adder may not be required in the calibration path. The BPD or two PDs generate a real-valued IF signal based on the delayed signal and the calibration path local oscillator signal, and then directly transmit it to the first phase-locked loop 210. In this case, the structure of the first phase-locked loop 210 can be seen in Figure 6c or Figure 6d above.

[0192] Understandably, regardless of the form of the intermediate frequency signal output from the calibration path, the intermediate frequency signal can be input to the processing element so that the processing element can calibrate the frequency-modulated light signal output by the light source on the calibration path according to the intermediate frequency signal, thereby achieving nonlinear frequency modulation.

[0193] The above content describes the possible structures of the first phase-locked loop 210 and each calibration path. In this application, the coherent calibration device includes a first phase-locked loop 210 and two calibration paths, namely the first calibration path 110 and the second calibration path 120. The detection signal in the first calibration path 110 and the detection signal in the second calibration path 120 are used to jointly detect the target. The structures of the first calibration path 110 and the second calibration path 120 can be any of the structures described above; the structures of these two calibration paths can be the same or different.

[0194] For example, taking two calibration paths with identical structures as an example, the connection relationship and coherent calibration process between the first calibration path 110 and the second calibration path 120 and the first phase-locked loop 210 are described below. It is understood that the following description can also be applied to other structures of the first calibration path 110 and / or the second calibration path 120, and this application does not specifically limit them.

[0195] Implementation Plan 1

[0196] Please refer to Figure 12a, which shows a schematic diagram of a coherent calibration device provided in Embodiment 1. In this coherent calibration device, the structures of the first calibration path 110 and the second calibration path 120 are shown in Figure 9b of Embodiment 1 above, and the structure of the first phase-locked loop 210 is shown in Figure 6a above. The first phase-locked loop 210 is a digital phase-locked loop, in which the frequency and phase detector is implemented by a software module executing a frequency and phase detection algorithm, and the low-pass filter is implemented by a software module executing a PID algorithm (such as a digital filter).

[0197] Taking the triangular wave linear frequency modulation shown in Figure 12b as an example, and referring to Figure 12a, in the first calibration path 110, the signal generator (also called the first signal generator) in the light source module 111 sends a first modulation signal L1 to the light source (also called the first light source). The first modulation signal L1 is a driving waveform whose frequency changes linearly with time in the form of a triangular wave. The light source performs triangular wave frequency modulation under this driving waveform and emits a first frequency-modulated optical signal R1 that is linear with the first modulation signal L1. Ideally, the frequency of the first frequency-modulated optical signal R1 also changes linearly with time in the form of a triangular wave. Similarly, in the second calibration path 120, the signal generator (also called the second signal generator) in the light source module 121 sends a second modulation signal L2 to the light source (also called the second light source). The second modulation signal L2 is also a driving waveform whose frequency changes linearly with time in the form of a triangular wave, but it is opposite to the driving waveform of the first modulation signal L1 in the first calibration path 110. The light source in the light source module 121 is subjected to triangular wave frequency modulation under the opposite driving waveform, and emits a second frequency-modulated optical signal R2 that is linear with the second modulation signal L2. Ideally, the frequency of the second frequency-modulated optical signal R2 also changes linearly with time in the form of a triangular wave, and the direction of change is roughly opposite to the direction of frequency modulation change of the second frequency-modulated optical signal R1, as shown in Figure 12b.

[0198] In the first calibration path 110, the first frequency-modulated optical signal R1 output by the light source is split into a delay signal R by the beam splitter in the delay frequency-discrimination optical path 112. 11 Calibration path local oscillator signal R 12 and detection signal R 13 Detection signal R 13 Input to target measurement channel 118 for target measurement, pending delay signal R 11 Calibration path local oscillator signal R 12 The signal then enters an unbalanced Mach-Zehnder interferometer (AMZI) constructed from optical fibers, where the longer path (i.e., the signal to be delayed, R) is used. 11 After being delayed by an optical delay line built from optical fibers, the signal enters the signal input terminal of a 90° optical mixer. The shorter path (i.e., the calibration path local oscillator signal R) is used. 12The signal is directly input to the local oscillator of the 90° optical mixer. The four outputs of the 90° optical mixer are connected to two BPDs, namely BPD11 and BPD12. The 0° and 180° signal outputs are connected to BPD11, and the 90° and 270° signal outputs are connected to BPD12. BPD11 calculates the difference between the 0° and 180° phase mixing signals output from the 90° optical mixer to obtain the in-phase component I1 of the delayed and discriminated first intermediate frequency signal S1, and outputs it. BPD12 calculates the difference between the 90° and 270° phase mixing signals output from the 90° optical mixer to obtain the quadrature component Q1 of the delayed and discriminated first intermediate frequency signal S1, and outputs it. Both the in-phase component I1 and the quadrature component Q1 are analog signals.

[0199] Optionally, BPD11 and BPD12 are followed by two amplifiers, namely amplifier 1151 and amplifier 1152. The in-phase component I1 and quadrature component Q1 in the analog domain are amplified by the two amplifiers 1151 and 1152 respectively and then output to two ADCs, namely ADC1161 and ADC1162. After being converted into in-phase component I1 and quadrature component Q1 in the digital domain by ADC1161 and ADC1162, they are output to processing element 114 (also referred to as the first processing element). Processing element 114 calls a summation algorithm to sum the in-phase component I1 and quadrature component Q1 in the digital domain to obtain the first intermediate frequency signal S1 = I1 + jQ1 in the digital domain, and outputs it to the first phase-locked loop 210. Simultaneously, processing element 114 also invokes a predistortion algorithm to process the first intermediate frequency signal S1 = I1 + jQ1 in the digital domain, generating a first predistortion signal P1 in the digital domain. This first predistortion signal P1 is output to DAC 117, where it is converted into a first predistortion signal in the analog domain and sent to the signal generator in the light source module 111. Thus, the driving waveform of the first modulation signal L1 generated by the signal generator in the light source module 111 is learned by the predistortion algorithm. Driven by the first predistortion signal P1, the nonlinearity between the first frequency-modulated light signal R1 emitted by the light source in the light source module 111 and the first modulation signal L1 can be calibrated, making the frequency of the first frequency-modulated light signal R1 linear with time.

[0200] Similarly, in the second calibration path 120, the second frequency-modulated optical signal R2 output by the light source is split into a delay signal R by a beam splitter. 21 Calibration path local oscillator signal R 22 and detection signal R 23 Detection signal R 23 Input to target measurement channel 128 for target measurement, pending delay signal R 21 Calibration path local oscillator signal R 22The signal then enters an unbalanced Mach-Zehnder interferometer (AMZI) constructed from optical fibers, where the longer path (i.e., the signal to be delayed, R) is used. 21 After being delayed by an optical delay line built from optical fibers, the signal enters the signal input terminal of a 90° optical mixer. The shorter path (i.e., the calibration path local oscillator signal R) is used. 22 The signal is directly input to the local oscillator of the 90° optical mixer. The four outputs of the 90° optical mixer are connected to two BPDs, namely BPD21 and BPD22. The 0° and 180° signal outputs are connected to BPD21, and the 90° and 270° signal outputs are connected to BPD22. BPD21 outputs the in-phase component I2 of the second intermediate frequency signal S2 after delay and frequency discrimination, and BPD22 outputs the quadrature component Q2 of the second intermediate frequency signal S2 after delay and frequency discrimination. Here, both the in-phase component I2 and the quadrature component Q2 are analog signals.

[0201] Optionally, BPD21 and BPD22 are followed by two amplifiers, namely amplifier 1251 and amplifier 1252. The in-phase component I2 and quadrature component Q2 in the analog domain are amplified by the two amplifiers 1251 and 1252 respectively and then output to two ADCs, namely ADC1261 and ADC1262. After being converted into in-phase component I2 and quadrature component Q2 in the digital domain by ADC1261 and ADC1262, they are output to processing element 124 (also known as the second processing element). Processing element 124 calls a summation algorithm to sum the in-phase component I2 and quadrature component Q2 in the digital domain to obtain the second intermediate frequency signal S2 = I2 + jQ2 in the digital domain, and outputs it to the first phase-locked loop 210.

[0202] Furthermore, after receiving the complex-form first intermediate frequency signal S1 = I1 + jQ1 and the complex-form second intermediate frequency signal S2 = I2 + jQ2, the first phase-locked loop 210 calls the frequency and phase discrimination algorithm to multiply the complex-form first intermediate frequency signal S1 = I1 + jQ1 and the complex-form second intermediate frequency signal S2 = I2 + jQ2 to obtain the error signal S in the digital domain. err And extract the error signal S err The phase signal in the signal is processed by a PID algorithm to form the first feedback signal P. 21 The signal is output to DAC127 in the second calibration path 120. Since the first intermediate frequency signal S1 = I1 + jQ1 and the second intermediate frequency signal S2 = I2 + jQ2 output from the first calibration path 110 and the second calibration path 120 are digital signals, the first feedback signal P... 21 It is also a digital signal; the DAC127 converts the first feedback signal P in the digital domain... 21 Converted into the first feedback signal P in the analog domain21 The first feedback signal P is output to the signal generator in the second calibration path 120. 21 The signal generator in the second calibration path 120 can be driven to calibrate the second frequency-modulated optical signal R2 output by the light source in the second calibration path 120, so that the frequency modulation slope of the second frequency-modulated optical signal R2 is opposite to that of the first frequency-modulated optical signal R1 output by the light source in the first calibration path 110 and the phase difference is locked, so as to realize the reverse frequency modulation of the two light sources.

[0203] Understandably, the detector signal R after the first frequency-modulated optical signal R1 is split... 13 The detection signal R after splitting with the second frequency-modulated optical signal R2 23 Used for joint target detection, therefore, when the first frequency-modulated optical signal R1 and the second frequency-modulated optical signal R2 are anti-frequency-modulated signals, the two detection signals R after beam splitting 13 and R 23 These two probe signals R have opposite phase noise. 13 and R 23 The reflected signal from a target will have opposite phase noise. Using the reflected signal with opposite phase noise for target ranging and velocity measurement can improve the signal-to-noise ratio of echo detection, reduce the phase noise of echo detection, and improve the accuracy of ranging and velocity measurement.

[0204] Optionally, the target measurement path 118 in the first calibration path 110 and the target measurement path 128 in the second calibration path 120 can be the same target measurement path or different target measurement paths. When they are the same target measurement path, the two detection signals R 13 and R 23 The light signals can be combined into a single beam using a beam combiner, then passed through various components on the same target measurement path before exiting into the detection space to jointly detect the target. When the target measurement paths are different, the two detection signals R... 13 and R 23 Each beam can pass through its corresponding target measurement path and exit into the detection space. Then, it is combined into a single beam by components within the detection space (such as the PBS or semi-transparent mirror shown in Figure 3a above) to detect the same target. Of course, other implementation methods are also possible, and no specific limitations are made here.

[0205] It should be noted that in the example of Figure 12a, the processing element 124 in the first calibration path 110 calls the predistortion algorithm to perform nonlinear calibration on the frequency-modulated light signal R1 output by the light source. Therefore, the first calibration path 110 has a nonlinear calibration function, while the second calibration path 120 does not. However, due to the presence of the first phase-locked loop 210, the second frequency-modulated light signal R2 output by the light source in the second calibration path 120 tracks the first frequency-modulated light signal R1 output by the light source in the first calibration path 110. Therefore, based on the nonlinear calibration of the first frequency-modulated light signal R1 output by the light source in the first calibration path 110, the second frequency-modulated light signal R2 output by the light source in the second calibration path 120 can also maintain the linearity of frequency with time.

[0206] Alternatively, in other examples, if it is desired to maintain the linearity of the light source frequency modulation in the second calibration path 120 more accurately, the second calibration path 120 can also have a nonlinear calibration function, as shown in Figure 13. The structure shown in Figure 13 differs from that in Figure 12a in that:

[0207] In the second calibration path 120, after the processing elements superimpose the complex form of the second intermediate frequency signal S2 = I2 + jQ2, in addition to sending the second intermediate frequency signal S2 = I2 + jQ2 to the first phase-locked loop 210, a predistortion algorithm is also invoked to process the second intermediate frequency signal S2 = I2 + jQ2 to generate the second predistortion signal P corresponding to the second calibration path 120. 22 The second predistortion signal P 22 It is a digital signal. Additionally, the first feedback signal P in the digital domain output by the first phase-locked loop 210... 21 Instead of directly entering the DAC127, the signal goes to the processing unit. The processing unit calls a summation algorithm to process the second predistorted signal P in the digital domain. 22 With the first feedback signal P in the digital domain 21 The signals are superimposed to generate a digital driving signal P2. This driving signal P2 is output to DAC127, where it is converted into an analog driving signal P2 and sent to the signal generator in the second calibration path 120. The driving signal P2 acts on the signal generator in the second calibration path 120, causing the driving waveform of the second modulation signal L2 generated by the signal generator to be determined by both the predistortion algorithm and the phase-locked loop algorithm. Under the drive of the driving signal P2, the waveform of the second frequency-modulated optical signal R2 output from the light source in the second calibration path 120 can follow the waveform of the first frequency-modulated optical signal R1 output from the light source in the first calibration path 110 in the opposite direction. Simultaneously, the nonlinearity of the frequency and time of the second frequency-modulated optical signal R2 can be calibrated.

[0208] Optionally, the processing element 114 in the first calibration path 110, the first phase-locked loop 210, and the processing element 124 in the second calibration path 120 can be independent elements, or they can be integrated into one element, such as a processing element, or partially integrated into one element while others are implemented separately. This application does not make any specific limitations on this.

[0209] The above implementation scheme 1 uses an AMZI built with optical fiber as the delay frequency discrimination optical path, and a 90° optical mixer is used as the quadrature demodulation signal for detection and demodulation. The output first intermediate frequency signal and the second intermediate frequency signal are both complex signals in the digital domain. The first phase-locked loop calculates the error signals of the first intermediate frequency signal and the second intermediate frequency signal in the digital domain and then performs phase locking to achieve interlocking of the frequency and phase of the light source frequency modulation in the two calibration paths, realize the coherence of the light source frequency modulation in the two calibration paths, and improve the accuracy of ranging and speed measurement.

[0210] Implementation Plan 2

[0211] Please refer to Figure 14, which shows a schematic diagram of a coherent calibration device provided in Implementation Scheme 2. In this coherent calibration device, the structures of the first calibration path 110 and the second calibration path 120 are shown in Figure 8 of Implementation Scheme 1 above, and the structure of the first phase-locked loop 210 is shown in Figure 6b above. The first phase-locked loop 210 is an analog phase-locked loop built using analog devices, including two phase-frequency detectors (PFDs), two filters, and an adder; these devices are all hardware modules. In some scenarios, the PFDs can also be replaced by multipliers. The analog signal output from the PFDs or multipliers passes through active or passive filters to generate a first feedback signal P that is positively correlated with the phase difference. 21 .

[0212] The calibration path in Implementation Scheme 2 is similar in structure to that in Implementation Scheme 1, with the key difference being that the delay-frequency discrimination optical path in Implementation Scheme 1 uses an AMZI (Advanced Multimode Interferometer) built from optical fiber, while the delay-frequency discrimination optical path in Implementation Scheme 2 uses an AMZI built from silicon-based optical waveguides. In other words, the optical delay line in Implementation Scheme 1 is an optical fiber delay line, while the optical delay line in Implementation Scheme 2 is an on-chip waveguide delay line. The 90° optical mixer uses an integrated mixer designed based on the principle of silicon-based multimode interferometers, meaning the 90° optical mixer and the on-chip waveguide delay line are integrated on a single waveguide. Furthermore, the photodetector in Implementation Scheme 1 uses two balanced detectors, while the photodetector in Implementation Scheme 2 uses a detector array, specifically comprising four photodetectors (PDs). Every two PDs are combined to achieve the function of a BPD (Browser-Based Photodetector).

[0213] Due to limitations in current manufacturing processes, the detector array cannot be integrated onto the waveguide. Therefore, in Figure 14, the detector array is fabricated separately off-chip. However, with advancements in manufacturing processes, the detector array may be integrated onto the same waveguide as the on-chip waveguide delay line and the 90° optical mixer in the future. This application does not impose any limitations on this.

[0214] Taking linear frequency modulation (LFM) as an example, as shown in Figure 14, in the first calibration path 110, the first LFM optical signal R1 output by the light source passes through the delayed frequency discrimination optical path 112 and the photodetector 113, and is transformed into the in-phase component I1 and the quadrature component Q1 of the first intermediate frequency signal S1. Both the in-phase component I1 and the quadrature component Q1 are analog signals. The in-phase component I1 and the quadrature component Q1 in the analog domain are output to the two PFDs in the first phase-locked loop 210, and also enter the adder in the processing element 114. The adder superimposes the in-phase component I1 and the quadrature component Q1 in the analog domain to obtain the complex form of the first intermediate frequency signal S1, S1 = I1 + jQ1. The processing element 114 calls the predistortion algorithm to process the first intermediate frequency signal S1 = I1 + jQ1 to obtain the first predistortion signal P1 in the analog domain. The first predistortion signal P1 is then output to the signal generator in the light source module 111. The first predistortion signal P1 is used to calibrate the linearity between the first modulation signal L1 output by the signal generator in the light source module 111 and the first frequency-modulated optical signal R1 output by the light source in the light source module 111.

[0215] Similarly, in the second calibration path 120, the second frequency-modulated optical signal R2 output by the light source, after passing through the delayed frequency discrimination optical path 122 and the photodetector 123, becomes the in-phase component I2 and the quadrature component Q2 of the second intermediate frequency signal S2. Both the in-phase component I1 and the quadrature component Q1 are analog signals. The in-phase component I2 and the quadrature component Q2 in the analog domain are output to the two PFDs in the first phase-locked loop 210, respectively.

[0216] In the first phase-locked loop 210, the in-phase component I1 of the first intermediate frequency signal S1 and the in-phase component I2 of the second intermediate frequency signal S2 are output to the same PFD. This PFD multiplies the in-phase components I1 and I2 in the analog domain to calculate the error signal S of the in-phase components in the analog domain. erri The error signal S of the in-phase component in this analog domain erri After being filtered by a subsequent filter, an in-phase feedback signal P is generated in the analog domain. 21i The result is then output to the adder in the first phase-locked loop 210. Similarly, the quadrature component Q1 of the first intermediate frequency signal S1 and the quadrature component Q2 of the second intermediate frequency signal S2 are output to another PFD, which multiplies the quadrature components Q1 and Q2 in the analog domain to calculate the error signal S of the quadrature components in the analog domain. errqThe error signal S of the orthogonal components in the analog domain errq After being filtered by a subsequent filter, an orthogonal feedback signal P is generated in the analog domain. 21q The output is also sent to the adder in the first phase-locked loop 210. The adder in the first phase-locked loop 210 outputs the in-phase feedback signal P in the analog domain. 21i and the orthogonal feedback signal P in the analog domain 21q Perform addition to obtain the first feedback signal P in the analog domain. 21 And output to the second calibration path 120, the first feedback signal P 21 This is used to make the second frequency-modulated optical signal R2 output by the light source in the second calibration path 120 have the opposite frequency modulation slope to the first frequency-modulated optical signal R1 output by the light source in the first calibration path 110 and lock the phase difference.

[0217] Optionally, in the second calibration path 120, the in-phase component I2 and the quadrature component Q2 in the analog domain also enter adder 1 in processing element 124. Adder 1 superimposes the in-phase component I2 and the quadrature component Q2 in the analog domain to obtain the complex form of the second intermediate frequency signal S2, S2 = I2 + jQ2. Processing element 124 calls the predistortion algorithm to process the second intermediate frequency signal S2 = I2 + jQ2 to obtain the second predistortion signal P in the analog domain. 22 and the second predistortion signal P 22 The output is sent to adder 2. The first feedback signal P in the analog domain is output by the first phase-locked loop 210. 21 It also enters adder 2 in processing element 124. Adder 2 processes the second predistorted signal P in the analog domain. 22 With the first feedback signal P in the analog domain 21 The signals are superimposed to generate a driving signal P2 in the analog domain. This driving signal P2 acts on the signal generator in the second calibration path 120 to modulate the second frequency-modulated optical signal R2 output by the light source in the second calibration path 120. This causes the frequency of the second frequency-modulated optical signal R2 to follow the frequency of the first frequency-modulated optical signal R1 output by the light source in the first calibration path 110 in the opposite direction and the phase difference is locked. At the same time, it calibrates the nonlinearity of the frequency and time of the second frequency-modulated optical signal R2.

[0218] The above implementation scheme 2 uses an AMZI based on silicon-based optical waveguides as the delay frequency discrimination optical path. The detection and demodulation adopts an integrated mixer designed based on the principle of silicon-based multimode interferometer. The output is the in-phase component and quadrature component of the first intermediate frequency signal and the second intermediate frequency signal in the analog domain. The first phase-locked loop calculates the error signals of the in-phase component and the quadrature component in the analog domain and performs phase-locked superposition to achieve interlocking of the frequency and phase of the light source frequency modulation in the two calibration paths, realize the coherence of the light source frequency modulation in the two calibration paths, and improve the accuracy of ranging and speed measurement.

[0219] Implementation Plan 3

[0220] Please refer to Figure 15, which shows a schematic diagram of a coherent calibration device provided in Implementation Scheme 3. In this coherent calibration device, the first phase-locked loop 210 is a digital phase-locked loop, and its structure is shown in Figure 12a above. The structures of the first calibration path 110 and the second calibration path 120 are shown in Implementation Scheme 2 above. For example, in each calibration path, the light source module includes a signal generator and a light source, the delay frequency discrimination optical path includes a first beam splitter and an optical delay line, and the photodetector is implemented by a balanced detector (BPD). Each calibration path also includes a power divider, a 90° phase shifter, a processing element, two ADCs and one DAC, and the connection relationship is shown in Figure 15.

[0221] In implementation scheme three, the delay-frequency discrimination optical path adopts an AMZI constructed with optical fiber, and the first calibration path 110 and the second calibration path 120 share the same optical delay line. In this case, the coherent calibration device also includes a beam combiner (also called an optical fiber coupler) and a second beam splitter (also called an optical fiber beam splitter). The two input ends of the beam combiner are respectively connected to the output ends of the signals to be delayed of the two first beam splitters in the two calibration paths. The output end of the beam combiner is connected to one end of the optical delay line, and the other end of the optical delay line is connected to the input end of the second beam splitter. The two output ends of the second beam splitter are respectively connected to the two BPDs in the two calibration paths.

[0222] Based on the above structure and connection relationship, as shown in Figure 15, in the first calibration path 110, the first frequency-modulated optical signal R1 output by the light source is split into a delay signal R by the first beam splitter. 11 Calibration path local oscillator signal R 12 and detection signal R 13 Detection signal R 13 Input is sent to target measurement channel 118 for target measurement, and the local oscillator signal R of the calibration channel is used. 12 The signal R to be delayed enters one input terminal of the BPD in the photodetector 113. 11 The light enters the beam combining element. Similarly, in the second calibration path 120, the second frequency-modulated optical signal R2 output by the light source is split into the delay signal R by the first beam splitter. 21 Calibration path local oscillator signal R 22 and detection signal R 23 Detection signal R 23 Input is sent to target measurement channel 128 for target measurement, and the local oscillator signal R of the calibration channel is used. 22 The signal R to be delayed enters one input terminal of the BPD in photodetector 123. 21 Enter the light combining element.

[0223] The optical combining element combines the delayed signal R in the first calibration path 110. 11The delay signal R in the second calibration path 120 21 After a beam of light is synthesized, it is output to an optical delay line. The light signal after being delayed by the optical delay line enters the second beam splitter and is split into the delayed signal in the first calibration path 110 and the delayed signal in the second calibration path 120.

[0224] The delayed signal in the first calibration path 110 enters another input terminal of the BPD in the photodetector 113, and interacts with the calibration path local oscillator signal R in the first calibration path 110. 12 The difference is calculated to generate a first intermediate frequency signal S1 (electrical signal) in real form. The first intermediate frequency signal S1 in real form is split into an in-phase component I1 and a signal to be phase-shifted (both are analog signals) by the power divider in the first calibration path 110. The in-phase component I1 of the first intermediate frequency signal S1 is converted into a digital signal by ADC1161 and then enters the processing element 114. The signal to be phase-shifted is phase-shifted by a 90° phase shifter in the first calibration path 110 and becomes the quadrature component Q1 of the first intermediate frequency signal S1. Then it is converted into a digital signal by ADC1162 and also enters the processing element 114. Processing element 114 calls a summation algorithm to sum the in-phase component I1 and quadrature component Q1 in the digital domain to obtain the first intermediate frequency signal S1 = I1 + jQ1 in the digital domain, and outputs it to the first phase-locked loop 210. At the same time, it calls a predistortion algorithm to process the first intermediate frequency signal S1 = I1 + jQ1 in the digital domain to generate the first predistortion signal P1 in the digital domain. The first predistortion signal P1 is output to DAC 117, which converts it into the first predistortion signal in the analog domain and sends it to the signal generator in the light source module 111 to calibrate the nonlinear relationship between the first modulation signal L1 output by the signal generator in the light source module 111 and the first frequency-modulated light signal R1 emitted by the light source in the light source module 111, so that the frequency of the first frequency-modulated light signal R1 is linear with time.

[0225] Similarly, the delayed signal in the second calibration path 120 enters another input terminal of the BPD in the photodetector 123, and interacts with the calibration path local oscillator signal R in the second calibration path 120. 22The difference is calculated to generate a second intermediate frequency (IF) signal S2 in real form. This real-form IF signal S2 is split by a power divider in the second calibration path 120 into an in-phase component I2 and a phase-shifting signal (both analog signals). The in-phase component I2 is converted to a digital signal by an ADC1261 and then enters the processing element 124. The phase-shifting signal is phase-shifted by a 90° phase shifter in the second calibration path 120, becoming a quadrature component Q2 of the IF signal S2. This quadrature component Q2 is then converted to a digital signal by an ADC1262 and also enters the processing element 124. The processing element 124 uses a summation algorithm to sum the in-phase component I2 and the quadrature component Q2 in the digital domain, obtaining the second IF signal S2 = I2 + jQ2 in the digital domain, and outputs it to the first phase-locked loop 210.

[0226] After receiving the complex form S1 = I1 + jQ1 of the first intermediate frequency signal and the complex form S2 = I2 + jQ2 of the second intermediate frequency signal in the digital domain, the first phase-locked loop 210 calls the frequency and phase discrimination algorithm to multiply the first intermediate frequency signal S1 = I1 + jQ1 and the second intermediate frequency signal S2 = I2 + jQ2 in the digital domain to obtain the error signal S in the digital domain. err And extract the error signal S err The phase signal in the signal is processed by a PID algorithm to form the first feedback signal P in the digital domain. 21 And output to the second calibration path 120. The first feedback signal P in the digital domain 21 The signal is converted into a first feedback signal P in the analog domain by DAC127 in the second calibration path 120. 21 The first feedback signal P is output to the signal generator in the second calibration path 120. 21 This is used to make the second frequency-modulated optical signal R2 output by the light source in the second calibration path 120 have the opposite frequency modulation slope to the first frequency-modulated optical signal R1 output by the light source in the first calibration path 110 and lock the phase difference.

[0227] Optionally, the processing element 124 is also equipped with a predistortion algorithm, and the first feedback signal P in the digital domain of the first phase-locked loop 210 output is... 21 The signal is then processed by processing element 124. Processing element 124 can also invoke a predistortion algorithm to process the second intermediate frequency signal S2 = I2 + jQ2, obtaining the second predistortion signal P in the digital domain. 22 Then, the summation algorithm is called to apply the second predistorted signal P. 22 and the first feedback signal P 21The signals are superimposed to generate a digital driving signal P2, which is then output to DAC127. DAC127 converts the digital driving signal P2 into an analog driving signal P2 and outputs it to the signal generator in the second calibration path 120. The driving signal P2 is used to modulate the second frequency-modulated optical signal R2 output by the light source in the second calibration path 120, so that the frequency of the second frequency-modulated optical signal R2 follows the frequency of the first frequency-modulated optical signal R1 output by the light source in the first calibration path 110 in the opposite direction and the phase difference is locked. At the same time, the frequency of the second frequency-modulated optical signal R2 is linear with time.

[0228] In Scheme 3 above, an AMZI optical fiber is used as the delay-frequency discrimination optical path. The detection and demodulation process involves first obtaining a real signal using balanced detection, then demodulating it into a complex signal using a 90° phase shift. The output consists of a first intermediate frequency (IF) signal and a second IF signal in the digital domain. The first phase-locked loop calculates the error signals of the first and second IF signals in the digital domain and performs phase locking to achieve coherence of the light source frequency modulation in the two calibration paths. Furthermore, in Scheme 3, the two calibration paths share the same delay-frequency discrimination optical path. The signals to be delayed after being split from the light sources in the two calibration paths are combined by a beam combiner into the same fiber delay line. After delay processing by the fiber delay line, the signals are then split by a second beam splitter into the two calibration paths to beat with the local oscillator signal of the local calibration path.

[0229] It should be noted that in the above implementation scheme three, the two signals R to be delayed in the first calibration path 110 and the second calibration path 120 are... 11 and R 21 The signals need to be combined into one path before being split into two. Therefore, to achieve accurate beam splitting, the two delay signals R... 11 and R 21 A wavelength difference is required. For example, the light source in the first calibration path 110 and the light source in the second calibration path 120 output two frequency-modulated light signals R1 and R2 with different wavelengths. These two frequency-modulated light signals R1 and R2 are split into two delay signals R with different wavelengths. 11 and R 21 These two signals R of different wavelengths to be delayed 11 and R 12 The optical signals are combined into a single multi-wavelength optical signal by a beam combiner. This multi-wavelength optical signal is then delayed by an optical delay line and then split into two delayed signals corresponding to the calibration paths by a second beam splitter. The delayed signals corresponding to the two calibration paths enter their respective photodetectors and beat with the local oscillator signals of the corresponding calibration paths.

[0230] The second beam splitter can be based on wavelength, power, or resonance; the specific method is not limited. For example, in wavelength-based beam splitting, the second beam splitter can separate pure delayed signals of different wavelengths. These delayed signals are output to their respective photodetectors and beat with the local oscillator signal of the calibration path at the same wavelength. In power-based or resonant-based beam splitting, although the second beam splitter may separate delayed signals with multiple wavelengths in each path (e.g., each delayed signal is a uniformly divided and mixed optical signal of various wavelengths), during beat frequency in the photodetector, the wavelength of the local oscillator signal in the calibration path will be used for beat frequency, and other wavelengths will not be used. Therefore, power-based or resonant-based beam splitting can also achieve subsequent beat frequency and processing functions.

[0231] Implementation Plan 4

[0232] Please refer to Figures 16a and 16b. Figure 16a shows a schematic diagram of the structure of a coherent calibration device provided in Embodiment 4, and Figure 16b shows a schematic diagram of the frequency modulation waveform of the coherent calibration device. The coherent calibration device includes four calibration paths: a first calibration path 110, a second calibration path 120, a third calibration path 130, and a fourth calibration path 140. Embodiment 4 can achieve phase locking of the frequency modulation of the four light sources in the four calibration paths. In other words, based on the first calibration path 110 and the second calibration path 120 in Embodiments 1 to 3 above, a third calibration path 130, a fourth calibration path 140, or other calibration paths are also allowed. Any calibration path can be in phase or out of phase with the light source frequency modulation of the first calibration path 110. For example, Figures 16a and 16b illustrate this with the third calibration path 130 being in phase with the light source frequency modulation of the first calibration path 110, while the second calibration path 120 and the fourth calibration path 140 are both out of phase with the light source frequency modulation of the first calibration path 110.

[0233] In one possible application scenario, the detection signals after beam splitting from the light sources in the four calibration paths 110-140 are used to jointly detect a target. Each pair of calibration paths with reverse-frequency modulated light sources corresponds to one detection channel. For example, referring to Figures 16a and 16b, the four calibration paths 110-140 have two sets of reverse-frequency modulated light sources. For instance, the first calibration path 110 and the second calibration path 120 have reverse-frequency modulated light sources, and the third calibration path 130 and the fourth calibration path 140 have reverse-frequency modulated light sources; or, the first calibration path 110 and the fourth calibration path 140 have reverse-frequency modulated light sources, and the third calibration path 130 and the second calibration path 120 have reverse-frequency modulated light sources. Taking the former as an example, the two detection signals R after beam splitting from the two light sources in the first calibration path 110 and the second calibration path 120... 13 and R 23When light is directed to a single detection channel (e.g., a scan line in a line scan scenario), the two detection signals R, after being split by the two light sources in the third calibration path 130 and the fourth calibration path 140, are generated. 33 and R 43 By scanning onto another detection channel (such as another scan line in a line scan scenario), the coherent calibration device can obtain the scanning range of two scan lines in one scan, which can increase the range of a single scan.

[0234] Understandably, the two calibration paths with inverse frequency modulation waveforms can be phase-locked using any of the above implementation schemes one through three. For example, Figure 16a uses the design in implementation scheme one as an example. Based on the waveform shown in Figure 16b, the second calibration path 120 and the fourth calibration path 140 are both inversely frequency-modulated with the light source of the first calibration path 110, while the third calibration path 130 is in phase with the light source of the first calibration path 110. Specifically, as shown in Figure 16a:

[0235] A first phase-locked loop (PLL) 210 is designed for the reverse frequency modulation waveform phase-locking of the first calibration path 110 and the second calibration path 120. The first PLL 210 is connected to the processing element 114 of the first calibration path 110 and the processing element 124 of the second calibration path 120. It is used to acquire the complex form of the first intermediate frequency (IF) signal S1 = I1 + jQ1 output by the processing element 114 and the complex form of the second IF signal S2 = I2 + jQ2 output by the processing element 124. The second IF signal S2 = I2 + jQ2 is compared with the first IF signal S1 = I1 + jQ1 to obtain the error signal S2 = I2 + jQ2 compared to the first IF signal S1 = I1 + jQ1. err2 And based on the error signal S err2 Output the first feedback signal P to the processing element 124 21 Processing element 124 processes the first feedback signal P. 21 (or also combined with the second predistortion signal P) 22 The second frequency-modulated optical signal R2 output from the light source in the second calibration path 120 is modulated so that the modulation slope of the second frequency-modulated optical signal R2 is opposite to that of the first frequency-modulated optical signal R1 output from the light source in the first calibration path 110 (reverse modulation), and the phase difference is locked.

[0236] Similarly, a second phase-locked loop 220 is designed for the in-phase frequency modulation waveform phase-locking of the first calibration path 110 and the third calibration path 130. The second phase-locked loop 220 is connected to the processing element 124 of the second calibration path 120 and the processing element 134 of the third calibration path 130. It is used to acquire the complex form of the second intermediate frequency signal S2 = I2 + jQ2 output by the processing element 124 and the complex form of the third intermediate frequency signal S3 = I3 + jQ3 output by the processing element 134. The third intermediate frequency signal S3 = I3 + jQ3 is compared with the second intermediate frequency signal S2 = I2 + jQ2 to obtain the error signal S3 = I3 + jQ3 compared to the second intermediate frequency signal S2 = I2 + jQ2. err3 And based on the error signal S err3 Output the second feedback signal P to the processing element 134 31 Processing element 134 processes the second feedback signal P. 31 (or also combined with the third predistortion signal P) 32 The third frequency-modulated optical signal R3 output from the light source in the third calibration path 130 is modulated such that the modulation slope of the third frequency-modulated optical signal R3 is opposite to that of the second frequency-modulated optical signal R2 output from the light source in the second calibration path 120 (reverse modulation), and the phase difference is locked. Since the modulation slope of the second frequency-modulated optical signal R2 is opposite to that of the first frequency-modulated optical signal R1 (reverse modulation) and the phase difference is locked, the modulation slope of the third frequency-modulated optical signal R3 will be the same as that of the first frequency-modulated optical signal R1 (in-phase modulation), and the phase difference will be locked.

[0237] Similarly, a third phase-locked loop 230 is designed for the reverse frequency modulation waveform phase-locking of the first calibration path 110 and the fourth calibration path 140. The third phase-locked loop 230 is connected to the processing element 114 of the first calibration path 110 and the processing element 144 of the fourth calibration path 140. It is used to acquire the complex form of the first intermediate frequency signal S1 = I1 + jQ1 output by the processing element 114 and the complex form of the fourth intermediate frequency signal S4 = I4 + jQ4 output by the processing element 144. The fourth intermediate frequency signal S4 = I4 + jQ4 is compared with the first intermediate frequency signal S1 = I1 + jQ1 to obtain the error signal S4 = I4 + jQ4 compared to the first intermediate frequency signal S1 = I1 + jQ1. err4 And based on the error signal S err4 Output the third feedback signal P to the processing element 144 41 Processing element 144 processes the data according to the third feedback signal P. 41 (or also combined with the fourth predistortion signal P) 42 The fourth frequency-modulated optical signal R4 output from the light source in the fourth calibration path 140 is modulated so that the modulation slope of the fourth frequency-modulated optical signal R4 is opposite to and in phase with the first frequency-modulated optical signal R1 output from the light source in the first calibration path 110, and the phase difference is locked.

[0238] The above implementation scheme four can achieve in-phase or out-of-phase locking of the frequency modulation of multiple calibration path light sources. Since the other calibration paths are directly or indirectly phase-locked with one of the calibration paths, the frequency-modulated optical signals modulated by the light sources in all calibration paths can maintain absolute consistency of slope (absolutely the same or absolutely opposite) and mutual locking of phase differences.

[0239] It should be noted that in Figure 16a above, the third calibration path 130 is locked to the second calibration path 120 to achieve phase-locked frequency modulation waveform of the third calibration path 130 and the first calibration path 110. However, in some other examples, the third calibration path 130 can also be locked to the fourth calibration path 140, which can also achieve phase-locked frequency modulation waveform of the third calibration path 130 and the first calibration path 110. This application does not make specific limitations on this.

[0240] Furthermore, the above implementation scheme four can be extended to coherent calibration devices with any number of calibration paths. For example, if the coherent calibration device includes N calibration paths, it needs N-1 phase-locked loops (PLLs). Each of the N-1 PLLs connects to two calibration paths, achieving reverse frequency locking of the light source frequencies of the two calibration paths, where N is a positive integer greater than or equal to 2. The detection signals in the N calibration paths can be used to detect the same target or different targets. The detection signal on each detection channel can include only the detection signal from one calibration path, or it can include the detection signals from a group of calibration paths with reverse frequency modulation, or it can include the detection signals from two or more in-phase and / or reverse-modulated calibration paths; there are no limitations.

[0241] Understandably, if the detection signals of N calibration paths are used to detect the same target, in order to achieve better noise suppression, N can be configured to be an even number. Furthermore, the N calibration paths contain the same number of in-phase frequency-modulated waveforms and out-of-phase frequency-modulated waveforms. In this way, the N calibration paths can be divided into N / 2 groups, with each group corresponding to one detection channel. The N / 2 groups combined to detect the same target can not only achieve mutual cancellation of phase noise in the echo signals obtained from each group of detections, but also increase the detection range of a single detection and improve detection efficiency.

[0242] Furthermore, the target measurement paths in the N calibration paths can be the same target measurement path or different target measurement paths. For example, taking the architecture shown in Figure 16a as an example, the target measurement path 118 in the first calibration path 110, the target measurement path 128 in the second calibration path 120, the target measurement path 138 in the third calibration path 130, and the target measurement path 148 in the fourth calibration path 140 can be the same target measurement path or different target measurement paths. When they are the same target measurement path, the four detection signals R in the four calibration paths 110 to 140 are...13 R 23 R 33 R 43 The light signals can be combined into a single beam using a beam combiner, then passed through various components on the same target measurement path before exiting into the detection space to jointly detect the target. When there are different target measurement paths, the four detection signals R... 13 R 23 R 33 R 43 Each beam can pass through its corresponding target measurement path and exit into the detection space. Then, it is combined into a single beam by components within the detection space (such as the PBS or semi-transparent mirror shown in Figure 3a above) to detect the same target. Of course, other implementation methods are also possible, and no specific limitations are made here.

[0243] Optionally, in some schemes, before inputting the two intermediate frequency signals into the corresponding phase-locked loops, the two intermediate frequency signals can be deformed in frequency and / or phase, such as frequency doubling, or mixed with other fixed frequency reference signals, or phase delay, etc. This application does not specifically limit this.

[0244] The coherent calibration device provided above can be applied to detection devices or systems with multiple frequency-modulated continuous wave sources, especially devices or systems using multiple inversely modulated frequency-modulated continuous wave sources, such as the aforementioned FMCW LiDAR, or optical frequency domain reflectometry (OFDR) systems, optical coherence tomography (OCT) systems, etc., without any specific limitations.

[0245] For example, taking FMCW LiDAR as an example, please refer to Figure 17a, which shows a possible application architecture of this coherent calibration device in FMCW LiDAR. In this application architecture, the frequency-modulated optical signals output by light source module 1 and light source module 2 are divided into two parts: the directly emitted detector signal and the local calibration signal. On one hand, the detector signal is divided into the detector local oscillator signal and the detector transmitted signal. The detector local oscillator signal directly enters its corresponding detector, while the detector transmitted signal is combined into one path after passing through a circulator, a reflector, and a semi-transparent mirror, and then enters a collimating lens for collimation processing to jointly detect the target. The echo signal reflected back by the target is split into the echo signals of the two light source modules after passing through the collimating lens, the semi-transparent mirror, and the reflector, and then enters the detector through a circulator to be mixed with the local oscillator signal of the respective detector to obtain the detector intermediate frequency signal S. 01 and S 02 .

[0246] On the other hand, the local calibration path signal enters the coherent calibration scheme proposed in this application. The coherent calibration scheme uses the delayed frequency discrimination optical path and photodetector corresponding to each of the two light source modules to perform delayed frequency discrimination and photodetection on the calibration path signals input to each module, obtain the two intermediate frequency signals S1 and S2 corresponding to the two light source modules, and call the predistortion algorithm to process the two intermediate frequency signals S1 and S2 to obtain two predistortion signals corresponding to the two light source modules, namely the first predistortion signal and the second predistortion signal. The first predistortion signal is output to the light source module 111 to calibrate the first frequency-modulated optical signal output by the light source module 111, making its frequency modulation slope linear with time. Simultaneously, the intermediate frequency signals S1 and S2 of the two calibration paths are also input to the first phase-locked loop 210. The first phase-locked loop 210 determines the first feedback signal based on the two intermediate frequency signals S1 and S2 of the calibration paths, and after superimposing the first feedback signal with the second pre-distortion signal, it outputs it to the light source module 121. This achieves the effect of the frequency modulation slope of the second frequency-modulated optical signal output by the light source module 2 and the frequency modulation slope and phase of the first frequency-modulated optical signal output by the phase-tracking light source module 1, thus solving the problem of incoherence of the swept frequency light source in the existing dual-light source FMCW LiDAR.

[0247] Based on the above FMCW LiDAR application architecture, please refer to Figure 17b, which shows the intermediate frequency signal S of the detector path before and after calibration using the coherent calibration scheme provided in this application. 01 and S 02 The spectrum comparison diagrams are shown in Figure 17b. The spectrum before calibration using the coherent calibration scheme is shown in (A), and the spectrum after calibration using the coherent calibration scheme is shown in (B). Combining Figures 17b (A) and (B), it can be seen that, without calibration, the intermediate frequency signal S of the FMCW LiDAR's probe path... 01 and S 02 The spectrum is severely broadened, with high noise, low signal-to-noise ratio, and inconsistent center frequencies. However, after applying the coherent calibration scheme proposed in this application, the intermediate frequency signals S of the two detector paths are significantly improved. 01 and S 02 The beat spectrum broadening is suppressed, the signal-to-noise ratio is improved, and the center frequency remains consistent.

[0248] Based on the structure and functional principle of the coherent calibration device described above, this application can also provide a coherent calibration method applicable to the coherent calibration device. The coherent calibration device can be the coherent calibration device in any of the above embodiments, specifically including a first phase-locked loop or a processing element in which the first phase-locked loop is located.

[0249] Please refer to Figure 18, which shows a schematic flowchart of a coherent calibration method provided in this application. The method includes the following steps:

[0250] Step 1801: Obtain the first intermediate frequency signal in the first calibration path and the second intermediate frequency signal in the second calibration path.

[0251] Here, the first intermediate frequency signal is the intermediate frequency signal generated after the first frequency-modulated optical signal emitted by the light source module in the first calibration path passes through the delayed frequency discrimination optical path and the photodetector in the first calibration path, and the second intermediate frequency signal is the intermediate frequency signal generated after the second frequency-modulated optical signal emitted by the light source module in the second calibration path passes through the delayed frequency discrimination optical path and the photodetector in the second calibration path.

[0252] Step 1802: Determine a first feedback signal based on the first intermediate frequency signal and the second intermediate frequency signal. The first feedback signal is used to calibrate the second frequency-modulated optical signal output by the light source module in the second calibration path, so that the frequency modulation slope of the second frequency-modulated optical signal is opposite to that of the first frequency-modulated optical signal output by the light source module in the first calibration path and the phase difference is locked.

[0253] Optionally, the first feedback signal may be determined by: determining the error signals of the first and second intermediate frequency signals based on the complex form of the first and second intermediate frequency signals, extracting the phase information from the error signals, and then determining the first feedback signal based on the phase information, wherein the first feedback signal is positively correlated with the phase information.

[0254] For example, if the complex form of the first intermediate frequency signal is:

[0255] The complex form of the second intermediate frequency signal is:

[0256] Therefore, the error signal is:

[0257] The phase information in this error signal is: Therefore, the first feedback signal satisfies the following condition: P 21 ∝-(k1τ1+k2τ2)t+Δφ1(t)+Δφ2(t)

[0258] In the above expressions, S1 and S2 represent the first and second intermediate frequency (IF) signals, respectively; I1 and I2 represent the real parts of the complex forms of the first and second IF signals, also known as in-phase components; Q1 and Q2 represent the imaginary parts of the complex forms of the first and second IF signals, also known as quadrature components; T1 and T2 represent the responsivity of the photodetectors in the first and second calibration paths, respectively; E1 and E2 represent the optical field intensities of the first and second frequency-modulated (FM) optical signals, respectively; k1 and k2 represent the frequency modulation slopes of the first and second FM optical signals, respectively; and τ1 and τ2 represent the delay durations of the delay-discriminate optical paths in the first and second calibration paths, respectively. These are the phase noises generated by the first and second frequency-modulated optical signals after passing through their respective delayed frequency-discriminating optical paths. These are the phase noises of the first and second frequency-modulated optical signals before they pass through the delayed frequency-discriminating optical path, respectively. These are the phase noises of the first and second frequency-modulated optical signals after passing through the delayed frequency-discriminating optical path, respectively.

[0259] Optionally, the first frequency-modulated optical signal is generated using a predistortion algorithm. Specifically, after obtaining the first intermediate frequency (IF) signal in the first calibration path, in addition to determining the first feedback signal by referring to the first IF signal, the first IF signal can also be processed using a predistortion algorithm to obtain a first predistortion signal. Then, the first predistortion signal is used to drive the light source module in the first calibration path to output the first frequency-modulated optical signal. This method can ensure that the frequency of the first frequency-modulated optical signal changes linearly with time.

[0260] Optionally, the second frequency-modulated optical signal can be generated using only the first feedback signal, or it can be generated by combining the first feedback signal and a predistortion algorithm. Taking the latter as an example, after obtaining the second intermediate frequency (IF) signal in the second calibration path, in addition to determining the first feedback signal by referring to the second IF signal, a predistortion algorithm can be used to process the second IF signal to obtain a second predistortion signal. Then, based on the second predistortion signal and the first feedback signal, the light source module in the second calibration path is driven to output the second frequency-modulated optical signal. This method not only ensures that the slope and phase of the second frequency-modulated optical signal follow the changes in the first frequency-modulated optical signal, but also guarantees that the frequency of the second frequency-modulated optical signal changes linearly with time.

[0261] Optionally, after outputting the first feedback signal to the light source module in the second calibration path, the first echo signal in the first calibration path and the second echo signal in the second calibration path can also be acquired. Then, the target can be identified jointly based on the first and second echo signals. The first echo signal is the echo signal obtained by detecting the target using the detection signal after splitting the first frequency-modulated optical signal, and the second echo signal is the echo signal obtained by detecting the target using the detection signal after splitting the second frequency-modulated optical signal. Based on this, the detection signals after splitting the first and second frequency-modulated optical signals can be used to jointly detect the target. Since the two frequency-modulated optical signals are inversely modulated, their phase noises are opposite, and the corresponding phase noises of the two echo signals are also opposite. Target identification based on the two echo signals with opposite phase noises can improve the accuracy of the identification.

[0262] Optionally, in implementing the coherent calibration method, in addition to acquiring the first and second intermediate frequency (IF) signals, a third IF signal from the third calibration path can also be acquired. A second feedback signal is determined based on the second and third IF signals. The third IF signal is the IF signal generated after the third frequency-modulated optical signal emitted by the light source module in the third calibration path passes through the delayed frequency discrimination optical path and photodetector in the third calibration path. The second feedback signal is used to calibrate the third frequency-modulated optical signal output by the light source module in the third calibration path, ensuring that the slope of the third frequency-modulated optical signal is opposite to that of the second frequency-modulated optical signal output by the light source module in the second calibration path, while maintaining a constant phase difference. Thus, since the slope of the second frequency-modulated optical signal is opposite to that of the first frequency-modulated optical signal, and the phase difference remains constant, the slope of the third frequency-modulated optical signal will be the same as that of the first frequency-modulated optical signal, and the phase difference will remain constant. In other words, by phase-locking the second calibration path to the first calibration path and phase-locking the third calibration path to the second calibration path, in-phase frequency modulation between the light source module in the third calibration path and the light source module in the first calibration path can be achieved.

[0263] Furthermore, optionally, a fourth intermediate frequency (IF) signal from the fourth calibration path can be acquired, and a third feedback signal can be determined based on the first and fourth IF signals. The fourth IF signal is the IF signal generated after the fourth frequency-modulated optical signal emitted by the light source module in the fourth calibration path passes through the delayed frequency discrimination optical path and photodetector in the fourth calibration path. The third feedback signal is used to calibrate the fourth IF signal output by the light source module in the fourth calibration path, ensuring that the slope of the fourth IF signal is opposite to that of the first IF signal output by the light source module in the first calibration path, while maintaining a constant phase difference. Thus, by phase-locking both the second and fourth calibration paths onto the first calibration path, reverse frequency modulation between the light source modules in multiple calibration paths and the light source module in the first calibration path can be achieved.

[0264] Furthermore, optionally, the detection signals obtained by splitting the first to fourth frequency-modulated optical signals output by the light source modules in the first to fourth calibration paths are used to merge the detected targets. The detection signals in the first and second calibration paths correspond to one detection channel, and the detection signals in the third and fourth calibration paths correspond to another detection channel. In this way, the echo signals from the two calibration paths on each detection channel can have opposite phase noise, and the scanning range of a single detection can be increased, thereby improving detection efficiency.

[0265] Based on the coherent calibration method described above, this application can also provide a coherent calibration apparatus that can be used to perform the above coherent calibration method. The relevant features can be found in the above method embodiments, and will not be repeated here.

[0266] In one possible implementation, please refer to Figure 19, which shows a possible structural schematic of the coherent calibration device. The coherent calibration device 1900 can be a chip or circuit, such as a chip or circuit disposed in a detection device, or a chip or circuit disposed in a device outside the detection device. The coherent calibration device 1900 can correspond to the first phase-locked loop or the processing element described above. The coherent calibration device 1900 can implement the steps performed in the method shown in Figure 18 above.

[0267] As shown in Figure 19, the coherent calibration device 1900 may include an acquisition unit 1910 and a determination unit 1920. When the coherent calibration device 1900 is working, the acquisition unit 1910 is used to acquire a first intermediate frequency signal in the first calibration path and a second intermediate frequency signal in the second calibration path. The determination unit 1920 is used to determine a first feedback signal based on the first intermediate frequency signal and the second intermediate frequency signal. The first feedback signal is used to calibrate the second frequency-modulated optical signal output by the light source module in the second calibration path, so that the frequency modulation slope of the second frequency-modulated optical signal is opposite to that of the first frequency-modulated optical signal output by the light source module in the first calibration path and the phase difference is locked.

[0268] For the concepts, explanations, detailed descriptions, and other steps related to the technical solutions provided in the embodiments of this application involving the coherent calibration device 1900, please refer to the descriptions of these contents in the foregoing methods or other embodiments, which will not be repeated here.

[0269] It should be understood that the division of units in the coherent calibration device 1900 described above is merely a logical functional division. In actual implementation, all or part of the units can be integrated into a single physical entity, or they can be physically separated. This application does not impose any specific limitations on this. The functions of each unit in the coherent calibration device 1900 can be referred to the implementation of the corresponding method embodiments, and will not be repeated here.

[0270] In one possible implementation, please refer to Figure 20, which shows another possible structural schematic diagram of the coherent calibration device. The coherent calibration device 2000 can be a chip or a chip system. Optionally, the chip system can be composed of chips or may include chips and other discrete devices. As shown in Figure 20, the coherent calibration device 2000 may include at least one processor 2010 and a memory 2020. At least one processor 2010 is coupled to the memory 2020, which may be located within or outside the coherent calibration device 2000. The memory 2020 stores the computer programs or instructions necessary for implementing any of the above method embodiments. The at least one processor 2010 completes the coherent calibration method in any of the above method embodiments by executing the computer programs or instructions stored in the memory 2020.

[0271] The coherent calibration device 2000 may also include a communication interface 2030, through which the coherent calibration device 2000 can interact with other devices. The communication interface 2030 may be a circuit, a bus, a transceiver, or any other device that can be used for information interaction, or a signal transceiver unit. When the coherent calibration device 2000 is a chip-type device or circuit, the communication interface 2030 may also be an input / output circuit, capable of inputting data (or receiving data) and outputting data (or sending data). At least one processor 2010 may be an integrated processor, a microprocessor, or an integrated circuit, and at least one processor 2010 may determine the output data based on the input data.

[0272] The aforementioned processor 2010 can be a general-purpose processor, digital signal processor, application-specific integrated circuit, field-programmable gate array or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component, and can implement or execute the methods, steps, and logic block diagrams disclosed in this application. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in this application can be directly manifested as being executed by a hardware processor, or executed by a combination of hardware and software modules within the processor.

[0273] The aforementioned memory 2020 can be non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD), or it can be volatile memory, such as random-access memory (RAM). Memory can also be any other medium capable of carrying or storing desired program code in the form of instructions or data structures, and accessible by a computer, but is not limited thereto. The memory 2020 in this application can also be a circuit or any other device capable of implementing storage functions for storing computer programs, computer program or instruction and / or data.

[0274] For the concepts, explanations, detailed descriptions, and other steps related to the technical solutions provided in the embodiments of this application involving the coherent calibration device 2000, please refer to the descriptions of these contents in the foregoing methods or other embodiments, which will not be repeated here.

[0275] Based on the coherent calibration apparatus described above, this application can also provide a detection apparatus, as shown in FIG21. The detection apparatus 2100 includes a coherent calibration apparatus 2110, which can be a coherent calibration apparatus in any of the above embodiments, such as the coherent calibration apparatus described in any of FIG4, FIG12a, FIG13-15, FIG16a, FIG19 or FIG20.

[0276] Optionally, as shown in Figure 21 above, the detection device 2100 may further include a window 2120, which is used to protect the internal coherent calibration device 2110 and can transmit the frequency-modulated light signal emitted by the coherent calibration device 2110.

[0277] It should be noted that the detection device architecture shown in Figure 21 is only an example. In other examples, the detection device may include more, fewer, or different structures, and each structure may include more, fewer, or different components. This application does not make any specific limitations in this regard.

[0278] Alternatively, the detection device 2100 can be a lidar, such as an FMCW LiDAR.

[0279] Based on the structure and functional principles of the detection device described above, this application can also provide a terminal device, as shown in Figure 22. This terminal device 2200 may include the coherent calibration device described above, or it may include a detection device 2210. The detection device 2210 may be a detection device from any of the above embodiments, such as the detection device 2100 in Figure 21.

[0280] Optionally, as shown in Figure 22 above, the terminal device 2200 may further include a processor 2220, which is used to call programs or instructions to control the operation of the detection device 2210. Furthermore, the processor 2220 may also receive target-related information from the detection device 2210. When the terminal device 2200 is a vehicle, the processor 2220 may also perform vehicle path planning, braking, or starting based on the acquired information. For example, the vehicle's position can be determined using latitude and longitude, or the vehicle's direction of travel and destination in the future can be determined using speed and orientation, or the number and density of obstacles around the vehicle can be determined using the distance to surrounding objects.

[0281] Furthermore, optionally, the terminal device 2200 may also include a memory 2230 for storing programs or instructions. Of course, the terminal device 2200 may also include other devices, such as wireless communication devices.

[0282] Processor 2220 may include one or more processing units. For example, processor 2220 may include an application processor (AP), an image signal processor (ISP), a controller, a DSP, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. Different processing units may be independent devices or integrated into one or more processors.

[0283] The memory 2230 includes, but is not limited to, random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. Exemplarily, the storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside within an ASIC.

[0284] For example, the terminal device 2200 may be a vehicle (e.g., unmanned vehicle, intelligent vehicle, electric vehicle, or digital car), robot, surveying equipment, drone, smart home device (e.g., television, robot vacuum cleaner, smart lamp, audio system, smart lighting system, electrical control system, home background music, home theater system, intercom system, or video surveillance), smart manufacturing equipment (e.g., industrial equipment), smart transportation equipment (e.g., AGV, unmanned transport vehicle, or truck), or smart terminal (mobile phone, computer, tablet, PDA, desktop computer, headphones, audio equipment, wearable device, in-vehicle device, virtual reality device, augmented reality device, etc.).

[0285] It should be noted that with the development of detection technology, the coherent calibration device structure provided in this application is also applicable to the same technical problems, and this application does not make specific limitations on it.

[0286] In the above content, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. In the textual description of this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0287] Additionally, in this application, the terms "optionally" or "exemplary" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design described as "optional" or "exemplary" in this application should not be construed as being more preferred or advantageous than other embodiments or design options. Alternatively, it can be understood that the use of the terms "exemplary" or "optional" is intended to present concepts in a specific manner and does not constitute a limitation of this application.

[0288] It is understood that the various numerical designations used in this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers described above does not imply the order of execution; the execution order of each process should be determined by its function and internal logic. The terms "first," "second," "third," and similar expressions are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as including a series of steps or units. A method, system, product, or device is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

Claims

1. A coherent calibration device, characterized in that include: The first calibration path, the second calibration path, and the first phase-locked loop; Each of the first calibration path and the second calibration path includes a light source module, a time-delayed frequency discrimination optical path, and a photodetector. The light source module in each calibration path is used to output a frequency-modulated optical signal. The frequency-modulated optical signal is converted into an intermediate frequency signal after passing through the time-delayed frequency discrimination optical path and the photodetector in each calibration path. The first phase-locked loop is used to acquire the first intermediate frequency signal output by the photodetector in the first calibration path and the second intermediate frequency signal output by the photodetector in the second calibration path, and outputs a first feedback signal to the light source module in the second calibration path. The first feedback signal is used to calibrate the second frequency-modulated light signal output by the light source module in the second calibration path, so that the second frequency-modulated light signal and the first frequency-modulated light signal output by the light source module in the first calibration path have opposite frequency modulation slopes and constant phase difference. The first frequency-modulated light signal and the second frequency-modulated light signal are used to jointly detect the target.

2. The apparatus of claim 1, wherein, The frequency-modulated optical signal output by the light source module in each calibration path is split into a local oscillator signal, a signal to be delayed, and a detection signal. The detection signal is used to detect the target. The signal to be delayed is processed by the delay frequency discrimination optical path in each calibration path and mixed with the local oscillator signal to obtain the intermediate frequency signal. The intermediate frequency signal is detected and output by the photodetector in each calibration path. The detection signals in the first calibration path and the detection signals in the second calibration path are used to merge the detection target.

3. The apparatus of claim 1 or 2, wherein, The coherent calibration device also includes a third calibration path and a second phase-locked loop; The second phase-locked loop is used to acquire the second intermediate frequency signal output by the photodetector in the second calibration path and the third intermediate frequency signal output by the photodetector in the third calibration path, and output a second feedback signal to the light source module in the third calibration path. The second feedback signal is used to calibrate the third frequency-modulated optical signal output by the light source module in the third calibration path, so that the third frequency-modulated optical signal and the second frequency-modulated optical signal have opposite frequency modulation slopes and constant phase difference.

4. The apparatus of claim 3, wherein, The coherent calibration device also includes a fourth calibration path and a third phase-locked loop; The third phase-locked loop is used to acquire the first intermediate frequency signal output by the photodetector in the first calibration path and the fourth intermediate frequency signal output by the photodetector in the fourth calibration path, and outputs a third feedback signal to the light source module in the fourth calibration path. The third feedback signal is used to calibrate the fourth frequency-modulated optical signal output by the light source module in the fourth calibration path, so that the fourth frequency-modulated optical signal and the first frequency-modulated optical signal have opposite frequency modulation slopes and constant phase difference. The first frequency-modulated optical signal, the second frequency-modulated optical signal, the third frequency-modulated optical signal, and the fourth frequency-modulated optical signal are used to jointly detect the target. The first frequency-modulated optical signal and the second frequency-modulated optical signal correspond to one detection channel, and the third frequency-modulated optical signal and the fourth frequency-modulated optical signal correspond to another detection channel.

5. The apparatus of any one of claims 1 to 4, wherein, The first phase-locked loop includes a frequency-phase detector and a low-pass filter; The frequency and phase detector is used to determine the error signal between the first intermediate frequency signal and the second intermediate frequency signal based on the complex form of the first intermediate frequency signal and the second intermediate frequency signal; The low-pass filter is used to determine the first feedback signal based on the error signal, wherein the first feedback signal is positively correlated with the error signal.

6. The apparatus of claim 5, wherein, The error signal satisfies the following condition: The first feedback signal satisfies the following condition: Among them, S err Let P be the error signal, R1 and R2 be the responsivity of the photodetectors in the first and second calibration paths, respectively, E1 and E2 be the light field intensities of the first and second frequency-modulated optical signals, k1 and k2 be the frequency modulation slopes of the first and second frequency-modulated optical signals, τ1 and τ2 be the delay durations of the delay-discriminate optical paths in the first and second calibration paths, and t be the detection time. These are the phase noises generated by the first frequency-modulated optical signal and the second frequency-modulated optical signal after passing through the delayed frequency-discriminating optical path, respectively.

7. The apparatus of claim 5 or 6, wherein, The frequency and phase detector includes a first phase detector and a second phase detector, the low-pass filter includes a first filter and a second filter, and the first phase-locked loop further includes an adder. The first phase detector is used to calculate the error signal of the in-phase component based on the in-phase component of the first intermediate frequency signal and the in-phase component of the second intermediate frequency signal. The second phase detector is used to calculate the error signal of the quadrature component based on the quadrature component of the first intermediate frequency signal and the quadrature component of the second intermediate frequency signal; The first filter is used to determine an in-phase feedback signal based on the error signal of the in-phase component, wherein the in-phase feedback signal is positively correlated with the error signal of the in-phase component. The second filter is used to determine an orthogonal feedback signal based on the error signal of the orthogonal component, wherein the orthogonal feedback signal is positively correlated with the error signal of the orthogonal component; The adder is used to superimpose the in-phase feedback signal and the quadrature feedback signal to obtain the first feedback signal.

8. The device of any one of claims 1 to 7, wherein, In any calibration path: The delay-discrimination optical path includes a beam splitter, an optical delay line, and a 90° optical mixer; the calibration path also includes a processing element. The beam splitter is used to split the frequency-modulated optical signal output by the light source module to obtain a signal to be delayed and a local oscillator signal, output the local oscillator signal to the 90° optical mixer, and output the signal to be delayed to the optical delay line. The optical delay line is used to delay the signal to be delayed to obtain the delayed signal; The 90° optical mixer is used to perform mixing processing on the delayed signal and the local oscillator signal to obtain mixed signals with phases of 0°, 90°, 180° and 270° respectively; The photodetector is used to determine the in-phase component of the intermediate frequency signal based on the mixed signals with phases of 0° and 180°, determine the quadrature component of the intermediate frequency signal based on the mixed signals with phases of 90° and 270°, and output the in-phase component and quadrature component of the intermediate frequency signal to the processing element. The processing element is used to generate a complex intermediate frequency signal based on the in-phase and quadrature components of the intermediate frequency signal, and send it to the first phase-locked loop.

9. The device of any one of claims 1 to 8, wherein, In any calibration path: The delay-frequency discriminant optical path includes a beam splitter and an optical delay line, and the calibration path also includes a power divider, a 90° phase shifter, and a processing element. The beam splitter is used to split the frequency-modulated optical signal output by the light source module to obtain a signal to be delayed and a local oscillator signal, output the local oscillator signal to the photodetector, and output the signal to be delayed to the optical delay line; The optical delay line is used to delay the signal to be delayed to obtain the delayed signal; The photodetector is used to generate a real-valued intermediate frequency signal based on the delayed signal and the local oscillator signal; The power divider is used to perform beam splitting processing on the real-number intermediate frequency signal to obtain the in-phase component and the phase-shifting signal of the intermediate frequency signal, output the in-phase component to the processing element, and output the phase-shifting signal to the 90° phase shifter; The 90° phase shifter is used to perform phase shifting processing on the signal to be phase shifted to obtain the quadrature components of the intermediate frequency signal; The processing element is used to generate a complex intermediate frequency signal based on the in-phase and quadrature components of the intermediate frequency signal, and send it to the first phase-locked loop.

10. The apparatus of claim 8 or 9, wherein, The photodetector is a detection array, or includes one or more balanced detectors (BPDs).

11. The apparatus of any one of claims 8 to 10, wherein, The optical delay line is either an optical fiber delay line or an on-chip waveguide delay line.

12. The apparatus of any one of claims 8 to 11, wherein, The first calibration path and the second calibration path share the same optical delay line.

13. The device of any one of claims 1 to 12, wherein, The first calibration path also includes a first processing element; The first processing element is used to acquire the first intermediate frequency signal output by the photodetector in the first calibration path and output a first pre-distortion signal to the light source module in the first calibration path. The first pre-distortion signal is used to drive the light source module in the first calibration path to output a first frequency-modulated light signal whose frequency changes linearly with time.

14. The apparatus of claim 13, wherein, The light source module in the first calibration path includes a first signal generator and a first light source, wherein the first signal generator is connected between the first processing element and the first light source; The first signal generator is used to acquire the first predistortion signal output by the first processing element and output the first modulation signal to the first light source. The first predistortion signal is used to calibrate the linearity between the first modulation signal output by the first signal generator and the first frequency-modulated light signal output by the first light source.

15. The device of any one of claims 1 to 14, wherein, The second calibration path also includes a second processing element; The second processing element is configured to determine a second predistortion signal based on the second intermediate frequency signal output by the photodetector in the second calibration path, superimpose the second predistortion signal with the first feedback signal output by the first phase-locked loop, and send the superimposed signal. The superimposed signal is used to drive the light source module in the second calibration path to output the second frequency-modulated optical signal. The frequency of the second frequency-modulated optical signal changes linearly with time, and its frequency modulation slope is opposite to that of the first frequency-modulated optical signal, while its phase difference is constant.

16. The device of any one of claims 1 to 15, wherein, The light source module in the second calibration path includes a second signal generator and a second light source; The second signal generator is used to acquire the first feedback signal or the superimposed signal and output a second modulation signal to the second light source. The second modulation signal is used to calibrate the linearity between the second modulation signal output by the second signal generator and the second frequency-modulated optical signal output by the second light source, as well as to calibrate the opposite frequency modulation slope and constant phase difference between the second frequency-modulated optical signal output by the second light source and the first frequency-modulated optical signal output by the first light source.

17. The device of any one of claims 1 to 16, wherein, The first phase-locked loop is a digital phase-locked loop or an analog phase-locked loop.

18. A detection device, characterized in that Includes the coherent calibration apparatus as described in any one of claims 1 to 17.

19. A terminal device, comprising: Includes the detection device as described in claim 18.

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